@article{pokharel_kuchoor_parakh_devkota_dawkins_ramaswamy_li_winkler_reynolds_iyer_2023, title={GaAs/GaAsSb Core-Shell Configured Nanowire-Based Avalanche Photodiodes up to 1.3?m Light Detection}, ISSN={["2574-0970"]}, DOI={10.1021/acsanm.2c03644}, abstractNote={We report the first study on a GaAs/GaAsSb core–shell (CS)-configured nanowire (NW)-based separate absorption, charge control, and multiplication region avalanche photodiode (APD) operating in the near-infrared (NIR) region. Heterostructure NWs consisted of GaAs and tunable band gap GaAs1–xSbx serving as the multiplication and absorption layers, respectively. A doping compensation of absorber material to boost material absorption, segment-wise annealing to suppress trap-assisted tunneling, and an intrinsic i-type and n-type combination of the hybrid axial core to suppress axial electric field are successfully adopted in this work to realize a room-temperature (RT) avalanche photodetection extending up to 1.3 μm. In an APD device operating at RT with a unity-gain responsivity of 0.2–0.25 A/W at ∼5 V, the peak gain of 160 @ 1064 nm and 18 V reverse bias, gain >50 @ 1.3 μm, are demonstrated. Thus, this work provides a foundation and prospects for exploiting greater freedom in NW photodiode design using hybrid axial and CS heterostructures.}, journal={ACS APPLIED NANO MATERIALS}, author={Pokharel, Rabin and Kuchoor, Hirandeep and Parakh, Mehul and Devkota, Shisir and Dawkins, Kendall and Ramaswamy, Priyanka and Li, Jia and Winkler, Christopher and Reynolds, Lew and Iyer, S.}, year={2023}, month={Mar} }
 @article{kanber_umerah_brindley_zhang_brown_reynolds_beltran-huarac_2023, title={Magneto-Mechanical Actuation Induces Endothelial Permeability}, volume={9}, ISSN={["2373-9878"]}, DOI={10.1021/acsbiomaterials.3c01571}, abstractNote={Cancer treatment is one of the major health problems that burden our society. According to the American Cancer Society, over 1.9 million new cancer cases and ∼0.6 million deaths from cancer are expected in the US in 2023. Therapeutic targeting is considered to be the gold standard in cancer treatment. However, when a tumor grows beyond a critical size, its vascular system differentiates abnormally and erratically, creating a heterogeneous endothelial barrier that further restricts drug delivery into tumors. While several methods exist, these prompt tumor migration and the appearance of new metastatic sites. Herein, we propose an innovative method based on magneto-mechanical actuation (MMA) to induce endothelial permeability. This method employs FDA-approved PEGylated superparamagnetic iron oxide nanoparticles (PEG-SPIONs) and alternating nonheating magnetic fields. MMA lies in the translation of magnetic forces into mechanical agitation. As a proof of concept, we developed a 2D cell culture model based on human umbilical vein endothelial cells (HUVEC), which were incubated with PEG-SPIONs and then exposed to different magnetic doses. After adjusting the particle concentration, incubation times, and parameters (amplitude, frequency, and exposure time) of the magnetic field generator, we induced actin filament remodeling and subsequent vascular endothelial-cadherin junction disruption. This led to transient gaps in cell monolayers, through which fluorescein isothiocyanate–dextran was translocated. We observed no cell viability reduction for 3 h of particle incubation up to a concentration of 100 μg/mL in the presence and absence of magnetic fields. For optimal permeability studies, the magnetic field parameters were adjusted to 100 mT, 65 Hz, and 30 min in a pulse mode with 5 min OFF intervals. We found that the endothelial permeability reached the highest value (33%) when 2 h postmagnetic field treatment was used. To explain these findings, a magneto-mechanical transduced stress mechanism mediated by intracellular forces was proposed. This method can open new avenues for targeted drug delivery into anatomic regions within the body for a broad range of disease interventions.}, number={12}, journal={ACS BIOMATERIALS SCIENCE & ENGINEERING}, author={Kanber, Mohammad and Umerah, Obum and Brindley, Stephen and Zhang, Xuanyi and Brown, Jared M. and Reynolds, Lew and Beltran-Huarac, Juan}, year={2023}, month={Nov}, pages={6902–6914} }
 @article{yang_zhang_reynolds_kumah_xu_2023, title={The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane-Derived Silicon Oxycarbide}, volume={1}, ISSN={["1527-2648"]}, url={https://doi.org/10.1002/adem.202201453}, DOI={10.1002/adem.202201453}, abstractNote={A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer‐derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero‐field‐cooled (ZFC) and field‐cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single‐domain NP for ceramic materials.}, journal={ADVANCED ENGINEERING MATERIALS}, author={Yang, Ni and Zhang, Xuanyi and Reynolds, Lewis and Kumah, Divine and Xu, Chengying}, year={2023}, month={Jan} }
 @article{devkota_parakh_ramaswamy_kuchoor_penn_reynolds_iyer_2022, title={A Study on the Effects of Gallium Droplet Consumption and Post Growth Annealing on Te-Doped GaAs Nanowire Properties Grown by Self-Catalyzed Molecular Beam Epitaxy}, volume={12}, ISSN={["2073-4344"]}, DOI={10.3390/catal12050451}, abstractNote={In this work, the effects of arsenic (As) flux used during gallium (Ga) seed droplet consumption and the post-growth annealing on the optical, electrical, and microstructural properties of self-catalyzed molecular beam epitaxially grown tellurium (Te)-doped GaAs nanowires (NWs) have been investigated using a variety of characterization techniques. NWs using the same amount of As flux for growth of the seed droplet consumption demonstrated reduced density of stacking faults at the NW tip, with four-fold enhancement in the 4K photoluminescence (PL) intensity and increased single nanowire photocurrent over their higher As flux droplet consumption counterparts. Post-growth annealed NWs exhibited an additional low-energy PL peak at 1.31 eV that significantly reduced the overall PL intensity. The origin of this lower energy peak is assigned to a photocarrier transition from the conduction band to the annealing assisted Te-induced complex acceptor state (TeAsVGa−). In addition, post-growth annealing demonstrated a detrimental impact on the electrical properties of the Te-doped GaAs NWs, as revealed by suppressed single nanowire (SNW) and ensemble NW photocurrent, with a consequent enhanced low-frequency noise level compared to as-grown doped NWs. This work demonstrates that each parameter in the growth space must be carefully examined to successfully grow self-catalyzed Te-doped NWs of high quality and is not a simple extension of the growth of corresponding intrinsic NWs.}, number={5}, journal={CATALYSTS}, author={Devkota, Shisir and Parakh, Mehul and Ramaswamy, Priyanka and Kuchoor, Hirandeep and Penn, Aubrey and Reynolds, Lewis and Iyer, Shanthi}, year={2022}, month={May} }
 @article{ramaswamy_devkota_pokharel_nalamati_stevie_jones_reynolds_iyer_2021, title={A study of dopant incorporation in Te-doped GaAsSb nanowires using a combination of XPS/UPS, and C-AFM/SKPM}, volume={11}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-021-87825-4}, abstractNote={Abstract We report the first study on doping assessment in Te-doped GaAsSb nanowires (NWs) with variation in Gallium Telluride (GaTe) cell temperature, using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), conductive-atomic force microscopy (C-AFM), and scanning Kelvin probe microscopy (SKPM). The NWs were grown using Ga-assisted molecular beam epitaxy with a GaTe captive source as the dopant cell. Te-incorporation in the NWs was associated with a positive shift in the binding energy of the 3d shells of the core constituent elements in doped NWs in the XPS spectra, a lowering of the work function in doped NWs relative to undoped ones from UPS spectra, a significantly higher photoresponse in C-AFM and an increase in surface potential of doped NWs observed in SKPM relative to undoped ones. The carrier concentration of Te-doped GaAsSb NWs determined from UPS spectra are found to be consistent with the values obtained from simulated I–V characteristics. Thus, these surface analytical tools, XPS/UPS and C-AFM/SKPM, that do not require any sample preparation are found to be powerful characterization techniques to analyze the dopant incorporation and carrier density in homogeneously doped NWs.}, number={1}, journal={SCIENTIFIC REPORTS}, author={Ramaswamy, Priyanka and Devkota, Shisir and Pokharel, Rabin and Nalamati, Surya and Stevie, Fred and Jones, Keith and Reynolds, Lew and Iyer, Shanthi}, year={2021}, month={Apr} }
