A new two-dimensional TeSe2 semiconductor: indirect to direct band-gap transitions

A novel two-dimensional (2D) TeSe2 structure with high stability is predicted based on the first-principles calculations. As a semiconductor, the results disclose that the monolayer TeSe2 has a wide-band gap of 2.392 eV. Interestingly, the indirect-band structure of the monolayer TeSe2 transforms into a direct-band structure under the wide biaxial strain (0.02–0.12). The lower hole effective mass than monolayer black phosphorus portends a high carrier mobility in TeSe2 sheet. The optical properties and phonon modes of the few-layered TeSe2 were characterized. The few-layer TeSe2 shows a strong optical anisotropy. Specially, the calculated results demonstrate that the multilayer TeSe2 has a wide range of absorption wavelength. Our result reveals that TeSe2 as a novel 2D crystal possesses great potential applications in nanoscale devices, such as high-speed ultrathin transistors, nanomechanics sensors, acousto-optic deflectors working in the UV-vis red region and optoelectronic devices.