Scanning Tunnelling Microscopy STM

Schematic diagram of the AFM showing the auxiliary STM used for detecting movement of the atomic force cantilever. Source Reprinted with permission from Woodruff DP, Delchar TA, Modern Techniques of Surface Science, Cambridge University Press, Cambridge, 460, 1994. Copyright 1994, Cambridge University Press. 

Measurement of interatomic distances of 0.1 nm-lOOum can be achieved with STM. 

It is not necessary for STM to be operated in a vacuum and work can be undertaken at atmospheric pressure and under liquids. At atmospheric pressure, the drag from the meniscus effect of absorbed moisture can be a problem therefore, some workers prefer to immerse the sample in water. 

Donnet et al [112-116] have used STM to charaeterize the surfaee of earbon fibers, as well as examine carbon fibers made from different precursors, PAN based high strength carbon fibers, and surface treated and activated carbon fibers. 

Other workers [117-119] have examined PAN based carbon fibers with STM. Effler et al [120] used STM in conjunction with X-ray analyzes to examine mesophase pitch based carbon fibers. Hoffman and co-workers [121] describe the advantages of STM for studying surface treated carbon fibers. 

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The ability to control the position of a fine tip in order to scan surfaces with subatomic resolution has brought scanning probe microscopies to the forefront in surface imaging techniques. We discuss the two primary techniques, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interested reader is referred to comprehensive reviews [9, 17, 18]. 

We have considered briefly the important macroscopic description of a solid adsorbent, namely, its speciflc surface area, its possible fractal nature, and if porous, its pore size distribution. In addition, it is important to know as much as possible about the microscopic structure of the surface, and contemporary surface spectroscopic and diffraction techniques, discussed in Chapter VIII, provide a good deal of such information (see also Refs. 55 and 56 for short general reviews, and the monograph by Somoijai [57]). Scanning tunneling microscopy (STM) and atomic force microscopy (AFT) are now widely used to obtain the structure of surfaces and of adsorbed layers on a molecular scale (see Chapter VIII, Section XVIII-2B, and Ref. 58). On a less informative and more statistical basis are site energy distributions (Section XVII-14) there is also the somewhat laige-scale type of structure due to surface imperfections and dislocations (Section VII-4D and Fig. XVIII-14). 

We confine ourselves here to scanning probe microscopies (see Section VIII-2B) scanning tunneling microscopy (STM) and atomic force microscopy (AFM), in which successive profiles of a surface (see Fig. VIII-1) are combined to provide a contour map of a surface. It is conventional to display a map in terms of dark to light areas, in order of increasing height above the surface ordinary contour maps would be confusing to the eye. 

Economy, J., Daley, M., Hippo, E. J. and Tandon, D., Elucidating the pore structure of activated carbon fibers through direct imaging using scanning tunneling microscopy (STM), Carbon, 1995, 33(3), 344 345... 

Scanning tunneling spectroscopy (STS) can, in principle, probe the electronic density of states of a singlewall nanotube, or the outermost cylinder of a multi-wall tubule, or of a bundle of tubules. With this technique, it is further possible to carry out both STS and scanning tunneling microscopy (STM) measurements at the same location on the same tubule and, therefore, to measure the tubule diameter concurrently with the STS spectrum. No reports have yet been made of a determination of the chiral angle of a tubule with the STM technique. Several groups have, thus far, attempted STS studies of individual tubules. 

The very new techniques of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) have yet to establish themselves in the field of corrosion science. These techniques are capable of revealing surface structure to atomic resolution, and are totally undamaging to the surface. They can be used in principle in any environment in situ, even under polarization within an electrolyte. Their application to date has been chiefly to clean metal surfaces and surfaces carrying single monolayers of adsorbed material, rendering examination of the adsorption of inhibitors possible. They will indubitably find use in passive film analysis. 

Film-forming chemical reactions and the chemical composition of the film formed on lithium in nonaqueous aprotic liquid electrolytes are reviewed by Dominey [7], SEI formation on carbon and graphite anodes in liquid electrolytes has been reviewed by Dahn et al. [8], In addition to the evolution of new systems, new techniques have recently been adapted to the study of the electrode surface and the chemical and physical properties of the SEI. The most important of these are X-ray photoelectron spectroscopy (XPS), SEM, X-ray diffraction (XRD), Raman spectroscopy, scanning tunneling microscopy (STM), energy-dispersive X-ray spectroscopy (EDS), FTIR, NMR, EPR, calorimetry, DSC, TGA, use of quartz-crystal microbalance (QCMB) and atomic force microscopy (AFM). 

Valette-Hamelin approach,67 and other similar methods 24,63,74,218,225 (2) mass transfer under diffusion control with an assumption of homogeneous current distribution73 226 (3) adsorption of radioactive organic compounds or of H, O, or metal monolayers73,142,227 231 (4) voltammetry232,233 and (5) microscopy [optical, electron, scanning tunneling microscopy (STM), and atomic force microscopy (AFM)]234"236 as well as a number of ex situ methods.237 246... 

Scanning tunneling microscopy (STM) Atomic force microscopy (AFM) 234-236... 

Scanning tunneling microscopy, STM ordered adlattices, 264 oxygen adlattices, 261 platinum, 261 sodium adlattices, 262 spillover-backspillover, 259 Self-consistent field, 269 Selectivity definition, 17... 

FIGURE B.3 Individual atoms can be seen as bumps on the surface of a solid by the technique called scanning tunneling microscopy (STM). This image is of silicon. 

Scanning tunnel microscopy (STM) was chosen as a tool for realization of this task (Wilkins et al. 1989). CdS nanoparticles were formed in a bilayer of cadmium arachidate deposited onto the surface of freshly cleaved graphite (Erokhin et al. 1995a). The graphite was used as the first electrode. Initially, STM was used for locahzing the position of the particles. Eigure 28 shows the images of different areas of the sample. The particles are vis-... 

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