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Kim M, Yoon M, Yang P, Kim T, Uhm J, Kim J, Pak H, Lee M, Joung B. P6422Sex-based disparities in incidence, treatment, and outcomes of sudden cardiac arrest. Eur Heart J 2017. [DOI: 10.1093/eurheartj/ehx493.p6422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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52
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Chen T, Chen WL, Foley BJ, Lee J, Ruff JPC, Ko JYP, Brown CM, Harriger LW, Zhang D, Park C, Yoon M, Chang YM, Choi JJ, Lee SH. Origin of long lifetime of band-edge charge carriers in organic-inorganic lead iodide perovskites. Proc Natl Acad Sci U S A 2017; 114:7519-7524. [PMID: 28673975 PMCID: PMC5530684 DOI: 10.1073/pnas.1704421114] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long carrier lifetime is what makes hybrid organic-inorganic perovskites high-performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photoexcited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance.
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Nam T, Jeong J, Ahn K, Kim Y, Yoon M, Song J, Ahn S, Chung W. EP-1264: Metabolic response and change in CEA level in rectal cancer patients treated with neoadjuvant CRT. Radiother Oncol 2017. [DOI: 10.1016/s0167-8140(17)31699-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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54
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Kronlage M, Bäumer P, Schwarz D, Schwehr V, Godel T, Heiland S, Pitarokoili K, Gold R, Bendszus M, Yoon M. Evaluation quantitativer MRT-Biomarker bei chronisch entzündlicher demyelinisierender Polyneuropathie (CIDP). ROFO-FORTSCHR RONTG 2017. [DOI: 10.1055/s-0037-1600393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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55
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Park J, Park C, Yoon M, Li AP. Surface Magnetism of Cobalt Nanoislands Controlled by Atomic Hydrogen. NANO LETTERS 2017; 17:292-298. [PMID: 28073266 DOI: 10.1021/acs.nanolett.6b04062] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Controlling the spin states of the surface and interface is key to spintronic applications of magnetic materials. Here, we report the evolution of surface magnetism of Co nanoislands on Cu(111) upon hydrogen adsorption and desorption with the hope of realizing reversible control of spin-dependent tunneling. Spin-polarized scanning tunneling microscopy reveals three types of hydrogen-induced surface superstructures, 1H-(2 × 2), 2H-(2 × 2), and 6H-(3 × 3), with increasing H coverage. The prominent magnetic surface states of Co, while being preserved at low H coverage, become suppressed as the H coverage level increases, which can then be recovered by H desorption. First-principles calculations reveal the origin of the observed magnetic surface states by capturing the asymmetry between the spin-polarized surface states and identify the role of hydrogen in controlling the magnetic states. Our study offers new insights into the chemical control of magnetism in low-dimensional systems.
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Yan Z, Chen L, Yoon M, Kumar S. The Role of Interfacial Electronic Properties on Phonon Transport in Two-Dimensional MoS 2 on Metal Substrates. ACS APPLIED MATERIALS & INTERFACES 2016; 8:33299-33306. [PMID: 27934181 DOI: 10.1021/acsami.6b10608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigate the role of interfacial electronic properties on the phonon transport in two-dimensional MoS2 adsorbed on metal substrates (Au and Sc) using first-principles density functional theory and the atomistic Green's function method. Our study reveals that the different degree of orbital hybridization and electronic charge distribution between MoS2 and metal substrates play a significant role in determining the overall phonon-phonon coupling and phonon transmission. The charge transfer caused by the adsorption of MoS2 on Sc substrate can significantly weaken the Mo-S bond strength and change the phonon properties of MoS2, which result in a significant change in thermal boundary conductance (TBC) from one lattice-stacking configuration to another for same metallic substrate. In a lattice-stacking configuration of MoS2/Sc, weakening of the Mo-S bond strength due to charge redistribution results in decrease in the force constant between Mo and S atoms and substantial redistribution of phonon density of states to low-frequency region which affects overall phonon transmission leading to 60% decrease in TBC compared to another configuration of MoS2/Sc. Strong chemical coupling between MoS2 and the Sc substrate leads to a significantly (∼19 times) higher TBC than that of the weakly bound MoS2/Au system. Our findings demonstrate the inherent connection among the interfacial electronic structure, the phonon distribution, and TBC, which helps us understand the mechanism of phonon transport at the MoS2/metal interfaces. The results provide insights for the future design of MoS2-based electronics and a way of enhancing heat dissipation at the interfaces of MoS2-based nanoelectronic devices.
