The major difference between atomic force microscopy and competing technologies such as optical microscopy and electron microscopy is that AFM does not use lenses or beam irradiation. In fact, the majority of SPM techniques are extensions of AFM that use this modality. Examples of such properties are mechanical properties like stiffness or adhesion strength and electrical properties such as conductivity or surface potential. Simultaneous with the acquisition of topographical images, other properties of the sample can be measured locally and displayed as an image, often with similarly high resolution. Examples of this include atomic manipulation, scanning probe lithography and local stimulation of cells. In manipulation, the forces between tip and sample can also be used to change the properties of the sample in a controlled way.
True atomic resolution of the silicon 7x7 surface-the atomic images of this surface obtained by STM had convinced the scientific community of the spectacular spatial resolution of scanning tunneling microscopy-had to wait a little longer before it was shown by Giessibl. The surface topography is commonly displayed as a pseudocolor plot.Īlthough the initial publication about atomic force microscopy by Binnig, Quate and Gerber in 1986 speculated about the possibility of achieving atomic resolution, profound experimental challenges needed to be overcome before atomic resolution of defects and step edges in ambient (liquid) conditions was demonstrated in 1993 by Ohnesorge and Binnig.
This is achieved by raster scanning the position of the sample with respect to the tip and recording the height of the probe that corresponds to a constant probe-sample interaction (see § Topographic image for more). This can be applied to perform force spectroscopy, to measure the mechanical properties of the sample, such as the sample's Young's modulus, a measure of stiffness.įor imaging, the reaction of the probe to the forces that the sample imposes on it can be used to form an image of the three-dimensional shape (topography) of a sample surface at a high resolution. In force measurement, AFMs can be used to measure the forces between the probe and the sample as a function of their mutual separation. The AFM has three major abilities: force measurement, topographic imaging, and manipulation.
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