Scanning tunneling microscopy electrode surface

Fig. VIII-2. Scanning tunneling microscopy images illustrating the capabilities of the technique (a) a 10-nm-square scan of a silicon(lll) crystal showing defects and terraces from Ref. 21 (b) the surface of an Ag-Au alloy electrode being electrochemically roughened at 0.2 V and 2 and 42 min after reaching 0.70 V (from Ref. 22) (c) an island of CO molecules on a platinum surface formed by sliding the molecules along the surface with the STM tip (from Ref. 41).

Matsumoto H, Inukai J and Ito M 1994 Structures of copper and halides on Pt(111), Pt(IOO) and Au(111) electrode surfaces studied by in situ scanning tunneling microscopy J. Eiectroanai. Chem. 379 223-31... 

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). 

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-... 

As mentioned above, the methods based on detection of electrons or ions or probing the electrode surface by these particles are generally handicapped by the necessity to move the studied electrode into vacuum, i.e. to work ex-situ. There are, however, two important exceptions to this rule electrochemical mass spectrometry and electrochemical scanning tunnelling microscopy. 

A detailed electrochemical study of Ni(l 11) electrodes in H2SO4 solution in conjunction with in situ scanning tunneling microscopy (STM) and in situ surface X-ray scattering methods (SXS, x-ray diffraction and x-ray reflectivity) was carried out by Scherer et al. [18]. 

Scanning electrochemical microscopy (SECM the same abbreviation is also used for the device, i.e., the microscope) is often compared (and sometimes confused) with scanning tunneling microscopy (STM), which was pioneered by Binning and Rohrer in the early 1980s [1]. While both techniques make use of a mobile conductive microprobe, their principles and capabilities are totally different. The most widely used SECM probes are micrometer-sized ampero-metric ultramicroelectrodes (UMEs), which were introduced by Wightman and co-workers 1980 [2]. They are suitable for quantitative electrochemical experiments, and the well-developed theory is available for data analysis. Several groups employed small and mobile electrochemical probes to make measurements within the diffusion layer [3], to examine and modify electrode surfaces [4, 5], However, the SECM technique, as we know it, only became possible after the introduction of the feedback concept [6, 7],... 

The last part of the chapter refers to the use of techniques that are relatively new. They consist of scanning tunneling microscopy and atomic force microscopy by which one can get better than 10 A resolution in looking at surfaces. A laser beam, in collaboration with a quadrupole mass spectrometer, can be used to detect local hydrogen with a resolution of about 0.1-1 pm. Finally, ideas of electronic noise are applied to the random fluctuations of the potential of an electrode and can give a value of the corrosion current without any influence of the IR drop. This has made the method particularly useful for nonaqueous solutions. 

Refs. [i] Conway BE (1999) Electrochemical processes involving H adsorbed at metal electrode surfaces. In Wieckowski A (ed) Interfacial electrochemistry, theory, experiment, and applications. Marcel Dekker, New York, pp 131-150 [ii] Climent V, Gomez R, Orts JM, Rodes A, AldazA, Feliu JM (1999) Electrochemistry, spectroscopy, and scanning tunneling microscopy images of small single-crystal electrodes. In Wieckowski A (ed) Interfacial electrochemistry, theory, experiment, and applications. MarcelDekker, New York, pp 463-475 [Hi] Calvo E] (1986) Fundamentals. The basics of electrode reactions. In Bamford CH, Compton RG (eds) Comprehensive chemical kinetics, vol. 26. Elsevier, Amsterdam, pp 1-78... 

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