Effect of substrate temperature on the properties of carbon-coated optical fibers prepared by plasma enhanced chemical vapor deposition

The effect of substrate temperature on the properties of carbon-coated optical fibers prepared by plasma enhanced chemical vapor deposition is studied. The substrate temperatures were set at 20, 150, 300, and 450 degrees C. The deposition rate of carbon films decreases with increasing substrate temperature, while the self-bias voltage during deposition increases. The results of analysis by Fourier transform infrared spectroscopy and determination of the optical band gap show that Sp(2) carbon sites in the coating structure increase as the substrate temperature increases. When the substrate temperature changes from 20 to 300 degrees C, the carbon coating surface becomes more compact. Alternatively, when the substrate temperature is increased to 450 degrees C, many nano-scale hillocks appear on the carbon coating surface. The carbon coating prepared at the substrate temperature of 300 degrees C has the highest water contact angle of 90 degrees and an excellent ability to sustain the thermal loading, so it is the best for production of carbon-coated optical fibers. (C) 2007 Elsevier B.V. All rights reserved.