Jul 21 2006
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Image Credits: i3d/shutterstock.com
Scanning Tunneling Microscopy (STM) has transformed the examination of solid surfaces. For the first time, it has facilitated tracking of images and conducting spectroscopy of such systems with atomic resolution.
Applications of Scanning Tunneling Microscopy
STM is also the only tool with the capability to rip atoms from the sample surface and relocate or control them. Since STM is limited to working with conducting surfaces, a whole range of imaging technologies based on different physical interactions emerged, such as the atomic force microscope (AFM). Success in regulating and imaging minute pieces of matter using AFM and STM has prompted the development of other scanning probe processes.
A Key Shortcoming of Scanning Probe Procedures
The main drawback of scanning probe processes is the slow, serial technique through which they function. This feature has restricted their use specifically in laboratory applications that involve atom-at-a-time maneuvers.
Topographical and Electrical Properties of Scanning Tunneling Microscopy
STM is the only device that enables researchers to explore both electrical and topographical properties of materials, which are critical for gaining insights into the behavior of microelectronic devices.
STM was invented by Gerd Binnig and Heinrich Rohrer of IBM, Zurich, in 1981. A very fine wire tip is drawn within a few Angstroms of a conductive surface. Due to the quantum mechanical effect known as “tunneling,” electrons can jump between the tip and the surface.
Extreme Precision of the Microscope
This effect drops very quickly with distance such that very minute changes in position can be measured. The other vital part of the microscope is a way to shift the tip across the surface with maximum precision. This is achieved using piezoelectric ceramics that expand or contract very marginally upon applying an electric field.
A feedback circuit shifts the tip normal to the surface to reduce differences in current. Then, the feedback data is processed into an atomic-scale picture. By increasing the voltage, a researcher can move atoms around, pile them up, or stimulate chemical reactions.