@article{xue_palmese_sekely_little_kish_muth_wierer_2024, title={Growth and characterization of AlInN/GaN superlattices}, volume={630}, ISSN={["1873-5002"]}, url={https://doi.org/10.1016/j.jcrysgro.2024.127567}, DOI={10.1016/j.jcrysgro.2024.127567}, abstractNote={Data are presented on near-lattice-matched Al1-xInxN/GaN superlattices (SLs) with superior morphology to thick AlInN layers. The SLs are grown by metalorganic chemical vapor deposition and consist of ∼3 nm thick AlInN, ∼1 nm thick GaN layers, and x=0.153 to 0.203. The SLs are grown with either 20 or 100 periods on GaN-on-sapphire or free-standing GaN substrates. Growth conditions are explored, and the In-content of the AlInN layers within the SL increases with growth temperature and pressure, while the growth rate decreases with pressure. Thick AlInN layers grown on GaN-on-sapphire exhibit island growth with a root mean square (rms) roughness of ∼0.65 nm, while the AlInN/GaN SLs have steplike morphology and rms ∼0.3 nm. Also, 80 nm thick AlInN/GaN SLs grown on GaN substrates exhibit nearly perfect steplike morphology with a lower rms of ∼0.13 nm and extremely low pit densities. The refractive index of the SLs is the weighted average of AlInN and GaN, and they emit light from the quantum states within the thin GaN layers. These AlInN/GaN SLs are a potential replacement for AlInN layers in optoelectronic and electronic devices that require steplike morphology and controlled pitting.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Xue, Haotian and Palmese, Elia and Sekely, Ben J. and Little, Brian D. and Kish, Fred A. and Muth, John F. and Wierer, Jonathan J.}, year={2024}, month={Mar} }
 @article{mohammadbagherpoor_muth_grant_2023, title={A Modular Endoscopic Tool and Laser Ablation Test-Bed for Studying Biological Tissue Ablation Control Strategies}, volume={5}, ISSN={["2576-3202"]}, DOI={10.1109/TMRB.2023.3309947}, abstractNote={Robotized laser endoscopic tools provided surgeons with increased accuracy for ablating tissue. Here, a new modular endoscopic laser scanner system test-bed was designed and fabricated for conducting experiments into control strategies. This new system used a continuous wave (CW) laser system specifically designed for the task. Experiments into biological tissue ablation with this new system were compared with experiments previously conducted using a pulsed laser system. The torque required to accurately position the light beam of the flexible fiber optic cable was derived by solving Maxwell’s equations. The new test-bed again included a photo-detector sensor, which was used to position the laser beam on the tissue and provide closed-loop feedback control. With this arrangement, laser beam tracking errors were shown to be smaller than in the original pulsed laser experiments, and the tissue ablation patterns were repeatable. Trials on biological tissue (chicken meat) with this new physical test-bed proved that the tissue ablation pattern experiments were consistent, robust, and accurate. A COMSOL simulation of heat propagation then showed that consistency between the experimental and the simulation results. It also gave indicators for additional test-bed design changes that are required for optimizing the control of laser beam/biological tissue ablation.}, number={4}, journal={IEEE TRANSACTIONS ON MEDICAL ROBOTICS AND BIONICS}, author={Mohammadbagherpoor, Hamed and Muth, John and Grant, Edward}, year={2023}, month={Nov}, pages={811–818} }
 @article{mohammadbagherpoor_acemoglu_mattos_caldwell_johnson_muth_grant_2022, title={Designing and Testing a Closed-Loop Magnetically Actuated Laser Scanning System for Tissue Ablation}, volume={16}, ISSN={["1932-619X"]}, DOI={10.1115/1.4053073}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF MEDICAL DEVICES-TRANSACTIONS OF THE ASME}, author={Mohammadbagherpoor, Hamed and Acemoglu, Alperen and Mattos, Leonardo S. and Caldwell, Darwin and Johnson, James J. and Muth, John and Grant, Edward}, year={2022}, month={Jun} }
 @article{tran_delgado-carrascon_muth_paskova_nawaz_darakchieva_paskov_2021, title={Erratum: "Phonon-boundary scattering and thermal transport in AlxGa1<bold>-</bold>xN: Effect of layer thickness" [Appl. Phys. Lett. <bold>117</bold>, 252102 (2020)]}, volume={118}, ISSN={["1077-3118"]}, DOI={10.1063/5.0054625}, abstractNote={First Page}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Tran, Dat Q. and Delgado-Carrascon, Rosalia and Muth, John F. and Paskova, Tania and Nawaz, Muhammad and Darakchieva, Vanya and Paskov, Plamen P.}, year={2021}, month={May} }
 @article{blumenschein_kadlec_romanyuk_paskova_muth_kadlec_2020, title={Dielectric and conducting properties of unintentionally and Sn-doped beta-Ga2O3 studied by terahertz spectroscopy}, volume={127}, ISSN={["1089-7550"]}, DOI={10.1063/1.5143735}, abstractNote={Dielectric and conducting properties of unintentionally doped bulk and Sn-doped thin film β-Ga2O3 samples were studied using time-domain terahertz spectroscopy. Complex permittivity and optical conductivity spectra from 0.25 to 2.5 THz were obtained experimentally over a broad temperature range. The low-temperature spectra of the unintentionally doped sample were fit using a model involving two oscillators. The parameters of one of them show an unusual temperature dependence, in particular, a pronounced increase in the oscillator strength upon heating above 50 K. This is interpreted as an absorption due to thermally activated charge carriers moving in localized potential minima linked to the unintentional doping. Upon heating, the influence of this optical conductivity mechanism strongly increases, and the sample becomes opaque in the THz range near 100 K. The nanocrystalline Sn-doped Ga2O3 thin film sample exhibits a much higher optical conductivity than the unintentionally doped bulk sample, and its spectra are remarkably stable over a broad temperature range (4–750 K). This first study of β-Ga2O3 based on phase-sensitive THz spectroscopy reveals how the impurities influence the high-frequency conductive properties of the material.}, number={16}, journal={JOURNAL OF APPLIED PHYSICS}, author={Blumenschein, Nick and Kadlec, Christelle and Romanyuk, Oleksandr and Paskova, Tania and Muth, John F. and Kadlec, Filip}, year={2020}, month={Apr} }
 @article{tran_delgado-carrasco_muth_paskova_nawaz_darakchieva_paskov_2020, title={Phonon-boundary scattering and thermal transport in AlxGa1-xN: Effect of layer thickness}, volume={117}, ISSN={["1077-3118"]}, DOI={10.1063/5.0031404}, abstractNote={Thermal conductivity of AlxGa1−xN layers with 0≤x≤0.96 and variable thicknesses is systematically studied by combined thermoreflectance measurements and a modified Callaway model. We find a reduction in the thermal conductivity of AlxGa1−xN by more than one order of magnitude compared to that of GaN, which indicates a strong effect of phonon-alloy scattering. It is shown that the short-mean free path phonons are strongly scattered, which leads to a major contribution of the long-mean free path phonons to the thermal conductivity. In thin layers, the long-mean free path phonons become efficiently scattered by the boundaries, resulting in a further decrease in the thermal conductivity. Also, an asymmetry of thermal conductivity as a function of Al content is experimentally observed and attributed to the mass difference between Ga and Al host atoms.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Tran, Dat Q. and Delgado-Carrasco, Rosalia and Muth, John F. and Paskova, Tania and Nawaz, Muhammad and Darakchieva, Vanya and Paskov, Plamen P.}, year={2020}, month={Dec} }
 @article{blumenschein_moser_heller_miller_green_popp_crespo_leedy_lindquist_moule_et al._2020, title={Self-Heating Characterization of $\beta$ -Ga2O3 Thin-Channel MOSFETs by Pulsed ${I}$ - ${V}$ and Raman Nanothermography}, volume={67}, ISSN={["1557-9646"]}, DOI={10.1109/TED.2019.2951502}, abstractNote={$\beta $ -Ga2O3 thin-channel MOSFETs were evaluated using both dc and pulsed ${I}$ – ${V}$ measurements. The reported pulsed ${I}$ – ${V}$ technique was used to study self-heating effects in the MOSFET channel. The device was analyzed over a large temperature range of 23 °C–200 °C. A relationship between dissipated power and channel temperature was established, and it was found that the MOSFET channel was heating up to 208 °C when dissipating 2.5 W/mm of power. The thermal resistance of the channel was found to be 73 °C-mm/W. The results are supported with the experimental Raman nanothermography and thermal simulations and are in reasonable agreement with pulsed ${I}$ – ${V}$ findings. The high thermal resistance underpins the importance of optimizing thermal management in future Ga2O3 devices.}, number={1}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Blumenschein, Nicholas A. and Moser, Neil A. and Heller, Eric R. and Miller, Nicholas C. and Green, Andrew J. and Popp, Andreas and Crespo, Antonio and Leedy, Kevin and Lindquist, Miles and Moule, Taylor and et al.}, year={2020}, month={Jan}, pages={204–211} }
 @article{tran_blumenschein_mock_sukkaew_zhang_muth_paskova_paskov_darakchieva_2020, title={Thermal conductivity of ultra-wide bandgap thin layers - High Al-content AlGaN and beta-Ga2O3}, volume={579}, ISSN={["1873-2135"]}, DOI={10.1016/j.physb.2019.411810}, abstractNote={Transient thermoreflectance (TTR) technique is employed to study the thermal conductivity of β-Ga2O3 and high Al-content AlxGa1-xN semiconductors, which are very promising materials for high-power device applications. The experimental data are analyzed with the Callaway's model taking into account all relevant phonon scattering processes. Our results show that out-of-plane thermal conductivity of high Al-content AlxGa1-xN and (−201) β-Ga2O3 is of the same order of magnitude and approximately one order lower than that of GaN or AlN. The low thermal conductivity is attributed to the dominant phonon-alloy scattering in AlxGa1-xN and to the strong Umklapp phonon-phonon scattering in β-Ga2O3. It is also found that the phonon-boundary scattering is essential in thin β-Ga2O3 and AlxGa1-xN layers even at high temperatures and the thermal conductivity strongly deviates from the common 1/T temperature dependence.}, journal={PHYSICA B-CONDENSED MATTER}, author={Tran, Dat Q. and Blumenschein, Nicholas and Mock, Alyssa and Sukkaew, Pitsiri and Zhang, Hengfang and Muth, John F. and Paskova, Tania and Paskov, Plamen P. and Darakchieva, Vanya}, year={2020}, month={Feb} }
 @article{blumenschein_paskova_muth_2019, title={Effect of Growth Pressure on PLD-Deposited Gallium Oxide Thin Films for Deep-UV Photodetectors}, volume={216}, ISSN={["1862-6319"]}, DOI={10.1002/pssa.201900098}, abstractNote={Pulsed laser deposition (PLD) is used to grow ‐oriented single‐crystalline β‐gallium oxide (β‐Ga2O3) thin films on c‐plane sapphire substrates by optimized growth temperature and pressure. The morphology and crystallinity of the thin films are examined using X‐ray diffraction and atomic force microscopy. The thin films are used as the semiconductor layer for metal–semiconductor–metal (MSM) photodetector (PD) devices with various electrode designs. The ultraviolet photodetectors are characterized under 250 nm illumination, showing a high current amplitude increase over dark current conditions that approaches three orders of magnitude at a 6 V bias for an optimized growth pressure of 1 × 10−3 torr. The photodetectors' transient response is also measured, allowing for the defect analysis to be performed. A peak spectral responsivity of 30.45 A W−1 is measured at 250 nm incident illumination.}, number={20}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Blumenschein, Nicholas and Paskova, Tania and Muth, John F.}, year={2019}, month={Oct} }
 @article{blumenschein_slomski_paskov_kaess_breckenridge_muth_paskova_2018, title={Thermal conductivity of bulk and thin film beta-Ga2O3 measured by the 3 omega technique}, volume={10533}, ISSN={["1996-756X"]}, DOI={10.1117/12.2288267}, abstractNote={Thermal conductivity of undoped and Sn-doped β-Ga2O3 bulk and single-crystalline thin films have been measured by the 3ω technique. The bulk samples were grown by edge-defined film-field growth (EFG) method, while the thin films were grown on c-plane sapphire by pulsed-laser deposition (PLD). All samples were with (-201) surface orientation. Thermal conductivity of bulk samples was calculated along the in-plane and cross-plane crystallographic directions, yielding a maximum value of ~ 29 W/m-K in the [010] direction at room temperature. A slight thermal conductivity decrease was observed in the Sn-doped bulk samples, which was attributed to enhanced phonon-impurity scattering. The differential 3ω method was used for β-Ga2O3 thin film samples due to the small film thickness. Results show that both undoped and Sndoped films have a much lower thermal conductivity than that of the bulk samples, which is consistent with previous reports in the literature showing a linear relationship between thermal conductivity and film thickness. Similarly to bulk samples, Sn-doped thin films have exhibited a thermal conductivity decrease. However, this decrease was found to be much greater in thin film samples, and increased with Sn doping concentration. A correlation between thermal conductivity and defect/dislocation density was made for the undoped thin films.}, journal={OXIDE-BASED MATERIALS AND DEVICES IX}, author={Blumenschein, N. and Slomski, M. and Paskov, P. P. and Kaess, F. and Breckenridge, M. H. and Muth, J. F. and Paskova, T.}, year={2018} }
 @article{yao_myers_malhotra_lin_bozkurt_muth_zhu_2017, title={A Wearable Hydration Sensor with Conformal Nanowire Electrodes}, volume={6}, ISSN={2192-2640}, url={http://dx.doi.org/10.1002/ADHM.201601159}, DOI={10.1002/ADHM.201601159}, abstractNote={A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low‐cost, wireless, and continuous monitoring of skin hydration and other health parameters.}, number={6}, journal={Advanced Healthcare Materials}, publisher={Wiley}, author={Yao, Shanshan and Myers, Amanda and Malhotra, Abhishek and Lin, Feiyan and Bozkurt, Alper and Muth, John F. and Zhu, Yong}, year={2017}, month={Jan}, pages={1601159} }
 @article{slomski_blumenschein_paskov_muth_paskova_2017, title={Anisotropic thermal conductivity of beta-Ga2O3 at elevated temperatures: Effect of Sn and Fe dopants}, volume={121}, ISSN={["1089-7550"]}, DOI={10.1063/1.4986478}, abstractNote={The thermal conductivity of undoped, Sn-doped, and Fe-doped β-Ga2O3 bulk crystals was measured by the 3ω technique in the temperature range of 295–410 K. A unique approach for extracting the thermal conductivity along the lateral and transverse heat flow directions was used in order to determine the thermal conductivity along different crystallographic directions. The data analysis at room temperature confirmed the expected anisotropy of the thermal conductivity of β-Ga2O3, revealing the highest value of ∼29 W/m K in the [010] direction. The thermal conductivity of the Sn-doped and Fe-doped β-Ga2O3 samples was found to be lower than that of the undoped samples due to the enhanced phonon-impurity scattering contribution, which reduces the thermal conductivity. This tendency was maintained for the thermal conductivity at elevated temperatures. The thermal conductivity in all samples decreased with increasing temperature, but the slope of the temperature dependence was found to depend on both the doping and the crystallographic orientation.}, number={23}, journal={JOURNAL OF APPLIED PHYSICS}, author={Slomski, M. and Blumenschein, N. and Paskov, P. P. and Muth, J. F. and Paskova, T.}, year={2017}, month={Jun} }
 @article{muth_2017, title={Building a 'deeper' understanding of underwater optical communications}, volume={53}, number={5}, journal={Laser Focus World}, author={Muth, J.}, year={2017}, pages={37–40} }
