ION-BEAM MIXING OF CHROMIUM OR ZIRCONIUM FILMS WITH SAPPHIRE

Ion beam mixing of thin metallic films deposited on sapphire substrate s was studied for Cr or Zr films deposited on single-crystal alpha-Al2 O3 substrates. Evidence for the influence of equilibrium thermodynamic factors was sought by comparing the effects of bombarding with O ions (300 and 1073 K) with those of bombarding with Ne ions (300 K). Therm odynamic calculations indicate that mixing might occur for Zr/sapphire at 1073 K but not at 300 K. On this basis, Cr/sapphire should not mix at either temperature. The implantation energy placed the peak O conc entration at the metal-sapphire interface in an attempt to maintain an equilibrium ratio of cations to anions to promote a radiation-induced chemical reaction across the interface. No evidence for long-range mi xing was found from Rutherford backscattering-ion channeling measureme nts. Other experiments employed a heavier ion (Kr) as the mixing ion ( 300 K) in order to increase the mixing efficiency. Rutherford backscat tering-ion channeling and X-ray photoelectron spectroscopy (XPS) were used to determine the extent and nature of any interface modification. The XPS results indicated that only metallic Cr was present near the interface in the as-deposited specimens and in those irradiated with K r at 300 K. Zirconium exhibited only the metallic state (Zr-0) in the as-deposited film but was present as both Zr-0 and Zr4+ after irradiat ion. Some metallic Al (Al-0) was detected near the Zr-sapphire interfa ce after irradiation, suggesting that a local chemical reaction betwee n Zr and the sapphire may have occurred during bombardment. No long-ra nge material transport was detected for any experimental condition exa mined; the width of the ''mixed'' region in each case was below the li mits of detection for RES or consistent with that expected for ballist ic effects.