Effects of hydrogen plasma treatment on microstructure evolution and electrical conductivity of electroless Ni–P coatings on polyimide and glass substrates

Electroless Ni–P coatings with various thicknesses were deposited on polyimide and glass substrates, and subsequently subjected to heat treatment in air as well as microwave-assisted hydrogen plasma treatment. The effects of substrate and hydrogen plasma treatment on the microstructure and electrical conductivity were examined in detail using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and the Hall Effect measurement. The results indicated that the substrate materials may influence the deposition rate, the grain size, the type of metastable phase, crystallinity, resistivity, carrier mobility, and carrier concentration of Ni–P coatings. Furthermore, the 600 W hydrogen plasma treatment for 1 min can yield coatings with a more uniform and lower resistivity, compared with coatings at the as-deposited state or after heating at 300 °C for 3 h in air. The Ni–P coatings after plasma treatment exhibited higher carrier mobility, whereas coatings at the deposited state exhibited higher carrier concentration. In addition, prior to plasma treatment, a heat treatment in air enhances the conductivity of Ni–P coatings.