Effect of non-diamond carbon content on the spatial distributions of emission sites of the diamond films

The influence: of non-diamond carbon in diamond films on the spatial distri butions of emission sites was investigated, and consequently the field emis sion mechanism was discussed. It was confirmed that when increasing the pos itive substrate bias or the CH4/H-2 concentration ratio, the non-diamond ca rbon content in the resulting films was markedly increased and the surface morphologies of the films lost their unique facet shape. An increase of non -diamond carbon content improved significantly the field emission propertie s and caused a dramatic increase of emission sites. It was observed from th e images of the films containing a small amount of non-diamond carbon that electron emission occurs predominantly at the sample edges and the reason f or this phenomenon could be attributed to the surface electron emission. Wi th increasing non-diamond carbon, the emission occurs at the center as well as at the edge of the sample. From this observation, it is proposed that t he emission from central region was caused by a preferential transport thro ugh the conducting pathways such as grain boundaries. (C) 2000 Elsevier Sci ence S.A. All rights reserved.