Near-field scanning microwave microscope using a dielectric resonator

We describe a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f=4.5 GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator for the TE011 mode. We tuned the resonance cavity to match the impedance of 50 Ω by using a tunable screw and could improve sensitivity and spatial resolution to better than 1 μm. To demonstrate the ability of local microwave characterization, the surface resistance dependence of the metallic thin films on film thickness has been mapped.