Preparation of nonlayered two-dimensional CdSe and effect of thickness on bandgap
Two-dimensional semiconductor materials with natural bandgap are expected to make up for the zero bandgap defect of graphene and break the bottleneck of its application in fields such as field effect transistors,switching devices,logic circuits.Compared with layered semiconductor materials,non-layered semiconductor materials are usually bound by strong ionic/covalent bonds and are isotropic,so it is a challenge to obtain their two-dimensional structures.In this paper,two-dimensional anisotropic growth of nonlayered CdSe on mica substrate was achieved by chemical vapor deposition.The microstructure,crystalline structure and optical prop-erties of two-dimensional CdSe were characterized in detail.The results show that the sample has a significant photoluminescence(PL)effect,indicating that the thickness thinning to nanometer level does not destroy the di-rect bandgap property of CdSe.In addition,with the decrease of thickness,PL peaks of the sample are gradually blue-shifted.In order to further explain this phenomenon,the energy band structures of CdSe with different thickness were studied using the first-principles caculation based on density functional theory.The results show that they all have direct bandgap,and the bandgap increases with the decreasing thickness,which is consistent with the experimental phenomenon.Therefore,the effective control of the bandgap can be achieved by adjusting the thickness of two-dimensional CdSe through the growth parameters,which has guiding significance for the performance improvement of related optoelectronic devices.
国家科技期刊平台
NSTL
万方数据
维普
