Tunnel barrier oxides consisting primarily of In2O3 formed on Pb–In–Au alloys by various thermal and rf‐plasma oxidation techniques were characterized in situ using ellipsometry and Auger Electron Spectroscopy (AES). The results were compared to measurements of the Josephson critical current density j1 and the specific capacitance of tunnel junctions fabricated on the same wafers. It was found for junctions with oxides consisting entirely of In2O3 that j1 exceeded 3 KA/cm2 and did not depend strongly on oxide thickness from about 3 nm (for thermally‐grown oxides) to 4.5–7 nm (for rf‐grown oxides). The addition of a thin layer of PbOx at the top of the barrier, either by backscattering during rf oxidation or by deposition onto a thermal oxide, caused by a substantial decrease in j1, while the presence of PbO in the bulk of the oxide had little effect. The specific capacitance of the lower current density junctions was essentially the same for either 3‐ or 4.5–6‐nm thick oxides and was consistent with a bar...

Tunnel barriers on Pb-In-Au alloy films

Tunnel barriers formed by rf oxidation of Pb–In–Au alloys and consisting largely of In2O3 have been studied by measuring the current density as a function of applied voltage j(V) for voltages up to 1 V. The junctions studied here, which were oxidized on Pb‐ or photoresist‐coated rf cathodes, showed no evidence of a barrier height below about 1 eV. A trapezoidal barrier with a height of at least 1 eV and a thickness equal to that of the oxide film, roughly 6 nm, would have a tunneling current far below that observed for these junctions. Furthermore, the measured j(V) curves were inconsistent with those calculated for a trapezoidal barrier, even for a barrier thickness less than the physical oxide thickness. The j(V) curves were, however, similar to those calculated for tunneling through a Schottky barrier in the indium oxide at the interface with the counterelectrode. Such a barrier, which is also suggested by recent measurements of oxide thickness and junction electrical properties at low voltages, might ...

Tunneling current density j(V) for Pb–In–Au alloy junctions and tunnel barrier modeling

Influence of preparation parameters on the tunnelling characteristics of PbBiIn/oxide/PbBiIn junctions

Sn—SnOx—Sn tunneling junctions were prepared by thermal oxidation of vacuum deposited Sn-films. The thickness growth of the oxide was followed by ellipsometric measurements. From logarithmic conductivity measurements the barrier heights were determined. The tunneling characteristic could be well described by the two-band-tunneling model using a value of 0.14 for the ratio of the effective masses in the oxide and the metal.

H. Wehr

Papers

Oxide growth and tunneling characteristics of Sn-SnO x -Sn junctions