Photoacoustic spectroscopy and thermal diffusivity measurement on hydrogenated amorphous carbon thin films deposited by plasma-enhanced chemical vapor deposition

• The thickness of the films was confirmed to be an important parameter.
• The thermo-optical analysis can indicate a suitable film for a specific application.
• The grown thin films have been examined using photoacoustic characterization techniques.

In this work, the photoacoustic spectroscopy and the open photoacoustic cell method are employed in the thermo-optical characterization of hydrogenated amorphous carbon thin films. The samples were fabricated in a modified plasma-enhanced chemical vapor deposition system with varying deposition time from 2 to 30 min. The optical absorption spectrum was determined for wavelengths of 300 to 2200 nm. The optical transmission spectrum was also recorded from photoacoustic spectroscopy. The energy gap was determined from the optical absorption spectra. The thermal diffusivity was found using open photoacoustic cell technique. The thickness of the films was confirmed to be an important parameter for the optimization of the fabrication process and the improvement of thermo-optical performances of the thin films. Spectroscopic results showed lower absorption and UV transparency for the thinner film. In the infrared region the − OH band decreased with increasing film thickness. On the other hand, the thermal diffusivity measurement presented an increase of this variable with decreasing film thickness.

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