Ion mixing in oxide-sapphire systems

Ion beam mixing of thin oxide films on sapphire substrates has been studied in order to examine any role of equilibrium thermodynamic parameters on the mixing process. Mixing experiments were performed with polycrystalline oxide films deposited on single crystalline α-Al2O3 substrates. According to the equilibrium phase diagrams, Cr2O3 is completely soluble in α-Al2O3, while ZrO2 is insoluble. The couples were irradiated with Cr ions (160 and 340 keV) or Kr ions to fluences of 4 x 1016 ions/cm2 at temperatures between 20 and 900 degrees C. Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, and transmission electron microscopy were used to analyze samples before and after irradiation to determine the extent and nature of interface modifications. No long-range mixing was detected under any condition studied; the width of the open-quotes mixedclose quotes region in each case was consistent with recoil mixing. The absence of long-range mixing is rationalized in terms of the different ranges of oxygen ions and cations