@article{kong_jin_kim_2014, title={Hot-Electron Transistors for Terahertz Operation Based on Two-Dimensional Crystal Heterostructures}, volume={2}, ISSN={2331-7019}, url={http://dx.doi.org/10.1103/PhysRevApplied.2.054006}, DOI={10.1103/physrevapplied.2.054006}, abstractNote={The authors explore the feasibility of ultrahigh-frequency devices by utilizing the unique features of two-dimensional (2D) crystals. These materials range from gapless semimetals to wide-band-gap insulators, and a number of them ($e.g.$ hexagonal boron nitride and transition metal dichalcogenides) can be integrated seamlessly with graphene, without causing defects, interfacial scattering centers, or degradation of properties. A detailed theoretical analysis indicates the potential for 2D crystal heterostructures that could process information at rates well over a terahertz--several times the current technological limit.}, number={5}, journal={Physical Review Applied}, publisher={American Physical Society (APS)}, author={Kong, Byoung Don and Jin, Zhenghe and Kim, Ki Wook}, year={2014}, month={Nov} }
 @article{mao_kong_kim_2014, title={Thermal transport properties of metal/MoS2 interfaces from first principles}, volume={116}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4890347}, DOI={10.1063/1.4890347}, abstractNote={Thermal transport properties at the metal/MoS2 interfaces are analyzed by using an atomistic phonon transport model based on the Landauer formalism and first-principles calculations. The considered structures include chemisorbed Sc(0001)/MoS2 and Ru(0001)/MoS2, physisorbed Au(111)/MoS2, as well as Pd(111)/MoS2 with intermediate characteristics. Calculated results illustrate a distinctive dependence of thermal transfer on the details of interfacial microstructures. More specifically, the chemisorbed case with a stronger bonding exhibits a generally smaller interfacial thermal resistance than the physisorbed. Comparison between metal/MoS2 and metal/graphene systems suggests that metal/MoS2 is significantly more resistive. Further examination of lattice dynamics identifies the presence of multiple distinct atomic planes and bonding patterns at the interface as the key origins of the observed large thermal resistance.}, number={3}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Mao, Rui and Kong, Byoung Don and Kim, Ki Wook}, year={2014}, month={Jul}, pages={034302} }
 @article{mao_kong_gong_xu_jayasekera_cho_kim_2013, title={First-principles calculation of thermal transport in metal/graphene systems}, volume={87}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.87.165410}, DOI={10.1103/physrevb.87.165410}, abstractNote={Thermal properties in the metal/graphene (Gr) systems are analyzed by using an atomistic phonon transport model based on Landauer formalism and first-principles calculations. The specific structures under investigation include chemisorbed Ni(111)/Gr, physisorbed Cu(111)/Gr and Au(111)/Gr, as well as Pd(111)/Gr with intermediate characteristics. Calculated results illustrate a strong dependence of thermal transfer on the details of interfacial microstructures. In particular, it is shown that the chemisorbed case provides a generally smaller interfacial thermal resistance than the physisorbed one due to the stronger bonding. However, our calculation also indicates that the weakly chemisorbed interface of Pd/Gr may be an exception, with the largest thermal resistance among the considered. Further examination of the electrostatic potential and interatomic force constants reveals that the mixed bonding force between the Pd and C atoms results in incomplete hybridization of Pd and graphene orbital states at the junction, leading effectively to two phonon interfaces and a larger than expected thermal resistance. Comparison with available experimental data shows good agreement. The result clearly suggests the feasibility of phonon engineering for thermal property optimization at the interface.}, number={16}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Mao, R. and Kong, B. D. and Gong, C. and Xu, S. and Jayasekera, T. and Cho, K. and Kim, K. W.}, year={2013}, month={Apr} }
