Spatially resolved characterization of the microwave properties of superconducting thin films by low temperature microwave scanning near-field microscopy

In this paper, we established a microwave scanning near-field microscope to characterize the local microwave properties of high temperature superconducting thin film and devices. Using a coaxial cavity together with a niobium tip as the probe, the microwave surface resistance can be imaged nondestructively at 3 GHz for thin film samples with a spatial resolution of several micrometers. Temperature dependence of the local microwave property can also be obtained through a temperature controlled sample stage cooled by liquid nitrogen. With this technique, we have studied the local microwave characteristics, especially the microwave surface resistance of the high temperature superconducting thin film and device. We believe this technique would be quite helpful in evaluating and improving the performance of the superconducting microwave devices.