Method of controlling the supercurrent of a Josephson junction device

Claim 1

A method of making oxide barrier junctions for Josephson junction devices which have uniform superconducting current characteristics substantially independent of oxygen pressure, comprising the steps of: providing a vacuum chamber having an inlet control valve and an outlet throttle control valve, providing a substrate, providing a masked pattern on a base electrode formed on said substrate, supporting said substrate on a cathode work holder in said vacuum chamber, providing an anode opposite said substrate on said work holder, providing a radio frequency power source coupled between said anode and said cathode work holder, providing a high vacuum in said vacuum chamber, introducing into said vacuum chamber substantially pure oxygen through said inlet control valve, regulating said inlet control valve and said outlet throttle control valve until a stabilized pure oxygen atmosphere having a pressure between 5×10 -3 and 30×10 -3 torr is achieved, regulating said inlet control valve and said outlet throttle control valve until the flow of oxygen into said vacuum chamber is optimized below 50 cubic centimeters per minute, generating an ionized plasma region juxtaposed said substrate at said cathode work holder by applying radio frequency power thereto, oxidizing said base electrode by oxygen ion bombardment to form an oxide barrier on the area of said base electrode which is not covered by said mask to form a homogeneous and consistent barrier junction which has reproducible and consistent current characteristics, and wherein said step of regulating said inlet control valve and said outlet throttle control valve further comprises the step of changing the pressure of the pure oxygen in said vacuum chamber until the zero voltage supercurrent of said oxide barrier being formed becomes substantially unchanged over a range of oxygen pressures.

Claim 2

A method of making oxide barrier junctions for Josephson junction devices which have uniform superconducting current characteristics substantially independent of oxygen pressure, comprising the steps of: providing a vacuum chamber having an inlet control valve and an outlet throttle control valve, providing a substrate, providing a masked pattern on a base electrode formed on said substrate, supporting said substrate on a cathode work holder in said vacuum chamber, providing an anode opposite said substrate on said work holder, providing a radio frequency power source coupled between said anode and said cathode work holder, providing a high vacuum in said vacuum chamber, introducing into said vacuum chamber substantially pure oxygen through said inlet control valve, regulating said inlet control valve and said outlet throttle control valve until a stabilized pure oxygen atmosphere having a pressure between 5×10 -3 and 30×10 -3 torr is achieved, regulating said inlet control valve and said outlet throttle control valve until the flow of oxygen into said vacuum chamber is optimized below 50 cubic centimeters per minute, generating an ionized plasma region juxtaposed said substrate at said cathode work holder by applying radio frequency power thereto, oxidizing said base electrode by oxygen ion bombardment to form an oxide barrier on the area of said base electrode which is not covered by said mask to form a homogeneous and consistent barrier junction which has reproducible and consistent current characteristics, and wherein said step of regulating said inlet control valve and said outlet throttle control valve further comprises the step of changing the pressure of the pure oxygen in said vacuum chamber until the zero voltage supercurrent of said oxide barrier being formed becomes substantially unchanged over a range of oxygen pressures.