Thermally and Ion-Induced Reactions of Metal with CuO Substrate
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THERMALLY AND ION-INDUCED REACTIONS OF METAL WITH CuO SUBSTRATE JIAN LI,S.Q.WANG AND J.W.MAYER Department of Materials Science and Engineering,Cornell University, Ithaca, NY 14853 ABSTRACT Thermally and ion-induced reactions of transition metals Zr,Ti,Cr and Ag with CuO substrates have been studied by Rutherford backscattering spectrometry and X-ray diffraction techniques. Reactions resulted in the configuration of ZrO2 /Cu 2 0/CuO from Zr/CuO structure and TiOx/Cu 2O from Ti/CuO structure after thermal annealing and ion irradiation. No significant reaction has been found in Cr/CuO after vacuum annealing at 410 0 C and 300 Key Xe ions irradiation at 2400C. Ag atoms balled up on CuO surface after annealing at 6100C. A comparison of the reaction layers has been made in both metal/SiO2 and metal/CuO systems after thermal annealing and ion irradiation. Both heats of reaction and bond strength in the substrates can influence the chemical reactivity between metal layer and substrate. I. Introduction Copper oxide, which plays an important part in high Tc superconductor materials, has some interesting properties. CuO is not stable in vacuum during thermal annealing. CuO thin films on Si0 2 substrates transform to Cu2 O after 750 0 C annealing in vacuum. A top layer of metal on CuO may enhance or reduce this phase transformation, because this metal layer may act as a sink for oxygen or a cap to prevent oxygen loss. In this study, we have investigated the chemical reaction of metal layers Zr,Ti,Cr and Ag,with CuO substrate. We have tried to correlate the reaction products to the heat of reaction in metal/CuO system, and made a comparison with the reaction in metal/Si0 2 . Ion beam mixing in metal/insulator systems has been extensively studied [1,2]. Farlow et.al [3] summerized the ion beam mixing of metal on insulators. The substrate dependence for refractory metals has been found. In this paper, we will study ion beam mixing in metal/CuO and metal/Si0 2 systems. The bond strength of the substrate may influence the interfacial reaction in M/CuO and M/Si0 2 systems for this low temperature ion irradiation processing. II.
Experimental procedure
CuO films (160 nm) were prepared by reactive sputtering Cu in oxygen ambient on SiO2 substrates. The base pressure in the sputtering chamber was0 5-9X10- Torr. The CuO/SiO 2 substrate was then baked at 300 C for 30 minutes before the coatings of metal films. The metals were deposited onto CuO/SiO 2 /Si substrates by either e-beam heating (Zr,Ti and Cr) or resistance heating deposition (Ag). For Zr/CuO reaction study, CuO bulk ceramic sample,which was mechanically polished, was also chosen as a substrate material. The film thickness was
Mat.Res. Soc. Symp. Proc. Vol. 128. -1989 Materials Research Society
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measured by Rutherford backscattering spectrometry showing that the film thickness for Zr,Ti,Cr and Ag are 110 nm,62 nm,59 nm and 72 nm,respectively. Thermal annealing was carried out in a vacuum of 2X10-7 Torr at temperatures ranging from 4100C to 6100C for a duration of 30 mi
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