Micro-imaging system using scanning DC-SQUID microscope

A micro-imaging system in a low temperature environment has been developed for the study of superconducting films and magnetic films and for the inspection of superconducting integrated circuits. The system consists of a micro DC-SQUID, a cryostat, a precise scanning stage, and a computer. Two different types of micro DC-SQUIDs were designed. One was a magnetometer (Bz) with a one-turn pick-up coil with a diameter of 10 mu m, and the other was a gradiometer (dBz/dx) with a planar first-order derivative pick-up coil. Each micro DC-SQUID was integrated on a 3mm x 3mm Si chip using thin Nb film fabrication technology. Preliminary experiments were made using the system and several magnetic images were obtained. We present observations of a thin superconducting Nb film pattern by applying the Meissner screening and the magnetic domains of a thin garnet ((YBi)(3)(FeAl)(5)O-12) film.