Fabrication of YBaCuO-Josephson-Junctions on MgO-Substrates Damaged by a Focused Ion Beam Prior to Film Deposition

Abstract
By using a focused Ga-ion-beam we have damaged micro-areas of MgO-substrates through a protective gold-layer. Two different types of damage are produced: the flat type is to damage the surface by the implantation of Ga-ions whereas the groove type is simply geometrical damage to the substrates by sputtering the MgO. A YBa2Cu3O7-x (YBaCuO)-film was deposited on the as prepared substrates and the final junction was then defined by photolithography and Ar-milling over the damaged region. Under microwave irradiation Shapiro-steps were observed on these junctions, and a R n×I c of up to 3 mV at 4.2 K was achieved for the flat type junctions.