 @article{paskov_slomski_leach_muth_paskova_2017, title={Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures - theory and experiment}, volume={7}, ISSN={["2158-3226"]}, DOI={10.1063/1.4989626}, abstractNote={The effect of Si doping on the thermal conductivity of bulk GaN was studied both theoretically and experimentally. The thermal conductivity of samples grown by Hydride Phase Vapor Epitaxy (HVPE) with Si concentration ranging from 1.6×1016 to 7×1018 cm-3 was measured at room temperature and above using the 3ω method. The room temperature thermal conductivity was found to decrease with increasing Si concentration. The highest value of 245±5 W/m.K measured for the undoped sample was consistent with the previously reported data for free-standing HVPE grown GaN. In all samples, the thermal conductivity decreased with increasing temperature. In our previous study, we found that the slope of the temperature dependence of the thermal conductivity gradually decreased with increasing Si doping. Additionally, at temperatures above 350 K the thermal conductivity in the highest doped sample (7×1018 cm-3) was higher than that of lower doped samples. In this work, a modified Callaway model adopted for n-type GaN at high temperatures was developed in order to explain such unusual behavior. The experimental data was analyzed with examination of the contributions of all relevant phonon scattering processes. A reasonable match between the measured and theoretically predicted thermal conductivity was obtained. It was found that in n-type GaN with low dislocation densities the phonon-free-electron scattering becomes an important resistive process at higher temperatures. At the highest free electron concentrations, the electronic thermal conductivity was suggested to play a role in addition to the lattice thermal conductivity and compete with the effect of the phonon-point-defect and phonon-free-electron scattering.}, number={9}, journal={AIP ADVANCES}, author={Paskov, P. P. and Slomski, M. and Leach, J. H. and Muth, J. F. and Paskova, T.}, year={2017}, month={Sep} }
 @article{yao_myers_malhotra_lin_bozkurt_muth_zhu_2017, title={Hydration Sensing: A Wearable Hydration Sensor with Conformal Nanowire Electrodes (Adv. Healthcare Mater. 6/2017)}, volume={6}, ISSN={2192-2640}, url={http://dx.doi.org/10.1002/ADHM.201770031}, DOI={10.1002/adhm.201770031}, abstractNote={A wearable skin hydration sensor is developed by Y. Zhu, J. F. Muth, and co-workers in article number 1601159. The sensor is made of silver nanowires inlaid in a silicone substrate, which renders the sensor flexible and stretchable. Integrated systems with multimodal sensing capability (e.g., hydration, strain/motion and electrophysiological sensing) are demonstrated in two form factors — wristband and chest patch. Image design by Shanshan Yao.}, number={6}, journal={Advanced Healthcare Materials}, publisher={Wiley}, author={Yao, Shanshan and Myers, Amanda and Malhotra, Abhishek and Lin, Feiyan and Bozkurt, Alper and Muth, John F. and Zhu, Yong}, year={2017}, month={Mar} }
 @article{slomski_paskov_leach_muth_paskova_2017, title={Thermal conductivity of bulk GaN grown by HVPE: Effect of Si doping}, volume={254}, ISSN={["1521-3951"]}, DOI={10.1002/pssb.201600713}, abstractNote={The thermal conductivity of bulk GaN grown by Hydride Phase Vapor Epitaxy with intentional Si doping was measured using the 3ω method. The effect of Si concentration ranging from 1.6 × 1016 to 7 × 1018 cm−3 on the thermal conductivity was studied over the temperature range of 295–470 K. The room temperature thermal conductivity was found to decrease with increasing Si doping from 245 to 210 W/m · K. Also, for each Si doped sample the thermal conductivity decreases with increasing temperature. The experimental data were analysed by a modified Callaway model and the contribution of different resistive phonon scattering process was examined. It was found that in n‐type GaN the phonon‐free‐electron scattering became an important resistive process that leads to a reduction of the thermal conductivity at high temperatures. At the highest free electron concentrations, electronic thermal conduction was found to play a role in addition to lattice thermal conduction and compete with the effects of phonon‐free‐electron scattering.}, number={8}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Slomski, Michael and Paskov, Plamen P. and Leach, Jacob H. and Muth, John F. and Paskova, Tania}, year={2017}, month={Aug} }
 @inproceedings{gray_muth_carr_2016, title={A MEMS infrared thermopile with phononic crystal structures and carbon nanotube absorption layer}, DOI={10.1109/icsens.2016.7808771}, abstractNote={We have fabricated MEMS infrared thermopiles from a silicon-on-insulator substrate where the buried oxide layer was used to form a membrane for thermal isolation of the detection area. The silicon wires of the thermocouples were patterned with a phononic crystal structure that consisted of 200nm holes on a 400nm pitch. The silicon was degenerately doped using a spin on dopant process to create the p, n-type regions. The absorption layer used was a 20um tall vertically-aligned, multi-walled, carbon nanotube layer. We measured the performance of our devices to have a D∗ of 3 ∗ 10<sup>7</sup> cmHz<sup>0.5</sup>W<sup>−1</sup> and a time response of 5–8 msec. We believe the performance of our design can be improved to exceed a D∗ of 10<sup>8</sup> cmHz<sup>0.5</sup>W<sup>−1</sup> by patterning the absorption layer.}, booktitle={2016 ieee sensors}, author={Gray, K. F. and Muth, J. F. and Carr, W.}, year={2016} }
 @article{dieffenderfer_goodell_mills_mcknight_yao_lin_beppler_bent_lee_misra_et al._2016, title={Low-Power Wearable Systems for Continuous Monitoring of Environment and Health for Chronic Respiratory Disease}, volume={20}, ISSN={2168-2194 2168-2208}, url={http://dx.doi.org/10.1109/JBHI.2016.2573286}, DOI={10.1109/jbhi.2016.2573286}, abstractNote={We present our efforts toward enabling a wearable sensor system that allows for the correlation of individual environmental exposures with physiologic and subsequent adverse health responses. This system will permit a better understanding of the impact of increased ozone levels and other pollutants on chronic asthma conditions. We discuss the inefficiency of existing commercial off-the-shelf components to achieve continuous monitoring and our system-level and nano-enabled efforts toward improving the wearability and power consumption. Our system consists of a wristband, a chest patch, and a handheld spirometer. We describe our preliminary efforts to achieve a submilliwatt system ultimately powered by the energy harvested from thermal radiation and motion of the body with the primary contributions being an ultralow-power ozone sensor, an volatile organic compounds sensor, spirometer, and the integration of these and other sensors in a multimodal sensing platform. The measured environmental parameters include ambient ozone concentration, temperature, and relative humidity. Our array of sensors also assesses heart rate via photoplethysmography and electrocardiography, respiratory rate via photoplethysmography, skin impedance, three-axis acceleration, wheezing via a microphone, and expiratory airflow. The sensors on the wristband, chest patch, and spirometer consume 0.83, 0.96, and 0.01 mW, respectively. The data from each sensor are continually streamed to a peripheral data aggregation device and are subsequently transferred to a dedicated server for cloud storage. Future work includes reducing the power consumption of the system-on-chip including radio to reduce the entirety of each described system in the submilliwatt range.}, number={5}, journal={IEEE Journal of Biomedical and Health Informatics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dieffenderfer, James and Goodell, Henry and Mills, Steven and McKnight, Michael and Yao, Shanshan and Lin, Feiyan and Beppler, Eric and Bent, Brinnae and Lee, Bongmook and Misra, Veena and et al.}, year={2016}, month={Sep}, pages={1251–1264} }
 @inproceedings{lim_malhotra_mills_muth_lee_misra_2016, title={Metal oxide gas sensing characterization by low frequency noise spectroscopy}, DOI={10.1109/icsens.2016.7808835}, abstractNote={This work demonstrates a new method for selective identification of low ppb concentrations of O3. Atomic layer deposited thin film SnO2 was used as a sensing layer. SnO2 sensitized quartz crystal microbalances (QCM) demonstrate expected mass loading behavior as well as unique frequency domain response towards synthetic air, O3, and NO2 at room temperature. Power spectral densities (PSD) of the response of each gas were calculated and contain peaks at different normalized frequencies. These PSD peaks are found to have significant differences in magnitude for each analyte and provide evidence of selective room temperature adsorption of gases on SnO2.}, booktitle={2016 ieee sensors}, author={Lim, M. and Malhotra, A. and Mills, S. and Muth, J. and Lee, B. and Misra, Veena}, year={2016} }
 @article{misra_bozkurt_calhoun_jackson_jur_lach_lee_muth_oralkan_oeztuerk_et al._2015, title={Flexible Technologies for Self-Powered Wearable Health and Environmental Sensing}, volume={103}, ISSN={["1558-2256"]}, DOI={10.1109/jproc.2015.2412493}, abstractNote={This article provides the latest advances from the NSF Advanced Self-powered Systems of Integrated sensors and Technologies (ASSIST) center. The work in the center addresses the key challenges in wearable health and environmental systems by exploring technologies that enable ultra-long battery lifetime, user comfort and wearability, robust medically validated sensor data with value added from multimodal sensing, and access to open architecture data streams. The vison of the ASSIST center is to use nanotechnology to build miniature, self-powered, wearable, and wireless sensing devices that can enable monitoring of personal health and personal environmental exposure and enable correlation of multimodal sensors. These devices can empower patients and doctors to transition from managing illness to managing wellness and create a paradigm shift in improving healthcare outcomes. This article presents the latest advances in high-efficiency nanostructured energy harvesters and storage capacitors, new sensing modalities that consume less power, low power computation, and communication strategies, and novel flexible materials that provide form, function, and comfort. These technologies span a spatial scale ranging from underlying materials at the nanoscale to body worn structures, and the challenge is to integrate them into a unified device designed to revolutionize wearable health applications.}, number={4}, journal={PROCEEDINGS OF THE IEEE}, author={Misra, Veena and Bozkurt, Alper and Calhoun, Benton and Jackson, Thomas N. and Jur, Jesse S. and Lach, John and Lee, Bongmook and Muth, John and Oralkan, Oemer and Oeztuerk, Mehmet and et al.}, year={2015}, month={Apr}, pages={665–681} }
 @article{dhawan_sharma_brickson_muth_2014, title={Incorporation of vanadium oxide films in optical fibers for temperature sensing and optical switching applications}, volume={4}, ISSN={["2159-3930"]}, DOI={10.1364/ome.4.001128}, abstractNote={Fiber optic temperature sensors were fabricated by depositing vanadium oxide thin films on the tips of optical fibers, and by incorporating vanadium oxide materials into the core of optical fibers. It was found that the properties of the initially amorphous vanadium oxide can be controllably converted to those of crystalline VOx compounds via the plasma arc of a fiber fusion splicer. These crystalline VOx compounds can then be over-coated with SiO2, and subsequently fused with another fiber to form an in-line fiber optic sensor. It was found that a well defined optical absorption edge was formed when the vanadium oxide (VOx) thin films were annealed using the plasma arc of a fusion splicer, suggesting the formation of crystalline VOx. Moreover, it was observed that the spectral position of this absorption edge varied with temperature in a reproducible way. The optical fiber devices described in this paper could also be employed for optical switching applications. Based on the spectral position of the band edge and the Raman spectra of the VOx films, deposited on the fiber optic tips, it was found that these annealed VOx films contained a mixture of different phases of vanadium oxide (VOx), in particular V2O5 and VO2. Furthermore, similar in-line optical fiber switches, based only on the insulator to metal phase transitions of VO2, can be fabricated by following the techniques described in this paper.}, number={6}, journal={OPTICAL MATERIALS EXPRESS}, author={Dhawan, Anuj and Sharma, Yashna and Brickson, Leandra and Muth, John F.}, year={2014}, month={Jun}, pages={1128–1139} }
 @article{cox_muth_2014, title={Simulating channel losses in an underwater optical communication system}, volume={31}, ISSN={["1520-8532"]}, DOI={10.1364/josaa.31.000920}, abstractNote={A Monte Carlo numerical simulation for computing the received power for an underwater optical communication system is discussed and validated. Power loss between receiver and transmitter is simulated for a variety of receiver aperture sizes and fields of view. Additionally, pointing-and-tracking losses are simulated.}, number={5}, journal={JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION}, author={Cox, William and Muth, John}, year={2014}, month={May}, pages={920–934} }
 @article{ishmael_slomski_luo_white_hunt_mandzy_muth_nesbit_paskova_straka_et al._2014, title={Thermal conductivity and dielectric properties of a TiO2-based electrical insulator for use with high temperature superconductor-based magnets}, volume={27}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/27/9/095018}, abstractNote={Quench protection is a remaining challenge impeding the implementation of high temperature superconductor (HTS)-based magnet applications. This is due primarily to the slow normal zone propagation velocity (NZPV) observed in Bi2Sr2CaCu2OX (Bi2212) and (RE)Ba2Cu3O7 − x (REBCO) systems. Recent computational and experimental findings reveal significant improvements in turn-to-turn NZPV, resulting in a magnet that is more stable and easier to protect through three-dimensional normal zone growth (Phillips M 2009; Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). These improvements are achieved by replacing conventional insulation materials, such as Kapton and mullite braid, with a thin, thermally conducting, electrically-insulating ceramic oxide coating. This paper reports on the temperature-dependent thermal properties, electrical breakdown limits and microstructural characteristics of a titanium oxide (TiO2) insulation and a doped-TiO2-based proprietary insulation (doped-TiO2) shown previously to enhance quench behavior (Ishmael S et al 2013 IEEE Trans. Appl. Supercond. 23 7201311). Breakdown voltages at 77 K ranging from ∼1.5 kV to over 5 kV are reported. At 4.2 K, the TiO2 increases the thermal conductivity of polyimide by about a factor of 10. With the addition of a dopant, thermal conductivity is increased by an additional 13%, and a high temperature heat treatment increases it by nearly an additional 100%. Similar increases are observed at 77 K and room temperature. These results are understood in the context of the various microstructures observed.}, number={9}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Ishmael, S. A. and Slomski, M. and Luo, H. and White, M. and Hunt, A. and Mandzy, N. and Muth, J. F. and Nesbit, R. and Paskova, T. and Straka, W. and et al.}, year={2014}, month={Sep} }
 @article{ladd_so_muth_dickey_2013, title={3D Printing of Free Standing Liquid Metal Microstructures}, volume={25}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201301400}, abstractNote={This paper describes a method to direct-write 3D liquid metal microcomponents at room temperature. The thin oxide layer on the surface of the metal allows the formation of mechanically stable structures strong enough to stand against gravity and the large surface tension of the liquid. The method is capable of printing wires, arrays of spheres, arches, and interconnects.}, number={36}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Ladd, Collin and So, Ju-Hee and Muth, John and Dickey, Michael D.}, year={2013}, month={Sep}, pages={5081–5085} }
 @article{ishmael_luo_white_hunte_liu_mandzy_muth_naderi_ye_hunt_et al._2013, title={Enhanced Quench Propagation in Bi2Sr2CaCu2Ox and YBa2Cu3O7-x Coils via a Nanoscale Doped-Titania-Based Thermally Conducting Electrical Insulator}, volume={23}, ISSN={["1558-2515"]}, DOI={10.1109/tasc.2013.2269535}, abstractNote={The significant amount of energy stored in a large high-field superconducting magnet can be sufficient to destroy the coil in the event of an unprotected quench. For magnets based on high-temperature superconductors (HTSs), such as Bi2Sr2CaCu2Ox (Bi2212) and YBa2Cu3O7-x (YBCO), quench protection is particularly challenging due to slow normal zone propagation. A previous computational study showed that the quench behavior of HTS magnets is significantly improved if the turn-to-turn electrical insulation is thermally conducting, enhancing 3-D normal zone propagation. Here, a new doped-titania electrical insulation with high thermal conductivity is evaluated. The thermal conductivity of the insulation is measured at cryogenic temperatures, and its chemical compatibility with Bi2212 round wires is determined. Thin layers of the insulation are deposited onto the surface of Bi2212 and YBCO wires, which are then wound into small coils to study the quench behavior. Results show that the critical current and homogeneity of Bi2212 coils are improved relative to coils reacted with mullite insulation. Relative to similar coils with conventional insulation (mullite for Bi2212 and Kapton for YBCO), the turn-to-turn quench propagation is increased by a factor of 2.8 in Bi2212 coils at 4.2 K and self-field and by a factor of 2.5 in YBCO coils at 4.2 K and 5 T. These results indicate that doped-titania insulation may significantly improve Bi2212 and YBCO coils. Increased normal zone propagation velocity enhances quench detection and quench protection, and the thinness of the insulation relative to the most common alternatives increases the magnet winding pack current density and reduces the coil specific heat.}, number={5}, journal={IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY}, author={Ishmael, Sasha and Luo, Haojun and White, Marvis and Hunte, Frank and Liu, X. T. and Mandzy, Natalia and Muth, John F. and Naderi, Golsa and Ye, Liyang and Hunt, Andrew T. and et al.}, year={2013}, month={Oct} }
