School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
Phys Chem Chem Phys. 2013 May 21;15(19):7098-105. doi: 10.1039/c3cp50233c.
Here we present first-principles calculations to investigate systematically the electronic behavior and the electron energy low-loss spectra (EELS) of monolayer, bilayer, four-layer, and bulk configurations of periodic GaX (X = S, Se), as well as the effect of mechanical strain on the electronic properties of the GaX monolayer. We predicate that the GaX monolayer is a semiconductor with an indirect band gap, however, the difference between the direct and indirect gaps is so small that electrons can transfer easily between this minimum with a small amount of thermal energy. Owning to strong surface effects, the electronic and dielectric properties of GaX vary drastically with number of layers in a sheet. In detail, the band gap increases from multilayer-to-single layer and EELS shifts towards larger wavelengths with a decrease in the layer thickness. Moreover, we demonstrate that the band gaps of GaX monolayers can be widely tuned by mechanical deformation, making them potential candidates for tunable nanodevices. The present study provides theoretical insight leading to a better understanding of these novel 2D structures.
我们通过第一性原理计算，系统地研究了单层、双层、四层和体相 GaX（X = S、Se）的电子行为和电子能量低损失谱（EELS），以及机械应变对 GaX 单层电子性质的影响。我们预测 GaX 单层是一种半导体，具有间接带隙，但直接带隙和间接带隙之间的差异非常小，以至于电子可以在少量热能的作用下很容易地在这个最小值之间转移。由于强烈的表面效应，GaX 的电子和介电性质随片层中层数的变化而剧烈变化。具体来说，带隙从多层到单层增加，EELS 随着层厚度的减小而向较大的波长移动。此外，我们证明 GaX 单层的带隙可以通过机械变形进行广泛调节，使它们成为潜在的可调谐纳米器件的候选者。本研究提供了理论见解，有助于更好地理解这些新型二维结构。