 @article{ramesh_davis_roros_eiben_fabiani_smith_reynolds_pourdeyhimi_khan_genzer_et al._2021, title={Dual-Responsive Microgels for Structural Repair and Recovery of Nonwoven Membranes for Liquid Filtration}, volume={3}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.0c01360}, DOI={10.1021/acsapm.0c01360}, abstractNote={This study presents dual-responsive colloidal microgels to repair nonwoven fiber mats (NWFs) and recover their native morphological and functional properties. The formulation comprises poly(N-isopr...}, number={3}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Ramesh, Srivatsan and Davis, Jack and Roros, Alexandra and Eiben, Justin and Fabiani, Thomas and Smith, Ryan and Reynolds, Lewis and Pourdeyhimi, Behnam and Khan, Saad and Genzer, Jan and et al.}, year={2021}, month={Mar}, pages={1508–1517} }
 @article{allen-perry_straka_keith_han_reynolds_gautam_autrey_2021, title={Tuning the Magnetic Properties of Two-Dimensional MXenes by Chemical Etching}, volume={14}, ISSN={["1996-1944"]}, DOI={10.3390/ma14030694}, abstractNote={Two-dimensional materials based on transition metal carbides have been intensively studied due to their unique properties including metallic conductivity, hydrophilicity and structural diversity and have shown a great potential in several applications, for example, energy storage, sensing and optoelectronics. While MXenes based on magnetic transition elements show interesting magnetic properties, not much is known about the magnetic properties of titanium-based MXenes. Here, we measured the magnetic properties of Ti3C2Tx MXenes synthesized by different chemical etching conditions such as etching temperature and time. Our magnetic measurements were performed in a superconducting quantum interference device (SQUID) vibrating sample. These data suggest that there is a paramagnetic-antiferromagnetic (PM-AFM) phase transition and the transition temperature depends on the synthesis procedure of MXenes. Our observation indicates that the magnetic properties of these MXenes can be tuned by the extent of chemical etching, which can be beneficial for the design of MXenes-based spintronic devices.}, number={3}, journal={MATERIALS}, author={Allen-Perry, Kemryn and Straka, Weston and Keith, Danielle and Han, Shubo and Reynolds, Lewis and Gautam, Bhoj and Autrey, Daniel E.}, year={2021}, month={Feb} }
 @article{devkota_parakh_johnson_ramaswamy_lowe_penn_reynolds_iyer_2020, title={A study of n-doping in self-catalyzed GaAsSb nanowires using GaTe dopant source and ensemble nanowire near-infrared photodetector}, volume={31}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/abb506}, abstractNote={This work reports a comprehensive investigation of the effect of gallium telluride (GaTe) cell temperature variation (TGaTe) on the morphological, optical, and electrical properties of doped-GaAsSb nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE). These studies led to an optimum doping temperature of 550 °C for the growth of tellurium (Te)-doped GaAsSb NWs with the best optoelectronic and structural properties. Te incorporation resulted in a decrease in the aspect ratio of the NWs causing an increase in the Raman longitudinal optical/transverse optical vibrational mode intensity ratio, large photoluminescence emission with an exponential decay tail on the high energy side, promoting tunnel-assisted current conduction in ensemble NWs and significant photocurrent enhancement in the single nanowire. A Schottky barrier photodetector (PD) using Te-doped ensemble NWs with broad spectral range and a longer wavelength cutoff at ∼1.2 µm was demonstrated. These PDs exhibited responsivity in the range of 580–620 A W−1 and detectivity of 1.2–3.8 × 1012 Jones. The doped GaAsSb NWs have the potential for further improvement, paving the path for high-performance near-infrared (NIR) photodetection applications.}, number={50}, journal={NANOTECHNOLOGY}, author={Devkota, Shisir and Parakh, Mehul and Johnson, Sean and Ramaswamy, Priyanka and Lowe, Michael and Penn, Aubrey and Reynolds, Lew and Iyer, Shanthi}, year={2020}, month={Dec} }
 @article{kumar_liu_li_iyer_reynolds_2020, title={Doping Dependent Magnetic Behavior in MBE Grown GaAs1-xSbx Nanowires}, volume={10}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-020-65805-4}, abstractNote={Abstract Intrinsic and Te-doped GaAsSb nanowires with diameters ~100–120 nm were grown on a p-type Si(111) substrate by molecular beam epitaxy (MBE). Detailed magnetic, current/voltage and low-energy electron energy loss spectroscopy measurements were performed to investigate the effect of Te-doping. While intrinsic nanowires are diamagnetic over the temperature range 5–300 K, the Te-doped nanowires exhibit ferromagnetic behavior with the easy axis of magnetism perpendicular to the longitudinal axis of the nanowire. The temperature dependence of coercivity was analyzed and shown to be in agreement with a thermal activation model from 50–350 K but reveal more complex behavior in the low temperature regime. The EELS data show that Te doping introduced a high density of states (DOS) in the nanowire above the Fermi level in close proximity to the conduction band. The plausible origin of ferromagnetism in these Te-doped GaAsSb nanowires is discussed on the basis of d 0 ferromagnetism, spin ordering of the Te dopants and the surface-state-induced magnetic ordering.}, number={1}, journal={SCIENTIFIC REPORTS}, author={Kumar, Raj and Liu, Yang and Li, Jia and Iyer, Shanthi and Reynolds, Lewis}, year={2020}, month={Jun} }
 @article{pokharel_ramaswamy_devkota_parakh_dawkins_penn_cabral_reynolds_iyer_2020, title={Epitaxial High-Yield Intrinsic and Te-Doped Dilute Nitride GaAsSbN Nanowire Heterostructure and Ensemble Photodetector Application}, volume={2}, ISSN={["2637-6113"]}, DOI={10.1021/acsaelm.0c00450}, abstractNote={Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in th...}, number={9}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={Pokharel, Rabin and Ramaswamy, Priyanka and Devkota, Shisir and Parakh, Mehul and Dawkins, Kendall and Penn, Aubrey and Cabral, Matthew and Reynolds, Lewis and Iyer, Shanthi}, year={2020}, month={Sep}, pages={2730–2738} }
 @article{nalamati_devkota_li_lavelle_huet_snyder_penn_garcia_reynolds_iyer_2020, title={Hybrid GaAsSb/GaAs Heterostructure Core-Shell Nanowire/Graphene and Photodetector Applications}, volume={2}, ISBN={2637-6113}, DOI={10.1021/acsaelm.0c00433}, abstractNote={We report the growth of vertical, high-quality GaAs0.9Sb0.1 nanowires (NWs) with improved density on oxygen (O2) plasma-treated monolayer graphene/SiO2/p-Si(111) by self-catalyzed molecular beam ep...}, number={10}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={Nalamati, Surya and Devkota, Shisir and Li, Jia and Lavelle, Robert and Huet, Benjamin and Snyder, David and Penn, Aubrey and Garcia, Roberto and Reynolds, Lewis, Jr. and Iyer, Shanthi}, year={2020}, pages={3109–3120} }
 @article{nalamati_sharma_deshmukh_kronz_lavelle_snyder_reynolds_liu_iyer_2019, title={A Study of GaAs1-xSbx Axial Nanowires Grown on Monolayer Graphene by Ga-Assisted Molecular Beam Epitaxy for Flexible Near-Infrared Photodetectors}, volume={2}, ISSN={["2574-0970"]}, DOI={10.1021/acsanm.9b00893}, abstractNote={We report the successful growth of high-quality GaAs1–xSbx nanowires on monolayer graphene/SiO2/p-Si (111) using molecular beam epitaxy (MBE) for the application of a flexible near-infrared photodetector. A systematic and detailed study of NW growth parameters, namely, growth temperature, V/III beam equivalent pressure (BEP) ratio, and Ga shutter opening duration, has been carried out. Growth of vertical ⟨111⟩ oriented nanowires on graphene with 4 K photoluminescence emission in the range 1.24–1.38 eV has been achieved. The presence of a weak D mode in Raman spectra of NWs grown on graphene suggests that NW growth did not alter the intrinsic properties of the monolayer graphene. High-resolution transmission electron microscopy and a selective area diffraction pattern confirmed the zinc-blende crystal structure of the NWs. This study suggests that Sb as a surfactant plays a critical role in the surface engineering of the substrate, leading to the superior optical quality of NWs exhibiting a higher 4 K phot...}, number={7}, journal={ACS APPLIED NANO MATERIALS}, author={Nalamati, Surya and Sharma, Manish and Deshmukh, Prithviraj and Kronz, Jeffrey and Lavelle, Robert and Snyder, David and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2019}, month={Jul}, pages={4528–4537} }
