When the sample is relatively robust, i.e. hard and strongly adhering, this allows imaging without tip-induced deformation in a broad range of tip-sample interaction force. One may choose using both softer cantilevers to obtain true surface topography and stiff cantilevers to ensure high topographic and phase contrast.

The harder the surface, the wider the choice of AFM techniques can be used for it investigation. Contact mode technique is still the speediest and roughest among the others.

When in Tapping mode, "hard" tapping conditions are usually used to obtain good material sensitive contrast in phase imaging, while "light" tapping keep maximum of topography data (see figure above).

"Light" tapping conditions imply lower free amplitudes and higher setpoint values.

Contact mode

Long cantilevers having relatively low spring constant below are usually used in Contact mode. The choice between SCD or LS tip depends on resolution needed.

When in liquid, one can use cantilevers without backside coating or probes with overall chemically inert Cr-Au coating having tip radius about 50 nm.

Tapping mode

The tip-sample interaction force depends on the adhesive properties of material, the sharpness of the probe tip and the scanning mode. If the experimental conditions permit, one should avoid using stiff cantilevers that may cause severe deformation and even damaging of the sample. Softer cantilevers usually show better and more reproducible results. However, in some experiments, e.g. very hard and/or sticky samples, stiff cantilevers are required. For unknown physical properties of the domains it is recommended using a probe of the 14 series that features an intermediate spring constant of ~5 N/m.

Sharper tips provide higher lateral resolution. This advantage should be balanced against the scanning speed.

For imaging in liquids, the choice of the probe is usually limited to those having resonant frequency of 50-70 kHz in air. It is generally recommended to use uncoated cantilevers in liquids or probes with overall chemically stable Cr-Au coating having tip radius about 50 nm.

Noncontact mode

Cantilevers having high spring constant of 20..100 N/m and highest possible resonant frequency are usually used in noncontact mode.