X-ray photoelectron study of high-energy He+ implanted a-SiC:H thin films

The implantation with high-energy He+ ion beam results in modification of the optical band-gap and absorption coefficient of a-Si1-xCx:H films. X-ray photoelectron spectroscopy was used to characterize a-Si1-xCx:H thin films deposited by r.f. magnetron sputtering and implanted with high-energy He+ ions. The non-implanted films show the expected variety of chemical bonds: silicon-silicon and silicon-carbon bonds, carbon being three- and fourfold coordinated. The X-ray and Raman spectra show that high-energy He+ ion implantation leads to the introduction of additional disorder in the films. The X-ray photoelectron spectra of the implanted films show that, in addition to the already mentioned changes, the high-energy He+ ion bombardment results in an increase of the threefold coordinated as compared to the fourfold coordinated carbon bonds, i.e. increased graphitization of the carbon content in the films. These structural modifications, due to the high-energy He+ ion implantation, are the reasons for the observed changes in the optical properties of the films.