Microwave microscopy using a superconducting quantum interference device

Authors :: Frederick C. Wellstood
D. T. Nemeth
Dieter Koelle
Frank Ludwig
A. H. Miklich
John Clarke
E. Dantsker
R. C. Black
Source :: Applied Physics Letters. 66:99-101
Publication Year :: 1995
Publisher :: AIP Publishing, 1995.
Abstract: We present results on a near‐field scanning probe microwave microscope which is based on the nonlinear behavior of a YBa2Cu3O7 direct‐current superconducting quantum interference device (SQUID). Our system has a spatial resolution of about 30 μm and derives its probing field from circulating currents in the SQUID loop. The frequency is set by the Josephson relation and is continuously tunable up to about 200 GHz. By imaging small patterned normal metal thin‐film samples of Cu and Nb at 77 K, we have confirmed the operating bandwidth of the system and investigated the nature of the imaging process.