School of Physics &Astronomy, The University of Nottingham, Nottingham, NG7 2RD, UK.
Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA-EMFL, 25 rue des Martyrs, 38042 Grenoble, France.
Sci Rep. 2016 Dec 23;6:39619. doi: 10.1038/srep39619.
The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a direct to an indirect band gap semiconductor as the number of layers is reduced. We investigate this direct-to-indirect bandgap crossover, demonstrate a highly tuneable optical response from the near infrared to the visible spectrum with decreasing layer thickness down to 2 layers, and report quantum dot-like optical emissions distributed over a wide range of energy. Our analysis also indicates that electron and exciton effective masses are weakly dependent on the layer thickness and are significantly smaller than in other vdW crystals. These properties are unprecedented within the large family of vdW crystals and demonstrate the potential of InSe for electronic and photonic technologies.
范德华（vdW）层状晶体的电子能带结构具有取决于组成、厚度和堆叠的特性。在这里，我们使用密度泛函理论和强磁场磁光来研究金属硫属化物 InSe，它是 vdW 层状晶体家族的最新成员，随着层数的减少，它从直接带隙半导体转变为间接带隙半导体。我们研究了这种直接到间接带隙的转变，证明了随着层厚度减小到 2 层，从近红外到可见光谱的高度可调谐光学响应，并报告了分布在很宽能量范围内的类似于量子点的光发射。我们的分析还表明，电子和激子有效质量对层厚度的依赖性较弱，并且比其他 vdW 晶体小得多。这些特性在 vdW 晶体的大家族中是前所未有的，展示了 InSe 在电子和光子技术中的潜力。
