@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{woodward_nepal_mitchell_feng_li_jiang_lin_zavada_dierolf_2011, title={Enhanced magnetization in erbium doped GaN thin films due to strain induced electric fields}, volume={99}, number={12}, journal={Applied Physics Letters}, author={Woodward, N. T. and Nepal, N. and Mitchell, B. and Feng, I. W. and Li, J. and Jiang, H. X. and Lin, J. Y. and Zavada, J. M. and Dierolf, V.}, year={2011} }
 @article{nepal_frajtag_zavada_el-masry_bedair_wetzel_khan_2011, title={Light emitting diodes based on sidewall m-plane epitaxy of etched GaN/sapphire templates}, volume={8}, ISSN={["1862-6351"]}, DOI={10.1002/pssc.201000983}, abstractNote={Abstract}, number={7-8}, journal={PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 7-8}, author={Nepal, N. and Frajtag, P. and Zavada, J. M. and El-Masry, N. A. and Bedair, S. M. and Wetzel, C and Khan, A}, year={2011} }
 @article{brown_hommerich_yamada_yamane_zavada_2011, title={Luminescence spectroscopy of europium doped gallium nitride powder prepared by a Na flux method}, volume={208}, number={1}, journal={Physica Status Solidi. A, Applications and Materials Science}, author={Brown, E. and Hommerich, U. and Yamada, T. and Yamane, H. and Zavada, J.}, year={2011}, pages={156–160} }
 @inproceedings{bluiett_peele_norman_brown_hommerich_trivedi_zavada_2011, title={Mid-infrared emission characteristics and energy transfer processes in doubly doped Tm, Tb: KPb2Br5 and Tm, Nd: KPb2Br5}, volume={33}, number={7}, booktitle={Optical Materials}, author={Bluiett, A. G. and Peele, D. and Norman, K. and Brown, E. and Hommerich, U. and Trivedi, S. B. and Zavada, J. M.}, year={2011}, pages={985–988} }
 @inproceedings{dahal_lin_jiang_zavada_2011, title={Near infrared photonic devices based on Er-doped GaN and InGaN}, volume={33}, number={7}, booktitle={Optical Materials}, author={Dahal, R. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2011}, pages={1066–1070} }
 @inproceedings{woodward_dierolf_lin_jiang_zavada_2011, title={Optical and magneto-optical properties of erbium doped InGaN and GaN epilayers}, volume={33}, number={7}, booktitle={Optical Materials}, author={Woodward, N. and Dierolf, V. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2011}, pages={1059–1062} }
 @article{li_kong_zavada_kim_2011, title={Strong substrate effects of Joule heating in graphene electronics}, volume={99}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3668113}, DOI={10.1063/1.3668113}, abstractNote={The effect of Joule heating on graphene electronic properties is investigated by self-consistent use of full-band Monte Carlo electron dynamics and three-dimensional heat transfer simulations. Several technologically important substrate materials are examined: SiO2, SiC, hexagonal BN, and diamond. Results illustrate that the choice of substrate has a major impact via heat conduction and surface polar phonon scattering. Particularly, the poor thermal conductivity of SiO2 leads to significant Joule heating and saturation velocity degradation in graphene characterized by the 1/n decay. Considering the overall characteristics, BN appears to compare favorably against the other substrate choices for graphene electronic applications.}, number={23}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Li, X. and Kong, B. D. and Zavada, J. M. and Kim, K. W.}, year={2011}, month={Dec}, pages={233114} }
 @article{semenov_zavada_kim_2011, title={Weak ferromagnetism of antiferromagnetic domains in graphene with defects}, volume={84}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.84.165435}, DOI={10.1103/physrevb.84.165435}, abstractNote={Magnetic properties of graphene with randomly distributed magnetic defects/vacancies are studied in terms of the Kondo Hamiltonian in the mean field approximation. It has been shown that graphene with defects undergoes a magnetic phase transition from a paramagnetic to a antiferromagnetic (AFM) phase once the temperature reaches the critical point $T_{N}$. The defect straggling is taken into account as an assignable cause of multiple nucleation into AFM domains. Since each domain is characterized by partial compensating magnetization of the defects associated with different sublattices, together they reveal a super-paramagnetic behavior in a magnetic field. Theory qualitatively describe the experimental data provided the temperature dependence of the AFM domain structure.}, number={16}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2011}, month={Oct} }
 @article{wang_steckl_nepal_zavada_2010, title={Electrical and magnetic properties of GaN codoped with Eu and Si}, volume={107}, number={1}, journal={Journal of Applied Physics}, author={Wang, R. and Steckl, A. J. and Nepal, N. and Zavada, J. M.}, year={2010} }
