Ion beam mixing of metal-sapphire interfaces

Thin films of Au, Ag have been evaporated on (0001) surface of sapphire and then the interfaces were irradiated with xenon ions. Ion energy of 1.5 MeV, fluences of 3×1015 to 2.2×1016 ions cm-2 and irradiation temperatures at 77 and 300 K were used. The evolutions of the interfaces were studied by different techniques such as Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), optical absorption, X-ray diffraction at glancing incidence and electrical resistivity measurements. Blistering is observed for all specimens bombarded with fluences as low as 3×1015 ions cm-2. The RBS analysis seems to show a ballistic mixing at Ag or Au-Al2O3 interfaces but X-ray diffraction at glancing incidence does not reveal any new compound formation at the interfaces. Nevertheless optical absorption shows the formation of silver or gold metallic precipitates embedded into Al2O3.