Scanning tunnel microscopy , point

Measurements using the Point Contact Method with Scanning Tunneling Microscopy. Journal of the American Chemical Society, 128, 7746-7747. 

Gimzewski, J. K., Moller, R., Pohl, D. W., and Schlittler, R. R. (1987). Transition from tunneling to point contact investigated by scanning tunneling microscopy and spectroscopy. Surface Sci. 189/190, 15-23. 

Development of scanning tunnel microscopy (STM) by Gerd Binnig and Heinrich Rohrer in 1981 pointed the way to breakthroughs in understanding basic chemical processes. Since then, STM and atomic force microscopy (AFM), as well as optical force microscopy proximal probes,1 have been used to manipulate individual atoms and molecules on surfaces. 

The basic principle of scanning tunneling microscopy (STM) is based on the tunneling current between a metallic tip, which is sharpened to a single atom point, and a conducting material (Fig. 1). A small bias voltage (mV to Y) is applied between an atomically sharp tip and the sample. 

Ciraci, S., andTekman, E. (1989),Theory of transition from the tunneling regime to point contact in scanning tunneling microscopy, Phys. Rev., 40,11969-11972. 

If one makes one of the electrodes a metal wire with a sharp tip at the end and the other electrode a planar sample separated by vacuum space, one has the basis for both point-contact electron vacuum tuimeling spectroscopy and scanning tunneling microscopy. The latter will be discussed in more detail in the next section on instrumentation. 

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