Modulation of the electronic property of hydrogenated 2D tetragonal Ge by applying external strain

Abstract

Inspired by the novel properties of a newly predicted two-dimensional (2D) tetragonal allotrope of Ge called 2D tetragonal Ge, first-principles calculations have been performed to explore the stability, and structural and electronic properties of 2D tetragonal Ge <i>via</i> hydrogenation, and the effect of external strain on structural and electronic properties of hydrogenated 2D tetragonal Ge is considered. Our calculations reveal that the hydrogenated 2D tetragonal Ge, α-GeH and β-GeH, are proved to be dynamically and thermally stable. Both α-GeH and β-GeH are semiconductors with a direct band gap of 0.953 eV and indirect band gap of 2.616 eV, respectively. When applying external strain from -7% to 7%, α-GeH is more energetically stable than β-GeH around the equilibrium geometry, β-GeH is more stable than α-GeH when external strains exceed a certain critical value, respectively. The direct band gap of α-GeH reduces rapidly from 2.008 eV to 0.036 eV as external strain increases from -7% to 7%, while the indirect band gap of β-GeH is changed slightly. Our results reveal that α-GeH and β-GeH can offer an intriguing platform for nanoscale device applications and spintronics.