Effect of annealing and applied bias on barrier shape in CoFe/MgO/CoFe tunnel junctions

Yuzi Liu*, Ann N. Chiaramonti, Daniel K. Schreiber, Hyunsoo Yang, Stuart S P Parkin, Olle G. Heinonen, Amanda K. Petford-Long

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Energy-filtered transmission electron microscopy and electron holography were used to study changes in the MgO tunnel barrier of CoFe/MgO/CoFe magnetic tunnel junctions (MTJs) as a function of annealing and in situ applied electrical bias. Annealing was found to increase the homogeneity and crystallinity of the MgO tunnel barrier. Cobalt, oxygen, and trace amounts of iron diffused into the MgO upon annealing. Annealing also resulted in a reduction of the tunneling barrier height, and decreased the resistance of the annealed MTJ relative to that of the as-grown sample. In situ off-axis electron holography was employed to image the barrier potential profile of a MTJ directly, with the specimen under electrical bias. Varying the bias voltage from -1.5 to +1.5 V was found to change the asymmetry of the barrier potential and decrease the effective barrier width as a result of charge accumulation at the MgO-CoFe interface.

Original languageEnglish (US)
Article number165413
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number16
StatePublished - Apr 12 2011

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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