Effect of substrate roughness and film thickness on the magnetic properties of CoFeB films on polymer substrate

Abstract

Correlation between the magnetic properties and surface morphology of CoFeB film has been investigated. The CoFeB films of various thicknesses are deposited on Ar plasma etched polymethyl methacrylate (PMMA) substrate. As the etching time increases, the substrate and surface roughness of the film increase, suggesting a conformal deposition that has a strong correlation between the substrate roughness and film surface. Furthermore, as the etching time increases, coercivity (Hc) increases, however, the saturation magnetization (Ms) decreases. The opposite characteristics of Hc and Ms with increasing etching time are related to domain-wall pinning and local anisotropy owing to the rough surface. In particular, the change in Hc is significantly different according to the film thickness with the increase in etching time. The different behaviors of Hc depending on the film thickness and etching time is due to the continuity or discontinuity of CoFeB film on the substrate. In addition, the magnetic properties and surface characteristics are different before and after the etching time of 2 min, indicating that the surface roughness formed by the Ar plasma etching and magnetic properties are closely correlated. These results can be effectively applied to the study of modulation of amorphous CoFeB films on polymer substrates.