Though Silicon is conducting in bulk due to the presence of the
dopants, the surface of the probe is always coated by a thin (2..4
nm) native oxide film. That's why using the conductivity of Si probes
for AFM measurements is only possible in UHV conditions after the
film is removed.
For imaging of electric properties of materials in ambient conditions,
probes with special conducting coatings are usually used.
Height image obtained in Tapping mode.
EFM map of the same area.
Height and phase images of the rubber-modified
isotactic polypropylene filled with carbon black. The images were
obtained in Electric Force Microscopy mode using NSC14 probes coated
with Pt. Images courtesy of S. Magonov (Veeco).
Probes
Ti coated
Probes with conductive wear-resistant 15 nm Pt coating on tip side
with excellent bonding to the Sillicon probe. Resulting tip radius
is about 25 nm. Cantilever backside may have optional Al reflective
coating.
Ti-Pt coated
Probes with overall conductive chemically inert 10-nm Pt coating
with 20-nm Ti sublayer on the tip and back side of the cantilever.
Resulting probe tip radius is about 40 nm. Cantilever bending withing
3° is possible.
Cr-Au coated
Probes with overall conductive chemically inert 20-nm Au coating
with 20-nm Cr sublayer on the tip and back side of the cantilever.
Resulting tip radius is about 50 nm. The coating may cause cantilever
bending withing 3°.