Growth and structural characterization of Fe/TaOx/Fe magnetic multilayers

Abstract

In this thesis, we are proposing to fabricate and structurally characterize Fe/TaOx/Fe magnetic multilayers as an initiative work towards magnetic tunnel junction (MTJ) structures with TaOx spacer layer. The multilayer structures were grown by magnetron sputtering technique and characterized by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Ellipsometry was used to find the refractive index and the hysteresis loops were taken by SQUID Magnetometer. It was found that Fe grew 45 degree tilted epitaxial single crystal on Si (001) substrate at room temperature. Ta growth on silicon had poor crystal quality due to large lattice mismatch between tantalum and silicon however Ta single layer on Fe was found to be single crystal with 0.72 FWHM. Reactive oxidation of Ta film resulted in formation of amorphous Ta2O5 with refractive index of 2.1. Fe, Ta, and TaOx single layer films were found to be uniform and smooth on silicon substrate. Bilayer of Fe/Ta and Fe/TaOx were also investigated to understand the behavior of single layer films on top of each other. Multilayers with Ta and TaOx spacer layers were successfully grown and these multilayers showed good structural properties. Furthermore, hysteresis loops of Fe films as thin as 50 nm showed magnetization comparable with the bulk Fe with the coercive field of 20 Oe.