Effect of Two-Step Deposition Process on Morphology and Optical Properties of Nanostructured Diamond Films

The morphology and optical properties of nanostructured diamond films affected by the two-step deposition process with changing CH4 concentration were investigated. The CH4 concentration was 1% for the first step and 2% for the second step. The films were prepared by chemical vapor deposition in a microwave plasma reactor with a CH4/H2 gas mixture. Nanocrystalline columnar-structured diamond film with lowering of sp2-bonded carbon content was achieved by the two-step deposition process. Unlike that of the single-step process with 1%CH4, the two-step process promoted the morphology to more uniform and smoother film. The two-step process increased the higher grain boundary as well as decreased the sp2-bonded carbon content in the film, as compared with the single-step process with 2%CH4Subscript text.