Abstract:

The microstructure and optical properties of nitrogen doped hydrogenated carbon DLC:N film deposited by rf plasma enhanced chemical vapor deposition(PECVD) method were studied with the help of AFM, Raman, FTIR and IRE spectrometer. Absorption intensities of the peaks CNH(1600cm^-1),CN(2200cm^-1) and NH(3250cm^-1) in the IR spectra increase with the ratio of flow N₂/CH₄. Raman spectra show that the shape of D and G band of DLC:N film varies slightly with the increase of N content, which means that the main structures of N doped films are still DLC. However, Gaussian fit results show that G band widens and the peak shifts to the low wavenumber in Raman spectra because amorphous C₃N₄ structure has formed in the film. AFM topographies and LFM images of DLC:N film confirm that the amorphous C₃N₄ exists as several tens nanometer particles in the film. IRE spectra analysis results show that refractive index of the film in infrared band(2~14 μm) slightly decreases from 1.8 to 1.6 with increased nitrogen content in the films.

Key words: microstructure, infrared properties, hydrogenated carbon nitride film