skip to main content

SciTech ConnectSciTech Connect

Title: Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer. The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.
Authors:
; ;  [1] ;  [2] ;  [1] ;  [2] ;  [2] ;  [2] ;  [1] ;  [2] ;  [2] ;  [2] ;  [1] ;  [2] ;  [2] ;  [2]
  1. Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
22398859
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 14; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; ATOMS; CHEMICAL BONDS; COBALT COMPOUNDS; COMPARATIVE EVALUATIONS; DIFFUSION; HETEROJUNCTIONS; IRON BORIDES; LAYERS; MAGNESIUM OXIDES; REDOX REACTIONS; SILICON OXIDES; SURFACES; TANTALUM; TUNNEL EFFECT; X-RAY PHOTOELECTRON SPECTROSCOPY