Magnetic field behavior of small sputtered step-edge junctions

YBa2Cu3O7 step-edge junctions with widths down to 0.5 mu m are fabricated on SrTiO3 substrates by Ar ion-beam milling of the steps, high-pressure on-axis magnetron sputtering, electron beam patterning and ion-beam etching of the microbridge. For ratios of film thickness to step height of similar to 1/2 the current-voltage characteristics show Shapiro steps under microwave irradiation and resistively shunted junction like behavior. The periodic dependence of the critical current upon the magnetic field resembles a Fraunhofer pattern. The period of the current variation Delta B-0 depends upon the width w of the junction according to the theoretical prediction for planar thin Josephson junctions: Delta B-0=1.84 phi(0)/w(2). Junctions with widths of 0.7 mu m possess a large magnetic field stability with Delta B-0 approximate to 100 G. Small junctions (w<1 mu m) exhibit voltage jumps in the Fraunhofer pattern, which are explained by flux penetration of single vortices into the electrodes. (C) 1996 American Institute of Physics.