 @article{kong_trew_kim_2013, title={Toward stimulated interaction of surface phonon polaritons}, volume={114}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4851717}, DOI={10.1063/1.4851717}, abstractNote={Thermal emission spectra mediated by surface phonon polariton are examined by using a theoretical model that accounts for generation processes. Specifically, the acoustic phonon fusion mechanism is introduced to remedy theoretical deficiencies of the near thermal equilibrium treatments. The model clarifies the thermal excitation mechanism of surface phonon polaritons and the energy transfer path under non-zero energy flow. When applied to GaAs and SiC semi-infinite surfaces, the nonequilibrium model predicts that the temperature dependence of the quasi-monochromatic peak can exhibit distinctly different characteristics of either sharp increase or slow saturation depending on the materials, which is in direct contrast with the estimate made by the near-equilibrium model. The proposed theoretical tool can accurately analyze the nonequilibrium steady states, potentially paving a pathway to demonstrate stimulated interaction/emission of thermally excited surface phonon polaritons.}, number={23}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Kong, B. D. and Trew, R. J. and Kim, K. W.}, year={2013}, month={Dec}, pages={233508} }
 @article{mao_kong_kim_jayasekera_calzolari_buongiorno nardelli_2012, title={Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions}, volume={101}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4752437}, DOI={10.1063/1.4752437}, abstractNote={Using calculations from first principles and the Landauer approach for phonon transport, we study the Kapitza resistance in selected multilayer graphene/dielectric heterojunctions (hexagonal BN and wurtzite SiC) and demonstrate (i) the resistance variability (∼50−700×10−10 m2K/W) induced by vertical coupling, dimensionality, and atomistic structure of the system and (ii) the ability of understanding the intensity of the thermal transmittance in terms of the phonon distribution at the interface. Our results pave the way to the fundamental understanding of active phonon engineering by microscopic geometry design.}, number={11}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Mao, R. and Kong, B. D. and Kim, K. W. and Jayasekera, T. and Calzolari, A. and Buongiorno Nardelli, M.}, year={2012}, month={Sep}, pages={113111} }
 @article{kong_zeng_gaskill_wang_kim_2012, title={Two dimensional crystal tunneling devices for THz operation}, volume={101}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4773514}, DOI={10.1063/1.4773514}, abstractNote={Two dimensional (2D) crystal heterostructures are shown to possess a unique opportunity for novel THz nonlinear devices. In contrast to the oxide tunneling barrier, the uniformity of 2D insulators in the thickness control provides an ideal condition for tunneling barriers in the atomic scale. Numerical calculations based on a first principles method clearly indicate the feasibility of diode operation with barriers as thin as two monolayers of hexagonal boron nitride or molybdenum disulfide when placed between graphene-metal asymmetric electrodes. Further analysis predicts the cut-off frequencies of the proposed device over 10 THz while maintaining strong nonlinearity for zero-bias rectification. Application of the tunneling structure to hot electron transistors is also investigated, illustrating the THz operation with superior power performance. The proposed concept provides an excellent opportunity for realizing active nonlinear devices in the frequency range inaccessible thus far.}, number={26}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Kong, B. D. and Zeng, C. and Gaskill, D. K. and Wang, K. L. and Kim, K. W.}, year={2012}, month={Dec}, pages={263112} }
 @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{kong_semenov_krowne_kim_2011, title={Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier}, volume={98}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3600330}, DOI={10.1063/1.3600330}, abstractNote={Tunneling surface current through a thin ferromagnetic barrier in a three-dimensional topological insulator is shown to possess an extraordinary response to the orientation of barrier magnetization. In contrast to conventional magnetoresistance devices that are sensitive to the relative alignment of two magnetic layers, a drastic change in the transmission current is achieved by a single layer when its magnetization rotates by 90 degrees. Numerical estimations predict a giant magnetoresistance as large as 800 % at room temperature and the proximate exchange interaction of 40 meV in the barrier. When coupled with electrical control of magnetization direction, this phenomenon may be used to enhance the gating function with potentially sharp turn-on/off for low power applications.}, number={24}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Kong, B. D. and Semenov, Y. G. and Krowne, C. M. and Kim, K. W.}, year={2011}, month={Jun}, pages={243112} }
