Structure and physical properties of stable isotopic amorphous carbon films

Hydrogenated amorphous carbon (a-C:H) films containing isotopes of carbon and hydrogen were deposited, and their structure and physical properties were evaluated to investigate the isotopic effects in an attempt to reduce the defect density of carbon films. These isotope films such as deuterated amorphous carbon (a-12C:D) and hydrogenated 13C carbon (a-13C:H) films were deposited under the same deposition condition by the radio frequency plasma CVD method from isotope methane gas. The ratio of sp2/sp3 carbon was same, the deuterium content of a-12C:D was smaller than hydrogen contents of other films. Although the smallest content of hydrogen or deuterium as the termination structure of the carbon network was observed for the a-12C:D film, the density of defects was also smallest in the film. The Tauc gap of the a-12C:D film was approximately 30% larger than the that of the other films. From these results, the deposition process of a-C:D film brings lower defect density compared with the deposition system for a-C:H.