Nanometer-scale surface features of the carbon film drastically improving field emission characteristics

It has been reported by many research groups that field emission (FE) from a sort of carbon-related materials show very low threshold fields even though the tips are not so sharp, where Fowler-Nordheim analysis indicates much lower effective work functions than real ones. This is called low-macroscopic field (LMF) emission and may open a possible new approach to low-cost field emitters with superior performance. Since all the proposed macroscopic models cannot explain the peculiar features, microscopic investigation on the LMF emission is required to clarify the mechanism [1,2]. In this paper, by using scanning tunneling microscopy (STM) including FE current imaging, we have microscopically observed the arc discharge-prepared carbon films [3] showing LMF emission features [4]. We have also examined the defect-induced highly oriented pyrolytic graphite (HOPG) surface [5] as a well-defined reference.