 @article{sharma_ahmad_dev_li_reynolds_liu_iyer_2019, title={Improved performance of GaAsSb/AIGaAs nanowire ensemble Schottky barrier based photodetector via in situ annealing}, volume={30}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/aae148}, abstractNote={In this work, we report on the p-i GaAsSb/AlGaAs nanowires (NWs) ensemble device exhibiting good spectral response up to 1.1 μm with a high responsivity of 311 A W−1, an external quantum efficiency of 6.1 × 104%, and a detectivity of 1.9 × 1010 Jones at 633 nm. The high responsivity of the NWs has been attributed to in situ post-growth annealing of GaAsSb axial NWs in the ultra-high vacuum. The enabling growth technology is molecular beam epitaxy for the Ga-assisted epitaxial growth of these NWs on Si (111) substrates. Room temperature Raman spectra, as well as temperature dependent micro-photoluminescence peak analysis indicated suppression of band tail states and non-radiative channels due to annealing. A similar improvement in in situ annealed p-i GaAsSb NW ensemble with an AlGaAs passivating shell was inferred from a reduction in the Schottky barrier height as well as the NW resistance compared to the as-grown NW ensemble. These results demonstrate in situ annealing of nanowires to be an effective pathway for improving the optoelectronic properties of the NWs and the device thereof.}, number={3}, journal={NANOTECHNOLOGY}, author={Sharma, Manish and Ahmad, Estiak and Dev, Durjoy and Li, Jia and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2019}, month={Jan} }
 @article{akouala_kumar_punugupati_reynolds_reynolds_mily_maria_narayan_hunte_2019, title={Planar Hall effect and anisotropic magnetoresistance in semiconducting and conducting oxide thin films}, volume={125}, ISSN={0947-8396 1432-0630}, url={http://dx.doi.org/10.1007/S00339-019-2592-Y}, DOI={10.1007/s00339-019-2592-y}, number={5}, journal={Applied Physics A}, publisher={Springer Science and Business Media LLC}, author={Akouala, Christer R. and Kumar, Raj and Punugupati, Sandhyarani and Reynolds, C. Lewis and Reynolds, Judith G. and Mily, Edward J. and Maria, Jon-Paul and Narayan, Jagdish and Hunte, Frank}, year={2019}, month={Apr} }
 @article{deshmukh_sharma_nalamati_reynolds_liu_iyer_2018, title={Molecular beam epitaxial growth of high quality Ga-catalyzed GaAs1-xSbx(x > 0.8) nanowires on Si (111) with photoluminescence emission reaching 1.7 mu m}, volume={33}, ISSN={["1361-6641"]}, DOI={10.1088/1361-6641/aae7b8}, abstractNote={The advancement of ternary GaAsSb mismatched alloy system toward the Sb-rich corner of the phase diagram in the nanowire (NW) configuration on silicon remains a challenge. A large lattice mismatch between the silicon substrate and GaAsSb with an Sb-rich composition, along with the low supersaturation and low solubility of Sb in the Ga droplet in the vapor–liquid–solid growth mechanism, causes significant issues during Ga-assisted molecular beam epitaxial growth of these NWs. In this work, we have carried out a systematic study of Sb-rich GaAs1–xSbx NWs grown on Si (111) using variations of the Ga, As, and Sb beam equivalent pressures (BEP) to minimize undesirable parasitic growth and achieve photoemission up to 1.7 μm. Ga-assisted molecular beam epitaxy is the enabling growth technology for the growth of these self-catalyzed GaAs1–xSbx (x > 0.8) NWs. The use of a dual substrate temperature approach along with low As background pressure and a low Ga BEP were found to be the key growth components in achieving a well-faceted NW morphology with a low parasitic layer on the substrate. Energy-dispersive x-ray spectroscopy analysis confirms uniform compositional homogeneity along the NWs, while selected-area electron diffraction patterns in the transmission electron microscope revealed a zinc-blende crystal structure. A peak μ-photoluminescence emission of 1680 nm with a narrow FWHM was obtained at 4 K. Raman spectra at room temperature exhibit only GaSb related LO and TO modes, which attest to the high quality of the NWs grown. This is a promising approach due to the broad scope of applicability to grow other mismatched alloy material systems in a NW configuration.}, number={12}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Deshmukh, Prithviraj and Sharma, Manish and Nalamati, Surya and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2018}, month={Dec} }
 @article{jagannadham_das_reynolds_el-masry_2018, title={Nature of electrical conduction in MoS2 films deposited by laser physical vapor deposition}, volume={29}, ISSN={0957-4522 1573-482X}, url={http://dx.doi.org/10.1007/s10854-018-9551-9}, DOI={10.1007/s10854-018-9551-9}, number={16}, journal={Journal of Materials Science: Materials in Electronics}, publisher={Springer Nature}, author={Jagannadham, K. and Das, K. and Reynolds, C. L. and El-Masry, N.}, year={2018}, month={Jun}, pages={14180–14191} }
 @article{ahmad_karim_bin hafiz_reynolds_liu_iyer_2017, title={A Two-Step Growth Pathway for High Sb Incorporation in GaAsSb Nanowires in the Telecommunication Wavelength Range}, volume={7}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-017-09280-4}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Ahmad, Estiak and Karim, Md Rezaul and Bin Hafiz, Shihab and Reynolds, C. Lewis and Liu, Yang and Iyer, Shanthi}, year={2017}, month={Aug} }
 @article{ahmad_ojha_kasanaboina_reynolds_liu_iyer_2017, title={Bandgap tuning in GaAs1-xSbx axial nanowires grown by Ga-assisted molecular beam epitaxy}, volume={32}, ISSN={["1361-6641"]}, DOI={10.1088/1361-6641/32/3/035002}, abstractNote={In this work we present a comprehensive study on the effects of Sb incorporation on the composition modulation, structural and optical properties of self-assisted axial GaAs1−xSbx nanowires of 2–6 μm in length grown on (111) Si substrate by molecular beam epitaxy. The Sb composition in the GaAs1−xSbx axial nanowire (NW) was varied from 2.8–16 at.%, as determined from energy dispersive x-ray spectroscopy. Lower Sb composition leads to thinner nanowires and inhomogeneous Sb composition distribution radially with a depleted Sb surface region inducing weak type-II optical emission, the presence of an additional peak at higher Bragg angle in the x-ray diffraction spectra and an electric-field-induced strong Raman LO mode. Higher Sb composition of 16 at.% leads to a more uniform Sb compositional distribution radially leading to type-I optical transitions exhibiting the lowest PL peak energy occurring at 1.13 eV. In addition, the high quality of these nanowires exhibiting pure zinc blende crystal structure, largely free of any planar defects, is borne out by high resolution transmission electron microscopy and selected area diffraction patterns. The shift and broadening of the Raman LO and TO modes reveal evidence of increased Sb incorporation in the nanowires. Significant improvement in optical characteristics was achieved by the incorporation of a Al0.2Ga0.8As passivating shell. The results are very promising and reveal the potential to further red shift the optical emission wavelength by fine tuning of the fluxes during growth.}, number={3}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Ahmad, Estiak and Ojha, S. K. and Kasanaboina, P. K. and Reynolds, C. L., Jr. and Liu, Y. and Iyer, S.}, year={2017}, month={Mar} }
 @article{el-masry_zavada_reynolds_reynolds_liu_bedair_2017, title={Electric field control of ferromagnetism at room temperature in GaCrN (p-i-n) device structures}, volume={111}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4986431}, DOI={10.1063/1.4986431}, abstractNote={We have demonstrated a room temperature dilute magnetic semiconductor based on GaCrN epitaxial layers grown by metalorganic chemical vapor deposition. Saturation magnetization Ms increased when the GaCrN film is incorporated into a (p-GaN/i-GaCrN/n-GaN) device structure, due to the proximity of mediated holes present in the p-GaN layer. Zero field cooling and field cooling were measured to ascertain the absence of superparamagnetic behavior in the films. A (p-GaN/i-GaCrN/n-GaN) device structure with room temperature ferromagnetic (FM) properties that can be controlled by an external applied voltage has been fabricated. In this work, we show that the applied voltage controls the ferromagnetic properties, by biasing the (p-i-n) structure. With forward bias, ferromagnetism in the GaCrN layer was increased nearly 4 fold of the original value. Such an enhancement is due to carrier injection of holes into the Cr deep level present in the i-GaCrN layer. A “memory effect” for the FM behavior of the (p-i-n) GaCrN device structure persisted for 42 h after the voltage bias was turned off. These measurements also support that the observed ferromagnetism in the GaCrN film is not due to superparamagnetic clusters but instead is a hole-mediated phenomenon.}, number={8}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={El-Masry, N. A. and Zavada, J. M. and Reynolds, J. G. and Reynolds, C. L., Jr. and Liu, Z. and Bedair, S. M.}, year={2017}, month={Aug}, pages={082402} }
