A new two-dimensional Te Se_2 semiconductor: indirect to direct band-gap transitions  

新型二维半导体TeSe_2:间接带隙到直接带隙的转变（英文）

作　　者：吴伯朝 尹久仁 丁燕怀 张平 

机构地区：[1]Institute of Rheological Mechanics, Xiangtan University [2]College of Civil Engineering & Mechanics, Xiangtan University

出　　处：《Science China Materials》2017年第8期747-754,共8页中国科学（材料科学（英文版）

基　　金：supported by the National Natural Science Foundation of China (21376199, 51002128 and 51401176);the Scientific Research Foundation of Hunan Provincial Education Department (17A205 and 15B235)

摘　　要：A novel two-dimensional（2D） Te Se_2 structure with high stability is predicted based on the first-principles calculations. As a semiconductor, the results disclose that the monolayer Te Se_2 has a wide-band gap of 2.392 e V. Interestingly, the indirect-band structure of the monolayer Te Se_2 transforms into a direct-band structure under the wide biaxial strain（0.02–0.12）. The lower hole effective mass than monolayer black phosphorus portends a high carrier mobility in Te Se_2 sheet. The optical properties and phonon modes of the few-layered Te Se_2 were characterized. The few-layer Te Se_2 shows a strong optical anisotropy. Specially, the calculated results demonstrate that the multilayer Te Se_2 has a wide range of absorption wavelength. Our result reveals that Te Se_2 as a novel 2D crystal possesses great potential applications in nanoscale devices, such as high-speed ultrathin transistors, nanomechanics sensors, acousto-optic deflectors working in the UV-vis red region and optoelectronic devices.本文基于第一性原理计算预测了一种新颖的二维稳定结构TeSe_2,结果显示单层TeSe_2是一种半导体材料,其带隙值为2.392 e V.有趣的是单层TeSe_2的间接能带在宽范围的双向负应变(0.02~0.12)作用下转变为直接能带.比单层黑磷烯更小的有效空穴电子质量预示了TeSe_2具有更高的载流子迁移速率.此外,对不同厚度TeSe_2的声子模及光学性质也进行了计算,结果显示不同厚度的TeSe_2具有较强的光学各向异性,尤其是多层TeSe_2具有更宽的吸收波长.这些结果表明,TeSe_2作为一种新颖的二维结构在纳米器件领域具有巨大的应用潜力,如高速超薄晶体管,纳米力学传感器,紫外–可见红光区声光偏振器及光电子器件等.

关 键 词：Te Se2 first-principles calculations direct band gap phonon modes optical absorption 

分 类 号：TN304[电子电信—物理电子学]