Formation of L10-ordered CoPt during interdiffusion of electron-beam-deposited Pt/Co bilayer thin films on Si/SiO2 substrates by rapid thermal annealing

Preparation of ordered CoPt on Si substrates is significant for expanding future applications of spintronic devices. In this study, ordered CoPt alloys including the L1(0) phase with a maximum coercivity of 2.1 kOe are formed in electron-beam-deposited 11.4 nm thick Pt/Co bilayer thin films on Si/SiO2 substrates via interdiffusion during rapid thermal annealing (RTA). The effects of RTA temperature on the magnetic properties, crystal structures, cross-sectional elemental profiles, and surface morphologies of the films are analyzed by vibrating sample magnetometer (VSM), grazing incidence x-ray diffraction (GI-XRD), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscope (SEM), respectively. For the as-deposited film, polycrystalline Pt was confirmed by uniform Debye-Scherrer rings of Pt. At 200 degrees C, interdiffusion between Co and Pt atoms in the film started to be observed by EDX elemental maps, and at 300 degrees C, alloying of Co and Pt atoms was confirmed by diffraction peaks corresponding to A1-disordered CoPt. At 400 degrees C, the in-plane coercivity of the film began to increase. At 700 degrees C, ordered CoPt alloys were confirmed by superlattice diffraction peaks. At 800 degrees C, a graded film containing L1(0)-ordered CoPt was found to be formed and a maximum coercivity of 2.1 kOe was observed by VSM, where the easy axis of magnetization was oriented along the in-plane direction. At 900 degrees C, deformation of the ordered CoPt alloys was observed by GI-XRD, and the grain size of the film reached a maximum.