 @article{sharma_deshmukh_kasanaboina_reynolds_liu_iyer_2017, title={Growth of defect-free GaAsSbN axial nanowires via self-catalyzed molecular beam epitaxy}, volume={32}, ISSN={["1361-6641"]}, DOI={10.1088/1361-6641/aa90b0}, abstractNote={Bandgap reduction of 10% by incorporation of a dilute amount of N is reported for the first time, in axial GaAsSb nanowires (NWs) grown on Si (111) via Ga-assisted molecular beam epitaxy. Impact of N incorporation on the surface morphology, NW growth kinetics, and their structural and optical properties were examined. Dilute nitride NWs with Sb composition of 7 at% did not exhibit any noticeable planar defects, as revealed by the absence of satellite twin peaks in the selected-area diffraction pattern and high-resolution transmission electron microscopy imaging. Point defects were also minimal in as-grown dilute nitride NWs, as ascertained from the comparison of low-temperature photoluminescence spectra as well as the shape and shift of Raman modes, with in situ annealed NWs in different ambients. Evidence of enhanced incorporation of N was found in the NWs in situ annealed in N ambient, but with deteriorated optical quality due to simultaneous creation of N-induced defects. The lack of any noticeable defects in the as-grown GaAsSbN NWs demonstrates the advantage of the vapor–liquid–solid mechanism responsible for growth of axial configuration over the vapor–solid growth mechanism for core–shell NWs as well as their thin film counterpart, which commonly exhibit N-induced point defects.}, number={12}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Sharma, Manish and Deshmukh, Prithviraj and Kasanaboina, Pavan and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2017}, month={Dec} }
 @article{wells_kumar_reynolds_peters_bradford_2017, title={Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites}, volume={111}, ISSN={["1077-3118"]}, DOI={10.1063/1.4999503}, abstractNote={Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies >400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/− oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites.}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Wells, Brian and Kumar, Raj and Reynolds, C. Lewis, Jr. and Peters, Kara and Bradford, Philip D.}, year={2017}, month={Dec} }
 @article{lampert_papanikolas_lappi_reynolds_2017, title={Intrinsic gain and gain degradation modulated by excitation pulse width in a semiconducting conjugated polymer}, volume={94}, ISSN={["1879-2545"]}, DOI={10.1016/j.optlastec.2017.03.019}, abstractNote={We have previously reported that substantially higher optical gain values can be achieved in the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) through use of transient excitation conditions. In the present paper, we report on a systematic investigation of this behavior to elucidate the physical mechanisms involved, which enables us to distinguish between the fundamental intrinsic gain and an excitation induced degraded gain. Using pump laser pulses having temporal widths longer and shorter than the photoluminescence (PL) decay time of MEH-PPV, both quasi-steady-state (QSS) and transient excitation regimes are explored in our encapsulated waveguide heterostructures [Si(1 0 0)/SiO2/MEH-PPV/poly(methyl methacrylate)]. Under transient excitation (25 ps pump pulses), extremely large optical gain is observed, reaching a value of 700 cm−1 at a maximum pump energy density of 85 µJ/cm2. However, under QSS conditions (8 ns pulses), considerably lower gain coefficients are achieved with a maximum of ∼130 cm−1 at an energy density of 2,000 µJ/cm2; this factor of 5 decrease in optical gain performance is observed at the same excitation density as that for transient excitation using ps pulses. We have also employed unencapsulated waveguide structures [Si(1 0 0)/SiO2/MEH-PPV/air], which allows us to achieve additional insight on gain degradation under QSS conditions. It is clear that the gain measured under transient conditions is more representative of the intrinsic gain whereas that determined in the QSS regime is degraded by defect-mediated dissociation of emissive states due to localized thermal and oxidative damage to the films. It is in the QSS regime in which most optical gain measurements to date have been performed. These results suggest that further optimization of MEH-PPV – and most likely other conjugated polymers – as a robust optical gain medium can be achieved by consideration of the excitation pulse width.}, journal={OPTICS AND LASER TECHNOLOGY}, author={Lampert, Zach E. and Papanikolas, John M. and Lappi, Simon E. and Reynolds, C. Lewis, Jr.}, year={2017}, month={Sep}, pages={77–85} }
 @article{kasanaboina_ojha_sami_reynolds_liu_iyer_2016, title={Effect of Growth Parameters and Substrate Surface Preparation for High-Density Vertical GaAs/GaAsSb Core-Shell Nanowires on Silicon with Photoluminescence Emission at 1.3 mu m}, volume={45}, ISSN={["1543-186X"]}, DOI={10.1007/s11664-015-4316-1}, number={4}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Kasanaboina, Pavan Kumar and Ojha, Sai Krishna and Sami, Shifat Us and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2016}, month={Apr}, pages={2108–2114} }
 @article{kasanaboina_sharma_deshmukh_reynolds_liu_iyer_2016, title={Effects of Annealing on GaAs/GaAsSbN/GaAs Core-Multi-shell Nanowires}, volume={11}, ISSN={["1556-276X"]}, DOI={10.1186/s11671-016-1265-4}, abstractNote={The effects of ex-situ annealing in a N2 ambient on the properties of GaAs/GaAsSbN/GaAs core-multi-shell nanowires on Si (111) substrate grown by self-catalyzed molecular beam epitaxy (MBE) are reported. As-grown nanowires exhibit band edge emission at ~0.99 eV with a shoulder peak at ~0.85 eV, identified to arise from band tail states. A large red shift of 7 cm(-1) and broadened Raman spectra of as-grown nanowires compared to that of non-nitride nanowires confirmed phonon localization at N-induced localized defects. On annealing nanowires to 750 °C, there was no change in the planar defects in the nanowire with respect to the as-grown nanowire; however, vanishing of the photoluminescence (PL) peak corresponding to band tail states along with enhanced band edge PL intensity, recovery of the Raman shift and increase in the Schottky barrier height from 0.1 to 0.4 eV clearly point to the efficient annihilation of point defects in these GaAsSbN nanowires. A significant reduction in the temperature-induced energy shift in the annealed nanowires is attributed to annihilation of band tail states and weak temperature dependence of N-related localized states. The observation of room temperature PL signal in the 1.3 μm region shows that the strategy of adding small amounts of N to GaAsSb is a promising route to realization of efficient nanoscale light emitters with reduced temperature sensitivity in the telecommunication wavelength region.}, journal={NANOSCALE RESEARCH LETTERS}, author={Kasanaboina, Pavan and Sharma, Manish and Deshmukh, Prithviraj and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2016}, month={Feb} }
 @article{ojha_kasanaboina_reynolds_rawdanowicz_liu_white_iyer_2016, title={Incorporation of Be dopant in GaAs core and core-shell nanowires by molecular beam epitaxy}, volume={34}, ISSN={["2166-2746"]}, DOI={10.1116/1.4943600}, abstractNote={Effective implementation of doped nanowires (NWs) in nanoscaled devices requires controlled and effective dopant incorporation. The one dimensional configuration of NWs poses a challenge for efficient doping due to the large number of surface states pinning the Fermi level close to the middle of the band gap and thus creating a large depletion layer at the surface. This effectively reduces the effective volume for doping. However, the flexibility of different architectures offered by the NWs, in particular, the core–shell configuration along with different growth mechanisms associated with the core and shell can be strategically used for efficient doping. In this work, the authors report on a catalyst free Ga-assisted approach for the growth of Be-doped GaAs NWs by molecular beam epitaxy. A systematic and a comprehensive study is reported using a variety of characterization techniques to determine the impact of NW configuration, Be cell temperature, and V/III beam equivalent pressure (BEP) ratio individually on doping incorporation in the NWs. Broadening of the photoluminescence spectra in the 1.49–1.51 eV range, as well as the longitudinal optical mode of the corresponding Raman spectra in combination with its red shift that is considered as a signature of higher Be incorporation, was found to occur for the core–shell configuration. Further, a lower V/III BEP ratio has a strong impact on enhancing the dopant incorporation.}, number={2}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Ojha, Sai Krishna and Kasanaboina, Pavan Kumar and Reynolds, Claude Lewis, Jr. and Rawdanowicz, Thomas A. and Liu, Yang and White, Ryan M. and Iyer, Shanthi}, year={2016}, month={Mar} }
