Filament metal contamination and Raman spectra of hot filament chemical vapor deposited diamond films

Chemical vapor deposited diamond films grown in a hot filament reactor usin g three filament metals (tungsten, tantalum, and rhenium) have been analyze d for their metal impurity content. This is the first report wherein all th ree common CVD filament metals have been examined and a single technique us ed for diamond film analysis. Tungsten carbide filaments yielded the lowest impurity level (few ppm by mass), whereas rhenium yielded the highest (par ts per thousand). The effects of filament temperature and addition of ammon ia or oxygen to the reactant gas mixture were examined. A correlation was o bserved between the metal content of the product films and their quality, a s judged using Raman spectroscopy. Films with the highest metal content yie lded Raman spectra showing the lowest fluorescence background, the smallest sp(2) carbon contribution, and the narrowest 1332 cm(-1) diamond line. (C) 1999 Elsevier Science S.A.