Deuterated amorphous carbon films: Film growth and properties

Deuterated amorphous carbon films (a-C:D) have been studied in the last few years in order to investigated possible isotopic effects in the film properties. When compared with films deposited in methane atmosphere, an important reduction of the deuterium content of the films was observed and the reasons for that are not well understood. In this work, we deposited amorphous carbon films by PECVD using methane and deuterated methane gas mixtures as precursor atmospheres. We also investigated the effects of the self-bias voltage. The hydrogen and deuterium content was measured by elastic recoil detection analysis and we observed the preferential incorporation of hydrogen over deuterium. The precursor atmosphere was monitored by mass spectrometry and only small differences can be observed in the obtained mass spectra. The possible reasons for the total hydrogen content are discussed. The film deposition rate, the film microstructure as revealed by Raman spectroscopy, the film hardness determined by nanoindentation and the internal stress are dependent on the precursor atmosphere, however a much stronger dependence on the self-bias voltage was observed for deuterated carbon films.