Atomic Force Microscopy: characterization of surface topography Andrius Martinavičius

AFM schematically Most AFMs use a laser beam deflection system, introduced by Meyer and Amer. The atomic force microscope senses force in nano-contacts at the nano-Newton level

AFM Cantilevers and Tips

Diamond-coated AFM tip FIB Sharp Tip Gold-coated Si 3 N 4 Tip Pyramidal, tetrahedral, or conical tips are the most common tip shapes AFM -Tips

Piezo Substrate P Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate Piezo Substrate P Jump to Contact Jump off contact Hysteresis Jump to Contact Jump off Contact Deflection-Displacement Characteristics AFM-Tip Approaching and Retracting

Deflection as a function of the distance Contact Region Non-Contact Region Stable Contact Unstable Very stable very damaging shear forces Too unstable but would be less damaging force-distance characteristics

Non-Contact and Contact modes In contact mode, also known as repulsive mode, an AFM tip makes soft “physical contact” with the surface. The cantilever is oscillated above the surface of the sample at such a distance that we are in the attractive regime.

Tapping Mode A cantilever with attached tip is oscillated at its resonant frequency and scanned across the sample surface. Tip touches sample for a very short time. The amplitude of the oscillations changes when the tip scans over bumps or depressions on a surface.

Contact Mode Non-contact Mode Tapping Mode AFM Modes

1 micron Tapping Mode vs. Contact Mode AFM Contact mode 2 microns Tapping mode 2 microns

Some examples DNQ151-1VH A is total roughness R a is average roughness R q is root- mean-square average roughness

Some roughness parameters R p is the height of the highest peak R v is the depth of the deepest valley R t is the sum of these two - total roughness

Some examples

Average roughness The average roughness is the area between the roughness profile and its mean line Digital expression

Root-Mean-Square Roughness Integral expression Digital expression

Some examples

Thank You for attention