The images above are scans of a silicon substrate in regions near field
oxide.  The oxide has been removed, so only the silicon is being imaged.
The dC/dz signal shows what appear to be dislocations in the substrate
between the surface and back electrode.  There is an indication in the
vdW signal that the faults lie near the surface.  The dislocations appear
to have no measurable impact upon the EPD signal.