Tunneling atomic force microscopy

TUNneling Atomic Force Microscopy (TUNA) is similar to CAFM in that it is also capable of providing electrical conductivity (dl/dV) maps to a spatial resolution of a couple of nanometers. Samples, however, must be less conductive than used in CAFM. Information is derived by measuring the current (100 fA-100 pA) passing to/from an atomically sharp tip and the sample surface. As conductivity is a function of film thickness, leakage paths, charge traps, and so on, these too can be mapped. Measurement of I versus F or I versus V curves allows for localized data to be extracted. 

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. 

Giancarlo L C and Flynn G W 1988 Scanning tunneling and atomic force microscopy probes of self-assembled, physisorbed monolayers A/ / . Rev. Phys. Chem. 49 297... 

Flansma P K, Elings V B, Marti O and Bracker C E 1988 Scanning tunnelling microscopy and atomic force microscopy application to biology and technology Science 242 209... 

A wide variety of measurements can now be made on single molecules, including electrical (e.g. scanning tunnelling microscopy), magnetic (e.g. spin resonance), force (e.g. atomic force microscopy), optical (e.g. near-field and far-field fluorescence microscopies) and hybrid teclmiques. This contribution addresses only Arose teclmiques tliat are at least partially optical. Single-particle electrical and force measurements are discussed in tire sections on scanning probe microscopies (B1.19) and surface forces apparatus (B1.20). 

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... 

Why are typical surface science techniques such as low-energy electron diffraction, scanning tunneling and atomic force microscopy generally unsuitable for studying supported catalysts ... 

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