Ion mixing in oxide-sapphire systems

Ion beam mixing of thin oxide films, Cr₂O₃ and ZrO₂, on sapphire substrates has been studied. The systems were chosen according to their solubilities in α-Al₂O₃: Cr₂O₃ is completely soluble, while ZrO₂ is insoluble. Mixing experiments were performed on 50-80 nm-thick Cr₂O₂ and ZrO₂ films deposited on α-Al₂O₃ by rf sputter deposition. Experiments were also performed on 50 nm thick Zr and Cr films deposited on α-Al₂O₃by electron beam evaporation. The oxide-sapphire specimens were bombarded with Cr ions at an energies between 160 and 340 keV to fluences near 5 x 10¹⁶ ions-cm^-2. Irradiations were also performed with 475 keV Kr ions, to similar fluences. These irradiations were performed at temperatures between 20°C and 900°C. The metal-sapphire samples were irradiated at 20°C with 320 keV Kr, to similar fluences. Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and transmission electron microscopy were used to analyze samples before and after irradiation to analyze the interface modifications. No long-range mixing was found to occur in any of the systems studied.