 @article{semenov_zavada_kim_2010, title={Electrically controlled magnetic switching based on graphene-magnet composite structures}, volume={107}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3354066}, DOI={10.1063/1.3354066}, abstractNote={A nonvolatile magnetic switch is proposed by utilizing the unique properties of graphene-ferromagnet composite structures. The basic mechanism relies on the role of graphene in mediating and modulating the effective exchange bias between adjacent magnetic layers, which can lead to electrically controlled rotation of magnetic bits. Readout of magnetization states is also achieved electrically through the magnetoresistance effect in the graphene channel. The proposed switch can be used to realize both the memory and programmable logic elements. Theoretical estimates illustrate the feasibility of the concept as well as its potential advantage of low power consumption (∼10−19 J) for the intrinsic switching operation.}, number={6}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2010}, month={Mar}, pages={064507} }
 @article{semenov_zavada_kim_2010, title={Electron spin relaxation in carbon nanotubes}, volume={82}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.82.155449}, DOI={10.1103/physrevb.82.155449}, abstractNote={The long standing problem of inexplicably short spin relaxation in carbon nanotubes (CNTs) is examined. The curvature-mediated spin-orbital interaction is shown to induce fluctuating electron spin precession causing efficient relaxation in a manner analogous to the Dyakonov-Perel mechanism. Our calculation estimates longitudinal (spin-flip) and transversal (decoherence) relaxation times as short as 150 ps and 110 ps at room temperature, respectively, along with a pronounced anisotropic dependence. Interference of electrons originating from different valleys can lead to even faster dephasing. The results can help clarify the measured data, resolving discrepancies in the literature.}, number={15}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2010}, month={Oct} }
 @article{feng_li_sedhain_lin_jiang_zavada_2010, title={Enhancing erbium emission by strain engineering in GaN heteroepitaxial layers}, volume={96}, number={3}, journal={Applied Physics Letters}, author={Feng, I. W. and Li, J. and Sedhain, A. and Lin, J. Y. and Jiang, H. X. and Zavada, J.}, year={2010} }
 @misc{dahal_lin_jiang_zavada_2010, title={Er-doped GaN and InxGa1-xN for optical communications}, volume={124}, journal={Rare earth doped iii-nitrides for optoelectronic and spintronic applications}, author={Dahal, R. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2010}, pages={115–157} }
 @inproceedings{luen_nepal_frajtag_zavada_brown_hommerich_bedair_el masry_2010, title={Ferromagnetism and near infrared luminescence in neodymium and erbium doped gallium nitride via diffusion}, volume={1183}, DOI={10.1557/proc-1183-ff06-01}, abstractNote={Abstract}, booktitle={Novel materials and devices for spintronics}, author={Luen, M. O. and Nepal, N. and Frajtag, P. and Zavada, J. M. and Brown, E. and Hommerich, U. and Bedair, S. M. and El Masry, N. A.}, year={2010}, pages={45–50} }
 @article{borysenko_mullen_barry_paul_semenov_zavada_nardelli_kim_2010, title={First-principles analysis of electron-phonon interactions in graphene}, volume={81}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.81.121412}, DOI={10.1103/physrevb.81.121412}, abstractNote={The electron-phonon interaction in monolayer graphene is investigated using density-functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic-phonon contribution that is much weaker than previously thought, revealing an important role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the already high values reported in suspended samples.}, number={12}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Borysenko, K. M. and Mullen, J. T. and Barry, E. A. and Paul, S. and Semenov, Y. G. and Zavada, J. M. and Nardelli, M. Buongiorno and Kim, K. W.}, year={2010}, month={Mar} }
 @article{semenov_zavada_kim_2010, title={Graphene spin capacitor for magnetic field sensing}, volume={97}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3462297}, DOI={10.1063/1.3462297}, abstractNote={An analysis of a magnetic field sensor based on a graphene spin capacitor is presented. The proposed device consists of graphene nanoribbons on top of an insulator material connected to a ferromagnetic source/drain. The time evolution of spin polarized electrons injected into the capacitor can be used for an accurate determination at room temperature of external magnetic fields. Assuming a spin relaxation time of 100 ns, magnetic fields on the order of ∼10 mOe may be detected at room temperature. The observational accuracy of this device depends on the density of magnetic defects and spin relaxation time that can be achieved.}, number={1}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2010}, month={Jul}, pages={013106} }
