Improved near-field scanning microwave microscope combined with electrical transport measurement for characterizing nonuniformity of electrical dissipation in YBa2Cu3O7−δ films of variable thickness

Abstract

An improved near-field scanning microwave microscope (NSMM) combined with electrical transport measurement was applied for characterizing nonuniformity of electrical dissipation in YBa2Cu3O7−δ (YBCO) films. We demonstrate identification of the current-obstructing defects in thin (thickness below 300nm) YBCO films by mapping microwave-induced electrical voltage (ΔV) and reflected microwave power on the sample. In addition, the technique was also found to be suitable for characterizing electrical dissipation in thick YBCO films of a few micrometer thick. In order to improve the spatial resolution to submicron regime, we have employed a hybrid probe tip with a submicron tip diameter and operate the NSMM to its second harmonic frequency to increase hot spot microwave absorption. A much improved spatial resolution in the submicrometer range for the microwave maps was achieved while maintaining the sensitivity in the ΔV measurement.