The description of LFM - Lateral Force Microscopy

Lateral Force Microscopy (LFM) is a secondary contact AFM mode that detects and maps relative differences in the frictional forces between the probe tip and the sample surface. In LFM, the scanning is always perpendicular to the long axis of the cantilever. Forces on the cantilever that are parallel to the plane of the sample surface cause twisting of the cantilever around its long axis. This twisting is measured by a quad-cell Position Sensitive PhotoDetector (PSPD), as with TRmode.

AFM tip lateral movement in LFM. Twisting of the cantilever usually arises from two sources: changes in surface friction and changes in topography. In the first case, the tip may experience greater friction as it traverses some areas, causing the cantilever to twist more. In the second case, the cantilever may twist when it encounters edges of topographical features. To separate one effect from the other, usually three signals are collected simultaneously: the trace and retrace LFM signals, and the AFM height (topography) signal. LFM applications include identifying transitions between different components in polymer blends and composites, identifying contaminants on surfaces, delineating coverage by coatings, and chemical force microscopy (CFM) using probe tips functionalized for specific chemical or biological species.

 

Examples (click to enlarge)


Topography.

Lateral force, trace.

Lateral force, retrace.
Material sample of Silicon Carbide (SiC). Scan size 5x5um. The images correlates together showing the areas of differnt mechanical properties (friction).

Topography.

Lateral force, trace.

Lateral force, retrace.
Polymer sample. Scan size 8x8um.

Atomic-scale friction on mica sample.
Scan size 3nm.


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