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Ming W, Yoon M, Du MH, Lee K, Kim SW. First-Principles Prediction of Thermodynamically Stable Two-Dimensional Electrides. J Am Chem Soc 2016; 138:15336-15344. [DOI: 10.1021/jacs.6b05586] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chen T, Foley BJ, Park C, Brown CM, Harriger LW, Lee J, Ruff J, Yoon M, Choi JJ, Lee SH. Entropy-driven structural transition and kinetic trapping in formamidinium lead iodide perovskite. SCIENCE ADVANCES 2016; 2:e1601650. [PMID: 27819055 PMCID: PMC5088641 DOI: 10.1126/sciadv.1601650] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/22/2016] [Indexed: 05/19/2023]
Abstract
A challenge of hybrid perovskite solar cells is device instability, which calls for an understanding of the perovskite structural stability and phase transitions. Using neutron diffraction and first-principles calculations on formamidinium lead iodide (FAPbI3), we show that the entropy contribution to the Gibbs free energy caused by isotropic rotations of the FA+ cation plays a crucial role in the cubic-to-hexagonal structural phase transition. Furthermore, we observe that the cubic-to-hexagonal phase transition exhibits a large thermal hysteresis. Our first-principles calculations confirm the existence of a potential barrier between the cubic and hexagonal structures, which provides an explanation for the observed thermal hysteresis. By exploiting the potential barrier, we demonstrate kinetic trapping of the cubic phase, desirable for solar cells, even at 8.2 K by thermal quenching.
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Mahalingam D, Patel M, Sachdev J, Hart L, Halama N, Ramanathan R, Sarantopoulos J, Liu X, Yazji S, Jäger D, Yoon M, Manzur G, Adib D, Kerschbaumer R, Tsimberidou A. Anti-oxidized macrophage migration inhibitory factor (oxMIF) antibody imalumab (BAX69) in advanced solid tumors: Final results of first-in-human phase 1 study. Ann Oncol 2016. [DOI: 10.1093/annonc/mdw368.08] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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60
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Shin D, Son J, Kim M, Yoon M, Lee S, Lim Y, Park J, Lee S, Park S. Development of Real-Time Monitoring System for Proton Pencil Beam Spot Position Using Fiber-Optic Cerenkov Radiation Sensor Array. Int J Radiat Oncol Biol Phys 2016. [DOI: 10.1016/j.ijrobp.2016.06.2157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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61
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Yoon M, Chen C. Clinical and surgical implications of EGFR mutations in non-small cell
lung cancer. Ann Glob Health 2016. [DOI: 10.1016/j.aogh.2016.04.294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Mahjouri-Samani M, Liang L, Oyedele A, Kim YS, Tian M, Cross N, Wang K, Lin MW, Boulesbaa A, Rouleau CM, Puretzky AA, Xiao K, Yoon M, Eres G, Duscher G, Sumpter BG, Geohegan DB. Tailoring Vacancies Far Beyond Intrinsic Levels Changes the Carrier Type and Optical Response in Monolayer MoSe2-x Crystals. NANO LETTERS 2016; 16:5213-5220. [PMID: 27416103 DOI: 10.1021/acs.nanolett.6b02263] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Defect engineering has been a critical step in controlling the transport characteristics of electronic devices, and the ability to create, tune, and annihilate defects is essential to enable the range of next-generation devices. Whereas defect formation has been well-demonstrated in three-dimensional semiconductors, similar exploration of the heterogeneity in atomically thin two-dimensional semiconductors and the link between their atomic structures, defects, and properties has not yet been extensively studied. Here, we demonstrate the growth of MoSe2-x single crystals with selenium (Se) vacancies far beyond intrinsic levels, up to ∼20%, that exhibit a remarkable transition in electrical transport properties from n- to p-type character with increasing Se vacancy concentration. A new defect-activated phonon band at ∼250 cm(-1) appears, and the A1g Raman characteristic mode at 240 cm(-1) softens toward ∼230 cm(-1) which serves as a fingerprint of vacancy concentration in the crystals. We show that post-selenization using pulsed laser evaporated Se atoms can repair Se-vacant sites to nearly recover the properties of the pristine crystals. First-principles calculations reveal the underlying mechanisms for the corresponding vacancy-induced electrical and optical transitions.
