Low energy ion beam oxidation process

A method for forming a structure capable of supporting Josephson tunneling current therethrough comprising the steps of:

• forming a base electrode on a substrate,
• forming an insulating tunnel barrier on said base electrode by a surface reaction process for growing an insulating compound layer on the surface of said base electrode, said tunnel barrier being sufficiently thin to support Josephson tunneling current therethrough, said surface reaction process comprising the steps of,
• forming an ion plasma with an ion source, said plasma being located in a plasma discharge chamber of said ion source,
• feeding a gas into said ion plasma which will form said insulating solid compound layer when ions of said gas reacts with the surface of said base electrode,
• extracting said ions out of said plasma to form a directed ion beam,
• applying a voltage potential to said ion source to accelerate ions of said gas to a low energy in a directed beam which impinges upon the surface of said base electrode to produce simultaneous sputter etching and insulating compound formation on the surface of said base electrode, wherein the final thickness of said insulating tunnel barrier occurs when the rate of insulating compound formation balances the rate of sputter etching, said final thickness of said tunnel barrier being a function of said voltage potential, and
• forming a layer of material on said insulating tunnel barrier to form a counterelectrode.