 @article{ladd_so_muth_dickey_2013, title={Microstructures: 3D Printing of Free Standing Liquid Metal Microstructures (Adv. Mater. 36/2013)}, volume={25}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201370225}, DOI={10.1002/ADMA.201370225}, abstractNote={A direct-write method for writing 3D freestanding, liquid-metal microcomponents from the binary eutectic alloy of gallium and indium at room temperature is described in work by Prof. Michael Dickey, Prof. John Muth, and co-workers on page 5081. The smallest components fabricated by the technique are of the order of 10 μm in size, and smaller–sized structures may be possible. The technique allows the formation of mechanically stable structures and is capable of printing wires, spheres, arches, and interconnects.}, number={36}, journal={Advanced Materials}, publisher={Wiley}, author={Ladd, Collin and So, Ju-Hee and Muth, John and Dickey, Michael D.}, year={2013}, month={Sep}, pages={4953–4953} }
 @article{reynolds_reynolds_mohanta_muth_rowe_everitt_aspnes_2013, title={Shallow acceptor complexes in p-type ZnO}, volume={102}, ISSN={["1077-3118"]}, DOI={10.1063/1.4802753}, abstractNote={We show that N-doped ZnO films grown on sapphire can exhibit significant (∼1018 cm−3) room-temperature p-type behavior when sufficient nitrogen (N) is incorporated and the material is annealed appropriately. Substitutional N on the oxygen (O) sublattice is a deep acceptor; however, shallow acceptor complexes involve N, H, and zinc vacancies (VZn). Combining secondary ion mass spectrometry, Raman-scattering, photoluminescence, and Hall-effect data, we establish the evolution of N from its initial incorporation on a Zn site to a final shallow acceptor complex VZn_NO_H+ with an ionization energy of ca. 130 meV. This complex is responsible for the observed p-type behavior.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Reynolds, J. G. and Reynolds, C. L., Jr. and Mohanta, A. and Muth, J. F. and Rowe, J. E. and Everitt, H. O. and Aspnes, D. E.}, year={2013}, month={Apr} }
 @article{cochenour_mullen_muth_2013, title={Temporal Response of the Underwater Optical Channel for High-Bandwidth Wireless Laser Communications}, volume={38}, ISSN={["1558-1691"]}, DOI={10.1109/joe.2013.2255811}, abstractNote={This paper describes a high-sensitivity, high-dynamic range experimental method for measuring the frequency response of the underwater optical channel in the forward direction for the purpose of wireless optical communications. Historically, there have been few experimental measurements of the frequency response of the underwater channel, particularly with regard to wireless communication systems. In this work, the frequency response is measured out to 1 GHz over a wide range of water clarities (approximately 1-20 attenuation lengths). Both spatial and temporal dispersions are measured as a function of pointing angle between the transmitter and the receiver. We also investigate the impact of scattering function and receiver field of view. The impact of these results to the link designer is also presented.}, number={4}, journal={IEEE JOURNAL OF OCEANIC ENGINEERING}, author={Cochenour, Brandon and Mullen, Linda and Muth, John}, year={2013}, month={Oct}, pages={730–742} }
 @article{luo_wellenius_lunardi_muth_2012, title={Transparent IGZO-Based Logic Gates}, volume={33}, ISSN={["1558-0563"]}, url={http://dx.doi.org/10.1109/led.2012.2186784}, DOI={10.1109/led.2012.2186784}, abstractNote={Optically transparent indium-gallium-zinc-oxide-based nand and nor gates and inverters were fabricated and characterized using transistors deposited at room temperature with 5-, 10-, and 20-μm gate lengths and beta ratio between 2.5 and 40. The nand and nor gates' operation frequencies were measured up to 5 kHz. The individual transistors were measured to have saturation mobility of 14 cm2/V ·s, subthreshold swing of 190 mV/dec, and current on/off ratios in excess of 108. Logic operations were satisfactorily demonstrated for bias voltage between 1 and 20 V. These results indicate that viable digital logic can be applied particularly where optical transparency or the use of novel flexible substrates is more important than the operating speeds.}, number={5}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Luo, Haojun and Wellenius, Patrick and Lunardi, Leda and Muth, John F.}, year={2012}, month={May}, pages={673–675} }
 @article{cochenour_mullen_muth_2011, title={Modulated pulse laser with pseudorandom coding capabilities for underwater ranging, detection, and imaging}, volume={50}, ISSN={["2155-3165"]}, DOI={10.1364/ao.50.006168}, abstractNote={Optical detection, ranging, and imaging of targets in turbid water is complicated by absorption and scattering. It has been shown that using a pulsed laser source with a range-gated receiver or an intensity modulated source with a coherent RF receiver can improve target contrast in turbid water. A blended approach using a modulated-pulse waveform has been previously suggested as a way to further improve target contrast. However only recently has a rugged and reliable laser source been developed that is capable of synthesizing such a waveform so that the effect of the underwater environment on the propagation of a modulated pulse can be studied. In this paper, we outline the motivation for the modulated-pulse (MP) concept, and experimentally evaluate different MP waveforms: single-tone MP and pseudorandom coded MP sequences.}, number={33}, journal={APPLIED OPTICS}, author={Cochenour, Brandon and Mullen, Linda and Muth, John}, year={2011}, month={Nov}, pages={6168–6178} }
 @article{cox_gray_muth_2011, title={Underwater optical communication using a modulating retroreflector}, volume={52}, number={5}, journal={Sea Technology}, author={Cox, W. and Gray, K. and Muth, J.}, year={2011}, pages={47–49} }
 @inproceedings{cox_simpson_muth_2011, title={Underwater optical communication using software defined radio over LED and laser based links}, DOI={10.1109/milcom.2011.6127621}, abstractNote={Underwater optical communication is an attractive means to achieve high datarate, low latency, and covert communication between underwater vehicles or sensor nodes. We demonstrate the viability of using a software defined radio system to communicate at Mbps rates using LEDs and lasers underwater and examine the performance of BPSK and GMSK simplex and duplex links.}, booktitle={2011 - Milcom 2011 Military Communications Conference}, author={Cox, W. C. and Simpson, J. A. and Muth, J. F.}, year={2011}, pages={2057–2062} }
 @inproceedings{simpson_cox_krier_cochenour_hughes_muth_2010, title={5 mbps optical wireless communication with error correction coding for underwater sensor nodes}, DOI={10.1109/oceans.2010.5664429}, abstractNote={One issue with underwater sensors is how to efficiently transfer large amounts of data collected by the node to an interrogating platform such as an underwater vehicle. It is often impractical to make a physical connection between the node and the vehicle which suggests an acoustic or optical wireless solution. For large amounts of data, the high bandwidth of underwater optical wireless is an advantage. A small, low-cost platform to demonstrate the potential of an optical wireless communications interface for underwater sensor nodes is demonstrated. To enhance the reliability and robustness of the optical wireless communication digital signal processing and error correction techniques are used. The system was tested in 3 and 7.7 meter tanks at 5 Mbps with the turbidity of the water controlled by the addition of Maalox.}, booktitle={Oceans 2010}, author={Simpson, J. A. and Cox, W. C. and Krier, J. R. and Cochenour, B. and Hughes, B. L. and Muth, J. F.}, year={2010} }
 @inproceedings{cox_gray_simpson_cochenour_hughes_muth_2010, title={A MEMS Blue/Green retroreflecting modulator for underwater optical communications}, DOI={10.1109/oceans.2010.5664432}, abstractNote={Short range, high bandwidth underwater optical communications links are potentially useful for retrieving stored information from underwater systems. However many underwater systems have limited power capacity or limited weight budget. The use of a modulating retroreflector eliminates the need for a transmitting laser on the data bearing platform and reduces the pointing requirements by retroreflecting the modulated light back to the interrogating source. Blue/green operation of a MEMS Fabry-Perot modulator was demonstrated at data rates of 500 kbps and 1 Mbps in a 7.7 meter tank with water conditions varied by the addition of Maalox as a scattering agent.}, booktitle={Oceans 2010}, author={Cox, W. C. and Gray, K. F. and Simpson, J. A. and Cochenour, B. and Hughes, B. L. and Muth, J. F.}, year={2010} }
 @article{wellenius_smith_wu_everitt_muth_2010, title={Effect of oxygen pressure on the structure and luminescence of Eu-doped Gd2O3 thin films}, volume={207}, ISSN={["1862-6300"]}, DOI={10.1002/pssa.201026071}, abstractNote={Abstract}, number={8}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Wellenius, Patrick and Smith, Eric R. and Wu, Pae C. and Everitt, Henry O. and Muth, John F.}, year={2010}, month={Aug}, pages={1949–1953} }
 @article{cochenour_mullen_muth_2010, title={Effect of scattering albedo on attenuation and polarization of light underwater}, volume={35}, ISSN={["0146-9592"]}, DOI={10.1364/ol.35.002088}, abstractNote={Recent work on underwater laser communication links uses polarization discrimination to improve system performance [Appl. Opt.48, 328 (2009)] [in Proceedings of IEEE Oceans 2009 (IEEE, 2009), pp. 1-4]. In the laboratory, Maalox antacid is commonly used as a scattering agent. While its scattering function closely mimics that of natural seawaters, its scattering albedo can be much higher, as Maalox particles tend to be less absorbing. We present a series of experiments where Nigrosin dye is added to Maalox in order to more accurately recreate real-world absorption and scattering properties. We consider the effect that scattering albedo has on received power and the degree of depolarization of forward-scattered light in the context of underwater laser communication links.}, number={12}, journal={OPTICS LETTERS}, author={Cochenour, Brandon and Mullen, Linda and Muth, John}, year={2010}, month={Jun}, pages={2088–2090} }
 @article{lou_lunardi_muth_2010, title={Fabrication of Nanoshell Arrays Using Directed Assembly of Nanospheres}, volume={10}, ISSN={["1558-1748"]}, url={http://dx.doi.org/10.1109/jsen.2009.2038586}, DOI={10.1109/jsen.2009.2038586}, abstractNote={Extraordinary transmission of light has been observed when light is incident on periodic nanostructures patterned metal films, which results from the interaction between the incident photons and the excited surface plasmon polaritons with wavenumbers constrained by the geometry and periodicity of the surface structure. Usually, the surface patterns are fabricated by Focused Ion Beam (FIB) milling, which is expensive and has low throughput. We employ the nanosphere lithography method to fabricate periodic nanoshell arrays on a gold film as an alternative to FIB milling. In this process, polystyrene nanospheres are deposited on glass substrates as a template for subsequent gold deposition. This results in the close-packed hexagonal nanoshell arrays patterned gold surface. The transmission spectra of the patterned surfaces show strong enhanced transmission in the red and IR wavelength regions, and the peak enhanced transmission wavelengths vary with the chemical environments above the surface.}, number={3}, journal={IEEE SENSORS JOURNAL}, author={Lou, Yi and Lunardi, Leda M. and Muth, John F.}, year={2010}, month={Mar}, pages={617–620} }
 @article{suresh_wellenius_baliga_luo_lunardi_muth_2010, title={Fast All-Transparent Integrated Circuits Based on Indium Gallium Zinc Oxide Thin-Film Transistors}, volume={31}, ISSN={["1558-0563"]}, url={http://dx.doi.org/10.1109/led.2010.2041525}, DOI={10.1109/led.2010.2041525}, abstractNote={We describe the fabrication and characterization of visible transparent small-scale indium gallium zinc oxide (IGZO) integrated circuits. The IGZO channel and indium tin oxide (ITO) contacts and interconnects were pulsed laser deposited at room temperature. Low-temperature (200 °C ) atomic-layer-deposited Al2O3 was used as the gate dielectric in bottom-gated thin-film transistors with field-effect mobility near 15 cm2/V·s. Logic inverters and ring oscillators were fabricated and characterized, with operations at frequencies as high as 2.1 MHz, corresponding to a propagation delay of less than 48 ns/stage with a supply voltage of 25 V. To the best of our knowledge, these are the fastest all-transparent oxide semiconductor circuits reported to date.}, number={4}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Suresh, Arun and Wellenius, Patrick and Baliga, Vinay and Luo, Haojun and Lunardi, Leda M. and Muth, John F.}, year={2010}, month={Apr}, pages={317–319} }
 @article{oh_kim_muth_serati_escuti_2010, title={High-Throughput Continuous Beam Steering Using Rotating Polarization Gratings}, volume={22}, ISSN={["1041-1135"]}, DOI={10.1109/LPT.2009.2037155}, abstractNote={A new beam steering concept comprising independently rotating, inline polarization gratings (PGs) is experimentally demonstrated. The approach, which we term Risley gratings, achieves high steering throughput within a large field-of-regard (FOR) in a fashion similar to Risley prisms, composed of wedged prisms. However, because PGs are patterned in thin liquid crystal layers, they enable a system with far less thickness, weight, and beam walk-off. Furthermore, large apertures are feasible and wavelengths from visible to infrared can be chosen. Any direction within a solid angle defined by twice the diffraction angle of each PG can be addressed mechanically. Here we demonstrate a Risley grating system with a 62° FOR and 89%-92% transmittance at 1550-nm wavelength, using two PGs with 6-¿m grating period.}, number={4}, journal={IEEE PHOTONICS TECHNOLOGY LETTERS}, author={Oh, Chulwoo and Kim, Jihwan and Muth, John and Serati, Steve and Escuti, Michael J.}, year={2010}, month={Feb}, pages={200–202} }
 @article{wellenius_smith_leboeuf_everitt_muth_2010, title={Optimal composition of europium gallium oxide thin films for device applications}, volume={107}, ISSN={["0021-8979"]}, DOI={10.1063/1.3319670}, abstractNote={Europium gallium oxide (EuxGa1-x)2O3 thin films were deposited on sapphire substrates by pulsed laser deposition with varying Eu content from x=2.4 to 20 mol %. The optical and physical effects of high europium concentration on these thin films were studied using photoluminescence (PL) spectroscopy, x-ray diffraction (XRD), and Rutherford backscattering spectrometry. PL spectra demonstrate that emission due to the D50 to F7J transitions in Eu3+ grows linearly with Eu content up to 10 mol %. Time-resolved PL indicates decay parameters remain similar for films with up to 10 mol % Eu. At 20 mol %, however, PL intensity decreases substantially and PL decay accelerates, indicative of parasitic energy transfer processes. XRD shows films to be polycrystalline and beta-phase for low Eu compositions. Increasing Eu content beyond 5 mol % does not continue to modify the film structure and thus, changes in PL spectra and decay cannot be attributed to structural changes in the host. These data indicate the optimal doping for optoelectronic devices based on (EuxGa1-x)2O3 thin films is between 5 and 10 mol %.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Wellenius, P. and Smith, E. R. and LeBoeuf, S. M. and Everitt, H. O. and Muth, J. F.}, year={2010}, month={May} }
