Effect of stress regulation on electronic structure and optical properties of TiOCl2 monolayer

Based on first-principles calculations, the electronic structure, the transport and optical properties ofTiOCl2 monolayer are systematically investigated. The vibrational, thermodynamic, and mechanical properties of TiOCl2 monolayer are studied by phonon spectrum, molecular dynamics and elastic constants calculations. All these results indicate that the TiOCl2 monolayer possesses good structural stability at room temperature and excellent mechanical properties. The electronic structure analysis shows that the TiOCl2 is an indirect bandgap (1.92 eV) semiconductor. Its band structure can be significantly affected by in-plane stress. Specifically, theTiOCl2 monolayer undergoes an indirect-to-direct band gap transition under -4% uniaxial stress along the a-axis and the gap size decreases to 1.66 eV. Moreover, the TiOCl2 monolayer exhibits obvious anisotropy characteristics, and its electron mobility is 803 cm2middotV-1middots-1 along the b-axis, whereas the hole mobility reaches2537 cm2middotV-1middots-1 along the a-axis. The wave peaks (valleys) of the absorptivity, reflectivity and transmittance shift toward the violet part of the visible band by the stress. All these appealing properties make the TiOCl2monolayer a promising candidate for applications in optoelectronic devices.