Effect of Thermal Annealing on Boron Diffusion, Micro-structural, Electrical and Magnetic properties of Laser Ablated CoFeB Thin Films

TL;DR

This study investigates how thermal annealing influences boron diffusion, crystallization, and the resulting electrical and magnetic properties of laser-ablated CoFeB thin films, revealing phase changes and property enhancements.

Contribution

It provides new insights into the effects of annealing on boron diffusion, crystallization, and magnetic properties of CoFeB thin films prepared by pulsed laser deposition.

Findings

Boron diffuses at the interface in both amorphous and crystalline phases.

Annealing at 400°C induces crystallization of CoFe with bcc structure.

Annealed films become metallic with increased coercivity.

Abstract

We report on Boron diffusion and subsequent crystallization of Co$_{40}$Fe$_{40}$B$_{20}$ (CoFeB) thin films on SiO$_2$/Si(001) substrate using pulsed laser deposition. Secondary ion mass spectroscopy reveals Boron diffusion at the interface in both amorphous and crystalline phase of CoFeB. High-resolution transmission electron microscopy reveals a small fraction of nano-crystallites embedded in the amorphous matrix of CoFeB. However, annealing at 400$^\circ$C results in crystallization of CoFe with \textit{bcc} structure along (110) orientation. As-deposited films are non-metallic in nature with the coercivity (H$_c$) of 5Oe while the films annealed at 400$^\circ$C are metallic with a H$_c$ of 135Oe.