Hydrogen-free carbon thin films prepared by new type surface-wave-sustained plasma (SWP)

In this paper is described the simple structure of a new type surface-wave-sustained plasma (SWP) source without a magnetic field surrounding the chamber wall. In the source, the plasma is excited and sustained by 2.45 GHz microwaves, and the plasma density is measured by a single Langmuir probe in the target direction. The results indicate that the electron density obtained in this system is as high as 9 × 10¹¹ cm^{- 3} even at a low pressure of 2.8 Pa. A graphite target (99.998%) and argon (99.999%) are used for depositing hydrogen-free amorphous carbon films by the new SWP source. The Raman spectra of the carbon films were obtained, and the results denote that the structure of the carbon films prepared by SWP is typical of diamond-like carbon; the Raman intensity ratio I_D/I_G is 2.97. The surface morphology was investigated by using an atomic force microscope (AFM). The images demonstrate that the hydrogen-free carbon films deposited by SWP have a very smooth surface, with a grain size of about 20 nm and surface roughness R_a of about 0.778 nm.