Effects of hydrogen flow rate on the growth and field electron emission characteristics of diamond thin films synthesized through graphite etching

Diamond film deposition on silicon was explored using our newly developed graphite etching technology in a microwave plasma reactor. The effects of hydrogen flow rate on the growth rate, morphology and field electron emission properties of the synthesized diamond were investigated systematically. The growth rate and nucleation density of diamond films increased significantly with the decrease of hydrogen flow rate. Nanocrystalline diamond films were obtained with a low hydrogen flow rate (i.e. 3 sccm or lower). Diamond quality is improved and the growth rates are much higher in this graphite etching process, compared to conventional H2 + 1% CH4 gas mixture. The results suggest that diamond growth is enhanced by activated hydrocarbon radicals formed through in-situ etching of graphite by atomic hydrogen. The turn-on electric field decreased and the emission current increased with the decrease of the hydrogen flow rate. The enhanced field electron emission property of the diamond films synthesized at lower hydrogen flow rate is attributed to the decreased diamond grain size because the small diamond grains increase the electron conduction channels which facilitate the electron transport inside diamond films.