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High-mobility material research for thin-film transistor with amorphous thallium–zinc–tin oxide semiconductor
摘要： The applicability of thallium–zinc–tin oxide (TlZnSnO) as a channel material for a thin-?lm transistor (TFT) was investigated by ?rst-principles simulation and cosputtering experiment with XZnSnO (X = Al, Ga or In). The electron effective mass (m*) of Tl0.4ZnSnO was simulated to be >0.153, which is much smaller than that of In0.4ZnSnO (0.246). An In0.4ZnSnO TFT exhibited a mobility (μ) of 32.0 cm2 V%1 s%1 in the experiment; therefore, the Tl0.4ZnSnO TFT was expected to have a higher mobility of approximately 50 cm2 V%1 s%1 following the relation (μ / 1/m*). Moreover, the Tl-related oxide semiconductor would provide better TFT stability because its oxide vacancy is more stable than that of an In-related oxide semiconductor.
关键词： first-principles simulation,thallium–zinc–tin oxide,mobility,cosputtering,electron effective mass,thin-?lm transistor
更新于2025-09-09 09:28:46
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Electronic structures and optical properties of IV A elements-doped 3C-SiC from density functional calculations
摘要： Electronic structures and optical properties of IV A elements (Ge, Sn and Pb)-doped 3C-SiC are investigated by means of the first-principles calculation. The results reveal that the structure of Ge-doped system is more stable with a lower formation energy of 1.249 eV compared with those of Sn- and Pb-doped 3C-SiC systems of 3.360 eV and 5.476 eV, respectively. Doping of the IV A elements can increase the band gap, and there is an obvious transition from an indirect band gap to a direct band gap. Furthermore, charge difference density analysis proves that the covalent order of bonding between the doping atoms and the C atoms is Ge–C > Sn–C > Pb–C, which is fully verified by population values. Due to the lower static dielectric constant, the service life of 3C-SiC dramatically improved in production practice. Moreover, the lower reflectivity and absorption peak in the visible region, implying its wide application foreground in photoelectric devices.
关键词： electronic structures,Silicon carbide,first-principles simulations,optical properties
更新于2025-09-09 09:28:46
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Impact of Mg doping contents on the n-type and p-type ZnO by first-principles calculations
摘要： The effect of Mg doping on the electrical properties of pure ZnO and Al-doped ZnO, Al-2N co-doped ZnO have been investigated. It was found that after Mg doping, the bandgap values increased with the increase of Mg doping concentration. After Mg was doped into the Al doped ZnO structure, it was found that as the Mg doping contents increased, the CBM gradually moved toward the higher energy direction, the VBM gradually moved toward the lower energy direction, resulting in an increase of the band gap. After Mg was doped into the Al-2N co-doped structure, the band structure of Al-2N-Mg co-doped ZnO had a shallow acceptor level, indicating that the incorporation of Mg is beneficial for the electrical properties of p-type ZnO. The absorption of Al-2N-Mg co-doped ZnO is higher than that of Al-2N co-doped ZnO in the range of the visible region, which has a significant meaning for the applications on solar cell devices.
关键词： optical properties,band structure,first-principles,p-type ZnO,Mg doping
更新于2025-09-09 09:28:46
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Prediction of two-dimensional organic topological insulator in metal-DCB lattices
摘要： Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z2) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z2 invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.
关键词： first-principles calculations,organic topological insulator,quantum spintronics,metal-DCB lattices,two-dimensional
更新于2025-09-09 09:28:46
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Density Functional Theory Analysis of Electronic and Optical Properties of Two-Dimensional Tantalum Carbides Ta <sub/><i>n</i> +1 </sub> C <i> <sub/>n</sub></i> ( <i>n</i> ?=?1, 2, 3)
摘要： Using first principles methods based on the density functional theory, the electronic structure and optical properties of Ta-containing MXenes (Tant1Cn, n ? 1, 2, 3) are theoretically studied. The results show that the monolayer thickness has a significant effect on the optical properties of Tant1Cn. In the infrared region (<1.6 eV), the thickest Ta4C3 monolayer with seven atomic layers has highest values of absorption coefficients, reflectivity and refraction index. In the visible region, Ta4C3 exhibits different optical characteristics as compared to Ta2C and Ta3C2 due to the different structure configuration and electron interaction. Moreover, a high transmittance over 50% is demonstrated for both Ta2C and Ta3C2, while Ta4C3 monolayer exhibits selectively transmitting feature with a low transmittance of 35% at 1.65 eV and a high transmittance of 84% at 2.25 eV, making Ta4C3 monolayer highly responsive when exposed to visible light and favorable for optical detection.
