Penta-MX2 ( M = Ni, Pd and Pt; X = P and As) monolayers: direct band- gap semiconductors with high carrier mobility

摘要

Two-dimensional binary MX2 (M = Ni, Pd and Pt; X = P and As) exhibiting a beautiful pentagonal ring network is discussed through first principles calculations. We predict that MX2 sheets possess narrow direct band gaps of about 0.3-0.8 eV and ultrahigh mobilities both for holes and electrons. The hole mobility of PdAs2 is even up to 50 x 10(4) cm(2) V-1 s(-1) and the electron mobility of PtAs2 is up to 25 x 10(4) cm(2) V-1 s(-1). Besides fascinating electronic properties, 2D MX2 also exhibits optical absorption over the entire visible-light range. Additionally, like graphene and carbon nanotubes, a MX2 sheet can be rolled into various forms of MX2 nanotubes as well. Interestingly, NiP2 nanotubes exhibit rich band gap behaviour which can be adjusted by the roll-up vector. With a desired band gap, high carrier mobility and optical properties, 2D MX2 sheets promise to be potential candidates for electronic devices.