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Hydrogenated amorphous boron (a-B:H) thin films were prepared by radio-frequency plasma deposition using B2H6 (10%) in H2 as precursor gas. The influence of the substrate temperature and self-bias on the a-B:H film structure was investigated. The boron and hydrogen atom densities were determined by ion-beam analysis. The film structure, especially the bonding of hydrogen to boron, was investigated by Fourier transform infrared (FTIR) spectroscopy. The FTIR data were quantified by using a new formalism which allows a proper calculation of the extinction coefficient from the FTIR spectra. The intensities of the different boron-hydrogen absorption bands were compared with the ion-beam analyzed hydrogen atom densities to determine the absorption strength of the B–H terminal and B–H–B bridge bonds. A non-negligible fraction of hydrogen is shown to be bonded to boron in a B–H–B bridge bond.

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Amorphous-hydrogenated boron (a-B:H) and carbon (a-C:H) thin films were prepared by radio-frequency plasma deposition using (B2H6+H2) or CH4 as a precursor gas. The film composition and density were investigated by ion-beam analysis. The films were eroded by hydrogen electron cyclotron resonance plasmas at floating potential and by atomic hydrogen dissociated by a hot filament. The temperature of the substrates was increased during the erosion process from 330 to 680 K. Erosion rates were measured in situ by ellipsometry. a-B:H films are shown to be much more resistant to erosion by hydrogen ions (H+) and atomic hydrogen (H0) than a-C:H films. In contrast to a-C:H films, no chemical erosion of a-B:H films by H0 was observed at temperatures below 600 K. Ion energies lower than the threshold energy for physical sputtering cause measurable erosion rates for a-B:H films. It is concluded that this is a synergistic effect of simultaneous H0 and H+ bombardment and it is designated as ion-induced chemical erosion.

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