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

In this Letter, we design Janus gamma- Sn 2 X Y ( X / Y = S, Se, Te) monolayers and predict their piezoelectricity and carrier mobility by using first-principles simulations. Janus gamma- Sn 2 X Y are found to be indirect semiconducting characteristics with a camel's back-like dispersion in the top valence band. We discovered that Janus gamma- Sn 2 X Y are piezoelectric with high out-of-plane piezoelectric coefficients. Our calculated results for the piezoelectricity demonstrate that the out-of-plane piezoelectric coefficient d(31) of Janus gamma-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 gamma-Sn2SSe is directionally isotropic, the electron mobility of both gamma-Sn2STe and gamma-Sn2SeTe exhibit high anisotropy along the two transport directions. The Janus gamma- Sn 2 X Y monolayers have high electron mobility, especially the electron mobility of gamma-Sn2STe exceeds 10(5) cm(2) V-1 s(-1), which is potential for nanoelectronic applications.