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Wang K, Huang B, Tian M, Ceballos F, Lin MW, Mahjouri-Samani M, Boulesbaa A, Puretzky AA, Rouleau CM, Yoon M, Zhao H, Xiao K, Duscher G, Geohegan DB. Interlayer Coupling in Twisted WSe2/WS2 Bilayer Heterostructures Revealed by Optical Spectroscopy. ACS NANO 2016; 10:6612-22. [PMID: 27309275 DOI: 10.1021/acsnano.6b01486] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
van der Waals (vdW) heterostructures are promising building blocks for future ultrathin electronics. Fabricating vdW heterostructures by stamping monolayers at arbitrary angles provides an additional range of flexibility to tailor the resulting properties than could be expected by direct growth. Here, we report fabrication and comprehensive characterizations of WSe2/WS2 bilayer heterojunctions with various twist angles that were synthesized by artificially stacking monolayers of WS2 and WSe2 grown by chemical vapor deposition. After annealing the WSe2/WS2 bilayers, Raman spectroscopy reveals interlayer coupling with the appearance of a mode at 309.4 cm(-1) that is sensitive to the number of WSe2 layers. This interlayer coupling is associated with substantial quenching of the intralayer photoluminescence. In addition, microabsorption spectroscopy of WSe2/WS2 bilayers revealed spectral broadening and shifts as well as a net ∼10% enhancement in integrated absorption strength across the visible spectrum with respect to the sum of the individual monolayer spectra. The observed broadening of the WSe2 A exciton absorption band in the bilayers suggests fast charge separation between the layers, which was supported by direct femtosecond pump-probe spectroscopy. Density functional calculations of the band structures of the bilayers at different twist angles and interlayer distances found robust type II heterojunctions at all twist angles, and predicted variations in band gap for particular atomistic arrangements. Although interlayer excitons were indicated using femtosecond pump-probe spectroscopy, photoluminescence and absorption spectroscopies did not show any evidence of them, suggesting that the interlayer exciton transition is very weak. However, the interlayer coupling for the WSe2/WS2 bilayer heterojunctions indicated by substantial PL quenching, enhanced absorption, and rapid charge transfer was found to be insensitive to the relative twist angle, indicating that stamping provides a robust approach to realize reliable optoelectronics.
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Saxena K, Lalezari S, Oldenburg J, Tseneklidou-Stoeter D, Beckmann H, Yoon M, Maas Enriquez M. Efficacy and safety of BAY 81-8973, a full-length recombinant factor VIII: results from the LEOPOLD I trial. Haemophilia 2016; 22:706-12. [PMID: 27339736 DOI: 10.1111/hae.12952] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2016] [Indexed: 11/28/2022]
Abstract
INTRODUCTION BAY 81-8973 (Kovaltry(®) ) is a full-length, unmodified recombinant human factor VIII (FVIII) with the same amino acid sequence as sucrose-formulated recombinant FVIII and is produced using additional advanced manufacturing technologies. AIM To demonstrate efficacy and safety of BAY 81-8973 for treatment of bleeds and as prophylaxis based on two different potency assignments. METHODS In LEOPOLD I (ClinicalTrials.gov identifier, NCT01029340), males aged 12-65 years with severe haemophilia A and ≥150 exposure days received BAY 81-8973 20-50 IU kg(-1) two or three times per week for 12 months. Potency was based on chromogenic substrate assay per European Pharmacopoeia and label adjusted to mimic one-stage assay potency. Patients were randomized for potency sequence and crossed over potency groups after 6 months, followed by an optional 12-month extension. Primary efficacy endpoint was annualized bleeding rate (ABR). Patients also received BAY 81-8973 during major surgeries. RESULTS Sixty-two patients received BAY 81-8973 prophylaxis and were included in the analysis. Median ABR was 1.0 (quartile 1, 0; quartile 3, 5.1) without clinically relevant differences between potency periods. Median ABR was similar for twice-weekly vs. three times-weekly dosing (1.0 vs. 2.0). Haemostasis was maintained during 12 major surgeries. Treatment-related adverse event (AE) incidence was ≤7% overall; no patient developed inhibitors. One patient with risk factors for cardiovascular disease developed a myocardial infarction. CONCLUSIONS BAY 81-8973 was efficacious in preventing and treating bleeding episodes, irrespective of the potency assignment method, with few treatment-related AEs. Caution should be used when treating older patients with cardiovascular risk factors.