关键词： tantalum carbides,first-principles calculations,MXenes,optical properties
更新于2025-09-09 09:28:46
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Correlation between thermal-vibration-induced large displacement of Cu atoms and phase transition in Cu4SnS4: First-principles investigation
摘要： First-principles (FP) calculations and first-principles molecular dynamics (FPMD) simulations for Cu4SnS4 were performed to clarify the origin of the structural phase transition at 232 K between the high-temperature phase (HP) and low-temperature phase (LP), which leads to an experimentally measured drastic change in the transport properties of Cu4SnS4. The results of the FP and PFMD calculations indicated that, rather than being caused by the so-called freezing of soft modes, the key driving force behind the phase transition in Cu4SnS4 is a large-scale displacement of the Cu atoms located at particular sites due to thermal vibration. In fact, tetrahedrally coordinated CuS4 is stabilized by the effect of the thermal vibration of Cu atoms in the HP whereas CuS3, which is in a trigonal planar environment, is stabilized in the LP.
关键词： first-principles calculation,molecular dynamics simulation,thermoelectric property,electronic structure,phase transition
更新于2025-09-09 09:28:46
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First-principles study of structural phase transformation and dynamical stability of cubic AlN semiconductors
摘要： Phase transformation and stability of cubic aluminium nitride (AlN) phases such as zinc-blende and rock-salt have been investigated using first-principles calculations based on density functional perturbation theory (DFPT) within quasi-harmonic approximation (QHA). The phonon dispersion relations of both the cubic phases have been calculated at various high-symmetry points of the Brillouin Zone. The pressure and volume dependence of phonon frequencies have been investigated. The application of pressure results in opposite trend of transverse acoustic (TA) phonon frequencies for rock-salt and zinc-blende AlN phases. The TA frequencies found to increase for the former one and decrease for the latter one with the increase in pressure. The dynamical instability results in a volume expansion of rock-salt AlN close to the equilibrium volume of zinc-blende AlN. Phase transformation of these cubic phases is further investigated by computing an equilibrium pressure-temperature phase diagram within QHA. The cubic rock-salt AlN is found to form at high pressures and temperatures than zinc-blende AlN. The temperature dependence of lattice constant and the corresponding volume thermal expansion coefficient of both the cubic phases have been investigated.
关键词： Aluminium nitride,First-principles calculations,Density functional perturbation theory,Quasi-harmonic approximation,Phase transformation,Dynamical stability
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A Compact Model of Drift and Diffusion Memristor Applied in Neuron Circuits Design
摘要： A compact model of memristor for unifying two switch characteristics, drift and diffusion has been proposed, based on the ion dynamic transport theory at the oxide interface layer. The model is verified by measured data in different oxide-material-based drift/diffusion memristors, and well fits DC/AC characteristics of both devices, under parameter variations and temperature evolution. Moreover, the applications of this model in neuron circuits design are shown.
关键词： adsorption effect,boron nitride nanotubes,first-principles calculations,small molecule
更新于2025-09-09 09:28:46
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Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films
摘要： Freestanding single bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of the supporting substrate on the topmost Bi bilayer are still under debate. Here, combined with scanning tunneling microscopy and first-principles calculations, we systematically study the electronic properties of Bi(111) thin films grown on a NbSe2 substrate. Two types of nonmagnetic edge structures, i.e., a conventional zigzag edge and a 2 × 1 reconstructed edge, coexist alternately at the boundaries of single bilayer islands, the topological edge states of which exhibit remarkably different energy and spatial distributions. Prominent edge states are persistently visualized at the edges of both single and double bilayer Bi islands, regardless of the underlying thickness of Bi(111) thin films. We provide an explanation for the topological origin of the observed edge states that is verified with first-principles calculations. Our paper clarifies the long-standing controversy regarding the topology of Bi(111) thin films and reveals the tunability of topological edge states via edge modifications.
关键词： topological insulator,scanning tunneling microscopy,edge states,first-principles calculations,Bi(111) thin films
更新于2025-09-09 09:28:46
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First-principles study of polar, nonpolar, and semipolar GaN surfaces during oxide vapor phase epitaxy growth
摘要： Stable structures of polar, nonpolar, and semipolar GaN surfaces undergoing oxide vapor phase epitaxy (OVPE) growth were examined with first-principles calculations. The relationships between temperature and pressure growth conditions and stable surface structures are described in surface phase diagrams. The results revealed that an O atom was stably incorporated into the N vacancy site in the N-polar and nonpolar surfaces. The desorption energy of the O atom from the GaN surfaces was estimated to be about 7 eV or higher. This indicates that the O atom did not readily desorb from the GaN surfaces under OVPE growth conditions at 1500 K. The desorption energy from the e000 (cid:2)1T surface was the highest and that from the e10 (cid:2)1 (cid:2)1T surface was the smallest among the calculated values. There was no significant difference in desorption energy among other surfaces.
关键词： first-principles calculations,desorption energy,OVPE,surface phase diagrams,GaN
更新于2025-09-04 15:30:14