The lattice expansion in the direction parallel to the film surface has been determined by X-ray diffraction for the two cases (1) as deposited and (2) after removal from the substrate, and the corresponding stress values ui and o'z have been calculated. Both a, and az are positive (tensile); δ
2<1×10
9 dyn/cm
2 for films thicker than 50nm, and (δ
1-δ
2)_??_1×10
9 dyn/cm
2 for 50nm<d (film thickness)<a few hundred nm; a, and az, as well as the grain size, increase with d up to d, V150nm, above which they remain constant. Larger values of ai and as are observed if the deposition conditions are such that epitaxy is enhanced. The stress build-up. in films on the substrate can be explained according to the grain growth model. It appears, moreover, that the local tensile stress in free films, δ
2, is balanced by a compressive stress in grain boundaries or surface layers.
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