 @article{ahmad_kasanaboina_karim_sharma_reynolds_liu_iyer_2016, title={Te incorporation in GaAs1-xSbx nanowires and p-i-n axial structure}, volume={31}, ISSN={["1361-6641"]}, DOI={10.1088/0268-1242/31/12/125001}, abstractNote={We report on in situ Te-doping in GaAs1−xSbx nanowires (NWs) grown via self-assisted molecular beam epitaxy. Enhanced Te incorporation in the NW at higher Te cell temperature was attested by the broadening of the x-ray diffraction peak and the presence of a strong coupled-LO phonon mode in the Raman spectra. Te-doping was estimated from the shift in the coupled-LO phonon mode to be ∼2.0 × 1018/cm3. The surfactant nature of the Te modulated the growth kinetics, which was manifested in an enhanced radial growth rate with improved photoluminescence (PL) characteristics at both room temperature (RT) and 4 K. No noticeable planar defects were observed as ascertained from the high-resolution transmission electron microscopy images and selected-area electron diffraction patterns. Finally, we demonstrate the experimental realization of a GaAs1−xSbx axial p-type/intrinsic/n-type (p-i-n) structure on a Si substrate with Te as the n-type dopant. The GaAs1−xSbx p-i-n NW structures exhibited rectifying current–voltage (I–V) behavior. The dopant concentration and the transport parameters estimated from the PL spectra and I–V curve were found to be in good agreement.}, number={12}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Ahmad, Estiak and Kasanaboina, P. K. and Karim, M. R. and Sharma, M. and Reynolds, C. L. and Liu, Y. and Iyer, S.}, year={2016}, month={Dec} }
 @article{kasanaboina_ojha_sami_reynolds_liu_iyer_2015, title={Bandgap tuning of GaAs/GaAsSb core-shell nanowires grown by molecular beam epitaxy}, volume={30}, ISSN={["1361-6641"]}, DOI={10.1088/0268-1242/30/10/105036}, abstractNote={Semiconductor nanowires have been identified as a viable technology for next-generation infrared (IR) photodetectors with improved detectivity and detection across a range of energies as well as for novel single-photon detection in quantum networking. The GaAsSb materials system is especially promising in the 1.3–1.55 μm spectral range. In this work we present band-gap tuning up to 1.3 μm in GaAs/GaAsSb core–shell nanowires, by varying the Sb content using Ga-assisted molecular beam epitaxy. An increase in Sb content leads to strain accumulation in shell manifesting in rough surface morphology, multifaceted growths, curved nanowires, and deterioration in the microstructural and optical quality of the nanowires. The presence of multiple PL peaks for Sb compositions ≥12 at.% and degradation in the nanowire quality as attested by broadening of Raman and x-ray diffraction peaks reveal compositional instability in the nanowires. Transmission electron microscope (TEM) images show the presence of stacking faults and twins. Based on photoluminescence (PL) peak energies and their excitation power dependence behavior, an energy-band diagram for GaAs/GaAsSb core–shell nanowires is proposed. Optical transitions are dominated by type II transitions at lower Sb compositions and a combination of type I and type II transitions for compositions ≥12 at.%. Type I optical transitions as low as 0.93 eV (1.3 μm) from the GaAsSb for Sb composition of 26 at.% have been observed. The PL spectrum of a single nanowire is replicated in the ensemble nanowires, demonstrating good compositional homogeneity of the latter. A double-shell configuration for passivation of deleterious surface states leads to significant enhancement in the PL intensity resulting in the observation of room temperature emission, which provides significant potential for further improvement with important implications for nanostructured optoelectronic devices operating in the near-infrared regime.}, number={10}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Kasanaboina, Pavan Kumar and Ojha, Sai Krishna and Sami, Shifat Us and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2015}, month={Oct} }
 @article{wilkins_paskova_reynolds_ivanisevic_2015, title={Comparison of the Stability of Functionalized GaN and GaP}, volume={16}, ISSN={["1439-7641"]}, DOI={10.1002/cphc.201500105}, abstractNote={Abstract}, number={8}, journal={CHEMPHYSCHEM}, author={Wilkins, Stewart J. and Paskova, Tania and Reynolds, C. Lewis, Jr. and Ivanisevic, Albena}, year={2015}, month={Jun}, pages={1687–1694} }
 @article{ebert_pulwin_reynolds_ramos_li_farrell_2015, title={Optimization of InGaP metamorphic buffers grown by MOVPE}, volume={414}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2014.10.022}, abstractNote={Inverted metamorphic multijunction solar cells have shown high solar conversion efficiencies and utilized InGaP based metamorphic (MM) buffers to change the lattice constant using compositional graded buffer layers while minimizing dislocation density in the final material layers. In this study, optimization of InGaP metamorphic buffers was done by systematically exploring key metalorganic vapor phase epitaxy (MOVPE) growth conditions and the MM buffer epitaxial stack structure. To optimize MOVPE growth parameters, growth temperature and V/III ratio were varied during the growth of a standard MM buffer test structure and the final InGaP buffer layer was characterized by photoluminescence, X-ray reciprocal space maps, atomic force microscope, cathodoluminesence, and ex situ bow measurements. The in situ measurement of wafer curvature was also monitored during MM buffer layer growth. Evaluation of material characterization data provided optimized growth conditions for the InGaP based MM buffer. The second part of this study evaluated the actual layer thickness and number of compositional graded steps in a MM buffer. Our results showed that in situ deflectometer measurements of the wafer curvature of the MM buffer layer can be correlated to ex situ determined strain relaxation of the final buffer layer of the MM buffer. Process optimization tests showed a growth temperature of 580 °C with a V/III ratio of 37 provided for the best surface roughness, highest PL intensity and also allowed for low dislocation defect density of the final buffer layer. Using the optimized growth conditions, further optimization of the step grade layers showed that a 350 nm thick grade layer for a six step layer MM buffer for a final buffer composition targeted for In0.8Ga0.2P provided the best surface roughness and 100% final buffer relaxation.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Ebert, C. and Pulwin, Z. and Reynolds, C. L., Jr. and Ramos, F. Sn. and Li, Y. and Farrell, S.}, year={2015}, month={Mar}, pages={21–26} }
 @article{kasanaboina_ahmad_li_reynolds_liu_iyer_2015, title={Self-catalyzed growth of dilute nitride GaAs/GaAsSbN/GaAs core-shell nanowires by molecular beam epitaxy}, volume={107}, ISSN={["1077-3118"]}, DOI={10.1063/1.4930887}, abstractNote={Bandgap tuning up to 1.3 μm in GaAsSb based nanowires by incorporation of dilute amount of N is reported. Highly vertical GaAs/GaAsSbN/GaAs core-shell configured nanowires were grown for different N contents on Si (111) substrates using plasma assisted molecular beam epitaxy. X-ray diffraction analysis revealed close lattice matching of GaAsSbN with GaAs. Micro-photoluminescence (μ-PL) revealed red shift as well as broadening of the spectra attesting to N incorporation in the nanowires. Replication of the 4K PL spectra for several different single nanowires compared to the corresponding nanowire array suggests good compositional homogeneity amongst the nanowires. A large red shift of the Raman spectrum and associated symmetric line shape in these nanowires have been attributed to phonon localization at point defects. Transmission electron microscopy reveals the dominance of stacking faults and twins in these nanowires. The lower strain present in these dilute nitride nanowires, as opposed to GaAsSb nanowires having the same PL emission wavelength, and the observation of room temperature PL demonstrate the advantage of the dilute nitride system offers in the nanowire configuration, providing a pathway for realizing nanoscale optoelectronic devices in the telecommunication wavelength region.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Kasanaboina, Pavan Kumar and Ahmad, Estiak and Li, Jia and Reynolds, C. Lewis, Jr. and Liu, Yang and Iyer, Shanthi}, year={2015}, month={Sep} }
