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Aluminum Oxide Layers as Possible Components for Layered Tunnel Barriers

E. Cimpoiasu·S. K. Tolpygo·X. Liu·N. Simonian·J. E. Lukens·R. F. Klie·Y. Zhu·K. K. Likharev
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Abstract

We have studied transport properties of Nb/Al/AlOx/Nb tunnel junctions with ultrathin aluminum oxide layers formed by (i) thermal oxidation and (ii) plasma oxidation, before and after rapid thermal post-annealing of the completed structures at temperatures up to 550 deg C. Post-annealing at temperatures above 300 deg C results in a significant decrease of the tunneling conductance of thermally-grown barriers, while plasma-grown barriers start to change only at annealing temperatures above 450 deg C. Fitting the experimental I-V curves of the junctions using the results of the microscopic theory of direct tunneling shows that the annealing of thermally-grown oxides at temperatures above 300 deg C results in a substantial increase of their average tunnel barriers height, from ~1.8 eV to ~2.45 eV, versus the practically unchanged height of ~2.0 eV for plasma-grown layers. This difference, together with high endurance of annealed barriers under electric stress (breakdown field above 10 MV/cm) may enable all-AlOx and SiO2/AlOx layered "crested" barriers for advanced floating-gate memory applications.

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E. Cimpoiasu, S. K. Tolpygo, X. Liu, N. Simonian, J. E. Lukens, R. F. Klie, Y. Zhu, K. K. Likharev. 2004-02-03. Aluminum Oxide Layers as Possible Components for Layered Tunnel Barriers. https://doi.org/10.1063/1.1763229

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