Single layer of MX3 (M = Ti, Zr; X = S, Se, Te): a new platform for nano-electronics and optics

Abstract

A serial of two-dimensional titanium and zirconium trichalcogenides nanosheets MX₃ (M = Ti, Zr; X = S, Se, Te) were investigated based on first-principles calculations. The evaluated low cleavage energy indicates that stable two-dimensional monolayers can be exfoliated from their bulk crystals in the experiment. Electronic studies reveal the very rich electronic properties in these monolayers, including metallic TiTe₃ and ZrTe₃, direct band gap semiconductor, TiS₃, and indirect band gap semiconductors, TiSe₃, ZrS₃ and ZrSe₃. The band gaps of all the semiconductors are between 0.57 and 1.90 eV, which implies their potential applications in nano-electronics. In addition, the calculated effective masses demonstrate the highly anisotropic conduction properties for all the semiconductors. Optically, TiS₃ and TiSe₃ monolayers exhibit good light absorption in the visible and near-infrared region, respectively, indicating their potential applications in optical devices. In particular, the highly anisotropic optical absorption of the TiS₃ monolayer suggests it could be used in designing nano-optical waveguide polarizers.