Laser Irradiation-Induced Structural Transition And Property Regulation Of 2D TiS₃

Laser irradiation is an important tool that can modulate the material structures and its properties.When a focused laser beam with high energy density is delivered on two-dimensional(2D)materials,structural transitions such as thickness thinning and phase transition will happen,thus changing their physical properties.Here,we systematically studied the laser irradiation effect on layered Titanium Trisulfide(TiS₃),which is a new type of 2D material that attracts researchers'interests.By the characterization of Raman spectroscopy,in combination with other techniques such as electron microscopy,atomic force microscopy and electrical characterization,we observed the transition from TiS₃ nanoflakes to TiS₂ that has a different crystal structure and stoichiometry.The transition phase diagram is also established,which shows that the major influence factors are the laser powers and flake thickness.The corresponding transition mechanism is attributed to the thermal degradation of TiS₃ to relatively more stable TiS₂ under high temperature,which originates from the laser irradiation induced heating effect.The irradiation using the highly focused laser beam can result in a local conversion process.While the covered TiS₂ and the original TiS₃forms an in-plane heterostructure,and tunes the electrical properties of the TiS₃ flakes.Furthermore,we discover that this laser-irradiation structural transition process can also be applied to other MX₃ materials,such as Zr S₃,Zr Se₃ and Nb Se₃.Our work thus provides a new methodology to tune the properties of MX₃ materials,broadening their applications to low-dimensional electronic and optoelectronic devices in the future.