Thesis-PDF - IAP/TU Wien

Figure 3.8: Schematic drawing of the principle of Magnetic Force Microscopy.
The resonant frequency of the cantilever is influenced while the
cantilever hovers in the magnetic field of the sample. Image adapted from
[63].
non-contact mode and changes its resonant frequency upon variation in the
present magnetic field (see Fig. 3.8).
- Cell membrane and lysis kinetics ([64])
- Measurement of scratch resistance, wear, and elastic and plastic mechanical
properties such as indentation hardness and the modulus of elasticity.
([65], [66], [67])
Figure 3.9: The amount of tilt (angle β) a cantilever has while scanning
the surface in contact mode can be used to derive friction coefficients of
that surface. If probe sensing is performed with an optical detector, a fourquadrant
photodiode can be used to measure bending and twisting of the
cantilever.
- Surface potential determination. After a first contact scan a second scan
is performed hovering a certain distance above the surface. This time a dcvoltage
is applied to the tip that equilibrates the local electrostatic potential
on the sample so as to eliminate forces on the AFM tip caused by electric
repulsion or attraction between tip and sample. This technique is called
scanning surface potential microscopy (SSPM). A real example is e.g. the
investigation of the electric surface potential of carbon nanotubes ([68]).
33