Wenhai Han & Hassan Tanbakuchi
A new AFM system incorporated with a microwave network analyzer is presented. A microwave signal is emitted from the vector network analyzer and transmitted through a resonant circuit to a conductive AFM probe which is in contact with a sample being scanned. The probe also serves as a receiver to capture the reflected microwave from the contact point and feeds it back to the network analyzer. By measuring the complex reflection coefficient, known as S11 parameter, the impedance of the sample at the contact point can be obtained. Direct detection of the reflected microwave can be used to map differences in capacitance, impedance, and dielectric properties of a variety of different materials. With a superimposed low-frequency modulation, changes of capacitance from the reflected microwave due to the depleted carriers under the probe can be used to map different dopants of semiconductors.
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