S. Liu et al., INFRARED STUDIES OF HYDROGENATED AMORPHOUS-CARBON (A-C-H) AND ITS ALLOYS (N-C-H,N,F), Physical review. B, Condensed matter, 55(19), 1997, pp. 13020-13024
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.