Scanning tunneling microscope techniques

Newer techniques that are responding to the need for atomic level imaging and chemical analysis include scanning tunneling microscopes (STMs), atomic force microscopes (AFMs) (52), and focused ion beams (FIBs). These are expected to quickly pass from laboratory-scale use to in-line monitoring apphcations for 200-mm wafers (32). 

This slow diffusion of a crucial new technique can be compared with the invention of the scanning tunnelling microscope (STM) by Binnig and Rohrer, first made public in 1983, like X-ray diffraction rewarded with the Nobel Prize 3 years later, but unlike X-ray diffraction quickly adopted throughout the world. That invention, of comparable importance to the discoveries of 1912,now(2 decades later) has sprouted numerous variants and has virtually created a new branch of surface science. With it, investigators can not only see individual surface atoms but they can also manipulate atoms singly (Eigler and Schweitzer 1990). This rapid adoption of... 

The main technique employed for in situ electrochemical studies on the nanometer scale is the Scanning Tunneling Microscope (STM), invented in 1982 by Binnig and Rohrer [62] and combined a little later with a potentiostat to allow electrochemical experiments [63]. The principle of its operation is remarkably simple, a typical simplified circuit being shown in Figure 6.2-2. 

Three scanning probe techniques are described in more detail below the scanning tunneling microscope, the atomic force microscope, and the friction force microscope. 

As stressed in the introduction, the main difficulty ofthe voltaic cell method of investigating systems is its lack of molecular specificity. Therefore, complementary information should be obtained by using techniques sensitive to the polar ordering and arrangement of molecules in a surface or interfacial layer, such as optical, spectroscopic, and scanning tunneling microscope methods. " ... 

The Scanning Tunneling Microscope has demonstrated unique capabilities for the examination of electrode topography, the vibrational spectroscopic imaging of surface adsorbed species, and the high resolution electrochemical modification of conductive surfaces. Here we discuss recent progress in electrochemical STM. Included are a comparison of STM with other ex situ and in situ surface analytic techniques, a discussion of relevant STM design considerations, and a semi-quantitative examination of faradaic current contributions for STM at solution-covered surfaces. Applications of STM to the ex situ and in situ study of electrode surfaces are presented. 

Bonnell, D.A. Scanning Tunneling Microscopy and Spectroscopy Theory, Techniques, and Applications, John Wiley Sons. Inc.. New York, NY, 1993. Ciemmer, C.R. and T,P. Beebe. Jr Graphite A Mimic for DNA and Other Biomolecules in Scanning Tunneling Microscope Studies. Science. 640 (February 8, 1991). 

Surface diffraction experiments have to be done in UHV. Otherwise the surfaces are covered with a monolayer of adsorbed molecules. At this point the reader might ask why do we not have to use UHV in scanning tunneling or the atomic force microscope In both techniques the tip penetrates through the surface contamination layer. In the scanning tunneling microscope it is often just invisible because contamination layers are usually not good conductors. In... 

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