Effects of radio-frequency powers on the properties of carbon coatings on optical fibers prepared by thermal chemical vapor deposition enhanced with inductively coupled plasma

This study investigates the effects of different radio-frequency (rf) powers on the characteristics of carbon coatings on optical fibers that are prepared by thermal chemical vapor deposition (thermal CVD) enhanced with inductively coupled plasma (ICP). Methane and nitrogen were used as the precursor gases, and rf-powers of ICP were set to 0, 50, 100, 200, 300, and 400 W. The deposition temperature, working pressure, and deposition time in the thermal CVD process were set to 1248 K, 4 kPa, and 2 h, respectively. Experimental results indicate that the deposition rate of carbon coatings increases as the rf-power increases from 0 to 200 W, but decreases as the rf-power exceeds 200 W. The mean crystallite size and ordered degree of carbon coatings decrease with increasing the deposition rate. Moreover, when the rf-power increases, the carbon coatings have more sp2 carbon atoms and shift to graphite-like. With the assistance of ICP, carbon coatings can be deposited by thermal CVD at a low working pressure (about 4 kPa). Furthermore, the deposition rate and film properties can be adjusted by the rf-power