Photoluminescence and Raman studies of hydrogenated amorphous carbon films deposited by the rf plasma-enhanced CVD method

Hydrogenated amorphous carbon films (a-C:H) were prepared by rf plasma-enhanced chemical vapour deposition. The film properties were examined by transmission electron microscopy, Raman and photoluminescence (PL) spectrometries. The results show clearly that the observed phenomena depend on the negative self-bias voltage (- V-b). The transitional bias for diamond-like carbon films and polymer-like carbon films is above and below 80 V, respectively. The PL of polymer-like carbon films can be easily observed by the eyes. When the irradiation laser power density is greater than 1 kW/cm(2), the PL peak position and intensity change with the exposure time. Initially, the PL intensity increases by twice its original value, and the spectrum begins to generate a new peak at 534 nm with a shoulder at 570 nm. Continuous irradiation gradually reduced the PL intensity to zero. The light-induced PL change of a-C:H films is enhanced by an increase of laser infrared radiation density.