By using first principles calculations, we theoretically investigate the electronic structures and the interfacial and optical properties of the two-dimensional tellurene (Te)–gallium arsenide (GaAs) van der Waals heterostructures (vdWHs), i.e., α-Te/GaAs and γ-Te/GaAs, formed using Te and GaAs monolayers. It has been demonstrated that, the semiconductor–semiconductor contacted α-Te/GaAs vdWH exhibits a type-II band alignment with a direct band gap of 0.28 eV while the metal–semiconductor contacted γ-Te/GaAs vdWH has a p-type Schottky contact with a Schottky barrier height (SBH) of 0.36 eV at the interface. The transition from type-II to type-III band alignment is observed firstly in the α-Te/GaAs vdWH when the in-plane biaxial strain is less than −5.2% and larger than 4.4%, meanwhile, the p-type Schottky contact to Ohmic contact transition may be realized in the γ-Te/GaAs vdWH when the in-plane biaxial strain is less than −2.4%. Finally, the maximum optical absorption coefficients of the α- and γ-Te/GaAs vdWHs have been found to be up to 31% and 29%, respectively, and may be modulated effectively by applying in-plane biaxial strain. The obtained results may be of importance in the design of nanoelectronic devices based on the proposed tellurene/GaAs vdWHs.

基于密度泛函理论与非平衡格林函数相结合的第一性原理计算方法, 系统地研究了通过碳原子(C)连接的同分异构喹啉分子(C₉H₅N)嵌于石墨烯纳米带电极间的分子电子器件输运性质. 研究结果表明: 器件电流在偏压[–0.3 V, +0.3 V]范围内呈线性变化, 电流在[–0.4 V, –0.9 V]和[+0.5 V, +0.8 V]范围内随着偏压的增大而减小, 呈现显著的负微分电阻效应; 当喹啉分子平面与石墨烯纳米带电极间存在一定夹角时, 器件电流呈现明显的负微分电阻效应且与喹啉分子平面旋转方向无关, 当喹啉分子平面与石墨烯纳米带电极垂直时, 器件电流截止. 以上研究结果得到偏压窗内透射系数积分以及零偏压下实空间电荷密度分布等的有力印证, 可为设计制作基于同分异构喹啉分子电子开关和负微分电阻器件提供理论依据.

Two-dimensional (2D) transition metal oxyhalides have garnered significant interest due to their unique physical properties and promising potential applications. By using density functional theory and the non-equilibrium Green's function method, the anisotropic mechanical, electronic, optical, and transport properties of the Janus TiOXY (X, Y = Cl, Br, I; X ≠ Y) monolayers are systematically investigated. The proposed Janus TiOClBr, TiOBrI, and TiOClI monolayers exhibit favorable thermodynamic, dynamic, and mechanical stabilities, respectively. The Young's modulus of the Janus TiOClBr, TiOBrI, and TiOClI monolayers is 43.19–75.40 N m⁻¹, 37.14–69.06 N m⁻¹, and 40.11–66.26 N m⁻¹, while their Poisson's ratios are 0.10–0.37, 0.12–0.38, and 0.11–0.34, respectively. The band gap of the semiconducting TiOClBr, TiOBrI, and TiOClI monolayer is 1.36 eV, 0.34 eV, and 0.46 eV, respectively. The Janus TiOClBr monolayer is found to be insensitive to the in-plane biaxial strain, while an indirect semiconductor-to-semimetal transition may be observed in the Janus TiOBrI and TiOClI monolayers under 4% and 4.9% compressive strain, respectively. The anisotropic optical properties as a function of photon energy of the Janus TiOClBr, TiOBrI, and TiOClI monolayers have been demonstrated. Remarkably, the constructed nanoelectronic devices based on the Janus TiOXY monolayers possess highly-anisotropic transport properties, such as the current–voltage curves, transmission spectra and local projected density of states (PDOS). The obtained results demonstrate that the 2D Janus TiOXY monolayers can be used as potential candidate platforms for novel nanoelectronic and optoelectronic applications.