The description of Non Contact AFM

Non-contact AFM (NC-AFM) is one of the near field microscopy techniques in which an AFM cantilever vibrates near the surface of the sample at the distance about of tens or hundreds of angstroms. The advantage of this method is practically no contact between the tip and the sample, thereby the force acting between them is a few orders of magnitude lower than on contact AFM. Due to this low force, one can measure soft or elastic samples as well as hard and stiff surfaces. Another advantage of this technique, is reduced risk of the sample's surface contamination with some particle from the tip. Moreover, the tip's wear in NC AFM proceeds much slower than in contact mode. The disadvantage of this method is that due to very small force acting between tip and sample, it is much more difficult to detect the interaction. Typically in NC-AFM the tip oscillates near its resonant frequency with an amplitude of a few nanometers. The change of the cantilever's oscillation amplitude (or resonant frequency) is detected as the tip approaches the surface. The feedback loop moves the scanner with the sample (or tip) forth or back in order to restore the amplitude or frequency, therefore the tip-sample distance is maintained.


Examples (click to enlarge)

Surface of the DVD disc. Scan size 50x50um.

Surface of the DVD disc. Scan size 3x3um.

An eye of the fly. Scan size 52x52um.

Graphite layer (HOPG). Scan field 10x10um. Single and multiple atomic steps are visible.

Graphite layer (HOPG). Scan field 1x1um. Atomic steps are visible.

Bacteriophage. Scan field 800x800nm.

Chemically developed nanoubes. Scan field 50x50um.

Chemically developed nanoubes. Scan field 1,5x1,5um.


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