Microstructure investigation on barrier shapes of double barrier magnetic tunnel junctions

Abstract

Barrier shapes and its detailed microstructures in the double barrier magnetic tunnel junctions were intensively investigated by both high resolution transmission electron microscopy and electron holography. Two broad (>2nm) potential wells (i.e., shapes of AlOx layers) with slanted interfaces were observed in the electron hologram of the as-deposited samples. However, in the hologram of the annealed samples, two narrowed (down to 1.18nm) and almost equal (height) potential wells with sharp and steep interfaces were acquired. This indicates that the value of tunnel magnetoresistance can be increased from 12.8% to 29.4% at room temperature by annealing treatment where the sharpness and height of the barriers played a critical role.