A. Tabata*, H. Yonedu**, Y. Suzuoki* and T. Mizutani**

*Center for Integrated Research in Science and Engineering, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
tabata@nuee.nagoya-u.ac.jp

**Department of Electrical Engineering, Nagoya University, Chikusa, Nagoya, 464-8603, Japan

Hydrogenated amorphous silicon carbide (a-Si1-xCx:H) is one of important materials for application in optoelectronic devices such as thin-film solar cells and so on. Recently, much attention has been paid to pulse-modulated (PM) glow discharge technique as a powerful method for the control of plasma. We have applied PM rf glow discharge technique to preparation of a-Si1-xCx:H films and investigated the effects of PM glow discharge on the film properties.

In this study, a-Si1-xCx:H films were prepared by using capacitively-coupled rf glow discharge from the mixture of gas of silane (2.5 sccm), methane (2.5 sccm) and helium (45 sccm) on Corning 7509 glasses and silicon wafers. the gas pressure, the rf power and the substrate temperature were 300 mTorr, 40 W and 250 C, respectively. The modulation frequency was 50 Hz, 500 Hz, 2 kHz or 5 kHz and the duty ration was 25%, 50% or 75%.

The concentration of hydrogen bonded to silicon atom in the films prepared by PM discharge (the PM films) remained unchanged for various modulation frequencies and duty rations and was almost equal to that in the film prepared by continuous wave discharge (the CW film). On the other hand, the concentration of hydrogen bonded to carbon atom in the PM film (except for 5 kHz, 75%) was about one half that in the CW film, was insensitive to modulation frequency and increased slightly with increasing duty ration. The IR absorption peak due to Si-CH3 wagging was decreased by using PM discharge, indicating the decrease in the concentration of hydrogen bonded to carbon atoms. The use of PM discharge technique improved the photoconductivity. One of the causes is the decrease in the number of C-H3 bonds. It is found that the PM glow discharge technique is powerful to improve photoconductivity of a-Si1-xCx:H film.