Growth of thin hydrocarbon films and hydrogen production in a cusp plasma device

A plasma device with a cusp magnetic field configuration and operating under steady state condition has been built to investigate surface deposition of hydrocarbon films at low temperature and, simultaneously, the cracking of methane in a plasma environment to hydrogen production. The gas (methane or a methane/argon mixture) has been fed to the plasma source (a cylindrical capacitively coupled rf type). The addition of a static magnetic field has increased the particle confinement time and, consequently, the hydrogen production rate. Here the preliminary results concerning the growth of thin hydrocarbon films and the dissociation of methane in the cusp plasma are presented. In our case, at the line and point cusp, we have a large flux of energetic particles as well as neutral, ions, thermal radicals that participate in the growth process. A fraction of the converted methane has been deposited on the substrates, at the line cusp, as amorphous hydrocarbon (a-C: H) film and amorphous carbon (a-C) film. The surface morphology of the film has been observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) has been used to determine the structure of the film. The results have indicated that the film has a prevalently amorphous structure with a presence of crystalline clusters.