Zinc Films on Copper Surfaces

Abstract

It was observed by Pinch that zinc in the films formed by condensation of vapour on a polished copper surface, diffused rapidly into the surface amorphous layer of the substrate at room temperature. On the other hand, Crater reported that such a diffusion phenomenon was not observed. In order to ascertain whether such diffusion takes place or not, we set two copper pieces, one with polished surface and the other with etched one, each parallel to the (110) plane of a single crystal, in the vacuum of an . electron diffraction apparatus and condensed zinc vapour on both surfaces simultaneously and observed the patterns reflected from them. The thieknesa of 'the films varied from 20 to 100A°. We could not observe any diffusion phenomenon, such as reported by Finch, in every' case and on' both surfaces.When these zinc films were heated in the vacuum of the apparatds, i. e. about 10-3 mm Hg, at 200-600°C, they were oxidized and became to zinc oxide. In these processes there formed a thin layer of brass at the boundary of the film and the substrate. This was ascertained by etching off the surface layer of zinc oxide.When zinc vapour was condensed on copper substrates which were maintained at 150-200°C, diffusion took place rapidly and twins of the spinel type of brass Were formed on the surface of copper single crystals.While zinc oxide, formed by oxidation of thin film gave normal pattern of ZnO, the one formed by oxidation of thick film gave somewhat different one which we call“ZnO pattern”for convenience. This pattern can be explained as being due to a ring fibers arrangement of zinc oxide crystals in, which fiber axes [001] are parallel to, and distributed uniformly in the surface of the substrate. Ψ-ZnO, reported by Finch, can also jbe explained as a ring fibre of zinc oxide crystals in which fibre axes [001] are distributed uniformly in the plane of the surface.