 @article{jayasekera_kong_kim_buongiorno nardelli_2010, title={Band Engineering and Magnetic Doping of Epitaxial Graphene on SiC (0001)}, volume={104}, ISSN={0031-9007 1079-7114}, url={http://dx.doi.org/10.1103/PhysRevLett.104.146801}, DOI={10.1103/physrevlett.104.146801}, abstractNote={Using calculations from first principles we show how specific interface modifications can lead to a fine-tuning of the doping and band alignment in epitaxial graphene on SiC. Upon different choices of dopants, we demonstrate that one can achieve a variation of the valence band offset between the graphene Dirac point and the valence band edge of SiC up to 1.5 eV. Finally, via appropriate magnetic doping one can induce a half-metallic behavior in the first graphene monolayer. These results clearly establish the potential for graphene utilization in innovative electronic and spintronic devices.}, number={14}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Jayasekera, Thushari and Kong, B. D. and Kim, K. W. and Buongiorno Nardelli, M.}, year={2010}, month={Apr} }
 @article{kong_sokolov_kim_trew_2010, title={Quasi-Coherent Thermal Emission in the Terahertz by Doped Semiconductors}, volume={10}, ISSN={1530-437X 1558-1748}, url={http://dx.doi.org/10.1109/JSEN.2009.2038133}, DOI={10.1109/jsen.2009.2038133}, abstractNote={We investigate thermal emission characteristics mediated by surface plasmon polaritons (SPPs) resonantly excited at a semiconductor-vacuum interface. The characteristic plasma and SPP resonant frequencies in the interval from 0.3 to 10 THz can be controlled with conventional doping densities. All of the cases under consideration (n-doped GaAs, GaN, and Si) demonstrate the spectral energy density in the near field that is several orders of magnitude larger than the blackbody radiation. The strongly resonant SPPs are also shown to enhance drastically the radiative heat transfer between two semi-infinite surfaces separated by nanometric distances. The possibility of extending spatially coherent emission through 1-D binary grating is examined based on a rigorous coupled-wave analysis. Our calculation results clearly indicate that <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -doped semiconductors with properly designed surface grating can achieve efficient directional thermal emission in the THz frequency range for potential use in a number of applications including sensing.}, number={3}, journal={IEEE Sensors Journal}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kong, B. D. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2010}, month={Mar}, pages={443–450} }
 @article{kong_paul_nardelli_kim_2009, title={First-principles analysis of lattice thermal conductivity in monolayer and bilayer graphene}, volume={80}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.80.033406}, DOI={10.1103/physrevb.80.033406}, abstractNote={Article on first-principles analysis of lattice thermal conductivity in monolayer and bilayer graphene.}, number={3}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Kong, B. D. and Paul, S. and Nardelli, M. Buongiorno and Kim, K. W.}, year={2009}, month={Jul} }
 @article{kong_sokolov_kim_trew_2008, title={Terahertz emission mediated by surface plasmon polaritons in doped semiconductors with surface grating}, volume={103}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2840063}, DOI={10.1063/1.2840063}, abstractNote={Doped semiconductors with one-dimensional surface gratings are studied theoretically for application to terahertz emission. The presence of free carriers supports thermally excited surface plasmon polaritons at the semiconductor-vacuum interface whose resonance frequency can be controlled by doping. The calculation based on the fluctuational electrodynamics shows that the near-field spectral energy density of this surface excitation can be many orders of magnitude larger than those in the blackbody radiation. At the same time, a rigorous coupled-wave analysis with a properly designed surface microstructure clearly indicates narrow angular lobes in the directional emissivity at the targeted frequencies, illustrating strong coupling between surface plasmon polaritons and propagating waves. Thus, doped semiconductors with engineered radiation may provide an efficient terahertz source with spatial and spectral control.}, number={5}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Kong, B. D. and Sokolov, V. N. and Kim, K. W. and Trew, R. J.}, year={2008}, month={Mar}, pages={056101} }