Effects of substrate pretreatment and methane fraction on the optical transparency of nanocrystalline diamond thin films

Publisher Website
Google Scholar
Abstract
Optical transmittance of the nanocrystalline diamond films has been studied as a function of grain size of the diamond powder used for substrate pretreatment and the methane fraction in the source gas. It has been observed that for CH4 fractions below 13%, the films grown on substrates pretreated with finer diamond powder are more transparent, while this trend reverses for CH4 fractions above 13%. These variations in the transparency of the films correlate very well with their corresponding surface roughness. Nanocrystalline/amorphous diamond films with transmittance of greater than 80% beyond 700 nm and with average surface roughness as low as 61 Å have been obtained for CH4 fractions as high as 42% in the source gas. Interestingly, these films do not show an obvious presence of any graphitic carbon, and the structural ordering of the amorphous sp3-bonded phase also seems to be insensitive to the CH4 content of the source gas.