Effect of the thermal treatments on the emission of a-Si1–xCx:H films

Hydrogenated amorphous silicon carbide (a-Si
_1-x
C
_x
:H) films were synthesized by Plasma Enhanced Chemical Vapor Deposition (PECVD) and their structural and optical properties were modified by a rapid thermal annealing (RTA) in nitrogen environment at different temperatures (400, 500, 600 and 800 °C). The structural and optical properties were studied by characterization techniques as Fourier Transformed Infrared Spectroscopy (FTIR) and Photoluminescence (PL). The a-Si
_1-x
C
_x
:H films with 56 % (R50) and 82 % (R300) of carbon content in gas phase emit a PL band in the green and blue region, respectively. The intensity of the PL band of the R50 film increases when it is subjected to RTA at 400 °C and 500 °C and it shifts to shorter wavelengths as the annealing temperature increases. On the other hand, the PL intensity of the R300 film decreases after the RTA processes and the PL band shifts to the blue-violet region. The increase of the PL intensity of the R50 film can be explained by the formation of new radiative recombination centers associated with oxygen and the shift has been attributed to structural changes. The oxygen atoms incorporated into the structure of the films during RTA processes were observed in the FTIR results. While the reduction of the PL intensity in the thermal treated R300 film can be related to the presence of atomic scale voids which promotes the oxidation of the film.