We present two approaches for studying the uniformity of a tunnel barrier. The first approach is based on measuring single-electron and two-electron tunneling in a hybrid single-electron transistor. Our measurements indicate that the effective area of a conduction channel is about one order of magnitude larger than predicted by theoretical calculations. With the second method, transmission electron microscopy, we demonstrate that variations in the barrier thickness are a plausible explanation for the larger effective area and an enhancement of higher order tunneling processes.
- tunnel junctions
Aref, T., Averin, A., van Dijken, S., Ferring, A., Koberidze, M., Maisi, V., Nguyend, H. Q., Nieminen, R. M., Pekola, J. P., & Yao, L. D. (2014). Characterization of aluminum oxide tunnel barriers by combining transport measurements and transmission electron microscopy imaging. Journal of Applied Physics, 116(7), 1-4. . https://doi.org/10.1063/1.4893473