 @article{smith_gruber_wellenius_muth_everitt_2010, title={Spectra and energy levels of Eu3+ in cubic phase Gd2O3}, volume={247}, ISSN={0370-1972 1521-3951}, url={http://dx.doi.org/10.1002/pssb.200945602}, DOI={10.1002/pssb.200945602}, abstractNote={In pulsed laser deposition of the sesquioxide semiconductor Gd2O3, adjusting the chamber oxygen pressure controls the crystalline structure of the host. This technique was used to deposit thin films of nominally 1.6% by weight europium‐doped, cubic phase Gd2O3 using 50 mTorr of oxygen. Structural measurements using high‐resolution transmission electron microscopy and selected area electron diffraction confirm the films were polycrystalline, cubic phase Eu:Gd2O3. The spectroscopic assignment of emission lines to specific radiative transitions within the trivalent Eu ion is confirmed by theoretical analysis of the appropriate crystal field Hamiltonian. Detailed crystal‐field splittings are presented for the 5DJ=0‐2 and 7FJ=0‐5 multiplet manifolds of Eu3+ in this host material.}, number={7}, journal={physica status solidi (b)}, publisher={Wiley}, author={Smith, Eric R. and Gruber, John B. and Wellenius, Patrick and Muth, John F. and Everitt, Henry O.}, year={2010}, month={May}, pages={1807–1813} }
 @article{wellenius_suresh_luo_lunardi_muth_2009, title={An Amorphous Indium-Gallium-Zinc-Oxide Active Matrix Electroluminescent Pixel}, volume={5}, ISSN={["1558-9323"]}, url={http://dx.doi.org/10.1109/jdt.2009.2024012}, DOI={10.1109/JDT.2009.2024012}, abstractNote={In this study, an active matrix pixel was fabricated and characterized using indium gallium zinc oxide (IGZO) thin-film transistors and a novel electroluminescent (EL) Eu:IGZO thin-film phosphor. The results show that even large and unoptimized IGZO devices are capable of modulating at the frequencies necessary for modern display technology. Furthermore, we demonstrate a rare-earth doped amorphous-oxide semiconductor (AOS) EL phosphor that can be modulated via a TFT.}, number={12}, journal={JOURNAL OF DISPLAY TECHNOLOGY}, author={Wellenius, Patrick and Suresh, Arun and Luo, Haojun and Lunardi, Leda M. and Muth, John F.}, year={2009}, month={Dec}, pages={438–445} }
 @article{mullen_cochenour_rabinovich_mahon_muth_2009, title={Backscatter suppression for underwater modulating retroreflector links using polarization discrimination}, volume={48}, ISSN={["2155-3165"]}, DOI={10.1364/AO.48.000328}, abstractNote={Free space optical links underwater have the potential to enable short range (<100 m) high-bandwidth (megabits per second) data links that have a low probability of detection and interception. The use of a retroreflecting free space optical link in water has the added advantage of allowing much of the weight and power burden of the link to remain at one end. While modulating retroreflectors have been successfully implemented in above-water links, the underwater environment introduces new challenges. The focus of this paper is to address these challenges and to investigate techniques for minimizing their effect on the link performance.}, number={2}, journal={APPLIED OPTICS}, author={Mullen, Linda and Cochenour, Brandon and Rabinovich, William and Mahon, Rita and Muth, John}, year={2009}, month={Jan}, pages={328–337} }
 @article{westcott_lou_muth_yousaf_2009, title={Patterned Hybrid Nanohole Array Surfaces for Cell Adhesion and Migration}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la9023234}, abstractNote={We report the fabrication of hybrid nanohole array surfaces to study the role of the surface nanoevironment on cell adhesion and cell migration. We use polystyrene beads and reactive ion etching to control the size and the spacing between nanoholes on a tailored self-assembled monolayer inert gold surface. The arrays were characterized by scanning electron microscopy and brightfield microscopy. For cell adhesion studies, cells were seeded to these substrates to study the effect of ligand spacing on cell spreading, stress fiber formation, and focal adhesion structure and size. Finally, comparative cell migration rates were examined on the various nanohole array surfaces using time-lapse microscopy.}, number={19}, journal={LANGMUIR}, author={Westcott, Nathan P. and Lou, Yi and Muth, John F. and Yousaf, Muhammad N.}, year={2009}, month={Oct}, pages={11236–11238} }
 @article{suresh_novak_wellenius_misra_muth_2009, title={Transparent indium gallium zinc oxide transistor based floating gate memory with platinum nanoparticles in the gate dielectric}, volume={94}, ISSN={["1077-3118"]}, DOI={10.1063/1.3106629}, abstractNote={A transparent memory device has been developed based on an indium gallium zinc oxide thin film transistor by incorporating platinum nanoparticles in the gate dielectric stack as the charge storage medium. The transfer characteristics of the device show a large clockwise hysteresis due to electron trapping and are attributed to the platinum nanoparticles. Effect of the gate bias stress (program voltage) magnitude, duration, and polarity on the memory window characteristics has been studied. Charge retention measurements were carried out and a loss of less than 25% of the trapped elec-trons was observed over 104 s indicating promising application as nonvolatile memory.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Suresh, Arun and Novak, Steven and Wellenius, Patrick and Misra, Veena and Muth, John F.}, year={2009}, month={Mar} }
 @article{wellenius_suresh_foreman_everitt_muth_2008, title={A visible transparent electroluminescent europium doped gallium oxide device}, volume={146}, ISSN={["0921-5107"]}, DOI={10.1016/j.mseb.2007.07.060}, abstractNote={Beta phase gallium oxide thin films deposited by pulsed laser deposition are efficient hosts for rare earth metals such as europium. In this study europium doped gallium oxide deposited on glass substrates is used to make red (611 nm) electroluminescent devices that are transparent to the visible spectrum. The conducting electrodes used are indium tin oxide (ITO), and a novel indium gallium zinc oxide (IGZO) layer also deposited by pulsed laser deposition. The origin of the red emission is the 5D0 to 7F2 transition and is consistent with photoluminescence and cathodoluminescence results. The turn on voltage of the device is about 45 V ac, and the device appears to be robust, operating at elevated voltages without degradation.}, number={1-3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Wellenius, P. and Suresh, A. and Foreman, J. V. and Everitt, H. O. and Muth, J. F.}, year={2008}, month={Jan}, pages={252–255} }
 @article{suresh_muth_2008, title={Bias stress stability of indium gallium zinc oxide channel based transparent thin film transistors}, volume={92}, ISSN={["0003-6951"]}, DOI={10.1063/1.2824758}, abstractNote={The effects of bias stress on transistor performance are important when considering nontraditional channel materials for thin film transistors. Applying a gate bias stress to indium gallium zinc oxide transparent thin film transistors was found to induce a parallel threshold voltage shift without changing the field effect mobility or the subthreshold gate voltage swing. The threshold voltage change is logarithmically dependent on the duration of the bias stress implying a charge tunneling mechanism resulting in trapped negative charge screening the applied gate voltage.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Suresh, A. and Muth, J. F.}, year={2008}, month={Jan} }
 @article{wellenius_suresh_muth_2008, title={Bright, low voltage europium doped gallium oxide thin film electroluminescent devices}, volume={92}, ISSN={["0003-6951"]}, DOI={10.1063/1.2824846}, abstractNote={Europium doped gallium oxide thin film electroluminescent devices with bright, red emission (611nm) and relatively low threshold voltages of 60V were produced using pulsed laser deposition. The use of transparent conducting electrodes of amorphous InGaZnO on transparent aluminum titanium oxide/indium tin oxide/7059 Corning glass substrates resulted in a device that is transparent throughout the visible spectrum. At 100V, with 1kHz excitation, the luminance was 221cd∕m2. The Sawyer-Tower circuit analysis and time dependent emission measurements suggest that the charge trapping at the aluminum titanium oxide/Ga2O3:Eu interface plays an important role in producing efficient emission.}, number={2}, journal={APPLIED PHYSICS LETTERS}, author={Wellenius, P. and Suresh, A. and Muth, J. F.}, year={2008}, month={Jan} }
 @article{dhawan_muth_2008, title={Engineering surface plasmon based fiber-optic sensors}, volume={149}, ISSN={["0921-5107"]}, DOI={10.1016/j.mseb.2007.09.076}, abstractNote={Ordered arrays of nanoholes with subwavelength diameters, and submicron array periodicity were fabricated on the tips of gold-coated optical fibers using focused ion beam (FIB) milling. This provided a convenient platform for evaluating extraordinary transmission of light through subwavelength apertures and allowed the implementation of nanostructures for surface plasmon engineered sensors. The fabrication procedure was straightforward and implemented on single mode and multimode optical fibers as well as etched and tapered fiber tips. Control of the periodicity and spacing of the nanoholes allowed the wavelength of operation to be tailored. Large changes in optical transmission were observed at the designed wavelengths, depending on the surrounding refractive index, allowing the devices to be used as fiber-optic sensors.}, number={3}, journal={MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS}, author={Dhawan, Anui and Muth, John F.}, year={2008}, month={Apr}, pages={237–241} }
 @misc{dhawan_ghosh_seyam_muth_2008, title={Fabric and yarn structures for improving signal integrity in fabric-based electrical circuits}, volume={7,348,285}, number={2008 Mar. 25}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Dhawan, A. and Ghosh, T. K. and Seyam, A. M. and Muth, J.}, year={2008} }
 @article{collazo_mita_rice_dalmau_wellenius_muth_sitar_2008, title={Fabrication of a GaN p/n lateral polarity junction by polar doping selectivity}, volume={5}, ISSN={1610-1634 1610-1642}, url={http://dx.doi.org/10.1002/pssc.200778624}, DOI={10.1002/pssc.200778624}, abstractNote={Abstract}, number={6}, journal={physica status solidi (c)}, publisher={Wiley}, author={Collazo, Ramón and Mita, Seiji and Rice, Anthony and Dalmau, Rafael and Wellenius, Patrick and Muth, John and Sitar, Zlatko}, year={2008}, month={May}, pages={1977–1979} }
 @article{dhawan_muth_leonard_gerhold_gleeson_vo-dinh_russell_2008, title={Focused in beam fabrication of metallic nanostructures on end faces of optical fibers for chemical sensing applications}, volume={26}, ISSN={["1071-1023"]}, DOI={10.1116/1.3013329}, abstractNote={Focused ion beam (FIB) fabrication of fiber optic sensors, mainly chemical sensors, which are based on plasmonics-active nanostructures formed on the cleaved tips of optical fibers, is reported. The nanostructures fabricated included nanoholes in optically thick metallic films as well as metallic nanopillars and nanorods. The sensing mechanism is based on detecting shifts in surface plasmon resonances (SPRs) associated with nanoholes in metallic films and localized SPRs of metallic nanopillars and nanorods, when the refractive index of the medium surrounding the nanostructures is changed. These sensors can be employed for the detection of chemical agents in air as well as liquid media surrounding the sensors. FIB milling was employed to fabricate ordered arrays of nanoholes in optically thick (100–240nm) metallic films deposited on cleaved end faces of multimode, four-mode, and single-mode optical fibers. Separately, metallic nanorods and nanopillars were formed by first depositing a metallic (gold or silver) film on tips of optical fibers, which was followed by FIB milling large area patterns to form freestanding nanorods and nanopillars. Utilizing FIB allows engineering nanostructure geometries, i.e., nanostructure shapes and sizes that are chosen based on the plasmon resonances associated with them. Formation of periodic arrays of nanoholes provides a means of tuning plasmon resonance peaks, associated with extraordinary transmission of light through the array of nanoholes in the metallic films, based on periodicity and shape of the nanoholes as well as on refractive index changes to form sensitive chemical sensors.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Dhawan, A. and Muth, J. F. and Leonard, D. N. and Gerhold, M. D. and Gleeson, J. and Vo-Dinh, T. and Russell, P. E.}, year={2008}, month={Nov}, pages={2168–2173} }
 @misc{dhawan_ghosh_muth_seyam_2008, title={Methods and systems for selectively connecting and disconnecting conductors in a fabric}, volume={7,329,323}, number={2008 Feb. 12}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Dhawan, A. and Ghosh, T. K. and Muth, J. and Seyam, A.}, year={2008} }
 @article{sarkar_suresh_myers_muth_misra_2008, title={Modulating indium gallium zinc oxide transistor characteristics with discrete redox states of molecules embedded in the gate dielectric}, volume={92}, ISSN={["0003-6951"]}, DOI={10.1063/1.2918981}, abstractNote={A hybrid inorganic-organic device has been fabricated by incorporating redox active molecules in indium gallium zinc oxide thin film transistors. These devices show a clear modulation of source-drain current characteristics, which is associated with the quantized energy states of the redox active molecules. The molecules show discreet redox peaks in the current characteristics of transistors and a true-molecular-based charge transport has been demonstrated in a completely solid state device.}, number={22}, journal={APPLIED PHYSICS LETTERS}, author={Sarkar, Smita and Suresh, Arun and Myers, Frank B. and Muth, John F. and Misra, Veena}, year={2008}, month={Jun} }
 @article{suresh_gollakota_wellenius_dhawan_muth_2008, title={Transparent, high mobility of InGaZnO thin films deposited by PLD}, volume={516}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.03.153}, abstractNote={Transparent oxide semiconductor, InGaZnO, thin films were prepared by pulsed laser deposition at room temperature. The carrier concentration was found to vary by several orders of magnitude from insulating to 1019 carriers/cm3 depending on the oxygen partial pressure during deposition. Hall mobilities as high as 16 cm2/V s were observed. This is approximately an order of magnitude higher than the mobility of amorphous silicon and indicates that InGaO3(ZnO)x with x ≤ 5 may be suitable for transparent, thin film transistor applications. Post-deposition annealing was found to strongly influence the carrier concentration while annealing effects on the electron mobility was less influential.}, number={7}, journal={THIN SOLID FILMS}, author={Suresh, Arun and Gollakota, Praveen and Wellenius, Patrick and Dhawan, Anuj and Muth, John F.}, year={2008}, month={Feb}, pages={1326–1329} }
 @article{arora_ghosh_muth_2007, title={Dielectric elastomer based prototype fiber actuators}, volume={136}, ISSN={["0924-4247"]}, DOI={10.1016/j.sna.2006.10.044}, abstractNote={Dielectric elastomer based prototype fiber actuators have been developed and evaluated. The work is motivated by the tremendous potential offered by the current multicomponent fiber forming technologies as a means to fabricate fiber actuators. To explore the potential, prototype fiber actuators have been fabricated using commercially available dielectric elastomer tubes and by applying appropriate compliant electrodes to inner cavity and outer walls of these tubes. The force and displacement generated by such actuators have been studied as a function of applied electric field under different prestrained conditions. In order to introduce anisotropy in the fiber behavior, two types of prestrains (uniaxial and uniform) were applied. Actuation strains of 7 and 18% were recorded for silicone tubes in the axial and radial directions, respectively. Polyurethane tubes produced significantly higher blocking force compared to silicone tubes. The results demonstrate significant influence of applied prestrain on actuation strains and blocking force measured under isometric condition.}, number={1}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Arora, Sohil and Ghosh, Tushar and Muth, John}, year={2007}, month={May}, pages={321–328} }
 @article{hwang_muth_ghosh_2007, title={Electrical and mechanical properties of carbon-black-filled, electrospun nanocomposite fiber webs}, volume={104}, ISSN={["1097-4628"]}, DOI={10.1002/app.25914}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Hwang, Jeesang and Muth, John and Ghosh, Tushar}, year={2007}, month={May}, pages={2410–2417} }
