Initial Growth of Metal Films Fabricated on a Substrate Excited by SAW.

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Abstract
Co and Fe ultra-thin films of various thicknesses coated with 50-Å-thick Cu film were prepared by vacuum evaporation on an LiNbO3 single-crystal substrate excited by surface acoustic waves (SAW) at 45 MHz. In order to clarify the detailed correlation between the SAW attenuation and the microstructure of the metallic film in the initial growth stage, the magnetization curves and megnetoresistance of Cu-coated ultra-thin films were investigated as functions of Co or Fe thickness, d, in connection with the SAW propagation properties during deposition. With increasing d, the behavior of the magnetization curves changed from superparamagnetic to ferromagnetic, and the magnetoresistance, which is similar to that of Co-Cu granular alloy films, vanished at d=dp, where the SAW attenuation reaches a maximum. From these results, it was concluded that the film thickness dp corresponds to the critical thickness at which the film structure changes from island-like to continuous.