Surfaces chemically sensitive imaging

Chap. 2, altered surface tensions of surface-treated polymers are directly accessible. In addition, laterally resolved maps of adhesive interactions are useful to investigate heterogeneous samples, such as multicomponent systems, or to record local functional group distributions. For quantitative AFM work, calibration procedures for the cantilever spring constant and the AFM detection system become important. In addition, the use of modified tips will be discussed as a means to enhance the applicability of AFM for chemically sensitive imaging. 

Fig. 13.28. Chemically sensitive image of the interface layer related to the ion-etched surface. The interface layer has a structure which results in a square image pattern.

The Case of Chemically Sensitive Imaging of Surfaces by Atomic Force Microscopy... 

Chemically sensitive imaging can be achieved in a general sense if a particular mode of AFM is sensitive to differences in a materials properties, which are then related to certain chemical functionahties exposed at or near the surface. 

Many groups are now trying to fit frequency shift curves in order to understand the imaging mechanism, calculate the minimum tip-sample separation and obtain some chemical sensitivity (quantitative infonuation on the tip-sample interaction). The most conunon methods appear to be perturbation theory for considering the lever dynamics [103], and quantum mechanical simulations to characterize the tip-surface interactions [104]. Results indicate that the... 

Krausch G, Hipp M, Bditau M, Mlynek J and Marti O 1995 High resolution imaging of polymer surfaces with chemical sensitivity Macromolecules 28 260... 

As in chemical sensitization, spectral sensitization is usually done after precipitation but before coating, and usually is achieved by adsorbing certain organic dyes to the silver haUde surfaces (47,48,212—229). Once the dye molecule is adsorbed to the crystal surface, the effects of electromagnetic radiation absorbed by the dye can be transferred to the crystal. As a result of this transfer, mobile electrons are produced in the conduction band of the silver haUde grain. Once in the conduction band, the electrons are available to initiate latent-image formation. 

XANES spectroscopy is also the basis of chemically sensitive X-ray imaging, as well as qualitative and quantitative microspectroscopy [306], ptXANES is attractive for chemical analysis, with its spatial resolution down to 10 ptm. Variations on the theme are surface EXAFS (SEXAFS), grazing incidence XAS and in situ time-resolved XAS investigations. Grazing angle XAFS can be used for the study of ultrathin multilayer systems. 

Figure 3 is a high-resolution image of a Si(l 11) in NaOH. It shows that the surface has a great chemical homogeneity and that the STM may have some chemical sensitivity. With the exception of a few sSi-OH [14] visible (white spots), which represent only 0.1 % of atomic sites, the surface is indeed (1x1) H-Si(lll). That =Si-OH appear as protrusions surrounded by a dark ring comes from an increased local density of states and a three-dimension (3D) potential distribution induced by the large... 

The ability of AFM to provide atomic-level resolution images of electrode surfaces under solution has proved invaluable in providing a greater understanding of the electrode-electrolyte interface, especially when used in conjunction with chemically sensitive surface techniques. The capability to topographically image any surface... 

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