 @article{suresh_wellenius_muth_2007, title={High performance transparent thin film transistors based on indium gallium zinc oxide as the channel material}, ISBN={["978-1-4244-1507-6"]}, ISSN={["2380-9248"]}, DOI={10.1109/iedm.2007.4419007}, abstractNote={The fabrication of high performance amorphous indium gallium zinc oxide (IGZO) transparent thin film transistors (TTFT) and their bias stress stability is presented. N-channel enhancement mode devices were fabricated with an extracted field effect mobility of ~ 11-15 cm2 V-1s-1, on/off current ratios > 107, subthreshold gate voltage swing of 0.20-0.25 V/decade, low off-state currents and good saturation. Low and tunable threshold voltages of 1-2 V were achieved. We conclude that a charge trapping mechanism at the semiconductor/dielectric interface is responsible for the threshold voltage shift after a gate bias stress. The threshold voltage is recovered when the bias is removed.}, journal={2007 IEEE INTERNATIONAL ELECTRON DEVICES MEETING, VOLS 1 AND 2}, author={Suresh, Arun and Wellenius, Patrick and Muth, John F.}, year={2007}, pages={587–590} }
 @article{adekore_pierce_davisb_barlage_muth_2007, title={Nitrogen acceptors in bulk ZnO (000(1)over-bar)) substrates and homoepitaxial ZnO films}, volume={102}, ISSN={["1089-7550"]}, DOI={10.1063/1.2751097}, abstractNote={Bulk single crystals of unintentionally doped ZnO having charge carrier concentration, ND−NA values of ∼1017 cm−3 were implanted with N+ ions at dosages of 1015 and 1016 cm−2 at 95 keV to a depth of 150 nm. The resulting p−n structure having acceptor concentrations ranging from 1017 to 1018 cm−3 was compared with nitrogen doped homoepitaxial films with ∼8×1017 cm−3 acceptors. Photoluminescence spectra acquired at 8 K showed an increase in the peak for the neutral donor-bound to acceptor-bound transition at 3.210 eV with increasing annealing temperature, thermal activation of a unique donor to acceptor transition due to nitrogen at 3.067 and 3.057 eV for implanted and epitaxial films, respectively; and an increase in the intensity of the defect-related green band at selected temperatures. Electroluminescence measurements at 300 K revealed an ultraviolet band, direct band-to-band recombination at 3.34 eV, donor-acceptor pair recombinations at 3.19 and 3.0 eV, and recombination in the green region centered at 2.49 eV. Current-voltage characteristics of implanted and homoepitaxial p−n diodes were also determined.}, number={2}, journal={JOURNAL OF APPLIED PHYSICS}, author={Adekore, B. T. and Pierce, J. M. and Davisb, R. F. and Barlage, D. W. and Muth, J. F.}, year={2007}, month={Jul} }
 @article{zhang_dhawan_wellenius_suresh_muth_2007, title={Planar ZnO ultraviolet modulator}, volume={91}, ISSN={["0003-6951"]}, DOI={10.1063/1.2770995}, abstractNote={A planar electroabsorption modulator suitable for spatial light modulation has been constructed. The device operates near the band edge of zinc oxide at 3.3eV and is based on broadening and shifting of the unconfined exciton with an externally applied electric field. The ZnO active layer was deposited on an aluminum/titanium oxide dielectric on an indium tin oxide conducting layer on glass. A transparent conductive InGaZnO layer on a spin on glass insulator served as the top contact, allowing high electric fields to be applied transverse to the ZnO layer. The modulator operates at room temperature in transmission mode with +45% modulation at 373nm and −18% modulation at 380nm at 140V applied bias, corresponding to ∼450kV∕cm electric field across the ZnO active layer.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Zhang, X. Y. and Dhawan, A. and Wellenius, P. and Suresh, A. and Muth, J. F.}, year={2007}, month={Aug} }
 @article{suresh_wellenius_dhawan_muth_2007, title={Room temperature pulsed laser deposited indium gallium zinc oxide channel based transparent thin film transistors}, volume={90}, ISSN={["0003-6951"]}, DOI={10.1063/1.2716355}, abstractNote={Indium gallium zinc oxide deposited by pulsed laser deposition at room temperature was used as a channel layer to fabricate transparent thin film transistors with good electrical characteristics: field effect mobility of 11cm2V−1s−1 and subthreshold voltage swing of 0.20V∕decade. By varying the oxygen partial pressure during deposition the conductivity of the channel was controlled to give a low off-current of ∼10pA and a drain current on/off ratio of ∼5×107. Changing the channel layer thickness was a viable way to vary the threshold voltage. The effect of the gate dielectric on the electrical behavior was also explored.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Suresh, Arun and Wellenius, Patrick and Dhawan, Anuj and Muth, John}, year={2007}, month={Mar} }
 @article{voitenko_muth_gerhold_cui_xu_2007, title={Tunable photoluminescence of polymer doped with PbSe quantum dots}, volume={27}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2006.09.018}, abstractNote={Semiconductor nanoparticle/polymer composites potentially allow the design of photonic materials for optoelectronic devices. The optical characteristics of PbSe quantum dots placed in polymer matrices are investigated for potential applications in electrically controlled absorption modulators and integrated optical circuit components. The photoluminescence yield, shape of absorption band, and effects of size variation of PbSe quantum dots on spectral features are analyzed near the absorption edge of host polymers for the different concentrations of nanocrystals in the composite. It was found that for quantum dots of nominally the same size, there is a strong dependence of position of the absorption peaks in the spectrum depending on the concentration of quantum dots. This results in the emission in the 1500–1600 nm range being tunable with quantum dot concentration. A second emission in the 1200–1300 nm range was also observed and energy transfer from the polymer matrix to the quantum dot appears to mediate the strength of this photoluminescence.}, number={5-8}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Voitenko, Igor and Muth, J. F. and Gerhold, Michael and Cui, Dehu and Xu, Jian}, year={2007}, month={Sep}, pages={1078–1081} }
 @article{mion_muth_preble_hanser_2006, title={Accurate dependence of gallium nitride thermal conductivity on dislocation density}, volume={89}, ISSN={["1077-3118"]}, DOI={10.1063/1.2335972}, abstractNote={The authors experimentally find that the thermal conductivity of gallium nitride depends critically on dislocation density using the 3-omega technique. For GaN with dislocation densities lower than 106cm−2, the thermal conductivity is independent with dislocation density. The thermal conductivity decreases with a logarithmic dependence for material with dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low dislocation density near 5×104cm−2.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Mion, C. and Muth, J. F. and Preble, E. A. and Hanser, D.}, year={2006}, month={Aug} }
 @article{park_reitmeier_fothergill_zhang_muth_davis_2006, title={Growth and fabrication of AlGaN-based ultraviolet light emitting diodes on 6H-SiC(0001) substrates and the effect of carrier-blocking layers on their emission characteristics}, volume={127}, ISSN={["0921-5107"]}, DOI={10.1016/j.mseb.2005.10.019}, abstractNote={Abstract Growth, fabrication, and the electrical and optical characterization of ultraviolet light emitting diodes and their components, including AlxGa1−xN films, quantum wells (QWs), and ohmic contacts, and the problems encountered in the process integration of these components have been investigated. Ni/Au ohmic contacts with specific contact resistivities of 2.2 × 10−4 and 2.0 × 10−2 Ω cm2 were achieved on annealed, Mg-doped ([Mg] ∼ 5 × 1019 cm−3), p-type GaN layers that had been cleaned in HCl at 85 °C and on the backside of the SiC substrates after annealing in nitrogen, respectively. The emission intensity of the diodes increased with an increase in the number of Al0.06Ga0.94N/Al0.10Ga0.90N QWs and with the use of Si-doped n-type barrier layers. The highest intensities of the principle emission at 353 nm were measured at all values of the injection current in the device with a p-type carrier-blocking layer at the top of the QWs; this device also exhibited the highest values of light output power. Growth of an n-type carrier-blocking layer at the bottom of the QWs had an adverse effect on their characteristics. A broad peak centered at ∼540 nm exhibited yellow luminescence and was present in the spectra acquired from all the devices. This peak is attributed to absorption of the ultraviolet emission by and re-emission from the p-GaN and/or to the luminescence from the AlGaN within QWs by current injection.}, number={2-3}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Park, JS and Reitmeier, ZJ and Fothergill, D and Zhang, XY and Muth, JF and Davis, RF}, year={2006}, month={Feb}, pages={169–179} }
 @article{dhawan_muth_2006, title={In-line fiber optic structures for environmental sensing applications}, volume={31}, ISSN={["1539-4794"]}, DOI={10.1364/OL.31.001391}, abstractNote={Fiber optic sensors based on the interaction of surface plasmons or evanescent waves with the surrounding environment are usually obtained by tapering an optical fiber, which significantly weakens the structure, or by use of just the end of the optical fiber. A fiber optic structure that maintains the structural integrity of the optical fiber with a long environmental interaction length is presented. Graded-index optical fiber elements are used as lenses, and a coreless optical fiber acts as the environmental interaction area. These elements are fused by an optical fiber splicer and result in a continuous fiber optic sensing system.}, number={10}, journal={OPTICS LETTERS}, author={Dhawan, Anuj and Muth, J. F.}, year={2006}, month={May}, pages={1391–1393} }
 @article{gollakota_dhawan_wellenius_lunardi_muth_saripalli_peng_everitt_2006, title={Optical characterization of Eu-doped β-Ga2O3 thin films}, volume={88}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2208368}, DOI={10.1063/1.2208368}, abstractNote={Europium-doped β-Ga2O3 thin films were grown on double-side polished c-axis (0001) sapphire substrates by pulsed laser deposition at 850°C. Transmission measurements of the films revealed a sharp band edge with a band gap at 5.0eV. The films exhibited intense red emission at 611nm (2.03eV) due to the transitions from D05 to F27 levels in europium, with intensities that increased with the concentration of europium. Time-resolved photoluminescence measurements revealed a temperature-insensitive lifetime of 1.4ms, which is much longer than the lifetimes of europium luminescence observed in GaN hosts.}, number={22}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Gollakota, P. and Dhawan, A. and Wellenius, P. and Lunardi, L. M. and Muth, J. F. and Saripalli, Y. N. and Peng, H. Y. and Everitt, H. O.}, year={2006}, month={May}, pages={221906} }
 @article{park_fothergill_wellenius_bishop_muth_davis_2006, title={Origins of parasitic emissions from 353 nm AlGaN-based ultraviolet light emitting diodes over SiC substrates}, volume={45}, ISSN={["0021-4922"]}, DOI={10.1143/jjap.45.4083}, abstractNote={The effects of p-GaN capping layer and p-type carrier-blocking layer on the occurrence of parasitic emissions from 353 nm AlGaN-based light emitting diodes (LEDs) have been investigated. LEDs without a p-type Al0.25Ga0.75N carrier-blocking layer showed a shoulder peak at ∼370 nm due to electron overflow into the p-Al0.10Ga0.90N cladding layer and subsequent electron–hole recombination in the acceptor levels. Broad emission between 380 and 450 nm from LEDs having a p-GaN capping layer was caused by luminescence at 420 nm from the p-GaN capping layer, which was optically pumped by 353 nm UV emission from the quantum wells. Broad, defect-related luminescence centered at ∼520 nm was emitted from the AlGaN layers within the quantum wells.}, number={5A}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS}, author={Park, JS and Fothergill, DW and Wellenius, P and Bishop, SM and Muth, JF and Davis, RF}, year={2006}, month={May}, pages={4083–4086} }
 @article{porter_muth_narayan_foreman_everitt_2006, title={Photoluminescence study of ZnO films codoped with nitrogen and tellurium}, volume={100}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2372312}, DOI={10.1063/1.2372312}, abstractNote={Epitaxial ZnO films codoped with tellurium and nitrogen were grown by pulsed laser deposition on c-axis oriented sapphire substrates. The codoping strategy allowed the resistivity of the films to be controlled over several orders of magnitude and may prove useful in the development of ZnO based light emitters. Photoluminescence studies of tellurium-doped, nitrogen-doped, tellurium and nitrogen codoped, and undoped ZnO films were conducted. Strong room temperature photoluminescence and stimulated emission were observed in the undoped and Te-doped films, but not in codoped films. Time-resolved photoluminescence measurements indicated that carrier lifetime was significantly reduced in doped ZnO as compared to undoped ZnO.}, number={12}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Porter, H. L. and Muth, J. F. and Narayan, J. and Foreman, John V. and Everitt, Henry O.}, year={2006}, month={Dec}, pages={123102} }
 @article{dhawan_muth_2006, title={Plasmon resonances of gold nanoparticles incorporated inside an optical fibre matrix}, volume={17}, ISSN={["0957-4484"]}, DOI={10.1088/0957-4484/17/10/011}, abstractNote={Metallic nanoparticles were incorporated into the core of standard telecommunication grade optical fibres. This creates a simple, yet robust, platform which can be used to investigate the properties of nanoparticles, for sensing, spectroscopy, and optical switching applications. The optical response of gold nanoparticles embedded in the optical fibre matrix was evaluated as a function of temperature and the use of the structure as an inline fibre-optic temperature sensor is described. A redshift in the localized surface plasmon (LSP) resonance related peak, as well as broadening of the plasmon resonance, was observed upon increasing the temperature of the nanoparticle containing fibre. The shift and broadening of the plasmon resonance were attributed to the temperature dependence of dielectric constants of metallic nanoparticles and the silica matrix and to plasmon–phonon interactions.}, number={10}, journal={NANOTECHNOLOGY}, author={Dhawan, Anuj and Muth, John F.}, year={2006}, month={May}, pages={2504–2511} }
 @article{mion_muth_preble_hanser_2006, title={Thermal conductivity, dislocation density and GaN device design}, volume={40}, ISSN={["0749-6036"]}, DOI={10.1016/j.spmi.2006.07.017}, abstractNote={The performance of high power transistor devices is intimately connected to the substrate thermal conductivity. In this study, the relationship between thermal conductivity and dislocation density is examined using the 3 omega technique and free standing HVPE GaN substrates. Dislocation density is measured using imaging cathodoluminescence. In a low dislocation density regime below 105 cm−2, the thermal conductivity appears to plateau out near 230 W/K m and can be altered by the presence of isotopic defects and point defects. For high dislocation densities the thermal conductivity is severely degraded due to phonon scattering from dislocations. These results are applied to the design of homoepitaxially and heteroepitaxially grown HEMT devices and the efficiency of heat extraction and the influence of lateral heat spreading on device performance are compared.}, number={4-6}, journal={SUPERLATTICES AND MICROSTRUCTURES}, author={Mion, C. and Muth, J. F. and Preble, Edward A. and Hanser, Drew}, year={2006}, pages={338–342} }
 @article{park_fothergill_zhang_reitmeier_muth_davis_2005, title={Effect of carrier blocking layers on the emission characteristics of AlGaN-based ultraviolet light emitting diodes}, volume={44}, ISSN={["0021-4922"]}, DOI={10.1143/jjap.44.7254}, abstractNote={ 
  AlGaN-based thin film heterostructures suitable for ultraviolet light emitting diodes have been grown and fabricated into working devices with and without p-type and n-type AlGaN carrier-blocking layers at the top and the bottom of the quantum wells, respectively. The principal emission from each device occurred at 353 nm. The highest intensities of this peak were measured at all values of the injection current in the device with a p-type carrier-blocking layer at the top of the quantum well; this device also exhibited the highest values of light output power. Growth of an n-type carrier-blocking layer at the bottom of the quantum wells had an adverse effect on the light emitting diode characteristics. A broad peak centered at ∼540 nm exhibited yellow luminescence and was present in the spectra acquired from all the devices. This peak is attributed to absorption of the UV emission by and re-emission from the p-GaN and/or to the luminescence from the AlGaN within quantum wells by current injection. The intensity of this peak increased and saturated by the same order of magnitude as the intensity of the UV emission at 353 nm. 
