Influence of structural and morphological properties on the "intrinsic" field emission of CVD diamond films

The "intrinsic" field emission properties of CVD diamond films, grown in a microwave plasma chemical vapour deposition setup, were investigated. The substrate temperature, content of methane and nitrogen in the process gas and the bias voltage were systematically varied. Parts of some samples were intentionally damaged by C-ion implantation, Morphological and structural properties of the films were analysed by scanning electron microscopy (SEM) and Raman spectroscopy. Field emission (FE) properties were measured by means of a field emission scanning microscope with a resolution of 1 mu m. All samples showed an "intrinsic" FE over those parts of the surface, on which "parasitic" FE, e.g. dust particles, could not be detected by in-situ SEM. The "intrinsic" electrical onset field strength (E-on) varied from 245 to 1000 MV m(-1). Significant differences in non-diamond content (e.g. amorphous carbon, graphite) had no or little influence on the FE strength. However, the surface morphology was correlated with E-on, suggesting geometrical field enhancement by rough micro structures, The electron potential barrier was located at the surface for good conducting films. In contrast, the barrier of an insulating film was located at the substrate-diamond interface, indicating an alternative emission mechanism. (C) 1998 Elsevier Science S.A.