Cross-sectional hydrogen content and mass density profiles of diamond-like carbon film by neutron and X-ray reflectivity

The cross-sectional profiles of hydrogen content and mass density of diamond-like carbon (DLC) film were investigated using X-ray and neutron reflectivity. DLC films were prepared using a plasma CVD technique by varying the H 2/(H 2 + CH 4) ratio gas source from 0 to 0.9. The cross-sectional hydrogen content and mass density profiles of the films were calculated by neutron and X-ray reflectivity, and the results were compared with those from elastic recoil detection analysis (ERDA). The fitted simulation showed that the mass density gradually decreased with increasing depth, whereas the hydrogen content increased with depth. In both ERDA and reflectivity measurements, the average hydrogen content was more than 30% in all films and tended to increase with the H 2/(CH 4 + H 2) ratio. However, there was a difference in hydrogen content values between the two analyses ranging from 5.1 % to 8.5%.