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Koo J, Yoon M, Chung W, Chung M, Kim D. SU-F-T-244: Radiotherapy Risk Estimation Based On Expert Group Survey. Med Phys 2016. [DOI: 10.1118/1.4956384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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66
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Moon S, Yoon M, Chung W, Chung M, Kim D. SU-F-T-17: A Feasibility Study for the Transit Dosimetry with a Glass Dosimeter in Brachytherapy. Med Phys 2016. [DOI: 10.1118/1.4956151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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67
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Son J, Kim M, Yoon M, Shin D. SU-F-T-174: Patient-Specific Point Dose Measurement Using Fiber Optic Radiation Sensor Using Cerenkov Radiation for Proton Therapeutic Beam. Med Phys 2016. [DOI: 10.1118/1.4956311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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68
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Kim D, Yoon M, Chung W, Chung M. SU-F-T-329: Characteristic Study of a Rado-Photoluminescenct Glass Dosimeter with Accumulated Dose. Med Phys 2016. [DOI: 10.1118/1.4956514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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69
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Moon S, Yoon M, Chung M, Chung W, Kim D. PO-0897: Comparison of hippocampus sparing extent according to the tilt of a patient head during WBRT. Radiother Oncol 2016. [DOI: 10.1016/s0167-8140(16)32147-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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70
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Lee B, Kim H, Sim J, Ahn S, Kim J, Han Y, Huh S, Kim D, Yoon M. EP-1987: Feasibility study of patient specific QA system for HDR brachytherapy in cervical cancer. Radiother Oncol 2016. [DOI: 10.1016/s0167-8140(16)33238-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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71
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Jeong S, Yoon M, Kim D, Chung W, Chung M. EP-1557: Development of dose calculation algorithm in homogeneous phantom through the transit dose. Radiother Oncol 2016. [DOI: 10.1016/s0167-8140(16)32807-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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72
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Yan Z, Chen L, Yoon M, Kumar S. Phonon transport at the interfaces of vertically stacked graphene and hexagonal boron nitride heterostructures. NANOSCALE 2016; 8:4037-4046. [PMID: 26817419 DOI: 10.1039/c5nr06818e] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Hexagonal boron nitride (h-BN) is a promising substrate for graphene based nano-electronic devices. We investigate the ballistic phonon transport at the interface of vertically stacked graphene and h-BN heterostructures using first principles density functional theory and atomistic Green's function simulations considering the influence of lattice stacking. We compute the frequency and wave-vector dependent transmission function and observe distinct stacking-dependent phonon transmission features for the h-BN/graphene/h-BN sandwiched systems. We find that the in-plane acoustic modes have the dominant contributions to the phonon transmission and thermal boundary conductance (TBC) for the interfaces with the carbon atom located directly on top of the boron atom (C-B matched) because of low interfacial spacing. The low interfacial spacing is a consequence of the differences in the effective atomic volume of N and B and the difference in the local electron density around N and B. For the structures with the carbon atom directly on top of the nitrogen atom (C-N matched), the spatial distance increases and the contribution of in-plane modes to the TBC decreases leading to higher contributions by out-of-plane acoustic modes. We find that the C-B matched interfaces have stronger phonon-phonon coupling than the C-N matched interfaces, which results in significantly higher TBC (more than 50%) in the C-B matched interface. The findings in this study will provide insights to understand the mechanism of phonon transport at h-BN/graphene/h-BN interfaces, to better explain the experimental observations and to engineer these interfaces to enhance heat dissipation in graphene based electronic devices.