 @inproceedings{oyebola_hommerich_brown_trivedi_bluiett_zavada_2010, title={Growth and optical spectroscopy of Ho-doped KPb2Cl5 for infrared solid-state lasers}, volume={312}, number={8}, booktitle={Journal of Crystal Growth}, author={Oyebola, O. and Hommerich, U. and Brown, E. and Trivedi, S. B. and Bluiett, A. G. and Zavada, J. M.}, year={2010}, pages={1154–1156} }
 @article{li_barry_zavada_buongiorno nardelli_kim_2010, title={Surface polar phonon dominated electron transport in graphene}, volume={97}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3525606}, DOI={10.1063/1.3525606}, abstractNote={The effects of surface polar phonons on the electronic transport properties of monolayer graphene are studied by using a Monte Carlo simulation. Specifically, the low-field electron mobility and saturation velocity are examined for different substrates (SiC, SiO2, and HfO2) in comparison to the intrinsic case. While the results show that the low-field mobility can be substantially reduced by the introduction of surface polar phonon scattering, corresponding degradation of the saturation velocity is not observed for all three substrates at room temperature. It is also found that surface polar phonons can influence graphene’s electrical resistivity even at low temperature, leading potentially to inaccurate estimation of the acoustic phonon deformation potential constant.}, number={23}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Li, X. and Barry, E. A. and Zavada, J. M. and Buongiorno Nardelli, M. and Kim, K. W.}, year={2010}, month={Dec}, pages={232105} }
 @article{nepal_zavada_lee_steckl_sedhain_lin_jiang_2009, title={Deep ultraviolet photoluminescence of Tm-doped AlGaN alloys}, volume={94}, ISBN={0003-6951}, number={11}, journal={Applied Physics Letters}, author={Nepal, N. and Zavada, J. M. and Lee, D. S. and Steckl, A. J. and Sedhain, A. and Lin, J. Y. and Jiang, H. X.}, year={2009} }
 @article{wang_steckl_brown_hommerich_zavada_2009, title={Effect of Si codoping on Eu3+ luminescence in GaN}, volume={105}, number={4}, journal={Journal of Applied Physics}, author={Wang, R. and Steckl, A. J. and Brown, E. E. and Hommerich, U. and Zavada, J. M.}, year={2009} }
 @article{nepal_luen_zavada_bedair_frajtag_el-masry_2009, title={Electric field control of room temperature ferromagnetism in III-N dilute magnetic semiconductor films}, volume={94}, ISSN={["1077-3118"]}, DOI={10.1063/1.3110963}, abstractNote={We report on the electrical field control of ferromagnetism (FM) at room temperature in III-N dilute magnetic semiconductor (DMS) films. A GaMnN layer was grown on top of an n-GaN substrate and found to be almost always paramagnetic. However, when grown on a p-type GaN layer, a strong saturation magnetization (Ms) was observed. This FM in GaMnN can be controlled by depletion of the holes in the GaMnN/p-GaN/n-GaN multilayer structures. We have demonstrated the dependence of the FM on the thickness of the p-GaN in this heterostructure and on the applied bias to the GaN p-n junction. The Ms was measured by an alternating gradient magnetometer (AGM) and a strong correlation between the hole concentration near the GaMnN/p-GaN interface and the magnetic properties of the DMS was observed. At room temperature an anomalous Hall effect was measured for zero bias and an ordinary Hall effect for reverse bias in a fully depleted p-GaN layer. This is in close agreement with the AGM measurement results.}, number={13}, journal={APPLIED PHYSICS LETTERS}, author={Nepal, N. and Luen, M. Oliver and Zavada, J. M. and Bedair, S. M. and Frajtag, P. and El-Masry, N. A.}, year={2009}, month={Mar} }
 @article{dahal_ugolini_lin_jiang_zavada_2009, title={Erbium-doped GaN optical amplifiers operating at 1.54 mu m}, volume={95}, number={11}, journal={Applied Physics Letters}, author={Dahal, R. and Ugolini, C. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2009} }
 @article{nepal_zavada_dahal_ugolini_sedhain_lin_jiang_2009, title={Optical enhancement of room temperature ferromagnetism in Er-doped GaN epilayers}, volume={95}, number={2}, journal={Applied Physics Letters}, author={Nepal, N. and Zavada, J. M. and Dahal, R. and Ugolini, C. and Sedhain, A. and Lin, J. Y. and Jiang, H. X.}, year={2009} }
