INFRARED STUDIES OF HYDROGENATED AMORPHOUS-CARBON (A-C-H) AND ITS ALLOYS (N-C-H,N,F)

We have used infrared (IR) absorption spectra to characterize a-C:H an d its alloys (a-C:H,N,F). The samples were deposited in an rf plasma-e nhanced chemical-vapor deposition system with various mixtures of CH4, N-2, and NF3 gases. IR spectra are analyzed in detail and the peak po sition assignments are based on the data published in the literature a nd calculation of the normal mode vibrational frequencies by assuming a simple force field and linear-molecular model. From IR analysis, we found that as the concentration of nitrogen and fluorine increases, th e ratio of sp(2)/sp(3) increases, while the hydrogen content decreases , The role of nitrogen is to break the symmetry and activate the olefi nic C=C stretching mode. The role of fluorine is to replace hydrogen a nd to form stronger C-F bond. This explained the improvement of the th ermal stability of electrical conductivity of a-C:H,N,F samples.