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