 @article{bayati_molaeil_richmond_nori_wu_kumar_narayan_reynolds_reynolds_2014, title={Modification of Properties of Yttria Stabilized Zirconia Epitaxial Thin Films by Excimer Laser Annealing}, volume={6}, ISSN={["1944-8252"]}, DOI={10.1021/am506298y}, abstractNote={This study focuses on the ultrafast improvement of surface wettability, electrical, and room temperature magnetic characteristics of cubic zirconia single crystalline thin films after laser annealing. The point defects generated by the laser treatment are envisaged to play a critical role in altering the above properties. Yttria stabilized zirconia (YSZ) thin films were epitaxially grown on Si(100) substrates by pulsed laser deposition technique and subsequently annealed by a KrF excimer laser beam (τ = 25 ns) using low-energy laser pulses. An atomically sharp interface, parallel to the film free surface, between laser annealed layer and the pristine region was observed. The single crystalline nature of thin films was preserved following the laser treatment. The laser-solid interaction with YSZ led to the introduction of point defects, i.e., oxygen vacancies, resulting in a strained structure which, in turn, resulted in the formation of a tetragonal-like zirconia. With the increase of number of laser pulses the laser treated films got highly disordered due to the high concentration of the point defects, while maintaining their crystalline nature. Although the surface of the pristine sample showed weak hydrophilic characteristics (contact angle ∼ 73°), the laser annealed samples exhibited significantly improved hydrophilic characteristics. It was found that there is an optimum number of laser pulses where the maximum hydrophilicity (contact angle ∼ 22°) is obtained. The carrier concentration in the sample with the highest hydrophilicity was determined to be higher by about 5 orders of magnitude compared to the pristine sample. This sample possessed the lowest electrical resistivity. The laser annealed YSZ epilayers showed a superior room-temperature ferromagnetic behavior, compared to the pristine samples. A 2-fold enhancement in the magnetization of the samples was observed following the laser treatment which is a clear demonstration of the key role of defects and their transient distribution throughout the lattice. All these observations were correlated with the formation of point defects due to the photon interaction with YSZ and absorption of energy of the KrF laser photons to produce defects.}, number={24}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Bayati, R. and Molaeil, R. and Richmond, A. and Nori, S. and Wu, F. and Kumar, D. and Narayan, J. and Reynolds, J. G. and Reynolds, C. L., Jr.}, year={2014}, month={Dec}, pages={22316–22325} }
 @misc{reynolds_reynolds_2014, title={Progress in ZnO Acceptor Doping: What Is the Best Strategy?}, volume={2014}, ISSN={["1687-8124"]}, DOI={10.1155/2014/457058}, abstractNote={This paper reviews the recent progress in acceptor doping of ZnO that has been achieved with a focus toward the optimum strategy. There are three main approaches for generating p-type ZnO: substitutional group IA elements on a zinc site, codoping of donors and acceptors, and substitution of group VA elements on an oxygen site. The relevant issues are whether there is sufficient incorporation of the appropriate dopant impurity species, does it reside on the appropriate lattice site, and lastly whether the acceptor ionization energy is sufficiently small to enable significant p-type conduction at room temperature. The potential of nitrogen doping and formation of the appropriate acceptor complexes is highlighted although theoretical calculations predict that nitrogen on an oxygen site is a deep acceptor. We show that an understanding of the growth and annealing steps to achieve the relevant acceptor defect complexes is crucial to meet requirements.}, journal={ADVANCES IN CONDENSED MATTER PHYSICS}, author={Reynolds, Judith G. and Reynolds, C. Lewis}, year={2014} }
 @article{reynolds_reynolds_crespo_gillespie_chabak_davis_2013, title={Dislocations as quantum wires: Buffer leakage in AlGaN/GaN heterostructures}, volume={28}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2013.76}, abstractNote={Abstract}, number={13}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Reynolds, C. Lewis, Jr. and Reynolds, Judith G. and Crespo, Antonio and Gillespie, James K. and Chabak, Kelson D. and Davis, Robert F.}, year={2013}, month={Jul}, pages={1687–1691} }
 @article{lampert_papanikolas_reynolds_2013, title={Enhancement of optical gain and amplified spontaneous emission due to waveguide geometry in the conjugated polymer poly[2-methoxy-5-(2 '-ethylhexyloxy)-p-phenylene vinylene]}, volume={102}, ISSN={["0003-6951"]}, DOI={10.1063/1.4793422}, abstractNote={We report enhanced amplified spontaneous emission (ASE) and optical gain performance in a conjugated polymer (CP)-based thin film waveguide (WG) Si(100)/SiO2/poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) by encapsulating the active layer with a transparent dielectric film of poly(methyl methacrylate) (PMMA). With index matched SiO2 and PMMA claddings, symmetric WGs are formed that exhibit increased mode confinement and reduced propagation loss enabling lower ASE threshold (40%) and higher optical gain (50%) compared to Si(100)/SiO2/MEH-PPV/air asymmetric WGs. An extremely large net gain coefficient of 500 cm−1 is achieved under picosecond pulse excitation, which is >4× larger than values previously reported in the literature. Fabrication of symmetric WGs requires no complex processing techniques, thus offering a simple, low-cost approach for effectively controlling the ASE behavior of CP-based WGs and related optical devices.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Lampert, Zach E. and Papanikolas, John M. and Reynolds, C. Lewis, Jr.}, year={2013}, month={Feb} }
 @article{lampert_lappi_papanikolas_reynolds_2013, title={Intrinsic optical gain in thin films of a conjugated polymer under picosecond excitation}, volume={103}, number={3}, journal={Applied Physics Letters}, author={Lampert, Z. E. and Lappi, S. E. and Papanikolas, J. M. and Reynolds, C. L.}, year={2013} }
 @article{lampert_lappi_papanikolas_reynolds_aboelfotoh_2013, title={Morphology and chain aggregation dependence of optical gain in thermally annealed films of the conjugated polymer poly[2-methoxy-5-(2 '-ethylhexyloxy)-p-phenylene vinylene]}, volume={113}, number={23}, journal={Journal of Applied Physics}, author={Lampert, Z. E. and Lappi, S. E. and Papanikolas, J. M. and Reynolds, C. L. and Aboelfotoh, M. O.}, year={2013} }
 @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{lampert_reynolds_papanikolas_aboelfotoh_2012, title={Controlling Morphology and Chain Aggregation in Semiconducting Conjugated Polymers: The Role of Solvent on Optical Gain in MEH-PPV}, volume={116}, ISSN={["1520-5207"]}, DOI={10.1021/jp304199u}, abstractNote={We report the results of a detailed investigation that addresses the influence of polymer morphology and chain aggregation, as controlled by the chemical nature of the solvent, on the optical gain properties of the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV). Using the variable stripe length technique in the picosecond regime, we have extensively studied the optical gain performance of asymmetric planar waveguides formed with thin MEH-PPV films spin-cast from concentrated chlorobenzene (CB) and tetrahydrofuran (THF) solutions onto thermally oxidized silicon substrates. CB and THF solvents were chosen based on their known ability to promote and effectively limit aggregate formation, respectively. Very large net gain coefficients are demonstrated, reaching values of 330 and 365 cm(-1), respectively, when optically pumping the waveguides with a maximum energy density of 85 μJ/cm(2). Our results clearly demonstrate that polymer morphology, and hence, the chain conformation dependence of the degree of aggregation in the films as controlled by the solvent, has minimal impact on the net gain. Moreover, the waveguides exhibit low loss coefficients of 10-20 cm(-1) at the ASE wavelength. These results question the importance of polymer morphology and aggregate formation in polymer-based optical devices operating at high excitation densities in the stimulated emission regime as would be characteristic of lasers and optical amplifiers.}, number={42}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Lampert, Zach E. and Reynolds, C. Lewis, Jr. and Papanikolas, John M. and Aboelfotoh, M. Osama}, year={2012}, month={Oct}, pages={12835–12841} }
 @article{dumcenco_levcenco_huang_reynolds_reynolds_tiong_paskova_evans_2011, title={Characterization of freestanding semi-insulating Fe-doped GaN by photoluminescence and electromodulation spectroscopy}, volume={109}, ISSN={["1089-7550"]}, DOI={10.1063/1.3592343}, abstractNote={A detailed optical characterization of a freestanding wurtzite semi-insulating Fe-doped GaN (SI-GaN:Fe) grown by hydride-vapor-phase-epitaxy was carried out by photoluminescence (PL) and contactless electroreflectance (CER) at 10 and 300 K, respectively, and photoreflectance at 300 K. Low-temperature PL spectrum of the Ga-face consisted of the Fe3+ impurity characteristic series of IR peaks with a sharp zero-phonon line (ZPL) at 1.299 eV, yellow and blue broad emission bands, and near-band-edge (NBE) emission in the ultraviolet region. The narrow linewidth of 135 μeV of the ZPL and the measured energy difference of ∼70 meV between the ZPL and E2 (high) phonon replica, which is sensitive to the lattice strain, shows good crystal quality and a strain-free incorporation of iron. The obtained transition energies of A, B, and C excitonic features in the CER spectra and the n = 2 excited states (2s) of the A and B excitons enable the estimation of the exciton binding energies. In addition to the free excitonic recombination, the PL spectrum of the Ga-face exhibited clear donor and acceptor related features in the NBE region, while the N-face exhibited a broad emission band related to the free-to-bound recombination only. The differences were explained by the presence of impurity-induced band-tail states in the N-face SI-GaN:Fe due to an increased impurity density and the incorporation of large volume vacancy-type defects.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Dumcenco, D. O. and Levcenco, S. and Huang, Y. S. and Reynolds, C. L., Jr. and Reynolds, J. G. and Tiong, K. K. and Paskova, T. and Evans, K. R.}, year={2011}, month={Jun} }
