0.4 μm spatial resolution with 1 GHz (λ=30 cm) evanescent microwave probe

Abstract

In this article we describe evanescent field imaging of material nonuniformities with a record resolution of 0.4 μm at 1 GHz (λg/750 000), using a resonant stripline scanning microwave probe. A chemically etched tip is used as a point-like evanescent field emitter and a probe–sample distance modulation is employed to improve the signal-to-noise ratio. Images obtained by evanescent microwave probe, by optical microscope, and by scanning tunneling microscope are presented for comparison. Probe was calibrated to perform quantitative conductivity measurements. The principal factors affecting the ultimate resolution of evanescent microwave probe are also discussed.