Determination of the thickness of Al[sub 2]O[sub 3] barriers in magnetic tunnel junctions.

The barrier thickness in magnetic spin-dependent tunnel junctions with Al[sub 2]O[sub 3] barriers has been measured using grazing incidence x-ray reflectivity and by fitting the tunneling current to the Simmons model. We have studied the effect of glow discharge oxidation time on the barrier structure, revealing a substantial increase in Al[sub 2]O[sub 3] thickness with oxidation. The greater thickness of barrier measured using grazing incidence x-ray reflectivity compared with that obtained by fitting current density-voltage to the Simmons electron tunneling model suggests that electron tunneling is localized to specific regions across the barrier, where the thickness is reduced by fluctuations due to nonconformal roughness. [ABSTRACT FROM AUTHOR]