Enhanced out-of-plane piezoelectricity and carrier mobility in Janus γ -Sn2XY (X /Y= S, Se, Te) monolayers: A first-principles prediction

In this Letter, we design Janus γ-Sn2XY (X/Y= S, Se, Te) monolayers and predict their piezoelectricity and carrier mobility by using first-principles simulations. Janus γ-Sn2XY are found to be indirect semiconducting characteristics with a camel's back-like dispersion in the top valence band. We discovered that Janus γ-Sn2XY are piezoelectric with high out-of-plane piezoelectric coefficients. Our calculated results for the piezoelectricity demonstrate that the out-of-plane piezoelectric coefficient d31 of Janus γ-Sn2STe is calculated to be 1.02 pm/V, larger than that of other 2D structures. Moreover, our calculations for the transport features reveal that while the carrier mobility of γ-Sn2SSe is directionally isotropic, the electron mobility of both γ-Sn2STe and γ-Sn2SeTe exhibit high anisotropy along the two transport directions. The Janus γ-Sn2XY monolayers have high electron mobility, especially the electron mobility of γ-Sn2STe exceeds 105 cm2 V–1 s–1, which is potential for nanoelectronic applications.