Abstract A method for trimming the zero voltage Josephson current of a tunnel junction including the steps of measuring the I-V characteristics of the completed junctions to quantify the change in I o necessary to meet the design requirements, placing the tested Josephson junctions on a metal block which is mounted in the sample chamber of an ion implanter structure which is pumped to 1.10 -6 Torr. The junctions, kept at room temperature and oriented at a direction nearly normal to the ion beam, are implanted with magnetically analyzed ions of energies 50 keV to 2300 keV. Spatial uniformity of the ion implant beam is ±2% over a sample. Uniform spatial implantation over a large area sample is obtained by either sweeping of the beam across the sample, or restoring the sample through a stationary beam, determining the required ion dose to effect trimming from calibration curves, remeasuring the I-V characteristics after implantation to confirm that the required I o trim was effected, and then completing the fabrication of the Josephson device according to standard processing.
A method for adjusting the zero voltage Josephson current (I o ) of a tunnel junction by implanting ion including the steps of providing first and second superconductive electrodes with a tunnel junction located between said first and second electrodes whereby tunneling current can flow therethrough between said superconductive electrodes, measuring the voltage-current characteristics of said tunnel junction, disposing said electrodes with said tunnel junction in an ion implantation structure, including an ion implantation beam, and implanting a boron ion species into said tunnel junction for trimming said zero voltage Josephson current I o by decreasing the junction energy gap.
Claim 2
Independent Claim
100 words
A method for adjusting the zero voltage Josephson current (I o ) of a tunnel junction by implanting ion including the steps of providing first and second superconductive electrodes with a tunnel junction located between said first and second electrodes whereby tunneling current can flow therethrough between said superconductive electrodes, measuring the voltage-current characteristics of said tunnel junction, disposing said electrodes with said tunnel junction in an ion implantation structure, including an ion implantation beam, and implanting a boron ion species into said tunnel junction for trimming said zero voltage Josephson current I o by decreasing the junction energy gap.
Claim 3
Dependent Claim
17 words
A method according to claim 1 wherein said ion species is magnetically analyzed 11 B boron ions.
Claim 4
Dependent Claim
39 words
A method according to claim 1 wherein said junctions are implanted with a beam of magnetically analyzed 11 B ions of energies in the range from 50 keV to 2300 keV at a direction substantially normal to said junctions.
Claim 5
Dependent Claim
35 words
A method according to claim 1 wherein said first superconductive electrode is composed of niobium, said second superconductive electrode is composed of lead, gold and indium, and said tunnel junction is composed of niobium oxide.
Claim 6
Dependent Claim
46 words
A method according to claim 4 wherein said ion species is magnetically ionized 11 B species with energies in the range of 50 keV to 2300 keV which are implanted with doses in the range from 10 13 /cm 2 to 10 15 /cm 2 .