 @article{bharatan_iyer_li_rawdanowicz_reynolds_2011, title={Study of molecular beam epitaxially grown InGaAsSbN/GaSb single quantum wells}, volume={29}, ISSN={["2166-2746"]}, DOI={10.1116/1.3555368}, abstractNote={InGaAsSbN quantum wells (QWs) have been investigated for potential light-emitting devices in the midinfrared region. This paper presents the growth and properties of molecular beam epitaxially grown InGaAsSbN single QWs using a variety of characterization techniques. A 10 K photoluminescence emission at 2.27 μm, with a lowest full width at half maxima of 5 meV which shifted to 2.30 μm on in situ annealing, has been observed. The presence of well resolved Pendellosung fringes in high resolution x-ray diffraction and sharp abrupt interfaces in the corresponding transmission electron microscope (TEM) images are indications of the high quality of these QWs. Raman spectroscopy studies reveal the presence of well resolved Raman peaks with higher intensity, along with the presence of sharp second order modes of GaSb, further attesting to the high quality of the QW structures grown. Investigation of the annealed samples using Z-contrast scanning TEM images reveals atomic interdiffusion between the QW and surrounding GaSb layers, increasing the effective thickness of the QW, which explains the redshift upon annealing.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Bharatan, Sudhakar and Iyer, Shanthi and Li, Jia and Rawdanowicz, Thomas A. and Reynolds, Lewis, Jr.}, year={2011}, month={May} }
 @article{grenko_ebert_reynolds_duscher_barlage_johnson_preble_paskova_evans_2010, title={Optimization of homoepitaxially grown AlGaN/GaN heterostructures}, volume={207}, ISSN={["1862-6300"]}, DOI={10.1002/pssa.200925508}, abstractNote={Abstract}, number={10}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Grenko, J. A. and Ebert, C. W. and Reynolds, C. L., Jr. and Duscher, G. J. and Barlage, D. W. and Johnson, M. A. L. and Preble, E. A. and Paskova, T. and Evans, K. R.}, year={2010}, month={Oct}, pages={2292–2299} }
 @article{reynolds_grenko_2009, title={Crystallographic plane dependent Fe and Si dopant incorporation and activation in InP}, volume={206}, ISSN={["1862-6300"]}, DOI={10.1002/pssa.200824271}, abstractNote={Abstract}, number={4}, journal={PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE}, author={Reynolds, C. Lewis, Jr. and Grenko, Judith A.}, year={2009}, month={Apr}, pages={691–696} }
 @article{bishop_reynolds_molstad_stevie_barnhardt_davis_2009, title={On the origin of aluminum-related cathodoluminescence emissions from sublimation grown 4H-SiC(11(2)over-bar0)}, volume={255}, ISSN={["0169-4332"]}, DOI={10.1016/j.apsusc.2009.02.036}, abstractNote={The spatial origins of emissions from homoepitaxial 4H-SiC(112¯0) films have been investigated by cathodoluminescence, secondary ion mass spectrometry, and electron trajectory simulations. At 15 keV (300 K), the spectrum contained three peaks. The most intense peak corresponded (3.18 eV) to the nitrogen donor-to-valence band transition. The lesser two peaks at 2.94 eV and 2.75 eV involved aluminum and oxygen impurities, respectively; both impurities were determined to be in high concentrations in the film–substrate interfacial region. At 25 keV (300 K) the primary emission broadened into a band at ∼3.10 eV. Deconvolution revealed three peaks; the most intense emission was again the nitrogen donor-to-valence band transition. The remaining two peaks at 3.02 eV and 2.90 eV were consistent with transitions involving aluminum impurities. The former peak was not observed in the spectra obtained at lower electron beam energies and was correlated with the conduction band-to-aluminum acceptor level transition. Monte-Carlo simulations showed the origin of the 25 keV (300 K) spectrum was the film–substrate interface. An analysis of the aluminum impurity concentration in this region revealed that the cause of the 3.02 eV emission was a dramatic increase in the concentration of aluminum (3 × 1016 cm−3 to 1 × 1018 cm−3). The emissions comprising the 3.10 eV band were further investigated at 6 K and 25 keV. The difference in the intensity of the conduction band-to-aluminum acceptor level transition at 6 K and 300 K was attributed to thermal impurity ionization and the spike in the interfacial aluminum concentration previously described.}, number={13-14}, journal={APPLIED SURFACE SCIENCE}, author={Bishop, S. M. and Reynolds, C. L. and Molstad, J. C. and Stevie, F. A. and Barnhardt, D. E. and Davis, R. F.}, year={2009}, month={Apr}, pages={6535–6539} }
 @article{biggerstaff_reynolds_zheleva_lelis_habersat_haney_ryu_agarwal_duscher_2009, title={Relationship between 4H-SiC/SiO2 transition layer thickness and mobility}, volume={95}, ISSN={["0003-6951"]}, DOI={10.1063/1.3144272}, abstractNote={The interfacial region between silicon carbide (SiC) and its native oxide contains a high density of interfacial traps, which is considered a major problem leading to a lower mobility that has hindered SiC metal oxide semiconductor field effect transistors from reaching their theoretical expectations. We investigate the microstructure and chemistry of the 4H-SiC∕SiO2 interface due to variations in nitric oxide annealing and aluminum implantation using Z-contrast imaging and electron energy loss spectroscopy. A transition layer with a carbon to silicon ratio greater than 1 is consistently observed on the SiC side of the interface in each of these samples, and the width of this transition layer is found to be inversely related to the effective channel mobility measured on fabricated devices.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Biggerstaff, T. L. and Reynolds, C. L., Jr. and Zheleva, T. and Lelis, A. and Habersat, D. and Haney, S. and Ryu, S. -H. and Agarwal, A. and Duscher, G.}, year={2009}, month={Jul} }
 @article{darling_reynolds_leonard_duscher_scattergood_koch_2008, title={Self-assembled three-dimensional Cu-Ge nanoweb composite}, volume={19}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/19/13/135603}, abstractNote={The inexpensive combination of cryogenically milled Cu3Ge powders sonochemically processed in a standard ultrasonic cleaner has led to the prototype of a heretofore undescribed class of material. This prototype is a nanostructured composite composed of 4.5 nm diameter Cu nanocrystals embedded in a three-dimensional (3D) amorphous CuGeO3 polyhedron web matrix. The diameters of the wires comprising the matrix are typically 5–15 nm. Complete structural and compositional characterization is reported to provide additional insight and firm designation on the observation of this previously undescribed class of material. The large surface to volume ratio of these nanoweb composites may offer unique advantages based on altered optical or electronic and magnetic properties. For example, quantum confinement of the Cu dots in the amorphous 3D nanowebs is possible. Nanostructures in general have altered properties compared to those of bulk materials and the same is expected in nanostructured composites.}, number={13}, journal={NANOTECHNOLOGY}, author={Darling, Kris A. and Reynolds, C. Lewis, Jr. and Leonard, Donovan N. and Duscher, Gerd and Scattergood, Ronald O. and Koch, Carl C.}, year={2008}, month={Apr} }
 @article{bishop_reynolds_liliental-weber_uprety_ebert_stevie_park_davis_2008, title={Sublimation growth of an in-situ-deposited layer in SiC chemical vapor deposition on 4H-SiC(1 1 (2)over-bar 0)}, volume={311}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2008.09.200}, abstractNote={Homoepitaxial growths of 4H-SiC(1 1 2¯ 0) epitaxial layers have been achieved using chemical vapor deposition from 1250 to 1600 °C and two process routes: (1) with and (2) without the addition of SiH4 and C2H4 to the growth ambient. An activation energy of 3.72 eV/atom (359 kJ/mol) was determined for the former route and associated with either reactions in the gas phase or the potential barrier associated with the temperature-dependent sticking coefficient. The activation energy for the latter route was 5.64 eV/atom (544 kJ/mol), which is consistent with published values for SiC sublimation epitaxy. Sublimation dominated the growth process at temperature ⩾1600 °C. The same effect resulted in the in-situ deposition of a thin film during the heating stage of route (1). At 1450 °C this layer was ∼100 nm thick and exhibited a specular surface microstructure with a roughness of 0.31 nm RMS. The in-situ-deposited layer was thus employed as an intermediate layer prior to epitaxial layer growth using route (1) at ∼1450 °C. Regions free of one- and two-dimensional defects were observed using cross-sectional transmission electron microscopy. Distinct interfaces were not observed between the substrate and the epitaxial layers.}, number={1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Bishop, S. M. and Reynolds, C. L., Jr. and Liliental-Weber, Z. and Uprety, Y. and Ebert, C. W. and Stevie, F. A. and Park, J. -S. and Davis, R. F.}, year={2008}, month={Dec}, pages={72–78} }
