After the basic EFM experiment, the implementation of a further
the Kelvin feedback, can help to detect work function differences on
surfaces as well as local charges.
students can image those work function differences on a dopant
grating made of silicon. They get an impression about the relation
possible lateral resolution in electrical images and the
carrier concentration on the sample surface. They also memorize some
basics about work functions,
e.g. that they are not detectable in
absolute values, onyl as relative values vs. a second material.