REACTIVE MAGNETRON SPUTTERING OF CNX THIN-FILMS AT DIFFERENT SUBSTRATE BIAS

The chemical binding states of C and N atoms, and optical properties o f carbon nitride (CNx) thin films deposited by unbalanced magnetron sp uttering, have been investigated as a function of the negative substra te bias (V-s). The film deposition rate increased slightly with increa sing V-s, having a weak maximum at floating potential (similar to 50 V ), and decreased sharply to zero for V-s > 150 V-s while N/C ratios di d not exhibit any significant variation. Raman spectroscopy was used t o reveal that the structure of the film is predominantly amorphous. Fo urier transform infra-red spectroscopy (FTIR), X-ray photoelectron spe ctroscopy (XPS) and electron energy loss spectroscopy (EELS) analyses showed that N atoms in the films were bound to C atoms through sp(2) a nd sp(3) configurations. Triple C-N bonds were also detected by FTIR. The ratio of sp(3) to sp(2) bonds increased with increasing V-s. The m aximum sp(3) concentration in CNx films was estimated to be similar to 20%. The optical band gap of CNx films was also found to increase wit h an increase in V-s. (C) 1997 Elsevier Science S.A.