Titanium Trisulfide Monolayer: Theoretical Prediction of a New Direct‐Gap Semiconductor with High and Anisotropic Carrier Mobility

A new two‐dimensional (2D) layered material, namely, titanium trisulfide (TiS 3 ) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS 3 monolayer is a direct‐gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in‐plane electron mobility of the 2D TiS 3 is highly anisotropic, amounting to about 10 000 cm 2  V −1  s −1 in the b direction, which is higher than that of the MoS 2 monolayer, whereas the hole mobility is about two orders of magnitude lower. Furthermore, TiS 3 possesses lower cleavage energy than graphite, suggesting easy exfoliation for TiS 3 . Both dynamical and thermal stability of the TiS 3 monolayer is examined by phonon‐spectrum calculation and Born–Oppenheimer molecular dynamics simulation. The desired electronic properties render the TiS 3 monolayer a promising 2D atomic‐layer material for applications in future nanoelectronics.