Raman Properties Study On Two Dimensional Atomic Crystal

Graphene and Two-dimensional?2D?layered material make great potential applications in electronics and optoelectronics for their unique lattice and band structure,as well as excellent physical and chemical properties.Raman spectroscopy is a fast,no damaged,and sensitive characterization tool,help researchers to further insights into basic properties of 2D materials.In this paper,we introduce preparation methods,main characterization methods and transfer methods.Based on Raman spectroscopy,we have done some research on the transferring of large area graphene,and give some suggests about how to transfer high qualities and large area graphene.Then,We systematically demonstrate the microscopic origin of molybdenum ditelluride?MoTe₂?2H-to-1T'phase transition.The main work and conclusion are as follows:?1?The CVD grown graphene compared with that of mechanical exfoliated graphene showed obvious shift.According to the Raman spectrum,the strain was confirmed as the most important reason.Besides,the defects appeared in some regions,that origin from the cracks and wrinkle formation during the transfer.?2?We demonstrated laser irradiation to trigger 2H?semiconductor?to 1T'?metallic?phase transition in few-layer MoTe₂.Raman and XPS can be used to confirm the phase transition.?3?For MoTe₂,the irradiation time and the laser power both have different effects for the phase transition.?4?Combined with the thinning effect in the laser irradiation process,it can be determined that the heat generated by the laser will sublimate the material and causes a certain Te vacancy,the ratio and number of Te vacancies are the key factors to control phase transition.And annealing will make the lattice of MoTe₂ phase structure become more stable.