Microstructural and magnetic properties of thermally mixed Ni/Si bilayers

Polycrystalline nickel layers, deposited on Si(1 1 0) wafers via electron beam evaporation to a thickness of 29 or 68-70 nm, were thermally annealed in vacuo at 493 or 530 K. The elemental interdiffusion across the Ni/Si interface was measured by means of Rutherford backscattering spectroscopy, and the relaxation of stress and grain growth by means of x-ray diffraction. At 530 K, a slight logarithmic increase in the interface variance with the annealing time, but no crystalline silicide formation was observed. The in-plane magneto-optical Kerr effect and magnetic force microscopy were used to investigate the changes in the magnetic properties. With increasing annealing time, the decrease in coercivity and gain in magnetic remanence were correlated with the relaxation of stress. Similarities with ion-irradiated Ni/Si couples will be discussed.