Structural change of a hydrogenated carbon film upon heating

We report, in this letter, the thermal annealing behaviour of a metastable crystalline hydrogenated carbon film prepared by plasma-enhanced chemical vapour deposition. X-ray diffraction, micro-Raman and Fourier-transform infrared (FTIR) spectrometers were used to monitor the structural transition in the film upon heating in the air. The resultant change in the film properties, e.g., the mass density and optical band gap, was investigated by specular x-ray reflectivity measurement and by optical reflectivity measurement in the visible and ultraviolet range. It was found that the structural change as well as the resultant change, in the film properties, is closely related to the release process of the bonded hydrogen in the film at elevated temperatures.