Scanning probe microscopy of high-temperature superconductors

High-temperature superconductors (HTS) and scanning probe microscopes have been developed at a rapid rate over the last decade and a half. The cross-linking between these two exciting fields has produced many beautiful-results and new possibilities that are still being explored. The highlights of these results are reviewed here, with emphasis on scanning microscopes based on tunnelling (STM), atomic force (AFM), magnetic force (MFM), the Hall effect (SHPM), a SQUID sensor, microwaves, near-field optics, or magneto-optic techniques. These tools are used in the characterization of HTS from the routine evaluation of surface topography to the sophisticated elucidation of the symmetry of the order parameter. Some more recent techniques and possible new directions are also discussed.