E. Camps

Electron evaporation of carbon using a high density plasma.

High-density plasmas are often used either in the preparation of thin films or for the modification of surfaces. However, except for collision-driven chemical reactions the electrons present are not used, although electron bombardment heating of the work piece nearly always occurs. Principally it is the ions and neutrals that are utilised for material processing. By suitable biasing of a conducting source material the electrons can be extracted from a high-density low-pressure plasma to such an extent that evaporation of this source material can be achieved. Due to the presence of the plasma and the flux of electrons a large proportion of the evaporant is expected to be ionised. We have used this novel arrangement to prepare thin films of carbon using a resonant high-density argon plasma and a water-cooled rod of high purity graphite. Multiple substrates were used both outside of, and immersed in, the plasma. We report the characteristics of the plasma (electron temperature and density, the ion energy and flux, and optical emission spectra), the deposition process (the evaporation rate and ion/neutral ratio), and the film properties (IR and UV/Vis absorption spectra, Raman spectra, elemental analysis, hardness and refractive index).

DLC films prepared by electron evaporation of graphite in an ECR plasma

Abstract Films of diamond-like carbon (DLC) have been prepared by a novel electron evaporation scheme in an argon plasma within a linear microwave ECR reactor. The electrons present in the high density ECR plasma are attracted to a biased graphite rod to such an extent that the carbon is thermally evaporated. The argon ions bombard the substrate with an energy determined by the plasma potential and the substrate bias. However, the plasma potential is determined by the size of the graphite rod as well as the applied voltage. The films have been analysed using the following techniques: profilometry (thickness and residual stress); ellipsometry (refractive index and thickness); Raman spectroscopy (atomic bonding); UV-Vis spectrophotometry (bandgap), PEELS (C sp3), EDX and RBS (chemical analysis). The results are discussed in terms of the knock-on subplantation model [Rad. Effects Defects Solids, 142 (1997) 63] and the recently published interpretation of the Raman spectra of carbon films [Phys. Rev. B, 61 (2000) 14095].