1994 Volume 22 Issue 11 Pages 908-916
The paper describes characteristics and formation mechanism of laser PVD films, which were deposited on Ti or other metallic substrates from Si3N4 or SiC ceramic targets in wide ranges of chamber pressure and substrate temperature by using CW Nd: YAG laser as an evaporator. Many small crystalline Si3N4 particles of 1 to 15 μm size in globular orgranular shapes and metallic Si particles in the hemispherical shape were observed in the flat and dense amorphous LPVD films from the Si3N4 target. Such particles are due to spatters ejected as the fraction of solid and/or Si liquid from the target surface. Nitrogen contents in the amorphous films were reduced considerably because Si3N4 was decomposed into Si and N on the laser irradiated site. Hard films of 8-12 GPa in Knoop hardness were obtained at the substrate temperature of 723-923 K under the pressure of 0.02-1 Pa. In the case of SiC, small granular particles of less than 5 pm were observed in the flat and smooth film. The SiC films ranging 10-36 GPa under the conditions of 623-873 K in substrate temperature and 0.03 Pa in pressure were much harder than those of Si3N4. The results of scratch test indicated that the adhesive strength of the LPVD film was better in the case of Ti than in the case of W. TEM observation of films or clusters formed on the Carbon substrate revealed that the evaporated atoms deposited directly on the substrate forming a dense amorphous film under the high vacuum of 0.01 Pa. On the other hand, under the pressure of more than 1 Pa, clusters or ultra-fine particles were once formed on the substrate and were transformed into the film by the thermal migration on the heated substrate.
