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Evidence for boron diffusion into sub-stoichiometric MgO (001) barriers in CoFeB/MgO-based magnetic tunnel junctions

Harnchana, V.; Hindmarch, A.T.; Sarahan, M.C.; Marrows, C.H.; Brown., A.P.; Brydson, R.M.D.

Evidence for boron diffusion into sub-stoichiometric MgO (001) barriers in CoFeB/MgO-based magnetic tunnel junctions Thumbnail


Authors

V. Harnchana

M.C. Sarahan

C.H. Marrows

A.P. Brown.

R.M.D. Brydson



Abstract

Evidence of boron diffusion into the MgO barrier of a CoFeB/MgO based magnetic tunnel junction has been identified using analytical scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy. Structures were deposited by DC/RF-magnetron sputtering, where defective, sub-stoichiometric MgO barriers degrading device performance have been previously mitigated against by deposition of thin Mg layers prior to MgO deposition. We show that despite the protection offered by the Mg layer, disorder in the MgO barrier is still evident by STEM analysis and is a consequence of the oxidation of the Co40Fe40B20 surface during MgO deposition. Evidence of boron diffusion from CoFeB into the MgO barrier in the as-deposited and annealed structure is also presented, which in the as-deposited case we suggest results from the defective structures at the barrier interfaces. Annealing at 375 °C results in the presence of B in the trigonal coordination of [BO3]3− in the MgO barrier and partial crystallization of the top electrode (we presume there is also some boron diffusion into the Ta capping layer). The bottom electrode, however, fails to crystallize and much of the boron is retained in this thicker electrode. A higher annealing temperature or lower initial boron content is required to crystallize the bottom electrode.

Citation

Harnchana, V., Hindmarch, A., Sarahan, M., Marrows, C., Brown., A., & Brydson, R. (2013). Evidence for boron diffusion into sub-stoichiometric MgO (001) barriers in CoFeB/MgO-based magnetic tunnel junctions. Journal of Applied Physics, 113(16), Article 163502. https://doi.org/10.1063/1.4802692

Journal Article Type Article
Publication Date Apr 1, 2013
Deposit Date Apr 24, 2013
Publicly Available Date Mar 28, 2024
Journal Journal of Applied Physics
Print ISSN 0021-8979
Electronic ISSN 1089-7550
Publisher American Institute of Physics
Peer Reviewed Peer Reviewed
Volume 113
Issue 16
Article Number 163502
DOI https://doi.org/10.1063/1.4802692
Keywords Boron, Electrodes, Annealing, Interface structure, Crystallization.

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Copyright Statement
© 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 113, 163502 (2013) and may be found at http://dx.doi.org/10.1063/1.4802692





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