Optical properties of nitrogen-rich carbon films deposited by dc magnetron sputtering

Nitrogen-rich carbon films were grown by d.c. magnetron sputtering from a graphite target in various nitrogen/argon gas mixtures using two different substrate temperatures. Infrared spectroscopical investigations were carried out in order to determine differences in the him composition and structure caused by the variation of the deposition conditions. The spectra are interpreted in terms of two bands which are typically found in the Raman spectra of CNx films. While the band at 1280 cm(-1) only slightly increases in absorption intensity with increasing nitrogen incorporation, the band at 1520 cm(-1) becomes much more pronounced. Both bands shift to higher wavenumbers with increasing nitrogen content. Additionally, the films show a decrease in the absorption above 2500 cm(-1). The existence of different functional groups absorbing at 2130 cm(-1) can be suppressed by substrate heating up to 400 degrees C during preparation, C=N groups absorbing above 2200 cm(-1), however, remain in the samples. In order to support the IR results additional ellipsometric measurements, investigations of him density and stoichiometry were performed. Heating the substrates during deposition leads to a reduced nitrogen incorporation.