The description of Surface Potential / Kelvin Probe AFM

Surface Potential (SP) imaging is a secondary imaging mode derived from TappingMode that maps the electrostatic potential on the sample surface. SP is a nulling technique. As the tip travels above the surface in LiftMode, the tip and the cantilever experience a force wherever the potential on the surface is different than the potential of the tip. The force is nullified by varying the voltage of the tip so that the tip is at the same potential as the region of the sample surface underneath it. SP imaging can be used to detect and quantify contact potential differences (CPD) on the surface. Surface Potential imaging is sometimes referred to as Scanning Kelvin Probe Microscopy (SKPM)

 

Examples (click to enlarge)


Fragment of integrated circiut. In central area the diffusion resistors are visible. CCD camera view.
 

Fragment of integrated circiut- topography. Area of diffusion resistors. Scan size 90x90um.

Fragment of integrated circiut- surface potential distribution. Visible resistors structures - dopand changed work function of the surface. Scan size 90x90um.

Topography of test sample. Some defect area is visible. Scan size 40x40um.

Surface potential distribution on the sample's surface. The distribution is significantly changed in defect area.

Topography of optoelectronic structure developed on GaAs substrate. Metallic contacts: ohmic on right hand side and Shottky on left hand side. Scan size 9,2x9,2um.

Surface potential distribution on the sample's surface. One can see the difference between the substrate and the metallic layers as well as inhomogenities within ohmic contact area.

Topography of GaAs substrate. Scan size 2x2um.

Surface potential distribution on GaAs substrate. One can see the influence of the contamination present due to metallic contact located next to the right side of the picture.


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