In-situ characterization of rapid crystallization of amorphous CoFeB electrodes in CoFeB/MgO/CoFeB junctions during thermal annealing

Wang, W. G.; Jordan-sweet, J.; Miao, G. X.; Ni, C.; Rumaiz, A. K.; Shah, L. R.; Fan, X.; Parsons, P.; Stearrett, R.; Nowak, E. R.; Moodera, J. S.; Xiao, J. Q.
December 2009
Applied Physics Letters;12/14/2009, Vol. 95 Issue 24, p242501
Academic Journal
We report the crystallization study of CoFeB/MgO/CoFeB magnetic tunnel junctions using in-situ, time-resolved synchrotron-based x-ray diffraction and transmission electron microscopy. It was found that the crystallization of amorphous CoFeB electrodes occurs on a time scale of seconds during the postgrowth high temperature annealing. The crystallization can be well fit by the Johnson–Mehl–Avrami model and the effective activation energy of the process was determined to be 150 kJ/mol. The solid-state epitaxy mode of CoFeB was found to involve separate crystallization at different locations followed by subsequent merging of small grains, instead of layer-by-layer growth of CoFeB film along the MgO template.


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