IMPURITY AND DEFECT INCORPORATION IN DIAMOND FILMS DEPOSITED AT LOW SUBSTRATE TEMPERATURES

The quality of CVD diamond films degrades severely with decreasing sub strate temperatures. In this report, the impurity and defect incorpora tion in diamond films deposited from a carbon-hydrogen-oxygen gas syst em at substrate temperatures between 560 and 345 degrees C has been in vestigated using elastic recoil detection (ERD), FTIR and micro-Raman spectroscopy. In approaching the low temperature limit which coincides with the formation of cauliflower morphologies, the hydrogen incorpor ation rises steeply. Hydrogen contents beyond 1 at.% have been measure d, roughly 20 times higher than in the upper temperature range. By con trast, there was a much smaller rate of rise in the concentration of n itrogen and oxygen, despite a marked change in the microstructure of t he deposited films. At the lowest substrate temperatures, the absolute hydrogen content measured by ERD increases more steeply than those me asured by FTIR spectroscopy, which refers to C-H stretch vibrations on ly. There is evidence that hydrogen is incorporated also in the bulk r ather than being concentrated at grain boundaries as at higher tempera tures. This conclusion is supported by micro-Raman spectroscopy exhibi ting significant peak broadening in the low temperature region. (C) 19 98 Elsevier Science S.A.