Growth and alloy formation of ultrathin Ni films on Co/Pt(111)

摘要

Low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to study the growth and the structural evolution of Ni/Co/Pt(111) following high-temperature annealing. From the oscillation of the specular beam of the LEED and Auger uptake curve, we concluded that the growth mode of thin Ni films on 1 ML Co/Pt(111) is at least 2 ML layer-by-layer growth before three-dimensional island growth begins. The alloy formation of Ni/1 ML Co/Pt(111) was analyzed by AES. The temperature for the intermixing of Ni and Co layers in the upper interface without diffusing into the bulk of Pt is independent of the thickness of Ni when a Co buffer is one atomic monolayer. After the temperature was increased, formations of Ni-Co-Pt alloy, Ni-Pt alloy and Co-Pt alloy were observed. The temperature required for the Ni-Co intermixing layer to diffuse into Pt bulk increases with the thickness of Ni. The interlayer distance as a function of annealing temperature for 1 ML Ni/1 ML Co/Pt(111) was calculated from the Ⅰ-Ⅴ LEED. The evolution of LEED patterns was also observed at different annealing temperatures.