Strain-induced semimetal-to-semiconductor transition and indirect-to-direct band gap transition in monolayer 1T-TiS2

We have investigated the effect of uniform plane strain on the electronic properties of monolayer 1T-TiS2 using first-principles calculations. In the absence of strain, we find monolayer TiS2 is a semimetal, with a small overlap of the valence band maximum and the conduction band minimum. The band overlap increases under compression; however under tensile, monolayer 1T-TiS2 experiences a transition from a semimetal to a semiconductor as a band gap emerges. Moreover, the electronic properties change from an indirect to a direct band gap upon application of greater tensile strain. Thus one can modulate the properties of monolayer TiS2 by applying the appropriate strain, thereby providing a route towards control in optoelectronic devices.