Abstract
The effect of different ammonia/acetylene (NH 3 /C 2 H 2 ) ratio on the characteristics of amorphous carbon films prepared by radio-frequency plasma enhanced chemical vapor deposition is investigated. Five kinds of carbon films are prepared with NH 3 /C 2 H 2 ratios of 0, 0.2, 0.5, 1, and 1.4. The radio-frequency power, substrate temperature, and working pressure were kept at 100W, 298K, and 28Pa, respectively. The thickness of all kinds of carbon films was about 100nm. Experimental results indicate that as the NH 3 /C 2 H 2 ratio increases from 0 to 1.4, the nitrogen/carbon ratio in carbon films increases from 0 to 6.9%. The nitrogen-carbon bonds and sp 2 carbon fraction of carbon films enlarge with increasing the NH 3 /C 2 H 2 ratio, while the ordered degree, Young's modulus, and hardness of carbon films decrease. Furthermore, when the nitrogen-doped amorphous hydrogenated carbon, a-C:H(N), film was deposited on p-silicon (p-Si) substrate, the forward electrical resistance of a-C:H(N)/p-Si device decreases with increasing the NH 3 /C 2 H 2 ratio. The quality factor (also called ideality factor) of a-C:H(N)/p-Si device is a measure of how closely this device follows the ideal diode equation, which has the best value of 1.3 at the NH 3 /C 2 H 2 ratio of 1.4. © 2012 Elsevier B.V.