  }, number={10}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS}, author={Park, JS and Fothergill, DW and Zhang, XY and Reitmeier, ZJ and Muth, JF and Davis, RF}, year={2005}, month={Oct}, pages={7254–7259} }
 @inproceedings{ghosh_dhawan_muth_2005, title={Electronic textiles today and potential for the future}, booktitle={Proceedings of International Conference on Emerging Trends in Polymers and Textiles : 7th, 8th January 2005}, publisher={New Delhi}, author={Ghosh, T. K. and Dhawan, A. and Muth, J.}, year={2005} }
 @article{porter_cai_muth_narayan_2005, title={Enhanced photoconductivity of ZnO films Co-doped with nitrogen and tellurium}, volume={86}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.1923194}, DOI={10.1063/1.1923194}, abstractNote={Zinc oxide films are typically found to be n type, and conductive under most growth conditions and growth methods. Co-doping with multiple elements is one strategy for improving the electrical and optical properties of zinc oxide materials for optoelectronic device applications. Using pulsed-laser deposition, thin ZnO films were grown on c-axis oriented sapphire. The films were co-doped with nitrogen and tellurium. Depending on the relative concentrations of the dopants, the resistivity of the films was observed to increase by several orders of magnitude, significantly improving the photoconductive response. The enhancement of the photosensitivity reached a maximum at a tellurium concentration of around 1020cm−3.}, number={21}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Porter, H. L. and Cai, A. L. and Muth, J. F. and Narayan, J.}, year={2005}, month={May}, pages={211918} }
 @article{muth_zhang_cai_fothergill_roberts_rajagopal_cook_piner_linthicum_2005, title={Gallium nitride surface quantum wells}, volume={87}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2123396}, DOI={10.1063/1.2123396}, abstractNote={Surface quantum-well emission has been observed from GaN-capped AlGaN∕GaN heterostructures grown by metalorganic chemical vapor deposition. The GaN cap, which forms the surface quantum well, is confined on one side by the vacuum level and on the other side by the AlGaN barrier layer. Photoluminescence at room temperature and cathodoluminescence studies show a strong emission peak corresponding to the lowest bound state of the surface quantum well and a correlation was made to the shift in surface quantum-well emission energy and the thickness of the GaN capping layer, which was varied from ∼15to40Å. The efficient surface quantum-well emission is indicative of low surface recombination velocities even without any surface passivation.}, number={19}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Muth, J. F. and Zhang, X. and Cai, A. and Fothergill, D. and Roberts, J. C. and Rajagopal, P. and Cook, J. W., Jr. and Piner, E. L. and Linthicum, K. J.}, year={2005}, month={Nov}, pages={192117} }
 @article{porter_mion_cai_zhang_muth_2005, title={Growth of ZnO films on C-plane (0001) sapphire by pulsed electron deposition (PED)}, volume={119}, ISSN={["0921-5107"]}, DOI={10.1016/j.mseb.2005.02.042}, abstractNote={Thin films of ZnO on C-plane (0 0 0 1) sapphire (α-Al2O3) substrates were grown by pulsed electron beam deposition (PED). Intense electron pulses, approximately 0.8 J/70 ns pulse produced by a channelspark pulsed electron source at a rate of 10 Hz were used to ablate sintered polycrystalline ZnO targets at an oxygen pressure of 15 mTorr. During growth, the sapphire substrate temperature was maintained at 700 °C. A 15 min growth produced a 250 nm film, as measured by a Dektak profilometer. Measurements by X-ray diffraction indicate c-axis oriented films. Cathodoluminescence (CL) data show strong band edge emission. Optical absorption data indicate a sharp band edge with clearly visible exciton absorption at room temperature, and resolved A and B excitons at 77 K. Thus, pulsed electron beam deposition of ZnO films is shown to be a viable technique for producing high quality ZnO films.}, number={2}, journal={MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY}, author={Porter, HL and Mion, C and Cai, AL and Zhang, X and Muth, JF}, year={2005}, month={May}, pages={210–212} }
 @misc{dhawan_ghosh_muth_seyam_2005, title={Methods and systems for selectively connecting and disconnecting conductors in a fabric}, volume={6,852,395}, number={2005 Feb. 8}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Dhawan, A. and Ghosh, T. K. and Muth, J. and Seyam, A.}, year={2005} }
 @article{cook_everitt_avrutsky_osinsky_cai_muth_2005, title={Refractive indices of ZnSiN2 on r-plane sapphire}, volume={86}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.1865325}, DOI={10.1063/1.1865325}, abstractNote={II – IV – N 2 wide band gap semiconductors such as ZnSiN2, ZnGeN2, and ZnSiGeN2 have potential uses for nonlinear materials and as lattice matching compounds for the growth of SiC and GaN devices. In this study, the dispersion of the TE and TM indices of refraction has been measured systematically using the prism coupling technique for an orthorhombic ZnSiN2 epitaxial layer grown on r-plane sapphire. The resulting index dispersion is extracted from the measured optical modes using a layered biaxial waveguide analysis, which shows that although the ZnSiN2 crystal is orthorhombic, for practical purposes it can be treated as a uniaxial material.}, number={12}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Cook, B. P. and Everitt, H. O. and Avrutsky, I. and Osinsky, A. and Cai, A. and Muth, J. F.}, year={2005}, month={Mar}, pages={121906} }
 @article{grant_luthy_muth_mattos_braly_seyam_ghosh_dhawan_natarajan_2004, title={Developing Portable Acoustic Arrays on a Large-Scale E-Textile Substrate}, volume={16}, DOI={10.1108/09556220410520379}, abstractNote={This research deals with the production of electronic textiles (e‐textiles) demonstrators. Initially, the research dealt with the creation of 4×5 microphone array on a large area conformal textile substrate. Once the interface electronics were connected to the 4×5 microphone array, this system became an effective acoustic array. Here, a new acoustic eight microphone array design has been designed, fabricated and tested. Changes were made to improve microphone array performance, and to optimize the associated software for data capture and analysis. This new design was based on UC‐Berkeley mote microcomputer technology. The mote‐based system addresses the issue of scaling acoustic arrays, to allow for distributing microphones over large‐areas, and to allow performance comparisons to be made with the original 4×5 microphone acoustic array.}, number={1/2}, journal={International Journal of Clothing Science and Technology}, author={Grant, E. and Luthy, K. A. and Muth, J. F. and Mattos, L. S. and Braly, J. C. and Seyam, Abdel-Fattah and Ghosh, T. and Dhawan, A. and Natarajan, K.}, year={2004}, pages={73–83} }
 @article{dhawan_seyam_ghosh_muth_2004, title={Woven fabric-based electrical circuits - Part I: Evaluating interconnect methods}, volume={74}, DOI={10.1177/004051750407401011}, abstractNote={ In recent years, a new area of research has emerged on textile-based electronics, called "electrotextiles." Most of the ongoing research in electrotextiles is driven by the motiva tion of creating multifunctional fiber assemblies that can sense, actuate, communicate, compute, etc. This paper discusses the development of fabric-based electrical circuits by interlacing conducting and nonconducting threads2 into woven textile structures. Wired interconnections of different devices attached to the conducting elements of these circuits are made by arranging and weaving conductive threads so that they follow desired electrical circuit designs. In a woven electrically conductive network, routing of electrical signals is achieved by the formation of effective electrical interconnects and disconnects. Resistance welding is identified as one of the most effective means of producing crossover point interconnects and disconnects. Interconnects are evaluated by measuring the DC resistance associated with the crossover points of conducting threads. }, number={10}, journal={Textile Research Journal}, author={Dhawan, A. and Seyam, Abdel-Fattah and ghosh and Muth, J. F.}, year={2004}, pages={913–919} }
 @article{dhawan_ghosh_seyam_muth_2004, title={Woven fabric-based electrical circuits - Part II: Yarn and fabric structures to reduce crosstalk noise in woven fabric-based circuits}, volume={74}, ISSN={["1746-7748"]}, DOI={10.1177/004051750407401103}, abstractNote={ One important problem in electronic textiles is crosstalk and lack of signal integrity between conductive lines. Two significant advantages of electronic textiles over tradi tional circuit boards are flexibility and the ability to scale to large areas. Capacitive and inductive crosstalk is aggravated by long parallel conductors, and varies as the electronic textile is flexed into different configurations. This paper evaluates crosstalk between woven parallel conductors. Two new thread structures—coaxial and twisted pair copper threads—to minimize cross talk are developed and evaluated. Significant reductions in crosstalk are obtained with the coaxial and twisted pair thread structures when compared with bare copper threads or insulated conductive threads. }, number={11}, journal={TEXTILE RESEARCH JOURNAL}, author={Dhawan, A and Ghosh, TK and Seyam, AM and Muth, JF}, year={2004}, month={Nov}, pages={955–960} }
 @misc{narayan_sharma_muth_2003, title={Method for making optoelectronic and microelectronic devices including cubic ZnMgO and/or CdMgO alloys}, volume={6,518,077}, number={2003 Feb. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Narayan, J. and Sharma, A. K. and Muth, J. F.}, year={2003} }
 @article{chang_cai_muth_kolbas_park_cuomo_hanser_bumgarner_2003, title={Optical and structural studies of hydride vapor phase epitaxy grown GaN}, volume={21}, ISSN={["0734-2101"]}, DOI={10.1116/1.1568346}, abstractNote={Thick films of hydride vapor phase epitaxy (HVPE) grown GaN were studied by various techniques. Time-integrated and time-resolved photoluminescence (PL) measurements were performed at room temperature and 77 K. The time-integrated PL spectrum has no observed deep-level transitions and a very narrow linewidth, which indicates good material quality. Time-resolved PL spectra are also presented and the temporal evolution of the PL around the band-gap exhibits a biexponential decay with a fast and a slow decay component. Cathodoluminescence, x-ray, and Raman spectroscopy were also used. The full width half maximum of the x-ray rocking curve for our sample is approximately 375 arcsec. The polarized Raman spectra exhibited only the allowed modes. The deposited GaN films were found to be relatively stress free. The x ray and Raman analysis also revealed that the HVPE-grown GaN films are of high crystal quality. The effect of thermal annealing on the sample was also investigated by time-integrated and time-resolved PL and Raman spectroscopy. No significant changes in the material were observed in either time-integrated or Raman spectroscopy. The film was thermally stable upon annealing up to 1000 °C in N2 ambient based on the results of these measurements. In time-resolve photoluminescence measurement, the temporal evolution of the band-edge transitions broadens after each annealing step and is significantly different after the 1000 °C anneal.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Chang, YC and Cai, AL and Muth, JF and Kolbas, RM and Park, M and Cuomo, JJ and Hanser, A and Bumgarner, J}, year={2003}, pages={701–705} }
 @article{oberhofer_muth_johnson_chen_fleet_cooper_2003, title={Planar gallium nitride ultraviolet optical modulator}, volume={83}, ISSN={["0003-6951"]}, DOI={10.1063/1.1615675}, abstractNote={A planar optical modulator operating near 360 nm suitable for ultraviolet spatial light modulation has been constructed. The modulator operates in transmission mode with a 18% change in transmission at 305 V. The modulator is based on using the electric field to shift and broaden the room-temperature resonance of the gallium nitride exciton with electric fields.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Oberhofer, AE and Muth, JF and Johnson, MAL and Chen, ZY and Fleet, EF and Cooper, GD}, year={2003}, month={Oct}, pages={2748–2750} }
 @article{park_sakhrani_maria_cuomo_teng_muth_ware_rodriguez_nemanich_2003, title={Wavelength-dependent Raman scattering of hydrogenated amorphous silicon carbon with red, green, and blue light excitation}, volume={18}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2003.0106}, abstractNote={This study presents results of wavelength-dependent Raman scattering from amorphous silicon carbon (a-Si:C:H). The a-Si:C:H films were produced by radio-frequency plasma-enhanced chemical vapor deposition. Prior results with amorphous carbon indicate that laser excitation selectively probes clusters with differing sizes. Our measurements with a-Si:C:H indicate that when using red (632.8 nm), green (514.5 nm), and blue (488.0 nm) excitation, the Raman D and G peaks shift to higher wave numbers as the excitation energy increases. The higher frequency is associated with smaller clusters that are preferentially excited with higher photon energy. It appears that photoluminescence occurs due to radiative recombination from intracluster transitions in Si-alloyed sp2-bonded carbon clusters}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Park, M and Sakhrani, V and Maria, JP and Cuomo, JJ and Teng, CW and Muth, JF and Ware, ME and Rodriguez, BJ and Nemanich, RJ}, year={2003}, month={Apr}, pages={768–771} }
 @article{chang_cai_johnson_muth_kolbas_reitmeier_einfeldt_davis_2002, title={Electron-beam-induced optical memory effects in GaN}, volume={80}, ISSN={["0003-6951"]}, DOI={10.1063/1.1469222}, abstractNote={Metastable effects in unintentionally doped GaN films grown on SiC substrates have been investigated using cathodoluminescence (CL). Memory effect patterns produced optically are observed in CL images. An electron beam can also produce memory effect patterns and the resulting changes in the luminescence spectra are quite similar for either optical or electron-beam-induced patterns. CL spectra reveal that the yellow luminescence at 2.2 eV increases significantly with little change in the band-edge emission in both cases. Samples that do not exhibit optically induced memory effects are also investigated and do not exhibit electron-beam-induced patterns, either. Monochromatic CL images at 540 and 365 nm confirm the similarity of optically and electron-beam-induced memory effects based on changes in luminescence spectra.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Chang, YC and Cai, AL and Johnson, MAL and Muth, JF and Kolbas, RM and Reitmeier, ZJ and Einfeldt, S and Davis, RF}, year={2002}, month={Apr}, pages={2675–2677} }
 @misc{grant_muth_cottle_dessent_cox_2002, title={Modular observation crawler and sensing instrument and method for operating same}, volume={6,450,104}, number={2002 Sep. 17}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Grant, E. and Muth, J. F. and Cottle, J. S. and Dessent, B. E. and Cox, J. A.}, year={2002} }
 @article{narayan_sharma_kvit_jin_muth_holland_2002, title={Novel cubic ZnxMg1-xO epitaxial hetero structures on Si (100) substrates}, volume={121}, number={1}, journal={Solid State Communications}, author={Narayan, J. and Sharma, A. K. and Kvit, A. and Jin, C. and Muth, J. F. and Holland, O. W.}, year={2002}, pages={9–13} }
