Ion Beam Mixing of Alternate Layers of Ni-Nb and Ni-Cr

Abstract

Alternating layers of Ni and Nb with a total thickness of 1060Å, and Ni and Cr with a total thickness of 840Å were deposited by electron beam evaporation on silicon. The individual layer thicknesses were adjusted in such a way as to obtain 50/50 at% compositions of Ni-Nb and Ni-Cr; the thicknesses were around 100Å for Ni and 170Å for Nb, and 100Å of Ni and 110Å of Cr. The films were bombarded with 350 keV Cr⁺ ions at a dose of 2 × 10 ions cm⁻². RBS and TEM techniques were used to study the mixing and microstructure. Almost complete mixing and amorphization have been observed for the Ni-Nb system. Ni-Cr film has revealed very little mixing compared to Ni-Nb film and the microstructure remained polycrystalline. Sputter (rf) deposited Ni-Cr film also remained polycrystalline both before and after ion irradiation. The Ni-Cr System appears to be an exception to the structural difference rule for amorphous phase formation by ion irradiation.