By means of density functional theory computations, we study band-gap tuning in multi-layer WSe₂ sheets by external electric fields. It shows that the fundamental band gap of WSe₂ film continuously decreases with an increasing vertical electric field, eventually rendering them metallic. The critical electric fields, at which the semiconductor-to-metal transition occurs, are predicted to be in the range of 0.6–2 V/nm depending on the number of layers. This gap-tuning effect yields a robust relationship, which is essentially characterized by the giant Stark effect (GSE) coefficient S, for the rate of change of band gap with applied external field. The GSE coefficient S is proportional to the number of layers and it can be expressed as (n − 1)c/2.

Arsenene has received considerable attention because of its unique optoelectronic and nanoelectronic properties. Nevertheless, the research on van der Waals (vdW) heterojunctions based on arsenene has just begun, which hinders the application of arsenene in the optoelectronic and nanoelectronic fields. Here, we systemically predict the stability and electronic structures of the arsenene/WS₂ vdW heterojunction based on first-principles calculations, considering the stacking pattern, electric field, and strain effects. We found that the arsenene/WS₂ heterostructure possesses a type-II band alignment. Moreover, the electric field can effectively tune both the band gap and the band alignment type. Additionally, the band gap could be tuned effectively by strain, while the band alignment type is robust under strain. Our study opens up a new avenue for the application of ultrathin arsenene-based vdW heterostructures in future nano- and optoelectronics applications. Our study demonstrates that the arsenene/WS₂ heterostructure offers a candidate material for optoelectronic and nanoelectronic devices.

半导体与金属接触是制作纳电子和光电子器件时非常重要的问题, 接触类型对器件的功能实现和性能影响很大. 为了制备高性能多功能化器件, 就必须对界面处的势垒高度和接触类型进行调控. 采用基于密度泛函理论的第一性原理计算研究了外电场作用下graphene/InSe范德瓦耳斯异质结的电子结构. 计算结果表明异质结中的graphene和InSe保留了各自的本征电子性质, 在界面处形成了欧姆接触. 外电场可以有效调控graphene/InSe异质结中的肖特基势垒, 不但可以调控肖特基势垒的高度, 而且可以调控界面接触类型. 外电场还可以有效调控graphene和InSe界面电荷转移的数量和方向.