Ion-beam-assisted deposition of nonhydrogenated a-Si:C films

Abstract

Amorphous silicon carbide (a-Si:C) films were prepared by low-energy ion-beam-assisted deposition (IBAD) in an attempt to remove structural defects in the "lattice" and improve the electrical characteristics of the film. The ion beam was generated by electron cyclotron resonance from an ultra-high-purity argon plasma. The deposition environment was first evacuated to a very high vacuum to eliminate all but trace amounts of water vapour and other gases so that improvements in the electrical and (or) structural properties of the film would be attributable to the influence of the densification by ion bombardment and not to contaminants. The IBAD process does improve the film characteristics by reducing the density of localized states at the Fermi level and the porosity of the film. However, even though these films have the best electrical characteristics obtained thus far for these kind of films, none of them exhibited device quality and none were observed to be photoconducting. A large density (≈1 at.%) of implanted argon atoms may be limiting the reduction in the defect density that might otherwise be achievable.