Ion beam mixing of chromium or zirconium films with sapphire

• Published in: Surface & coatings technology 1996-09, Vol.83 (1), p.151-155
• Main Authors: McHargue, Carl J., Joslin, D.L., White, C.W., daSilva, M.F., Alves, E., Soares, J.C.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cr-sapphire; Defects and impurities: doping, implantation, distribution, concentration, etc; Exact sciences and technology; Ion beam mixing; Metal-ceramics; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Zr-sapphire
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/0257-8972(96)02845-9

Ion beam mixing of thin metallic films deposited on sapphire substrates was studied for Cr or Zr films deposited on singlecrystal α-Al 2O 3 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). Thermodynamic 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 concentration 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 mixing was found from Rutherford backscattering-ion channeling measurements. Other experiments employed a heavier ion (Kr) as the mixing ion (300 K) in order to increase the mixing efficiency. Rutherford backscattering-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 Kr at 300 K. Zirconium exhibited only the metallic state (Zr 0) in the as-deposited film but was present as both Zr 0 and Zr 4+ after irradiation. Some metallic Al (Al 0) was detected near the Zr-sapphire interface after irradiation, suggesting that a local chemical reaction between Zr and the sapphire may have occurred during bombardment. No long-range material transport was detected for any experimental condition examined; the width of the “mixed” region in each case was below the limits of detection for RBS or consistent with that expected for ballistic effects.