Investigation on the structural property of the sputtered hcp-phase boron nitride tunnel barrier for spintronic applications

Chaoyi Peng,Xiaohui Chao,Jian-Ping Wang,P Quarterman,Shaoqian Yin,Delin Zhang

doi:10.1063/1.5130463

Abstract

Recently, two-dimensional (2D) materials have attracted considerable interest for use in spintronic applications, especially hexagonal close-packed (hcp)-phase boron nitride (BN) as a tunnel barrier. In this paper, we experimentally investigated the structural properties of a sputtered hcp-BN thin film. By optimizing the experimental conditions, we obtained the stoichiometric BN thin film with a ratio of 1:1 of the Ar/N2 sputtering gas. Then the Co/BN/Co magnetic tunnel junction (MTJ) stacks were prepared to study the crystalline structure of the BN tunnel barrier and their epitaxial relationship. We found that the as-deposited BN tunnel barrier layer follows the texture of the bottom Co layer and forms a polycrystalline structure. After the high-temperature treatment of the MTJ stack, texturing of the BN tunnel barrier layer is observed, however, this annealing process makes the BN tunnel barrier noncontinuous and induces serious interdiffusion between layers. These results will open the door for development of spintronic devices based on MTJs with hcp-phase BN tunnel barrier and hcp-phase perpendicular magnetic anisotropy ferromagnetic layer.

Highlights

Magnetic tunnel junctions (MTJs) have attracted significant attention in the past decades due to their promising application in next-generation ultra-high density and non-volatile memory devices.1–4 The fundamental structure of a magnetic tunnel junction (MTJ) is two ferromagnetic layers separated by an insulating tunnel barrier (e.g. MgO).5,6 When passing through the MTJ devices, the charge current will be polarized and a resulting spin current can be generated
The samples were measured by Auger electron spectroscopy (AES) to identify the composition of the boron nitride (BN) thin films
We find that the mixed Ar/N2 gas helps obtain the stoichiometric BN thin films

Summary

Introduction

Magnetic tunnel junctions (MTJs) have attracted significant attention in the past decades due to their promising application in next-generation ultra-high density and non-volatile memory devices.1–4 The fundamental structure of a MTJ is two ferromagnetic layers separated by an insulating tunnel barrier (e.g. MgO).5,6 When passing through the MTJ devices, the charge current will be polarized and a resulting spin current can be generated. A high-temperature (850 ○C) sputtering environment may improve the crystalline structure of the BN tunnel barrier following, as reported by P.

Results

Conclusion