Effects of uniaxial strain on elastic and electronic properties of hydrogenated XC (X=Si, Ge, and Sn) monolayers by first-principles calculations

Abstract

We performed density functional theory calculations to investigate the uniaxial strain effects on the elastic and electronic properties of chair and boat conformers of fully hydrogenated XC (X=Si, Ge, Sn) monolayers. The stress-strain relation shows that hydrogenation reduces their ideal strength, but the critical strain along the zigzag direction increases significantly. When hydrogenated, all the chair conformers are ΓΓ-direct bandgap semiconductors, and of which, the chair conformers GeCH2 and SnCH2 almost maintain the ΓΓ-direct band gap in our considered uniaxial strain range. Besides, the band gap of boat conformers SiCH2 and SnCH2 experiences an indirect-direct transition with a small zigzag-direction strain. Furthermore, the calculated results of the structural and electronic properties of the XC/XCH2 vdW heterostructures showed that XC/XCH2(chair) vdW heterostructures owe type-II band alignment characteristics. Such the band alignments are expected to facilitate the spatial separation of electrons and holes after photoexcitation, which can be utilized in photovoltaic devices.