 @article{tiwari_jin_kvit_kumar_muth_narayan_2002, title={Structural, optical and magnetic properties of diluted magnetic semiconducting Zn1-xMnxO films}, volume={121}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(01)00464-1}, abstractNote={We have investigated the structural, optical and magnetic properties of high quality epitaxial Zn1−xMnxO (diluted magnetic semiconductor) films. These films were deposited on (0001) sapphire substrate by a pulsed laser deposition technique. The nonequilibrium nature of the laser–material interaction allowed us to dope higher Mn contents (x=0.36) than allowed by thermal equilibrium limit (x∼0.13). All the films investigated here were found to be single phased and epitaxial with (0001) orientation. As the Mn concentration increases in the system, the c-axis lattice constant was found to increase linearly. Optical transmittance study showed an increase in the insulating band-gap (Eg) with increase in Mn atomic fraction x following Eg=3.270+2.760x−4.988x2eV. DC magnetization measurements showed the paramagnetic nature of the system.}, number={6-7}, journal={SOLID STATE COMMUNICATIONS}, author={Tiwari, A and Jin, C and Kvit, A and Kumar, D and Muth, JF and Narayan, J}, year={2002}, pages={371–374} }
 @misc{roberts_parker_muth_leboeuf_aumer_bedair_reed_2002, title={Ultraviolet-visible metal-semiconductor-metal photodetectors fabricated from InxGa1-xN (0 <= x <= 0.13)}, volume={31}, number={1}, journal={Journal of Electronic Materials}, author={Roberts, J. C. and Parker, C. A. and Muth, J. F. and Leboeuf, S. F. and Aumer, M. E. and Bedair, S. M. and Reed, M. J.}, year={2002}, month={Jan}, pages={L1–6} }
 @article{park_maria_cuomo_chang_muth_kolbas_nemanich_carlson_bumgarner_2002, title={X-ray and Raman analyses of GaN produced by ultrahigh-rate magnetron sputter epitaxy}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1506781}, abstractNote={Thick films of GaN were studied by x-ray diffraction and Raman spectroscopy. The GaN thick films were deposited on (0001) sapphire using ultrahigh-rate magnetron sputter epitaxy with typical growth rates as high as 10–60 μm/min. The width of the x-ray rocking curve from the (0002) reflection for the sample produced by this technique is ∼300 arcsec, which is unprecedented for GaN produced by a sputtering-type process. Our recent sample shows an x-ray rocking curve width of 240 arcsec. Only allowed modes were observed in the polarized Raman spectra. The background free carrier concentration is lower than 3×1016 cm−3. The phonon lifetime of the Raman E2(2) mode of the sputtered GaN was comparable to that of bulk single crystal GaN grown by sublimation. The quality of the film was uniform across the wafer. The film was thermally stable upon annealing in N2 ambient. The x-ray and Raman analyses revealed that the sputtered GaN films are of high crystalline quality.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Park, M and Maria, JP and Cuomo, JJ and Chang, YC and Muth, JF and Kolbas, RM and Nemanich, RJ and Carlson, E and Bumgarner, J}, year={2002}, month={Sep}, pages={1797–1799} }
 @article{chang_oberhofer_muth_kolbas_davis_2001, title={Optical metastability of subband gap (2.2 eV) yellow luminescence in GaN}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1381417}, abstractNote={Optical metastability has been studied in undoped GaN films grown on SiC substrates having a previously deposited AlN buffer layer. Brief exposures to a higher intensity ultraviolet light resulted in temporary changes in the optical properties of the GaN layer. The photoinduced changes created high contrast patterns on samples that could be observed under an optical microscope with lower intensity ultraviolet excitation. The subband gap yellow photoluminescence peak at 2.2 eV increased significantly after the patterns were created. This change slowly returned (hours) to its initial value at room temperature. The retention time decreased to a few seconds at temperatures above 100 °C. The data showed that a 1.34 eV thermal activation energy exists, which suggests that the cause of these metastable properties is related to the subband gap yellow luminescence.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Chang, YC and Oberhofer, AE and Muth, JF and Kolbas, RM and Davis, RF}, year={2001}, month={Jul}, pages={281–283} }
 @article{teng_aboelfotoh_davis_muth_kolbas_2001, title={Photoluminescence and electrical characteristics of the two-dimensional electron gas in Si delta-doped GaN layers}, volume={78}, ISSN={["1077-3118"]}, DOI={10.1063/1.1353836}, abstractNote={We have studied the electrical and photoluminescence (PL) properties of a Si delta-doped GaN layer grown by metalorganic chemical vapor deposition. The Hall mobility and electron sheet concentration are 726 cm2/V s and 1.9×1012 cm−2, respectively, at 2 K. A PL peak located at 78 meV below the band gap of GaN is observed at 77 K. This PL peak is attributed to the radiative recombination between electrons in the two-dimensional quantum states and photoexcited holes in GaN, which is consistent with simulation results using a one-dimensional Poisson and Schrödinger equation solver. The peak disappears at temperatures higher than 77 K and is not observed in uniformly doped GaN layers.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Aboelfotoh, MO and Davis, RF and Muth, JF and Kolbas, RM}, year={2001}, month={Mar}, pages={1688–1690} }
 @article{balkas_sitar_bergman_shmagin_muth_kolbas_nemanich_davis_2000, title={Growth and characterization of GaN single crystals}, volume={208}, ISSN={["0022-0248"]}, DOI={10.1016/S0022-0248(99)00445-5}, abstractNote={Up to 3 mm long GaN single crystals were grown by sublimation of cold pressed GaN pellets or evaporation of gallium (Ga) metal under an ammonia (NH3) flow in a dual heater, high-temperature growth system. A growth rate of 500 μm/h along the [0 0 0 1] direction was achieved using a source temperature of 1200°C, a total pressure of 760 Torr, and an NH3 flow rate of 50 sccm. The resulting crystals were transparent, possessed low aspect ratios and well-defined growth facets. The only impurity present at high concentrations was oxygen (3×1018 atoms/cm3). Photoluminescence studies conducted at 77 K showed a sharp emission peak centered at 359 nm. Time-dependent photoluminescence measurements revealed optical metastability in bulk GaN. Raman spectroscopy yielded narrow peaks representing only the modes allowed for the wurtzite structure. All characterization studies confirmed excellent crystalline and optical quality of the obtained single crystals.}, number={1-4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Balkas, CM and Sitar, Z and Bergman, L and Shmagin, IK and Muth, JF and Kolbas, R and Nemanich, RJ and Davis, RF}, year={2000}, month={Jan}, pages={100–106} }
 @misc{narayan_sharma_muth_2000, title={Optoelectronic and microelectronic devices including cubic ZnMgO and/or CdMgO alloys}, volume={6,423,983}, number={2000 Oct. 13}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Narayan, J. and Sharma, A. K. and Muth, J. F.}, year={2000} }
 @article{teng_muth_kolbas_hassan_sharma_kvit_narayan_2000, title={Quantum confinement of E-1 and E-2 transitions in Ge quantum dots embedded in an Al2O3 or an AlN matrix}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125650}, abstractNote={Alternating layers of Ge quantum dots embedded in either Al2O3 or AlN matrices were deposited on sapphire substrates by pulsed-laser deposition. The characteristics of the dots are shown to be independent of the surrounding matrix. The dots size (73, 130, 160, and 260 ű5%) was controlled by the laser energy density and deposition time, and was characterized by high-resolution transmission electron microscopy. The dots were single crystalline with no apparent GeOx interfacial layers. Transmission spectroscopy at room temperature and 77 K was used to probe the above-band-edge absorption of the Ge nanodots. The spectral positions of both E1/E1+Δ1 and E2 transitions were found to shift to higher energy in the absorption spectra with decreasing nanodot sizes. This indicates that strong quantum-confinement effect permits the optical properties of Ge dots to be modified in a controlled manner.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Kolbas, RM and Hassan, KM and Sharma, AK and Kvit, A and Narayan, J}, year={2000}, month={Jan}, pages={43–45} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_narayan_2000, title={Quantum confinement of E1 and E2 transitions in Ge quantum dots embedded in Al203 or an AlN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={2000} }
 @article{teng_muth_ozgur_bergmann_everitt_sharma_jin_narayan_2000, title={Refractive indices and absorption coefficients of MgxZn1-xO alloys}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125912}, abstractNote={Indices of refraction for MgxZn1−xO epitaxial films grown by pulsed-laser deposition on sapphire substrates with x up to 0.36 were determined in the range of wavelength 457–968 nm by analysis of optical transmission spectra and prism-coupled waveguide measurements. The dispersion follows the first-order Sellmeier dispersion equation. Absorption coefficients, exciton energy gaps, and binding energies of MgxZn1−xO alloys were determined by transmission spectroscopy. The excitonic absorption features were clearly visible at room temperature despite alloy broadening. These results provide important information for the design and modeling of ZnO/MgZnO heterostructure optoelectronic devices.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Teng, CW and Muth, JF and Ozgur, U and Bergmann, MJ and Everitt, HO and Sharma, AK and Jin, C and Narayan, J}, year={2000}, month={Feb}, pages={979–981} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_2000, title={Size effect in germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Nanophase and Nanocomposite Materials III  (Materials Research Society proceedings; vol. 581)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, editor={H. Hahn, S. Komarneni and Parker, J. C.Editors}, year={2000} }
 @inproceedings{sharma_jin_narayan_teng_muth_kolbas_holland_2000, title={Structural and optical property investigations on Mg-Alloying in epitaxial zinc oxide films on sapphire}, number={2000}, booktitle={MRS Internet Journal of Nitride Semiconductor Research}, author={Sharma, A. K. and Jin, C. and Narayan, J. and Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Holland, O. W.}, year={2000} }
 @article{muth_brown_johnson_yu_kolbas_cook_schetzina_1999, title={Absorption coefficient and refractive index of GaN, AlN and AlGaN alloys}, volume={4S1}, number={G5.2}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Muth, J. F. and Brown, J. D. and Johnson, M. A. L. and Yu, Z. H. and Kolbas, R. M. and Cook, J. W. and Schetzina, J. F.}, year={1999} }
 @article{joshkin_parker_bedair_muth_shmagin_kolbas_piner_molnar_1999, title={Effect of growth temperature on point defect density of unintentionally doped GaN grown by metalorganic chemical vapor deposition and hydride vapor phase epitaxy}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.370727}, abstractNote={We report on the investigation of the effect of growth temperature on point defect density of unintentionally doped GaN grown by atmospheric pressure metalorganic chemical vapor deposition and hydride vapor phase epitaxy. A correlation between photoluminescence (PL) spectra and the concentration of donors and acceptors in unintentionally doped GaN is presented. The effects of oxygen and native acceptors on the electrical and optical properties of GaN epitaxial layers are discussed and a classification of PL data is presented. On this basis we show that oxygen creates a shallow donor in GaN with an activation energy of about 23.5±1 meV. We determine that the concentration of native acceptors in GaN increases with an increase in growth temperature. These native acceptors, probably gallium antisites (GaN) and/or gallium vacancies (VGa), are nonradiative defects. We show that a second donor level in GaN has an activation energy of about 52.5±2.5 meV and produces a PL peak with an energy of about 3.45 eV at low temperatures. From Hall investigations we show that a third donor in GaN has an activation energy of 110±10 meV.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Joshkin, VA and Parker, CA and Bedair, SM and Muth, JF and Shmagin, IK and Kolbas, RM and Piner, EL and Molnar, RJ}, year={1999}, month={Jul}, pages={281–288} }
 @article{yu_johnson_brown_el-masry_muth_cook_schetzina_haberern_kong_edmond_1999, title={Epitaxial lateral overgrowth of GaN on SiC and sapphire substrates}, volume={4S1}, DOI={10.1557/s1092578300002878}, abstractNote={The epitaxial lateral overgrowth (ELO) process for GaN has been studied using SiC and sapphire substrates. Both MBE and MOVPE growth processes were employed in the study. The use of SiO2 versus SiNx insulator stripes was investigated using window/stripe widths ranging from 20 μm/4 μm to 3 μm/15 μm. GaN film depositions were completed at temperatures ranging from 800 °C to 1120 °C. Characterization experiments included RHEED, TEM, SEM and cathodolumenescence studies. The MBE growth experiments produced polycrystalline GaN over the insulator stripes even at deposition temperatures as high as 990 °C. In contrast, MOVPE growth produced single-crystal GaN stripes with no observable threading dislocations.}, number={G4.3}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Yu, Z. H. and Johnson, M. A. L. and Brown, J. D. and El-Masry, N. A. and Muth, J. F. and Cook, J. W. and Schetzina, J. F. and Haberern, K. W. and Kong, H. S. and Edmond, J. S.}, year={1999} }
 @article{muth_kolbas_sharma_oktyabrsky_narayan_1999, title={Excitonic structure and absorption coefficient measurements of ZnO single crystal epitaxial films deposited by pulsed laser deposition}, volume={85}, ISSN={["1089-7550"]}, DOI={10.1063/1.370601}, abstractNote={The optical properties of high quality single crystal epitaxial zinc oxide thin films grown by pulsed laser deposition on c-plane sapphire substrates were studied. It was found that annealing the films in oxygen dramatically improved the optical and electrical properties. The absorption coefficient, band gap, and exciton binding energies were determined by transmission measurements and photoluminescence. In both the annealed and the as-deposited films excitonic absorption features were observed at both room temperature and 77 K. In the annealed films the excitonic absorption peaks were substantially sharper and deep level photoluminescence was suppressed.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Muth, JF and Kolbas, RM and Sharma, AK and Oktyabrsky, S and Narayan, J}, year={1999}, month={Jun}, pages={7884–7887} }
 @article{bergmann_ozgur_casey_muth_chang_kolbas_rao_eom_schurman_1999, title={Linear optical properties of a heavily Mg-doped Al0.09Ga0.91N epitaxial layer}, volume={74}, ISSN={["0003-6951"]}, DOI={10.1063/1.124102}, abstractNote={The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Bergmann, MJ and Ozgur, U and Casey, HC and Muth, JF and Chang, YC and Kolbas, RM and Rao, RA and Eom, CB and Schurman, M}, year={1999}, month={May}, pages={3188–3190} }
