Atomic-Scale Structure and Local Chemistry of CoFeB-MgO Magnetic Tunnel Junctions

TY - JOUR

T1 - Atomic-Scale Structure and Local Chemistry of CoFeB-MgO Magnetic Tunnel Junctions

AU - Wang, Zhongchang

AU - Saito, Mitsuhiro

AU - McKenna, Keith P.

AU - Fukami, Shunsuke

AU - Sato, Hideo

AU - Ikeda, Shoji

AU - Ohno, Hideo

AU - Ikuhara, Yuichi

PY - 2016/3/9

Y1 - 2016/3/9

N2 - Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving and chemically identifying each individual stacking layer remains challenging due to spatially localized features that complicate characterizations limiting understanding of the physics of MTJs. Here, we combine advanced electron microscopy, spectroscopy, and first-principles calculations to obtain a direct structural and chemical imaging of the atomically confined layers in a CoFeB-MgO MTJ, and clarify atom diffusion and interface structures in the MTJ following annealing. The combined techniques demonstrate that B diffuses out of CoFeB electrodes into Ta interstitial sites rather than MgO after annealing, and CoFe bonds atomically to MgO grains with an epitaxial orientation relationship by forming Fe(Co)-O bonds, yet without incorporation of CoFe in MgO. These findings afford a comprehensive perspective on structure and chemistry of MTJs, helping to develop high-performance spintronic devices by atomistic design.

AB - Magnetic tunnel junctions (MTJs) constitute a promising building block for future nonvolatile memories and logic circuits. Despite their pivotal role, spatially resolving and chemically identifying each individual stacking layer remains challenging due to spatially localized features that complicate characterizations limiting understanding of the physics of MTJs. Here, we combine advanced electron microscopy, spectroscopy, and first-principles calculations to obtain a direct structural and chemical imaging of the atomically confined layers in a CoFeB-MgO MTJ, and clarify atom diffusion and interface structures in the MTJ following annealing. The combined techniques demonstrate that B diffuses out of CoFeB electrodes into Ta interstitial sites rather than MgO after annealing, and CoFe bonds atomically to MgO grains with an epitaxial orientation relationship by forming Fe(Co)-O bonds, yet without incorporation of CoFe in MgO. These findings afford a comprehensive perspective on structure and chemistry of MTJs, helping to develop high-performance spintronic devices by atomistic design.

KW - atomic structure

KW - CoFeB-MgO

KW - local chemistry

KW - magnetic tunnel junction

KW - scanning transmission electron microscopy

UR - http://www.scopus.com/inward/record.url?scp=84960491279&partnerID=8YFLogxK

U2 - 10.1021/acs.nanolett.5b03627

DO - 10.1021/acs.nanolett.5b03627

M3 - Article

AN - SCOPUS:84960491279

SN - 1530-6984

VL - 16

SP - 1530

EP - 1536

JO - Nano Letters

JF - Nano Letters

IS - 3

ER -