Study on sputtering power dependence of the structural properties of sputtered CoCrPt

Abstract

The structural properties of sputtered CoCrPt at levels of 0.1, 0.3, 0.5, and 1 kW sputtering power were measured by x-ray diffraction, small-angle x-ray scattering (SAXS), x-ray absorption fine structure, and transmission electron microscope (TEM). XRD indicated a continuous increase in the intensity of the peak of hcp(002) orientation, as sputtering power increases. SAXS, on the other hand, in the range of 0.5°–3°, indicated the presence of scattering center for the 0.1 and 0.3 kW samples alone, not for the others. Similarly discontinuous were the spectra produced by x-ray absorption near-edge structure of Co K edge. Only the 0.1 kW sample showed a spectrum different from the others. This means that the electronic state for 0.1 kW sample is different from that for the others. TEM observation, carried out to examine the structural morphology, indicated a clear small-grain structure for the 0.1 kW sample, less clearly defined grains for the 0.3 kW sample, and no observable grains for the others after chemical etching pretreatment. The grain size for the 0.1 and 0.3 kW samples are about 100 and 200 Å, respectively. The grain is considered to consist of a Co-rich boundary and Pt-rich inside region from the chemical analysis of the solvent. The sputtering power dependence of the structural properties is able to be explained consistently as follows. As the sputtering power decreases, the segregated grain structure appears and affects SAXS. When the segregated grain size becomes smaller, it affects the electronic state. The different sputtering power dependence of structural properties comes from the different correlation lengths included in the measurements. Therefore, to understand the relationship between the magnetic and structural properties, structural investigation should include various range orders.