In situ ion beam processing for Josephson junction fabrication

The use of ion beam processing in fabricating Josephson junction tunnel devices introduces several advantages over other plasma discharge techniques both in substrate precleaning and oxidation. The ion flux and ion energy can be controlled independently, the energy spread is narrow, the source plasma is isolated from the substrates and chamber, and the whole procedure is carried out in low pressure environment, thus reducing contamination due to background gas and backscattering. Ion beam oxidation has been used to produce both room temperature diodes and Josephson junctions. In this work Nb-NbOx-PbInAu Josephson junctions were fabricated with ion beam oxidation preceded by a fixed ion beam cleaning step. The effects of the oxidation time and the ion energy in the oxidation beam on junction characteristics were studied. (Auth.)