 @article{darling_guduru_reynolds_bhosle_chan_scattergood_koch_narayan_aboelfotoh_2008, title={Thermal stability, mechanical and electrical properties of nanocrystalline Cu3Ge}, volume={16}, ISSN={0966-9795}, url={http://dx.doi.org/10.1016/j.intermet.2007.11.005}, DOI={10.1016/j.intermet.2007.11.005}, abstractNote={The intermetallic ɛ1 compound Cu3Ge was produced through a mechanical alloying procedure that enables the formation of a nanograined microstructure. There is a dependence of grain size (20–11 nm) on milling conditions. The microstructure remained very stable even at temperatures up to 500 °C for 5 h which is a minimum of 76% of the melting temperature. The materials produced by these methods were in the form of powders with particle size ranging from 200 nm to 10 μm. The morphology of the particles varied with the largest being rough and irregular and the smallest being spherical. Preliminary resistivity measurements showed low resistivity, 8.8 μΩ cm, which is comparable to that previously reported for thin films with grain sizes thousands of times larger. Nanoindentation was also performed, yielding an elastic modulus of ∼110 GPa.}, number={3}, journal={Intermetallics}, publisher={Elsevier BV}, author={Darling, Kris A. and Guduru, R.K. and Reynolds, C. Lewis, Jr and Bhosle, Vikram M. and Chan, Ryan N. and Scattergood, Ronald O. and Koch, Carl C. and Narayan, J. and Aboelfotoh, M.O.}, year={2008}, month={Mar}, pages={378–383} }
 @article{reynolds_patel_2008, title={Tunneling entity in different injection regimes of InGaN light emitting diodes}, volume={103}, ISSN={["1089-7550"]}, DOI={10.1063/1.2906326}, abstractNote={The forward I-V characteristics of InGaN-based light emitting diodes heteroepitaxially grown have previously been shown to be dominated by tunneling over a wide range of bias, as indicated by unrealistic values for the ideality factor. Comparison of the electrical characteristics in different bias regimes for InGaN light emitting diodes (LEDs) to expressions for the tunneling current enables one to achieve an understanding of the tunneling entities involved. At low bias for LEDs grown on sapphire, data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations and are characterized by an energy near 200meV. This component is absent for those devices homoepitaxially grown. In the intermediate bias regime, LEDs both heteroepitaxially and homoepitaxially grown exhibit a tunneling component that is proposed to be associated with the heavy hole tunneling via intermediate states and to have a characteristic energy near 80meV.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Reynolds, C. L., Jr. and Patel, A.}, year={2008}, month={Apr} }
 @article{bishop_reynolds_liliental-weber_uprety_zhu_wang_park_molstad_barnhardt_shrivastava_et al._2007, title={Polytype stability and microstructural characterization of silicon carbide epitaxial films grown on [11(2)over bar0]- and [0001]-oriented silicon carbide substrates}, volume={36}, ISSN={["1543-186X"]}, DOI={10.1007/s11664-006-0076-2}, number={4}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Bishop, S. M. and Reynolds, C. L., Jr. and Liliental-Weber, Z. and Uprety, Y. and Zhu, J. and Wang, D. and Park, M. and Molstad, J. C. and Barnhardt, D. E. and Shrivastava, A. and et al.}, year={2007}, month={Apr}, pages={285–296} }
 @article{young_reynolds_swarninathan_walters_2005, title={Influence of Zn doping profiles on excitation dependence of photoluminescence intensity in InGaAsP heterostructures}, volume={41}, ISSN={["1350-911X"]}, DOI={10.1049/el:20052347}, abstractNote={It is known that the Zn doping profile in strained multi-quantum-well (MQW) InGaAsP lasers strongly affects the electro-optical characteristics of these devices and their temperature sensitivity. A systematic investigation of the excitation dependence of the active layer photoluminescence (PL) intensity from compressively strained InGaAsP MQW pin laser material with different Zn doping profiles is described. When the pn junction lies within the active region, the excitation dependence of the PL intensity is superlinear at low excitation and linear at higher excitation. As the Zn profile is set back from the heterointerface creating a displaced pn junction from the active region, the excitation dependence is superlinear and linear at 300 K but becomes linear for all excitation powers at 77 K. The implications of these observations are discussed.}, number={18}, journal={ELECTRONICS LETTERS}, author={Young, DK and Reynolds, CL and Swarninathan, V and Walters, FS}, year={2005}, month={Sep}, pages={1008–1010} }
 @article{przybylek_reynolds_walters_2004, title={Improved contact resistance and linearity in optoelectronic devices with an intermediate quaternary layer}, volume={96}, ISSN={["1089-7550"]}, DOI={10.1063/1.1801160}, abstractNote={The importance of the heterojunction between the contact and cladding layers in the contact resistance of optoelectronic devices is investigated. The incorporation of a quaternary layer, intermediate in composition, between these layers is shown to provide specific contact resistances at least 60% lower with some Rc values <10−7Ωcm2 and high-speed tandem modulators with an improved linearity and reduced series resistance. The lowering of the potential barrier for hole transport is most likely responsible for these observations. The thermal stability is quite good.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Przybylek, GJ and Reynolds, CL and Walters, FS}, year={2004}, month={Nov}, pages={5788–5791} }
 @article{grenko_reynolds_schlesser_hren_bachmann_sitar_kotula_2004, title={Nanoscale GaN whiskers fabricated by photoelectrochemical etching}, volume={96}, ISSN={["0021-8979"]}, DOI={10.1063/1.1788841}, abstractNote={GaN whiskers with nanoscale dimensions have been fabricated by photoelectrochemical (PEC) etching in dilute H3PO4 electrolyte. Etching in lower concentration H3PO4 electrolyte for 1 h or for a short time of 5 min at a higher concentration results in individual whiskers with a density of ∼2×109cm−2 and diameters to 15nm. It is observed that ∼10% of them have formed nearly perfect hexagonal plates on the top of the whiskers, which appear to evolve into flowerlike features upon extended etching to 12 min. Such hexagonal plates have not been reported previously in the PEC etching of GaN. The presence of a dislocation along the central axis of the needles is clearly demonstrated, and the etch pattern is suggested to be related to the growth mechanism for GaN on sapphire. When etched for times >30min, these whiskers are typically arranged in clusters with a density of 2–5×107cm−2 and have ten or more whiskers contributing to the central top of the cluster.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Grenko, JA and Reynolds, CL and Schlesser, R and Hren, JJ and Bachmann, K and Sitar, Z and Kotula, PG}, year={2004}, month={Nov}, pages={5185–5188} }
 @article{grenko_reynolds_schlesser_bachmann_rietmeier_davis_sitar_2004, title={Selective etching of GaN from AlGaN/GaN and AlN/GaN structures}, volume={9}, DOI={10.1557/s1092578300000405}, abstractNote={Thick GaN layers as well as AlGaN/GaN and AlN/GaN heterostructures grown by metalorganic vapor phase epitaxy have been photoelectrochemically (PEC) etched in various dilute electrolytes, and bandgap-selective etching has been demonstrated in heterostructures. This result is a significant step forward in the fabrication of group III-nitride devices and one-dimensional photonic bandgap (PBG) structures in the deep UV. Based on initial results from thick GaN layers, a method was developed to achieve self-stopping selective etching of thin GaN layers in AlGaN/GaN and AlN/GaN heterostructures. Selective PEC etching requires the use of a suitable light source with photon energies larger than the bandgap of GaN, but smaller than that of AlGaN or AlN, thus enabling selective hole generation in the GaN layers to be etched. Additionally, it is imperative to use an electrolyte that supports PEC etching of GaN without chemically etching AlGaN or AlN.}, number={5}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Grenko, J. A. and Reynolds, C. L. and Schlesser, R. and Bachmann, K. and Rietmeier, Z. and Davis, R. F. and Sitar, Z.}, year={2004} }