STM imaging, of metal

The surface chemical composition plays an important role in STM imaging of metal surfaces. It is a well-known fact in STM experiments that... 

The development of scanning probe microscopies and x-ray reflectivity (see Chapter VIII) has allowed molecular-level characterization of the structure of the electrode surface after electrochemical reactions [145]. In particular, the important role of adsorbates in determining the state of an electrode surface is illustrated by scanning tunneling microscopic (STM) images of gold (III) surfaces in the presence and absence of chloride ions [153]. Electrodeposition of one metal on another can also be measured via x-ray diffraction [154]. 

Pontifex G H ef a/1991 STM imaging of small metal partioles formed in anodio oxide pores J. Phys. Chem. 95 9989... 

A dramatic illustration of the effect of metal ions on DNA structure is seen in the STM images of DNA circles in the presence of either MgCl2 or ZnBr2 (46). The shape of the DNA circles of 168-base-pair (bp) length... 

Sonnenfeld, R. SPIE 88 Conference Proceedings, in press) have both reported in situ STM images of electrode surfaces on which metals have been electrochemically deposited. Morita et. al. (61) have examined Ag surfaces in situ in the presence of chloride ion. 

FIG. 28. The formation of upd layers often involves complex interactions between the anion, upd metal, and substrate. An example is provided by the (Vs X vVs) R30° STM image of the copper/sulfate upd layer formed on Au(lll) and the SXS of the interfacial structure. (Adapted from Refs. 148, 351, 353.)... 

Fig. 5 Montage image combining an STM image of the Ag oxide structure (from bottom left) superimposed over the proposed oxide structure (from top right). The numbers, n = 1-5, correspond to the symmetrically different positions within the middle silver layer sandwiched between two O layers. Agi and Ag2 have metallic character, as they are exclusively bonded to silver atoms in the substrate below, whereas Ags, Ag4, and Ags are directly bonded to oxygen inside the oxide rings and are ionic in nature. Both Ag4 and Ags sites sit above threefold sites of the underlying (111) lattice atoms, whereas Ags occupies a top site. Reprinted with permission from Bocquet et at.. Journal of the American Chemical Society, 2003, 125, 3119. 2003, American Chemical Society.

Using the expressions of the tunneling matrix elements derived in Chapter 3, theoretical STM images can be calculated. In this section, we discuss the theoretical STM images of the simple metal surface we presented in the previous subsection. 

The corrugation inversion due to tip states is a universal phenomenon in the STM imaging of low-Miller-index metal surfaces. For most metals (except several alkali and alkaline earth metals, which have rarely been imaged by STM), the nearest-neighbor atomic distance a 3 A. Consequently, the numerical coefficients on Eq. (5.61) are very close to those for Au(lll). 

The STM images of large superstructures on metal surfaces exhibit a very simple form. As shown first time by Tersoff and Hamann (1983, 1985), at the low-bias limit, the STM images of large superstructures on metal surfaces are independent of tip electronic states, and an STM image is simply a contour of an important quantity of the sample surface only the Fermi-level local density of states (LDOS), taken at the center of curvature of the tip. An attempt was also made to interpret the observed atom-resolved images of semiconductors... 

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