Scanning substrates

SIAM Scanning interferometric apertureless microscopy [103b] Laser light is reflected off the substrate, and scattering between an AFM tip and sample is processed interferometrically Diffraction Surface structure... 

Christoph R, Siegenthaler H, Rohrer H and Wiese H 1989 In s/fu scanning tunneiiing microscopy at potentiai controiied Ag(100) substrates Electrochim. Acta 34 1011... 

Monolayers of alkanetliiols adsorbed on gold, prepared by immersing tire substrate into solution, have been characterized by a large number of different surface analytical teclmiques. The lateral order in such layers has been investigated using electron [1431, helium [144, 1451 and x-ray [146, 1471 diffraction, as well as witli scanning probe microscopies [122, 1481. Infonnation about tire orientation of tire alkyl chains has been obtained by ellipsometry [149], infrared (IR) spectroscopy [150, 151] and NEXAFS [152]. 

Fig. 46. Schematic drawing of the failure surface of a lap joint prepared from hot-dipped galvanized steel substrates (top) and TOF-SIMS line scans showing the distribution of several mass numbers as a function of distance from the edge of the overlap (bottom). Reproduced by permission of John Wiley and Sons from Ref. [57].

Visually, failure was mostly eohesive within the adhesive (see Figs. 34 and 46). However, there was a small area of apparent interfacial failure ( initiation zone ) located at one end of each substrate. Line scans were eondueted aeross the initiation zone, from the edge of the substrate to the area of cohesive failure within the adhesive. From the line scans, it was apparent that there were patehes of polymer present in the initiation zone, even when failure appeared to be interfaeial (see Fig. 46). SIMS images of the initiation zone were constructed for various mass numbers (see Figs. 47-49). The images showed well-defined cation-rieh... 

The development of a host of scanning probe devices such as the atomic force microscope (AFM) [13-17] and the surface forces apparatus (SFA) [18-22], on the other hand, enables experimentalists to study almost routinely the behavior of soft condensed matter confined by such substrates to spaces of molecular dimensions. However, under conditions of severe confinement a direct study of the relation between material properties and the microscopic structure of confined phases still remains an experimental challenge. 

In the overpotential deposition regime we observed that nanosized Al was deposited in the initial stages. Eurthermore, a transfer of Al from the scanning tip to the Al covered substrate was observed. We accidentally succeeded in an indirect tip-induced nanostructuring of Al on growing Al (Eigure 6.2-6). 

Refers to the physical substrate to which biological samples are attached to create features (spots). In gene expression profiling arrays are hybridized with labeled sample and then scanned and analyzed to generate data. 

Such effects are observed inter alia when a metal is electrochemically deposited on a foreign substrate (e.g. Pb on graphite), a process which requires an additional nucleation overpotential. Thus, in cyclic voltammetry metal is deposited during the reverse scan on an identical metallic surface at thermodynamically favourable potentials, i.e. at positive values relative to the nucleation overpotential. This generates the typical trace-crossing in the current-voltage curve. Hence, Pletcher et al. also view the trace-crossing as proof of the start of the nucleation process of the polymer film, especially as it appears only in experiments with freshly polished electrodes. But this is about as far as we can go with cyclic voltammetry alone. It must be complemented by other techniques the potential step methods and optical spectroscopy have proved suitable. 

Fig. 13. Cyclic voltammograin for the charging/discharging of polyaniline on Pt substrate at different scan rates, ref. 214 (reprinted by permission of the publisher, The Electrochemical Society, Inc.)...

The dependence of friction on sliding velocity is more complicated. Apparent stick-slip motions between SAM covered mica surfaces were observed at the low velocity region, which would disappear when the sliding velocity excesses a certain threshold [35]. In AFM experiments when the tip scanned over the monolayers at low speeds, friction force was reported to increase with the logarithm of the velocity, which is similar to that observed when the tip scans on smooth substrates. This is interpreted in terms of thermal activation that results in depinning of interfacial atoms in case that the potential barrier becomes small [36]. 

The results show that the C5o-Pst star-shaped polymer L-B hlms are hrmly fixed on the surface of the substrate, even after the surface was scanned for many times. The topography, high density, order and preferred orientation of the hlms are dominating factors in friction. The C5o-Pst him could play a signihcant role in microtribological applications. 

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