 @article{sedhain_ugolini_lin_jiang_zavada_2009, title={Photoluminescence properties of erbium doped InGaN epilayers}, volume={95}, number={4}, journal={Applied Physics Letters}, author={Sedhain, A. and Ugolini, C. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2009} }
 @inproceedings{brown_hommerich_yamada_yamane_zavada_2009, title={Spectroscopic characterization of Praseodymium doped Gallium Nitride powder prepared by a Na flux method}, volume={488}, number={2}, booktitle={Journal of Alloys and Compounds}, author={Brown, E. and Hommerich, U. and Yamada, T. and Yamane, H. and Zavada, J. M.}, year={2009}, pages={628–631} }
 @inproceedings{hommerich_hanley_brown_trivedi_zavada_2009, title={Spectroscopic studies of the 1.5 mu M (I-4(15/2) -> I-4(13/2)) emission from polycrystalline ceramic Er:YAG and Er:KPb2Cl5}, volume={488}, number={2}, booktitle={Journal of Alloys and Compounds}, author={Hommerich, U. and Hanley, C. and Brown, E. and Trivedi, S. B. and Zavada, J. M.}, year={2009}, pages={624–627} }
 @article{dahal_ugolini_lin_jiang_zavada_2008, title={Current-injected 1.54 mu m light emitting diodes based on erbium-doped GaN}, volume={93}, number={3}, journal={Applied Physics Letters}, author={Dahal, R. and Ugolini, C. and Lin, J. Y. and Jiang, H. X. and Zavada, J. M.}, year={2008} }
 @article{nepal_zavada_lee_steckl_2008, title={Dynamics of ultraviolet emissions in Tm-doped AIN using above band gap excitation}, volume={93}, number={6}, journal={Applied Physics Letters}, author={Nepal, N. and Zavada, J. M. and Lee, D. S. and Steckl, A. J.}, year={2008} }
 @article{semenov_zavada_kim_2008, title={Electrical Control of Exchange Bias Mediated by Graphene}, volume={101}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.101.147206}, DOI={10.1103/physrevlett.101.147206}, abstractNote={The role of graphene in mediating the exchange interaction is theoretically investigated when placed between two ferromagnetic dielectric materials. The calculation based on a tight-binding model illustrates that the magnetic interactions at the interfaces affect not only the graphene band structure but also the thermodynamic potential of the system, leading to an effective exchange bias between magnetic layers. The analysis indicates a strong dependence of the exchange bias on the properties of the mediating layer, revealing an efficient mechanism of electrical control even at room temperature.}, number={14}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2008}, month={Oct} }
 @article{enaya_semenov_zavada_kim_2008, title={Magnetic polaron for a spin memory application}, volume={104}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3000482}, DOI={10.1063/1.3000482}, abstractNote={A memory concept based on the interfacial exchange energy between itinerant holes in a quantum dot and magnetic ions in an adjacent magnetic insulator is theoretically investigated. A model based on the free energy analysis demonstrates the existence of bistable states through the mechanism of bound collective magnetic polaron, whose formation and dissolution can be controlled electrically via a gate bias pulse. The parameter window suitable for bistability is discussed along with the conditions that support maximum nonvolatility. The analysis is extended to the influence of material choices as well as different designs. The calculation results clearly indicate the possibility of room temperature operation, given the availability of insulating ferromagnetic or antiferromagnetic materials whose Curie temperature is above room temperature.}, number={8}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Enaya, H. and Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2008}, month={Oct}, pages={084306} }
 @article{semenov_zavada_kim_2008, title={Magnetoresistance in bilayer graphene via ferromagnet proximity effects}, volume={77}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.77.235415}, DOI={10.1103/physrevb.77.235415}, abstractNote={A drastic modification of electronic band structure is predicted in bilayer graphene when it is placed between two ferromagnetic insulators. Due to the exchange interaction with the proximate ferromagnet, the electronic energy dispersion in the graphene channel strongly depends on the magnetization orientation of two ferromagnetic layers, $\mathbf{M_{1}}$ and $\mathbf{M_{2}} $. While the parallel configuration $\mathbf{M_{1}}= \mathbf{M_{2}}$ leads to simple spin splitting of both conduction and valence bands, an energy gap is induced as soon as the angle $\theta$ between $\mathbf{M_{1}}$ and $% \mathbf{M_{2}}$ becomes non-zero with the maximum achieved at $\theta=\pi$ (i.e., antiparallel alignment). Consequently, bilayer graphene may exhibit a sizable magnetoresistive effect in the current-in-plane configuration. A rough estimate suggests the resistance changes on the order of tens of percent at room temperature. This effect is expected to become more pronounced as the temperatures decreases.}, number={23}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Semenov, Y. G. and Zavada, J. M. and Kim, K. W.}, year={2008}, month={Jun} }
