Chapter 7. Performing Measurements
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Fig. 7-28. Images of surface topography and distribution of lateral forces
7.1.3. Spreading Resistance Imaging
7.1.3.1. Brief Description
The Spreading Resistance Imaging mode is a very efficient AFM mode. It is employed in
various fields, including defects in conductive and low conductive films, materials
characterization in terms of local resistance etc. This mode uses a conductive probe that
comes in contact with the sample surface. The probe is applied to a bias voltage. The
resulting current through the sample is measured as a function of the probe position
simultaneously with surface topography acquisition. The latter uses the Constant Force
mode. It is easy to prove that, under the assumption of constancy of contact probe-surface
resistance for a given bias voltage, the detected current is proportional to local resistance of
the sample.
Among typical applications of the mode are finding actual geometrical dimensions of
source-drain regions in MIS transistors, localization of p-n junctions, study of dopants
distribution in semiconductors etc.
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