Theoretical study of optical and electronic properties of silicether/graphether heterostructure

Abstract

Since the discovery and synthesis of graphene, two-dimensional graphether and silicether materials have been predicted as novel semiconductors. A novel two-dimensional silicether/graphether heterostructure is designed by combining silicether and graphether, which has unique optical and electronic properties due to the properties of a single material synthesized by heterostructures. The electronic and optical properties of silicether/graphether heterostructure are studied by the first-principles calculations based on density functional theory. The binding energy and layer spacing for each of all considered 16 stacking patterns of the heterostructures are calculated. The results show that different stacking patterns have a small effect on the binding energy of the heterostructure. When the layer spacing is 2.21 Å, the stacking pattern in which the concave oxygen atoms of graphether are on the top of the concave oxygen atoms of silicether is the most stable. In addition, it has an indirect band gap of 0.63 eV, which is smaller than that of the silicether and graphether, respectively. By changing the external electric field and the biaxial strain strength, the band gap of the silicether/graphether heterostructure shows tunability. The compressive strain can increase the band gap of silicether/graphether heterostructure, while the band gap decreases with the tensile strain increasing. Especially, when the compressive strain is greater than –6%, the heterostructure undergoes an indirect-to-direct band gap transition, which is beneficial to its applications in optical devices. When the external electric field is applied, the band gap of the heterostructure changes linearly with the strength of the electric field, and the indirect band gap characteristic is maintained. The absorption coefficient of silicether/graphether heterostructure shows a strong peak in the ultraviolet light region. The maximum absorption coefficient can reach up to 1.7 × 10<sup>5</sup> cm<sup>–1</sup> around 110 nm. Compared with that of monolayer graphether and silicether, the optical absorption of the heterostructure is significantly enhanced within the range from more than 80 nm to less than 170 nm. The results show that silicether/graphether heterostructure has an outstanding optical absorption in the ultraviolet region. Moreover, the silicether/graphether heterostructure also shows considerable absorption coefficient (1 × 10<sup>4</sup>—4 × 10<sup>4</sup> cm<sup>–1</sup>) in the visible region, which makes it a potential material in photovoltaic applications. This work may provide a novel material with a promising prospect of potential applications in nanodevices.