Scanning probe microscopy is a branch of microscopy that creates images of surfaces using a physical probe that scans a specimen. SPM covers several related technologies for imaging and measuring surfaces on a fine scale, down to the level of molecules and atoms. Today, it is still one of the most diffused techniques for surface characterisation. An image of the surface is obtained by mechanical moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a function of position. SPM was founded with the invention of the scanning tunneling microscope in 1981. Scanning probe microscopes allow scientists to image, characterize and even manipulate material structures at exceedingly small scales including features of atomic proportions.

Probe Techniques

The three most applied scanning probe techniques are:

Scanning Tunneling Microscopy/Spectroscopy (STM/STS) measures a weak electrical current flowing between tip and sample as they are held a very distance apart.

Atomic Force Microscopy (AFM) measures the interaction force between the tip and surface. The tip may be dragged across the surface, or may vibrate as it moves. The interaction force will depend on the nature of the sample, the probe tip and the distance between them.

Scanning Near-Field Optical Microscopy (SNOM) scans a very small light source very close to the sample. Detection of this light energy forms the image. SNOM can provide resolution below that of the conventional light microscope down to 10Å.