Structural studies of diamond thin films grown from dc arc plasma

Abstract

Diamond thin films grown from a dc-arc discharge in CH4/H2 mixtures on Si wafers were examined by transmission electron microscopy and Raman spectroscopy. This deposition method provides good diamond crystallinity at high CH4 concentrations (3%–9%). Seeding the substrate with 5 nm diamond particles at a density of 2 × 1012 cm−1 followed by argon laser irradiation to reduce their agglomeration gives, just after starting deposition, a density of growth centers of 1010cm−2. At 3% CH4 concentration the film grows with almost perfect crystallites. Richer CH4 mixtures (5% and 9%) produce crystallites with twins and stacking faults. An amorphous 20–70 nm SiC interlayer is present at these CH4 concentrations, which was not observed at 3% CH4. Amorphous sp3- and sp2-bonded carbon was detected by Raman spectroscopy at all CH4 concentrations and correlated with TEM data.