Adjust The Work Function Of Graphene Films

Graphene has many excellent physical and chemical properties due to its two-dimensional hexagonal honeycomb crystal structure.It has broad application prospects in micro-electronic devices,and is considered as a"revolutionary material"and"future material"in the 21st century.In graphene-based electronic devices,the existence of the contact resistance between graphene and metal greatly affects the carrier mobility.The contact resistance is closely related to the work function of graphene,therefore it is necessary to know more about the work function of graphene in order to develop graphene-based devices.In this thesis,graphene films were prepared by chemical vapor deposition（CVD）method at the temperature of 980℃and the deposition time was 30 min,40 min and60 min,respectively.The effects of annealing treatment,supporting substrate and light irradiation on the structure,morphology and work function of graphene films were investigated.The main research contents are as follows:（1）Effects of annealing on the work function of graphene films were investigated.The surface potential of graphene films before and after annealing was characterized by Kelvin probe force microscope（KPFM）,and the corresponding work function was calculated.The results show that the work function of graphene decreases significantly due to annealing.Combined with Raman spectra and atomic force microscopy characterization,the effect mechanism of annealing on the work function of graphene film was demonstrated.（2）Effects of light irradiation on the work function of graphene films on Si O₂/Si and Cu substrate were investigated.The results show that the light irradiation can result in the change of the work function of graphene films and the change is related to the substrate due to the different doping type from the substrate.The effect of light irradiation on the work function of graphene on copper substrate is greater than that on Si O₂/Si substrate.