Laser PVD of Al_2O_3(Surface Processing)
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A fundamental investigation of Laser PVD (Physical Vapor Deposition) of alumina ceramics on nickel substrate was performed in broad ranges of substrate temperature and chamber pressure (vacuum degree) by using a cw Nd: YAG laser heat source. Amorphous alumina films were produced at a substrate temperature below 1000K, above which films had Al_2O_3 crystalline structure. Deposition rates were 10 to 30nm/s (0.6 to 2μm/min), which were considerably higher than those of other PVD processes. Exfoliation occurred at the substrate temperature of 600K or lower and the chamber pressure of 5×10^<-2> Pa or higher. Cracks were present in the crystalline films after laser PVD at 1070K, probably because larger thermal stress might be induced in the film during cooling from higher temperature due to a considerable difference in linear expansion coefficient between the film and the substrate. Films of 10GPa (Hk=1000) or harder could be obtained at more than 600K in the chamber pressure range of 10^<-3> to 10^<-2>Pa (10^<-5> to 10^<-4> Torr), and a film of Hk=40GPa was produced at 1070K and 6.5×10^<-3>Pa. The adhesive strength between the film and the substrate appeared to increase with a rise in the substrate temperature.
- Transactions of JWRI
Transactions of JWRI 19 (1), 113-118, 1990-06