[EDP2] Digital, Quantum Information Technology, Materials and Fabrication

[EDP2-11] Photoemission Electron Microscopy of Ion Irradiated YBCO Josephson Junctions

*Rochelle Y. Qu¹, Alex M Boehm², Jay C. LeFebvre¹, Adhilsha Parachikunnumal¹, Nicole Chin ¹, Andrew Kim², Michael Titze², Alex A. Belianinov², Edward S. Bielejec², Taisuke Ohta², Shane A. Cybart¹ (1. University of California, Riverside (United States of America), 2. Sandia National Laboratories (United States of America))

Keywords:

YBCO,Anisotropy,Josephson Junction,Photoemission Electron Microscopy,Focused Ion Beam,Tunneling

We report using use Photoemission Electron Microscopy (PEEM) to study the anisotropic electrical properties of Yttrium Barium Copper Oxide (YBCO). Focused Helium Ion Beam (FHIB) lithography was used to directly write Josephson junctions and other patterns into YBCO thin films. Test samples were measured with PEEM for visualizing work-function variations. In unirradiated films, we observe two distinct domain types, with a 25 meV work-function contrast attributed to CuO- and BaO- terminated regions. Data analysis suggests an anisotropy factor of 1.5 consistent with in-plane tunneling transport studies. After helium ion irradiation, the transition temperature of the YBCO film is reduced and resistivity increases. Post-irradiation PEEM images reveal distinct contrast between irradiated and non-irradiated regions, correlating with an increase in resistivity. By comparing PEEM measurements with tunneling transport data, we establish connections between nanoscale surface properties and junction performance. These insights inform strategies for engineering reproducible, scalable superconducting circuits, advancing applications in very-large-scale superconducting electronics and quantum technologies.