Scanning Capacitance Microscopy
Scanning Capacitance Microscopy is kind of dynamic
EFM. Generally
[1] in
EFM. the cantilever is biased directly by V
tip=V
dc + V
ac sin(wt), where V
ac is referred to as the driving voltage. Scanning is executed on some height h above the sample surface in according with the profile defined during the first scanning in Semicontact mode. The capacitive force F
cap(z) between the tip and a sample surface at potential V
s is
F
cap(z) =(1/2) (V
tip - V
s)
2(dC/dz)
where C(z) is the tip-surface capacitance dependent on tip geometry, surface topography and tip-surface separation z.
Second harmonic of the capacitive force depends only on (dC/dz) and V
ac
F
cap2w(z) =(1/2)(dC/dz) V
ac2sin(2wt)
and can be used for acquisition additional information, e.g distribution of the surface capacity over the sample. For maximization of the second harmonic oscillations the ac frequency w is adjusted to be equal to half of cantilever resonance frequency w
r.
References
- Nanotechnology 12, 485 (2001).
- Appl. Phys. Lett. 52, 1103 (1988).
- J. Appl. Phys. 61, 4723 (1987).
