双轴应变对g-ZnO/WS2异质结电子结构及光学性质影响的第一性原理计算

单层g-ZnO由于吸收光谱宽而受到研究者关注,但载流子复合是单层g-ZnO作为光催化剂无法避免的问题,如何降低电子空穴对复合率,提高单层g-ZnO对可见光利用率成为值得研究的问题,搭建异质结并对其进行双轴应变是一种可行的办法。本文采用第一性原理方法,研究双轴应变对g-ZnO/WS₂异质结电子结构及光学性质的调控规律。结果表明:g-ZnO/WS₂异质结禁带宽度为1.646 eV,由于异质结体系内部产生内置电场,降低了其光生载流子的复合率,同时异质结光吸收带边拓展至可见光区域。对异质结实施应变后,除压缩应变(-2.5%)体系外,其余应变体系吸收带边均出现红移现象,并且红移程度和对电荷的束缚能力均随着应变的增加而增强。相比于未实施应变的体系,应变体系对光生电子载流子的阻碍作用更强,其光催化能力得到更大提高。以上结果说明搭建g-ZnO/WS₂异质结并对其进行双轴应变对异质结的电子结构及光学性质具有显著的调控作用,使其在窄禁带及红外、可见光半导体器件和光催化材料等领域具有应用价值。

First-Principles Calculation of Influence of Biaxial Strain on Electronic Structure and Optical Properties of g-ZnO/WS2 Heterojunction

Researchers have drawn attention to monolayer g-ZnO because of its broad absorption spectrum, but carrier recombination is an unavoidable problem for monolayer g-ZnO as a photocatalyst. How to reduce electron hole pair recombination rate and improve visible light utilization by monolayer g-ZnO are worth investigating, and builting heterojunctions and biaxial strain on them is a viable approach. As a result, this paper uses the first-principles method to investigate how biaxial strain affects the electronic structure and optical properties of g-ZnO/WS₂ heterojunctions. The results show that the band gap of the g-ZnO/WS₂ heterojunction is 1.646 eV, which reduces the recombination rate of photogenerated carriers due to the built-in electric field generated inside the heterojunction system. The edge of the heterojunction optical absorption spectrum, on the other hand, expands to the visible region. With the exception of the compressive strain (-2.5%) system, the absorption band edges of all strained systems show red-shift. With strain applied to the heterojunction increases, the degree of red-shift and the ability to bind charge of it increases. With the stronger strain on the heterojunction, the capacity of the hindrance of photogenerated electron-carriers recombination is stronger than that of the unstrained system. Moreover, its photocatalytic capability is also better than that of the unstrained system. The results show that the builting g-ZnO/WS₂ heterojunction and biaxial strain on them have significant modulating effects on the electronic structure and optical properties of the heterojunction, making it useful for applications such as narrow-band, infrared and visible semiconductor devices, photocatalytic materials, and so on.