Low temperature scanning-tip microwave near-field microscopy of YBa₂Cu₃O_7-x films

We have explored the low temperature capability of a scanning-tip microwave near-field microscope to study superconductors. The shift in the quality factor of the microscope resonator can be used to obtain the temperature dependence of the surface resistance of a local region under the tip. Patterned YBa₂Cu₃O_7-x films were scanned at various temperatures and surface resistance mapping was performed with high spatial resolution at 1.2 GHz. Superconducting transitions at different positions on a film can be detected. Edge-region defects in wet-etched patterns were observed and were shown to be nonsuperconducting at microwave frequencies at 80 K. © 1997 American Institute of Physics.