The film properties and the heat change properties of new electroless plated Ni‐Mo‐P alloy films, which were deposited from a newly developed simpler bath with direct addition of Na2MoO4 , were investigated as a basis for developing new functional thin film. Both amorphous and crystallized Ni‐Mo‐P alloy films were prepared by simply controlling the Na2MoO4 concentration in the baths. The maximum molybdenum content of 14.9 atom percent (22.3 weight percent) was attained at a Na2MoO4 concentration of 0.020 mol dm−3, and the films having high resistivity and high thermal stability were obtained. The formation of solid solution between Ni matrix and codeposited Mo was indicated on the basis of comparison with bulk Ni‐Mo alloy. The amorphous Ni‐Mo‐P alloy film had much better thermal stability than did the amorphous Ni‐P alloy film. In the case of crystallized Ni‐Mo‐P alloy film, the small grain size of electroless Ni‐Mo‐P alloy film was maintained even after heat‐treatment up to 400°C. The crystallization process of the amorphous and crystallized Ni‐Mo‐P alloy films by heat‐treatment was quite different from that of an ordinary electroless Ni‐P alloy film. Three structural changes resulting from heat‐treatment were observed in electroless Ni‐Mo‐P alloy films, namely, the formation of Ni3P , the crystallization of Ni‐Mo alloy, and the transformation of Ni‐Mo alloy. A schematic model of Ni‐Mo‐P alloy films composed of two phases or zones, namely, the Ni‐Mo and Ni‐Mo‐P, was proposed to explain the heat change properties of Ni‐Mo‐P alloy films.

An electroless plating bath for amorphous Ni‐W‐P alloy films was developed and their heat change properties were investigated from the viewpoint of W codeposition effect. The alloy films kept amorphous state with increasing W content even though the P content decreased. Moreover, the films became more amorphous, and their thermal stability increased with an increase of W content in the deposit. The tungsten content was varied from 0 to 20.8 weight percent (w/o) with a decrease in P content from 14.0 to 6.2 w/o by increasing the Na2WO4 concentration in the bath. Two characteristic heat change behaviors were observed in the Ni‐W‐P alloy films. One was the formation of metastable phase in spite of low P content. The other was direct formation of Ni‐W alloy phase. The tungsten codeposition increased the thermal stability of amorphous Ni‐W‐P alloy films plated from the baths with higher Na2WO4 concentration by suppressing the Ni crystallization prior to the Ni3P compound formation. The thermal changes of resistivity strongly depended on the crystallization of the Ni3P compound and Ni alloy phase. Both crystallization reactions were controlled by the P and W contents in the deposits.

The magnetic and electric properties of electroless Ni–P films after heat treatment are investigated as a function of the P content in the deposit. The residual Ni, which means the surplus Ni (crystallized Ni) after Ni3P formation, is confirmed to determine the film properties of resistivity and saturation magnetization. Moreover, they depend only on the P content and are independent of the preparation conditions. The saturation magnetization, M s, and the reciprocal of resistivity, ρ-1, are proportional to the amount of the residual Ni after sufficient heat treatment. An equation, showing the correlation between the P content and the resistivity or magnetization of the deposit after sufficient heat treatment, is proposed on the basis of the characters of ferromagnetic and metallic conductivity of the residual Ni matrix.

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Electroless Ni–Mo–B alloy films from a bath using dimethylamine–borane(1/1) (DMAB) as a reducing agent were investigated. Only a small amount of Mo-complex addition to the bath decreased the boron content and increased the molybdenum content drastically. The maximum molybdenum content and maximum resistivity under as-plated conditions were obtained as 22.1 wt% and 322 μΩ cm respectively. Such a high resistivity is characteristic of Ni–Mo–B alloy films. Both crystallized and amorphous states of Ni–Mo–B alloy films, whose Mo contents were above 20 wt% with a small amount of boron, were prepared by controlling the Mo-complex concentration in the bath. The heat change properties of Ni–Mo–B alloy films were quite different from those of the electroless Ni alloy films reported previously. The resistivity of Ni–Mo–B alloy films after heat treatment at 500 or 600 °C became higher than that of those created under as-plated conditions. The structure transformation of Ni–Mo–B alloy films after heat treatment was quite different from that of ordinary electroless Ni alloy films. The Ni–Mo–B alloy film after heat treatment was confirmed by TEM observation to show a mosaic-like structure. Therefore, it was thought that such a high resistivity and such thermal properties of Ni–Mo–B alloy films are caused by such a mosaic-like structure.