STRUCTURAL AND OPTICAL CHARACTERIZATION OF BORON–NITROGEN-DOPED AMORPHOUS CARBON FILMS DEPOSITED BY r.f. PECVD

Abstract

Boron–nitrogen-doped amorphous carbon (a-C:H:B:N) films have been deposited onto glass and n-type Si(100) substrates by radio frequency (r.f.) plasma-enhanced chemical vapor deposition at a frequency of 13.56 MHz at room temperature using CH 4 as precursor of carbon source and H2 as a carrier gas. The film deposition was performed in the presence of crystalline boron source at different flow rates of 0, 6, 8, 10, 12 sccm of nitrogen under constant r.f. power and fixed partial pressure of mixed CH 4, N 2, and H 2 gases. Effects of boron and nitrogen doping on the bonding states, growth kinetics and optical properties of the as-deposited films have been examined by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. The experimental results show that the incorporation of boron and nitrogen has a considerable effect on the properties of the deposited films. FTIR spectra show that the nitrogen is bonded to carbon and hydrogen as C=N , N–H and C–H bonding configurations in the as-deposited film. The incorporation of boron and nitrogen shifts the G-peak towards the higher wave number and an increase in the I D /I G ratio demonstrating the graphitic character of the a-C:H:B:N films. Optical band gap is found to be reduced from 1.62 to 1.35 eV with the increase in nitrogen concentration in the presence of boron.