SURFACE-RESISTANCE IMAGING WITH A SCANNING NEAR-FIELD MICROWAVE MICROSCOPE

We describe near-field imaging of sample sheet resistance via frequenc y shifts in a resonant coaxial scanning microwave microscope. The freq uency shifts are related to local sample properties, such as surface r esistance and dielectric constant. We use a feedback circuit to track a given resonant frequency, allowing measurements with a sensitivity t o frequency shifts as small as two parts in 10(6) for a 30 ms sampling time. The frequency shifts can be converted to sheet resistance based on a simple model of the system. (C) 1997 American Institute of Physi cs.