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(a) In situ site-specific current-voltage characteristics for as-grown (◆) and annealed at for 1 h (●) CoFe/MgO/CoFe MTJs. In situ TEM images for the (b) as-grown and (c) annealed specimens, corresponding to the curves in (a). The TEM images are small representative sections of a larger image corresponding to an area probed by the 100 nm diameter tip.
Conductance curves numerically derived from the curves in Fig. 1. The minimum of the as-grown curve (◆) is shifted from 0 V by , while the annealed curve (●) is shifted by only .
Ex situ HREM images of (a) as-grown and (b) annealed MTJs. Superimposed on each image is a spectrum of the average mass density as a function of position through the barrier calculated from the one-dimensional APT profiles on an absolute scale. The mass contrast in the TEM images agrees with the average mass density calculated from the APT reconstruction.
One-dimensional concentration profiles obtained from APT reconstructions of (a) as-grown and (b) annealed samples. The interfaces between the CoFe/CoFe oxide/MgO/CoFe are relatively sharp in the as-grown specimen compared to the annealed specimen. Upon annealing, Co and Fe penetrate the MgO layer, Mg diffuses into the CoFe oxide layer, and O diffuses into the bottom CoFe layer.
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