Characterization of Raman spectroscopy of DLC films deposited on inner surface

Diamond-like carbon (DLC) films deposition on inner surface of a stainless steel tube with 100 mm in length and 10 mm in inner diameter is carried out in direct current glow discharge plasma of Ar/CH4 mixed gas with a flow ratio of 20% CH4, and the influence of pressure and deposition time on micro-structure of the films is investigated by Raman spectroscopy. It is found that the position of both G and D line, the width (FWHM) of both G and D line and the ID/IG ratio and drop firstly and then rise along with the pressure increase, the lowest values occur when the pressure is 20Pa. On the other hand, along with the time evolution the position of both G and D line shift to the lower wave-number, the width (FWHM) and the ID/IG ratio of both G and D line decrease. These results reveal that the DLC films become harder, more ordered and more diamond-like with higher sp3 content, and the size of sp3 cluster grows larger along with the time evolution. (authors)