 @article{enaya_semenov_kim_zavada_2008, title={Nonvolatile Memory via Spin Polaron Formation}, volume={7}, ISSN={1536-125X 1941-0085}, url={http://dx.doi.org/10.1109/TNANO.2008.926332}, DOI={10.1109/TNANO.2008.926332}, abstractNote={A nonvolatile memory is explored theoretically by utilizing the magnetic exchange interaction between localized holes and an adjacent ferromagnetic (FM) material. The active device consists of a buried semiconductor quantum dot (QD) and an FM insulating layer that share an interface. The hole population in the QD is controlled by particle transfer with a reservoir of itinerant holes over a permeable barrier. A theoretical model based on the free energy calculation demonstrates the existence of a bistable state through the mechanism of a collective spin polaron, whose formation and dissolution can be manipulated electrically via a gate bias pulse. The parameter space window suitable for bistability is examined along with the conditions that support maximum nonvolatility. The limitation of QD size scaling is analyzed in terms of the bit retention time.}, number={4}, journal={IEEE Transactions on Nanotechnology}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Enaya, H. and Semenov, Y.G. and Kim, K.W. and Zavada, J.M.}, year={2008}, month={Jul}, pages={480–483} }
 @article{nepal_mahros_bedair_el-masry_zavada_2007, title={Correlation between photoluminescence and magnetic properties of GaMnN films}, volume={91}, ISSN={["1077-3118"]}, DOI={10.1063/1.2823602}, abstractNote={GaMnN films grown by metal-organic chemical vapor deposition were studied by photoluminescence (PL) spectroscopy and hysteresis measurements. Depending on the growth conditions of these GaMnN films, hysteresis measurements along the easy axis of magnetization show a transformation from magnetic to nonmagnetic behavior. The PL spectra of both magnetic and nonmagnetic GaMnN films exhibited GaN band edge and deep-level impurity transitions at 3.4 and 1.3eV, respectively. The PL emission intensity of the 1.3eV emission peak is stronger considerably for magnetic GaMnN films and is believed to be due to the Mn3+ intraband transition.}, number={24}, journal={APPLIED PHYSICS LETTERS}, author={Nepal, N. and Mahros, Amr M. and Bedair, S. M. and El-Masry, N. A. and Zavada, J. M.}, year={2007}, month={Dec} }
 @article{enaya_semenov_kim_zavada_2007, title={Electrical Manipulation of Nonvolatile Spin Cell Based on Diluted Magnetic Semiconductor Quantum Dots}, volume={54}, ISSN={0018-9383}, url={http://dx.doi.org/10.1109/TED.2007.894377}, DOI={10.1109/TED.2007.894377}, abstractNote={In this paper, electrical manipulation of a memory cell based on a semiconductor nanostructure consisting of a diluted magnetic semiconductor (DMS) quantum dot (QD) and a reservoir of itinerant holes separated by an energy barrier is investigated theoretically. The operating principle takes advantage of the paramagnetic-ferromagnetic (PM-FM) phase transition mediated by the itinerant holes in the DMS QD that can lead to electrically controlled write/erase operations. Nonvolatility can be achieved when the structure is properly designed to reach a thermodynamic equilibrium at both the PM and FM configurations (i.e., bistability). Assuming a parabolic confining potential in the QD, the performance characteristics of the proposed nanostructure are analyzed including the scalability and the lifetime. An advantage of this memory concept is the extremely small dissipative energy for write/erase functions due to the open-circuit nature of the process. A readout scheme enabling electrical detection, with the repetition rate up to the 10-100-MHz range, is also explored by utilizing only two contacts. Finally, a potential application of the proposed memory cell is discussed as a rudimentary device for logic AND and OR operations}, number={5}, journal={IEEE Transactions on Electron Devices}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Enaya, Hani and Semenov, Yuriy G. and Kim, K. W. and Zavada, John M.}, year={2007}, month={May}, pages={1032–1039} }
