退火处理对CVD生长石墨烯薄膜功函数的影响

Effect of annealing on work function of CVD-grown graphene films

通过退火处理去除了石墨烯薄膜上的吸附气体和杂质,改变了石墨烯表面吸附情况.利用原子力显微镜和开尔文扫描探针显微镜,对退火处理前后的石墨烯薄膜表面进行了原位扫描,分别得到其退火前、后的表面形貌和表面接触电势差图.根据表面接触电势差测量结果进一步计算其功函数,并对退火处理导致的功函数变化机理进行分析.结果表明:退火处理使得石墨烯薄膜与SiO_(2)衬底间的水分子层逸出,从而导致石墨烯薄膜与SiO_(2)衬底间距减小,降低了石墨烯薄膜的P型掺杂水平,使得费米能级上升、石墨烯薄膜功函数减小.

The annealing was used to remove the adsorbed gases and impurities on graphene film,and the state of graphene surface was changed.The surface of graphene film before and after annealing was characterized in situ by atomic force microscope and Kelvin probe force microscope.The surface morphology and surface potential map of graphene film before and after annealing were obtained respectively.The work function was calculated according to the surface potential map,and the change mechanism of work function induced by annealing was analyzed.The results show that the annealing treatment causes the escape of water molecular between the graphene film and substrate,which reduces the gap between graphene film and SiO_(2)substrate and the P-type doping level of graphene film,resulting in the increasing of the Fermi level and the decreasing of work function.