Tem and X-Ray Investigation of Single Crystal-Like Zirconia Films Fabricated by Dual Ion Beam Deposition
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This study reports the deposition of biaxially aligned YSZ on amorphous, polycrystalline metallic, polycrystalline ceramic, and single crystal Si substrates using dual ion beam deposition. Several X-ray diffraction techniques are used to evaluate the film orientation. High resolution cross-sectional TEM is used to examine the evolution of crystallographic film alignment on an amorphous quartz substrate beginning at the film/substrate interface. The data suggest a nucleation controlled mechanism governs texture development in dual ion beam deposition. EXPERIMENTAL The IBAD apparatus consists of a 3 cm Kaufmann ion source (Commonwealth Scientific, Alexandria, VA) and a 3 cm RF ion source (Ion Tech, Inc., Ft. Collins, CO). The plasma from the Kaufmann ion source with 1000 eV beam energy sputters a sintered polycrystalline YSZ target. The ion beam current and beam energy from the assisting RF ion source are 30 mA and 300 eV, respectively. A plasma bridge neutralizer (PBN) is operated with excess current used to neutralize both ion beams and the insulating YSZ target. Argon is used for the PBN and sputtering ion beam, and Ar with 8 wt% 02 is used for the assisting ion beam. Amorphous quartz, polycrystalline Hastelloy, polycrystalline tetragonal stabilized zirconia (TZP), and (100) Si substrates were used in this study. The hastelloy and TZP substrates were ground and polished to a -250 nm finish. Substrates were ultrasonically cleaned in a series of organic solvents and mounted onto a stainless steel block using silver paste. The substrate block was heated ex situ to remove organic constituents from the silver paste. The substrate normals were placed at an angle of 550 from the assisting ion beam. Ion bombardment caused the substrate temperature to rise from 25°C to 180'C during deposition. Transmittance spectra from films deposited on transparent substrates were obtained using a UV/Vis spectrophotometer (Beckmann DU640 Spectrophotometer, Fullerton, CA). Film thickness was calculated from the interference fringes using the envelope technique reported by Swanepeol." This thickness value was correlated with that obtained from cross-sectional SEM fracture surfaces. The orientation of the films was characterized by 0-20 X-ray diffraction, X-ray rocking curves, and X-ray phi scans. Bright field high resolution TEM and cross sectional SEM are used to evaluate the film microstructure. RESULTS AND DISCUSSION YSZ films were deposited on amorphous quartz, polycrystalline zirconia, single crystal Si, and Hastelloy substrates using a sputtering ion beam energy of 1000 eV and an assisting ion beam energy of 300 eV. The films featured exclusive (200) normal orientation, as determined by 0-20 X-ray diffraction. The film orientation is substrate independent, as nearly identical phi scans were observed on all substrates. This observation is contrary to the substrate-dependent orientation observed for YSZ films deposited by ion assisted, electron beam evaporation.7-10 The highly aligned YSZ film deposited on an amorphous quartz substrat
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