Surface structure and field emission properties of few-layer graphene flakes

Abstract

Correlations between field emission properties and surface structure of few-layer graphene (FLG) flakes have been examined. Films consisting of flakes oriented perpendicularly to a flat Si substrate were obtained by the direct current plasma enhanced chemical vapour deposition method. FLG flakes had thickness of 5–10 nm and width and height of 1–3 µm. The field emission characteristics of the films were studied depending on the surface modifications produced by thermal oxidation and ion bombardment processes. It was found that thermal oxidation in the air at temperatures near 650 °C produced a big amount of 100 nm through-hole defects in the lateral sides of the flakes. Nevertheless, the field emission properties after oxidation had not changed. At the same time, electron emission in the harsh ion bombardment conditions led to the strong degradation of the field emission properties. However, no considerable changes in the morphology and composition of the films were revealed. Using structural analysis of the FLG flakes performed by transmission and scanning electron microscopy and Raman technique, the possible mechanisms responsible for the observed field emission changes are discussed.