Infrared and Optical Properties of Amorphous Fluorinated Hydrocarbon Films Deposited with the Method of ECR Plasma

摘要

Using CH_4 and CF_4 precursor gases, amorphous fluorinated hydrocarbon (a-C:F:H) films were prepared with the method of microwave electronic cyclotron resonant (ECR) plasma chemical vapor deposition. Deposition rate of the film firstly increases and then decreases with variable flow ratios R {[CF_4]/([CF_4] + [CH_4]} due to the competition between deposition and etching process. Results from Fourier-transform infrared transmission spectroscopy of these films show that C-F bond configuration in a-C:F:H films evolves with the variable gas flow ratios R. The locations of the C-F peaks in IR spectra shift to higher frequency with the increase of R, and finally the structure in films with R >75% takes on a PTFE-like structure, which mainly consists of -CF_2- chain. The change of optical band gap Eg deduced by a Tauc plot with R is also discussed.