Development of a near-field scanning microwave microscope for imaging non-uniformities and defects in conducting and High-Tc Superconducting (HTS) films.

摘要

Identifying defects and non-superconducting regions in high-temperature superconductors is of great importance because they limit the material's capability to carry higher current densities. A technique that combines near-field scanning microwave microscopy (NSMM) with I-V measurement capable of obtaining multiple sets of complementary information on the same sample area was developed. This technique takes advantage of the NSMM's unique capability to function both as a field emitter that can locally heat areas on the surface of a current-biased sample and map the current flow and also as a detector to map the spatial non-uniformity in electromagnetic properties of the sample including loss, dielectric constant, and surface morphology. Comparison with simulations based on a heat diffusion model has also been made to achieve quantitative understanding of the experimental data. Macroscopic and microscopic defects in both conducting and HTS films were clearly identified and imaged using this technique with adequate sensitivity and resolution.