Ion-Probe Measurement of Oxygen Self-Diffusion in Single-Crystal Al2O3 |
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| Authors: | DAVID J REED&#; B J WUENSCH&#; |
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| Affiliation: | Ceramics Division, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 |
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| Abstract: | Anion self-diffusion coefficients normal to (1102) were obtained for single-crystal Al2O3 in a 1.3 × 10 3 N/m2 (10?5 torr) vacuum at 1585° to 1840°C. Tracer was supplied from an initial 650 to 1300 A Al218O3 layer produced by the oxidation of vapor-deposited Al metal films in an 18O2 atmosphere at 520°C. Concentration gradients extended over depths of 3000 to 5000 A and were measured by mass spectrometry of material sputtered from the samples with a beam of Ar+ ions. Crystals which had not been preannealed to remove surface damage displayed enhanced diffusion. Diffusion coefficients from preannealed crystals may be described by D0 =6.4×105cm2/s, with an activation energy of 188 ± 7 kcal/mol. The diffusion is interpreted as an extrinsic vacancy mechanism. |
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