The Effects of Substrate Position on Electroless Polyol Deposited Nanostructured FeNi Films

The nanostructured FeNi thin films were deposited on a polycrystalline Cu substrate by reducing constituent metal salts in refluxing ethylene glycol. The effect of substrate position was investigated. During deposition, the substrate was subject to one of the following processes: (a) complete immersion in solution, (b) repeated immersion followed by suspension above solution (denoted as quenching), and (c) suspension above the solution. Compared to the conventional polyol synthesis of FeNi where Fe concentration could not exceed 30 at%, the quenching process dramatically increased Fe at% to above 40%. Complete suspension of substrate above the solution resulted in Fe-rich films where Fe at% >90%. The microhardness, adhesion, and magnetic properties of deposited films showed a strong dependence on the long-range and short-range order of the film, which, in turn, depended on the substrate position. Quenched films with ordered local Ni environment and higher crystallinity had the highest Vickers hardness, best adhesion to substrate, and largest saturation magnetization compared to those deposited on substrates placed in other positions. The oxidation of Fe occurring in the vapor deposition significantly affected the film properties.