AFM Contact Modes

 

Static Force Mode

Static mode, or contact mode, is the original and simplest mode to operate an AFM. In this mode, the probe is in continuous contact with the surface while the probe raster scans the sample. In other words, the probe "drags" across the sample and measures the mechanical contact force.

The most common configuration of static mode is to operate it in constant force or deflection feedback mode. In this mode, the cantilever deflection is the feedback parameter. The cantilever deflection is set by the user and is related to how hard the tip pushes against the surface so that the user controls how gentle or aggressive the interaction between the probe and the sample is.

Butterfly wing – Contact Mode in air

20µm x 20µm – Z range 300nm

 

Lateral Force Mode (LFM)

Lateral force mode or frictional force mode is a form of static mode (contact mode). In lateral force mode, the imaging is exactly as it is in static mode except the cantilever fast scanning motion is generally performed perpendicular to the axis of the cantilever, as opposed to a freedom of scan rotation for conventional static mode.

This mode is particularly effective for measuring the friction of a surface as the side to side twisting of the cantilever by torque, measured as the probe raster scans along the surface. Lateral force measurements can be converted to frictional force through calibration of the torsional spring constant of the cantilever.

SBS-PMMA – Superposition of topography and friction

25µm x 25µm – Z range 135nm

 

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Dr. Stefano Pergolini
Dr. Stefano Pergolini

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