 @article{xiao_kim_zavada_2007, title={Imaging properties of a metallic photonic crystal}, volume={101}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2737771}, DOI={10.1063/1.2737771}, abstractNote={Imaging effects in metallic photonic crystals (PCs) are examined theoretically based on the finite difference time-domain method. The analysis shows that, in metallic PC-based systems, far-field images do form at the opposite side of the PC “lens” and more importantly, follow the rule of geometric optics with respect to the changes in the source position as a direct proof of negative refraction. However, the comparison of ideal left-handed media with a metallic PC suggests that the focusing effect in the PC based system is different from that of the ideal left-handed media in many aspects, due to the inhomogeneous nature of the PC. Particularly, strong dependence on the individual geometry as well as the frequency in the PC-based system renders the effective index sensitive to the variations and potentially limits its application as a superlens.}, number={11}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Xiao, D. and Kim, K. W. and Zavada, J. M.}, year={2007}, month={Jun}, pages={113105} }
 @article{mahros_luen_emara_bedair_berkman_el-masry_zavada_2007, title={Magnetic and magnetotransport properties of (AlGaN/GaN): Mg/(GaMnN) heterostructures at room temperature}, volume={90}, ISSN={["0003-6951"]}, DOI={10.1063/1.2749717}, abstractNote={Dilute magnetic semiconductor films (GaMnN) are highly resistive, making transport measurements difficult to achieve. However, when GaMnN films are sandwiched between p-type doped (AlGaN∕GaN) strained-layer superlattices, holes from the superlattice interact with the Mn3+∕2+ ions and transport measurements were realized. The authors have found also that the ferromagnetic properties of GaMnN critically depend on the level of p-type doping in the superlattice. They report anomalous Hall effect measurements in this (AlGaN∕GaN):Mg∕(GaMnN) multilayered structure. The current results also demonstrate the role of carriers, especially holes, in mediating the ferromagnetic properties of GaMnN dilute magnetic semiconductor films.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Mahros, Amr M. and Luen, M. O. and Emara, A. and Bedair, S. M. and Berkman, E. A. and El-Masry, N. A. and Zavada, J. M.}, year={2007}, month={Jun} }
 @article{semenov_kim_zavada_2007, title={Spin field effect transistor with a graphene channel}, volume={91}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2798596}, DOI={10.1063/1.2798596}, abstractNote={A spin field effect transistor (FET) is proposed by utilizing a graphene layer as the channel. Similar to the conventional spin FETs, the device involves spin injection and spin detection by ferromagnetic source and drain. Due to the negligible spin-orbit coupling in the carbon based materials, spin manipulation in the channel is achieved via electrical control of the electron exchange interaction with a ferromagnetic gate dielectric. Numerical estimates indicate the feasibility of the concept if the bias can induce a change in the exchange interaction energy of the order of meV. When nanoribbons are used for a finite channel width, those with armchair-type edges can maintain the device stability against the thermal dispersion.}, number={15}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Semenov, Y. G. and Kim, K. W. and Zavada, J. M.}, year={2007}, month={Oct}, pages={153105} }
 @article{xiao_kim_lazzi_zavada_2006, title={Tunable waveguiding in electrically programmable VO2-based photonic crystals}, volume={99}, ISSN={["1089-7550"]}, DOI={10.1063/1.2200873}, abstractNote={The feasibility of electrically programmable waveguiding in a photonic crystal (PC) is explored based on the metal-insulator transition of vanadium dioxide (VO2). Unlike the ordinary PCs, wave propagation in the desired structure may be switched on/off or redirected by applying an electrical bias on the selective electrodes by taking advantage of the electrically induced VO2 phase transition and subsequent modulation of dielectric properties. The characteristics of the two-dimensional VO2-based PCs with line defects are analyzed using the iterative plane wave and finite difference time domain methods. Particularly, the influence of the Drude relaxation on waveguiding is examined as the high rate typical for metallic VO2 can lead to the signal loss. An optimized structure is proposed to minimize the loss and simplify the fabrication.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Xiao, D. and Kim, K. W. and Lazzi, G. and Zavada, J. M.}, year={2006}, month={Jun} }
 @inproceedings{emara_berkman_zavada_el-masry_bedair, title={Strain relaxation in InxGa1-xN/GaN quantum well structures}, volume={8}, number={7-8}, booktitle={Physica status solidi c: current topics in solid state physics, vol 8, no 7-8}, author={Emara, A. M. and Berkman, E. A. and Zavada, J. and El-Masry, N. A. and Bedair, S. M.} }