 @article{sharma_narayan_muth_teng_jin_kvit_kolbas_holland_1999, title={Optical and structural properties of epitaxial MgxZn1-xO alloys}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.125340}, abstractNote={The optical and structural properties of high-quality single-crystal epitaxial MgZnO films deposited by pulsed-laser deposition were studied. In films with up to ∼36 at. % Mg incorporation, we have observed intense ultraviolet band edge photoluminescence at room temperature and 77 K. The highly efficient photoluminescence is indicative of the excitonic nature of the material. Transmission spectroscopy was used to show that the excitonic structure of the alloys was clearly visible at room temperature. High-resolution transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy/ion channeling were used to verify the epitaxial single-crystal quality of the films and characterize the defect content. Post-deposition annealing in oxygen was found to reduce the number of defects and to improve the optical properties of the films. These results indicate that MgZnO alloys have potential applications in a variety of optoelectronic devices.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Jin, C and Kvit, A and Kolbas, RM and Holland, OW}, year={1999}, month={Nov}, pages={3327–3329} }
 @article{hassan_sharma_narayan_muth_teng_kolbas_1999, title={Optical and structural studies of Ge nanocrystals embedded in AlN matrix fabricated by pulsed laser deposition}, volume={75}, ISSN={["1077-3118"]}, DOI={10.1063/1.124648}, abstractNote={We have fabricated Ge nanostructures buried in a matrix of AlN grown on Si(111) by pulsed laser deposition at the substrate temperature of 500 °C. The characterization of these structures was performed using high-resolution transmission electron microscopy (HRTEM), photoluminescence, and Raman spectroscopy. The HRTEM results show that the Ge islands are single crystal with a pyramidal shape. The average size of Ge islands was determined to be ∼15 nm, which could be varied by controlling laser deposition and substrate parameters. The Raman spectrum showed a peak of the Ge–Ge vibrational mode downward shifted up to 295 cm−1 which is caused by quantum confinement of phonons in the Ge dots. The photoluminescence of the Ge dots (size ∼15 nm) was blueshifted by ∼0.266 eV from the bulk Ge value of 0.73 eV at 77 K, resulting in a distinct peak at ∼1.0 eV. The transmission measurements carried out on different samples having Ge dot sizes of 7, 8, and 13 nm deposited on sapphire substrate showed the above band edge transitions of Ge, which were also blueshifted in accordance with the quantum confinement effect. The importance of pulsed laser deposition in fabricating novel nanostructures is emphasized.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Hassan, KM and Sharma, AK and Narayan, J and Muth, JF and Teng, CW and Kolbas, RM}, year={1999}, month={Aug}, pages={1222–1224} }
 @misc{shmagin_muth_kolbas_1999, title={Optical information storage systems and methods using heterostructures comprising ternary group III-V nitride semiconductor materials}, volume={5,875,052}, number={1999 Feb. 23}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M.}, year={1999} }
 @article{bergmann_ozgur_casey_everitt_muth_1999, title={Ordinary and extraordinary refractive indices for AlxGa1-xN epitaxial layers}, volume={75}, ISSN={["0003-6951"]}, DOI={10.1063/1.124278}, abstractNote={Dispersion of the ordinary and extraordinary indices of refraction for wurtzite AlxGa1−xN epitaxial layers with x=0.00, 0.04, 0.08, 0.11, and 0.20 in the range of wavelengths 457<λ<980 nm were measured via a prism-coupled waveguide technique. The quantitative accuracy of x is ±10% and the accuracy of the refractive indices is ∼±0.01. The dispersion is found to be well described by a 1st-order Sellmeier dispersion formula. A simple functional form is presented that allows calculation of the refractive indices as functions of x and λ.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Bergmann, MJ and Ozgur, U and Casey, HC and Everitt, HO and Muth, JF}, year={1999}, month={Jul}, pages={67–69} }
 @inproceedings{teng_muth_kolbas_hassan_sharma_kvit_narayan_1999, title={Quantum confinement of above-band-bap transitions in Ge quantum dots embedded in an Al2O3 or AIN matrix}, booktitle={Optical microstructural characterization of semiconductors  (Materials Research Society proceedings, vol. 588)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Teng, C. W. and Muth, J. F. and Kolbas, R. M. and Hassan, K. M. and Sharma, A. K. and Kvit, A. and Narayan, J.}, editor={J. Piqueras, T. Sekiguchi and Unlu, M. S.Editors}, year={1999} }
 @inproceedings{hassan_sharma_narayan_muth_teng_kolbas_1998, title={Germanium nanostructures fabricated by pulsed laser deposition}, booktitle={Microcrystalline and nanocrystalline semiconductors--1998: symposium held November 30-December 3, 1998, Boston, Massachusetts, U.S.A.}, author={Hassan, K. M. and Sharma, A. K. and Narayan, J. and Muth, J. F. and Teng, C. W. and Kolbas, R. M.}, year={1998} }
 @inproceedings{sharma_dovidenko_oktyabrsky_moxey_muth_kolbas_narayan_1998, title={Growth of high quality single crystal ZnO films on sapphire by pulsed laser ablation}, booktitle={Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A.  (Materials Research Society symposia proceedings ; v. 526).}, publisher={Warrendale, Pa.: Materials Research Society}, author={Sharma, A. K. and Dovidenko, K. and Oktyabrsky, S. and Moxey, D. E. and Muth, J. F. and Kolbas, R. M. and Narayan, J.}, year={1998}, pages={305} }
 @inproceedings{wei_sharma_narayan_ravindra_oktyabrsky_sankar_muth_kolbas_narayan_1998, title={Microstructure and IR range optical properties of pure DLC and DLC containing dopants prepared by pulsed laser deposition}, booktitle={Advances in laser ablation of materials: Symposium held April 13-16, 1998, San Francisco, California, U.S.A.  (Materials Research Society symposia proceedings ; v. 526).}, publisher={Warrendale, Pa.: Materials Research Society}, author={Wei, Q. and Sharma, A. K. and Narayan, R. J. and Ravindra, N. M. and Oktyabrsky, S. and Sankar, J. and Muth, J. F. and Kolbas, R. M. and Narayan, J.}, year={1998}, pages={331} }
 @inproceedings{shmagin_muth_kolbas_dupuis_grudowski_eiting_park_shelton_lambert_1998, title={Optical metastability in InGaN/GaN heterostructures}, booktitle={Compound semiconductors 1997: Proceedings of the IEEE Twenty-fourth International Symposium on Compound Semiconductors held in San Diego, California, 8-11 September 1997}, publisher={Bristol; Philadelphia: Institute of Physics Pub.}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Dupuis, R. D. and Grudowski, P. A. and Eiting, C. J. and Park, J. and Shelton, B. S. and Lambert, D. J. H.}, year={1998}, pages={375–378} }
 @inproceedings{kolbas_shmagin_muth_1998, title={Optical properties of wide bandgap II-V nitride semiconductors}, booktitle={1998 5th International Conference on Solid-State and Integrated Circuit Technology: Proceedings, October 21-23, 1998, Beijing, China}, author={Kolbas, R. M. and Shmagin, I. K. and Muth, J. F.}, editor={M. Zhang and Tu, K. N.Editors}, year={1998}, pages={609–612} }
 @article{osinsky_gangopadhyay_yang_gaska_kuksenkov_temkin_shmagin_chang_muth_kolbas_1998, title={Visible-blind GaN Schottky barrier detectors grown on Si(111)}, volume={72}, ISSN={["0003-6951"]}, DOI={10.1063/1.120755}, abstractNote={We report novel GaN detectors grown by molecular beam epitaxy on Si(111) substrates. Wurtzite structure epitaxial GaN exhibits room-temperature photoluminescence with a band-edge-related emission width as narrow as 7 nm and intensities comparable to high quality layers grown on sapphire by metalorganic chemical vapor deposition. Spectral response of lateral geometry Schottky detectors shows a sharp cutoff at 365 nm with peak responsivities of ∼0.05 A/W at 0 V, and ∼0.1 A/W with a −4 V bias. The dark current is ∼60 nA at −2 V bias. The noise equivalent power is estimated to be 3.7×10−9 W over the response bandwidth of 2.2 MHz.}, number={5}, journal={APPLIED PHYSICS LETTERS}, author={Osinsky, A and Gangopadhyay, S and Yang, JW and Gaska, R and Kuksenkov, D and Temkin, H and Shmagin, IK and Chang, YC and Muth, JF and Kolbas, RM}, year={1998}, month={Feb}, pages={551–553} }
 @article{muth_lee_shmagin_kolbas_casey_keller_mishra_denbaars_1997, title={Absorption coefficient, energy gap, exciton binding energy, and recombination lifetime of GaN obtained from transmission measurements}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.120191}, abstractNote={The absorption coefficient for a 0.4-μm-thick GaN layer grown on a polished sapphire substrate was determined from transmission measurements at room temperature. A strong, well defined exciton peak for the A and B excitons was obtained. The A, B, and C excitonic features are clearly defined at 77 K. At room temperature, an energy gap Eg=3.452±0.001 eV and an exciton binding energy ExA,B=20.4±0.5 meV for the A and B excitons and ExC=23.5±0.5 meV for the C exciton were determined by analysis of the absorption coefficient. From this measured absorption coefficient, together with the detailed balance approach of van Roosbroek and Shockley, the radiative constant B=1.1×10−8 cm3/s was obtained.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Muth, JF and Lee, JH and Shmagin, IK and Kolbas, RM and Casey, HC and Keller, BP and Mishra, UK and DenBaars, SP}, year={1997}, month={Nov}, pages={2572–2574} }
 @article{shmagin_muth_kolbas_krishnankutty_keller_mishra_denbaars_1997, title={Observation of lasing from photopumped InGaN/GaN heterostructures in an edge emitting configuration}, volume={81}, ISSN={["0021-8979"]}, DOI={10.1063/1.364058}, abstractNote={Optically pumped lasing from InGaN/GaN single heterojunctions (SH) was observed in an edge emitting configuration at 77 K. The heterojunctions were grown by atmospheric pressure metalorganic chemical vapor deposition on c-plane sapphire substrates. The frequency tripled output of a mode-locked titanium:sapphire laser with a pulse width of 250 fs, operating at 280 nm, was used as the photoexcitation source. The nonlinear dependence of output emission intensity on input power density, the observations of a strongly polarized output emission, and distinct Fabry–Perot modes are discussed.}, number={4}, journal={JOURNAL OF APPLIED PHYSICS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Krishnankutty, S and Keller, S and Mishra, UK and DenBaars, SP}, year={1997}, month={Feb}, pages={2021–2023} }
 @article{shmagin_muth_kolbas_dupuis_grudowski_eiting_park_shelton_lambert_1997, title={Optical data storage in InGaN/GaN heterostructures}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119900}, abstractNote={Optical storage data was realized using an InGaN/GaN single heterostructure. It was observed that exposure to a high power density ultraviolet light temporarily changes the optical properties of the InGaN epitaxial layer. The photo-induced changes can be observed under an optical microscope with low intensity ultraviolet excitation. This effect was used to create high contrast optical patterns on the sample at room temperature and 77 K. The photo-induced changes completely disappear in about four hours at room temperature. After the recorded pattern is erased, the information can be rewritten without a change in efficiency or retention time.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Dupuis, RD and Grudowski, PA and Eiting, CJ and Park, J and Shelton, BS and Lambert, DJH}, year={1997}, month={Sep}, pages={1382–1384} }
 @article{shmagin_muth_lee_kolbas_balkas_sitar_davis_1997, title={Optical metastability in bulk GaN single crystals}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119577}, abstractNote={Bulk GaN single crystals were grown from cold pressed GaN powder by sublimation in flowing ammonia. Optical transmission measurements indicated that the absorption coefficient for the transparent samples is 50 cm−1 in the wavelength region from 650 to 400 nm. Optical metastability in bulk GaN crystals was studied through time dependent photoluminescence both at room and liquid–nitrogen temperatures. The observation included decreasing output intensity of the ultraviolet emission attributed to the band edge and increasing output intensity of a new emission band centered at 378 nm at room temperature. At liquid–nitrogen temperature, the photoinduced emission band consisted of at least one LO-phonon replica of the zero-phonon line centered at 378 nm. The ratio of output intensities of the photoinduced band to the band edge increased by a factor of 10 during 27 min of exposure time. The photoinduced effect is attributed to the metastable nature of traps in bulk GaN.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Lee, JH and Kolbas, RM and Balkas, CM and Sitar, Z and Davis, RF}, year={1997}, month={Jul}, pages={455–457} }
 @article{shmagin_muth_kolbas_krishnankutty_keller_abare_coldren_mishra_denbaars_1997, title={Photoluminescence characteristics of GaN/InGaN/GaN quantum wells}, volume={26}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-997-0172-y}, number={3}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Krishnankutty, S and Keller, S and Abare, AC and Coldren, LA and Mishra, UK and DenBaars, SP}, year={1997}, month={Mar}, pages={325–329} }
 @article{shmagin_muth_kolbas_mack_abare_keller_coldren_mishra_denbaars_1997, title={Reconfigurable optical properties in InGaN/GaN quantum wells}, volume={71}, ISSN={["0003-6951"]}, DOI={10.1063/1.119935}, abstractNote={Reconfigurable optical properties were studied in InGaN/GaN multiple quantum well (MQW) structures. It was observed that a short time exposure to a high intensity ultraviolet light results in long term, but reversible changes of the optical properties of InGaN/GaN MQW samples. The photoinduced changes can be observed using an optical microscope under low intensity ultraviolet light and are visible as a high contrast pattern. The retention time at room temperature for 12 and 20 MQW samples was longer than five days and four weeks, respectively. The effect was studied at room and cryogenic temperatures.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Shmagin, IK and Muth, JF and Kolbas, RM and Mack, MP and Abare, AC and Keller, S and Coldren, LA and Mishra, UK and DenBaars, SP}, year={1997}, month={Sep}, pages={1455–1457} }
 @inproceedings{balkas_sitar_zheleva_bergman_shmagin_muth_kolbas_nemanich_davis_1996, title={Growth of bulk AIN and GaN single crystals by sublimation}, booktitle={III-V nitrides: symposium held December 2-6, 1996, Boston, Massachusetts, U.S.A.  (Materials Research Society symposia proceedings ; v. 449)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Balkas, C. M. and Sitar, Z. and Zheleva, T. and Bergman, L. and Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Nemanich, R. and Davis, R. F.}, year={1996}, pages={41–46} }
 @inbook{shmagin_muth_kolbas_krishnankkutty_keller_mishra_denbaars_1996, title={Stimulated emission and gain measurements from InGaN/GaN heterostructures}, booktitle={III-V nitrides: Symposium held December 2-6, 1996, Boston, Massachusetts, U.S.A.(Materials Research Society symposia proceedings ; v. 449)}, publisher={Pittsburgh, Pa.: Materials Research Society}, author={Shmagin, I. K. and Muth, J. F. and Kolbas, R. M. and Krishnankkutty, S. and Keller, S. and Mishra, U. K. and DenBaars, S. P.}, year={1996}, pages={1209–1214} }