Key Laboratory of Automobile Materials of MOE and College of Materials Science and Engineering, Jilin University, Changchun 130012, China.
Nanoscale. 2018 May 3;10(17):7991-7998. doi: 10.1039/c7nr09486h.
Atomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention due to the large tunability in the band gap (from 1.4 to 2.6 eV) and high carrier mobility. The intriguingly high dependence of the band gap on layer thickness may lead to novel device applications, although its origin remains poorly understood, and is generally attributed to the quantum confinement effect. In this work, we demonstrate via first-principles calculations that strong interlayer coupling may be mainly responsible for this phenomenon, especially in the fewer-layer region, and it could also be an essential factor influencing other material properties of β-InSe and γ-InSe. The existence of strong interlayer coupling manifests itself in three aspects: (i) indirect-to-direct band gap transitions with increasing layer thickness; (ii) fan-like frequency diagrams of the shear and breathing modes of few-layer flakes; and (iii) strong layer-dependent carrier mobilities. Our results indicate that multiple-layer InSe may be deserving of attention from FET-based technologies and may also be an ideal system to study interlayer coupling, possibly inherent in other 2D materials.
原子级薄的二维（2D）硒化铟（InSe）由于其带隙（1.4 到 2.6 eV）具有很大的可调谐性，以及高载流子迁移率，因此引起了相当大的关注。带隙对层厚的高依赖性可能导致新的器件应用，尽管其起源仍不清楚，通常归因于量子限制效应。在这项工作中，我们通过第一性原理计算证明，强层间耦合可能是主要原因，尤其是在少层区域，它也可能是影响β-InSe 和 γ-InSe 其他材料性质的一个重要因素。强层间耦合的存在表现在三个方面：（i）随着层厚的增加，间接带隙到直接带隙的转变；（ii）少层薄片的剪切和呼吸模式的扇形频图；（iii）强烈的层依赖性载流子迁移率。我们的结果表明，多层 InSe 可能值得基于 FET 的技术关注，也可能是研究层间耦合的理想系统，层间耦合可能存在于其他二维材料中。
