Electronic Properties And Mechanical Properties Of 2D TiS₃:A First Principles Study

Graphene,a single atomic layer of carbon in a hexagonal lattice,has potential applications in various fields,such as electronic and photonic devices owing to the extraordinary physical and chemical properties.This invigorates enormous research interests in other two-dimensional?2D?layered materials as well as their one dimensional?1D?derivatives.In 2015,a new class of 2D layered materials,namely,group-IVB transition metal trichalcogenides?TMTCs?,has been proposed.A typical representative is TiS₃ whose monolayer is predicted to possess a direct band gap of?1eV,and owns relatively high carrier mobility.Moreover,few-layer TiS₃ sheets and TiS₃ nanoribbons have been realized in the laboratory via mechanical exfoliation in 2015.The modest band gap?relatively high carrier mobility,as well as high chemical stability in open air render TiS₃ monolayer a promising 2D material for nanoelectronic and nanophotonic applications.In this study,by using first-principles,we investigate the mechanisms and electronic properties of monolayer TiS₃,the main conclusions are summarized below:1)Mechanical properties and carrier mobility of monolayer TiS₃ under elastic strain.The in-plane stiffness and Poisson's ratio are calculated and the results show that monolayer TiS₃ is much harder than black phosphorus and perhaps has the highest out-plane Poisson's?1.32 and 1.66 along x and y direction?among known monolayer structures.In addition,the band gap and carrier mobility behaves differently along different directions in response to the elastic tensile strain.Besides,the difference in election/hole mobility along y direction can be enhanced dramatically via applying x-direction strain.All these results are helpful for future researches on monolayer TiS₃.2)Bending effects in TiS₃ nanoribbons.The bending energy of the TiS₃ nanoribbons is quadratic in the bending curvature and the bending stiffness is 27.4eV/16.9eV for TiS₃R-a/b,respectively.The calculated effective thickness of TiS₃ is 6.2 A,which as expected is in agreement with the experimental result.Based on this,we define an intrinsic Young's modulus of monolayer TiS₃,which is 213.2GPa/136.6GPa for TiS₃R-a/b.Moreover,the band gap of TiS₃R-b and the electronic properties of TiS₃R-a are independent on the bending curvature.