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Ming W, Wang ZF, Zhou M, Yoon M, Liu F. Formation of Ideal Rashba States on Layered Semiconductor Surfaces Steered by Strain Engineering. NANO LETTERS 2016; 16:404-409. [PMID: 26651374 DOI: 10.1021/acs.nanolett.5b04005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Spin splitting of Rashba states in two-dimensional electron system provides a promising mechanism of spin manipulation for spintronics applications. However, Rashba states realized experimentally to date are often outnumbered by spin-degenerated substrate states at the same energy range, hindering their practical applications. Here, by density functional theory calculation, we show that Au one monolayer film deposition on a layered semiconductor surface β-InSe(0001) can possess "ideal" Rashba states with large spin splitting, which are completely situated inside the large band gap of the substrate. The position of the Rashba bands can be tuned over a wide range with respect to the substrate band edges by experimentally accessible strain. Furthermore, our nonequilibrium Green's function transport calculation shows that this system may give rise to the long-sought strong current modulation when made into a device of Datta-Das transistor. Similar systems may be identified with other metal ultrathin films and layered semiconductor substrates to realize ideal Rashba states.
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Tian M, Mahjouri-Samani M, Eres G, Sachan R, Yoon M, Chisholm MF, Wang K, Puretzky AA, Rouleau CM, Geohegan DB, Duscher G. Structure and Formation Mechanism of Black TiO2 Nanoparticles. ACS NANO 2015; 9:10482-8. [PMID: 26393371 DOI: 10.1021/acsnano.5b04712] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The remarkable properties of black TiO2 are due to its disordered surface shell surrounding a crystalline core. However, the chemical composition and the atomic and electronic structure of the disordered shell and its relationship to the core remain poorly understood. Using advanced transmission electron microscopy methods, we show that the outermost layer of black TiO2 nanoparticles consists of a disordered Ti2O3 shell. The measurements show a transition region that connects the disordered Ti2O3 shell to the perfect rutile core consisting first of four to five monolayers of defective rutile, containing clearly visible Ti interstitial atoms, followed by an ordered reconstruction layer of Ti interstitial atoms. Our data suggest that this reconstructed layer presents a template on which the disordered Ti2O3 layers form by interstitial diffusion of Ti ions. In contrast to recent reports that attribute TiO2 band-gap narrowing to the synergistic action of oxygen vacancies and surface disorder of nonspecific origin, our results point to Ti2O3, which is a narrow-band-gap semiconductor. As a stoichiometric compound of the lower oxidation state Ti(3+) it is expected to be a more robust atomic structure than oxygen-deficient TiO2 for preserving and stabilizing Ti(3+) surface species that are the key to the enhanced photocatalytic activity of black TiO2.
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Huang B, Yoon M, Sumpter BG, Wei SH, Liu F. Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in Transition-Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2015; 115:126806. [PMID: 26431007 DOI: 10.1103/physrevlett.115.126806] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Indexed: 06/05/2023]
Abstract
Developing practical approaches to effectively reduce the amount of deep defect levels in semiconductors is critical for their use in electronic and optoelectronic devices, but this still remains a very challenging task. In this Letter, we propose that specific alloying can provide an effective means to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties. Specifically, we demonstrate that for transition-metal dichalcogenides, such as MoSe_{2} and WSe_{2}, where anion vacancies are the most abundant defects that can induce deep levels, the deep levels can be effectively suppressed in Mo_{1-x}W_{x}Se_{2} alloys at low W concentrations. This surprising phenomenon is associated with the fact that the band edge energies can be substantially tuned by the global alloy concentration, whereas the defect level is controlled locally by the preferred locations of Se vacancies around W atoms. Our findings illustrate a concept of alloy engineering and provide a promising approach to control the defect properties of semiconductors.
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