Scanning probe microscopy includes scanning tunneling microscopy and atomic force microscopy.
Scanning tunneling microscopy (STM) is a technique that allows for imaging solid surfaces based on the so-called tunneling current. The tunneling current starts to flow when a sharp tip approaches a conducting surface at a distance of approximately one nanometer. The tip is mounted on a piezoelectric tube, which allows tiny movements by applying a voltage at its electrodes. The electronics of the STM system control the tip position in such a way that the tunneling current and, hence, the tip-surface distance is kept constant, while at the same time scanning a small area of the sample surface. This movement is recorded and can be displayed as an image of the surface topography. Under ideal circumstances, the individual atoms of a surface can be resolved and displayed.
The STM in now being used to write with atoms. Individual atoms are moved into place on a surface with an STM. Chemists or engineers can design surfaces at the nanometer level, and STM can move atoms into place.
