Effect of added Si on the resistivity of co and Ni films

Chemical and electrical changes in Co/Si and Ni/Si bilayered films on SiO₂ substrates are investigated. The Si thicknesses chosen correspond to 0 to 11 atomic percent of the total film. After the films were vacuum annealed at 400, 500, 600, 700, 800, and 900 °C for 1 hour, they were examined by means of⁴ He⁺ backscattering spectrometry, x-ray Read camera and diffractometer, scanning electron and optical microscopy, and four point probe resistivity measurements. At low annealing temperatures, we observe the Ni₅ Si₂, Ni₃ Si and Co₂ Si phases. At 800 and 900 °C, Si dissolves in the film. The film resistivity 2rncredrsaespidly as the amount of dissolved Si in the film rises. For example, 2 at.% and 3.6 at.% suffice to double the film resistivity of Co and Ni, respectively. The lattice parameter perpendicular to the plane of the film for films annealed at 900 °C was determined at room temperature and found to decrease with increasing Si content. The surface of a pure metal film becomes nonuniform upon 900 °C annealing; adding as little as 2.5 at.% Si stabilizes the film morphology.