Amorphous hydrogenated carbon nitride thin films (a-CNx:H) have been prepared by plasma-enhanced chemical vapor deposition of N2 and CH4 gases using a helical resonator discharge. The structural and optical properties of the deposited a-CNx:H films have been systematically studied as a function of the substrate temperature and radio frequency (rf) substrate bias. The chemical structure and elemental composition of the a-CNx:H films were characterized by Fourier transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The optical properties of the films were evaluated using transmission ultraviolet-visible spectroscopy. The morphology of the films was investigated by scanning electron microscopy and atomic force microscopy. The FT-IR and XPS studies demonstrate the presence of carbon-nitrogen bonds with hydrogenated components in the films. The film composition ratio N/C was found to vary from 0.127 to 0.213 depending on the deposition conditions. The Raman spectra, showing the G and D bands, indicate that the a-CNx:H films have a graphitic structure. It can be found that the optical band-gap Eg of a-CNx:H films is associated with graphitic clusters, while the decrease in Eg is correlated with an increase in the size and number of graphitic clusters. Combining the results of Raman and optical measurements, it can be concluded that a progressive graphitization of the films occurs with increasing the substrate temperature and rf substrate bias power, corresponding to bias voltage.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)