Oxidation Mechanism of the Surface of A15 Superconductors
The oxidation process of the surface of the superconductors is usually employed in the fabrication of the Josephson tunnel junctions1–6. In the case of A15 superconductors such as Nb3Ge, Nb3Sn, Nb3A1, Nb3Si and V3Si, the native oxide is not always a good tunnel barrier. One case (Nb3Sn and Nb3A1) it is good, in other case (Nb3Ge and V3Si) it is not.1–5 In order to clarify the reason, the oxidation process of the surface of the A15 superconductors was studied by the in-situ observation of x-ray photoelectron spectroscopy (XPS). The XPS technique can reveal nondestructively the composition, thickness,quality of the oxide layer. This is one of the most promising techniques for investigating the structure of the native oxide-layer and tunnel barrier within a thickness of about 5 nm.
KeywordsAl2o Vanadium Sno2 Sapphire Auger
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