Preparation of Al2O3 thin films by ion-beam-induced CVD: Structural effects of the bombardment with accelerated ions

Al2O3 thin films were prepared on fused quartz by ion-beam-induced CVD. Using this method, the substrate is bombarded with O-2(+) ions (1 and 10 keV) while a flow of Al(CH3)(3) is directed onto its surface. The films were very homogeneous and flat as observed by SEM. Examination by TEM shows a microstructure formed by small (d < 100 Angstrom), compacted grains. Analysis of the local environment around aluminium was carried out for the films and for bombarded gamma-Al2O3 samples by X-ray absorption spectroscopy (EXAFS and XANES). The films were amorphous, but at 1273 K they crystallized yielding the alpha-Al2O3 structure. High energy (10 keV) O-2(+) ions produce a less heterogeneous environment around Al than low energy (1 keV) ions. The ability of EXAFS/XANES spectroscopy to characterize ion-beam-bombarded substrates is discussed.