Atomic force microscopes AFMs

Fig. VIII-1. Schematic illustration of the scanning tunneling microscope (STM) and atomic force microscope (AFM). (From Ref. 9.)...

Fig. Vni-3. (a) Atomic force microscope (AFM) and (b) transmission electron microscope (TEM) images of lead selenide particles grown under arachidic acid monolayers. (Pi Ref. 57.)...

It is remarkable that tire roots of the SFA go back to the early 1960s [1], Tabor and Winterton [2] and Israelachvili and Tabor [3] developed it to the current state of the art some 15 years before the invention of the more widely used atomic force microscope (AFM) (see chapter B1.19). 

That simulation study [49] aimed at a microscopic interpretation of single molecule atomic force microscope (AFM) experiments [50], in which unbinding forces between individual protein-ligand complexes have been m( asured... 

Newer techniques that are responding to the need for atomic level imaging and chemical analysis include scanning tunneling microscopes (STMs), atomic force microscopes (AFMs) (52), and focused ion beams (FIBs). These are expected to quickly pass from laboratory-scale use to in-line monitoring apphcations for 200-mm wafers (32). 

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. 

A very similar technique is atomic force microscope (AFM) [38] where the force between the tip and the surface is measured. The interaction is usually much less localized and the lateral resolution with polymers is mostly of the order of 0.5 nm or worse. In some cases of polymer crystals atomic resolution is reported [39], The big advantage for polymers is, however, that non-conducting surfaces can be investigated. Chemical recognition by the use of specific tips is possible and by dynamic techniques a distinction between forces of different types (van der Waals, electrostatic, magnetic etc.) can be made. The resolution of AFM does not, at this moment, reach the atomic resolution of STM and, in particular, defects and localized structures on the atomic scale are difficult to see by AFM. The technique, however, will be developed further and one can expect a large potential for polymer applications. 

FIGURE 21.20 Tapping-mode atomic force microscopic (AFM) height image left) and phase image right) of NRIO sample. The stmctures indicated hy circles are considered to he carhon hlack (CB) fillers. 

Atomic force microscope (AFM) is a powerful nanotechnology tool for molecular imaging and manipulations. One major factor limiting resolution in AFM to observe individual biomolecules such as DNA is the low sharpness of the AFM tip that scans the sample. Nanoscale 1,3,5,7-tetrasubstituted adamantane is found to serve as the molecular tip for AFM and may also find application in chemically well-defined objects for calibration of commercial AFM tips [113]. 

Technologically, the most important member of the scanning probe family is perhaps the atomic force microscope (AFM), which has found applications in... 

Recent developments have allowed atomic force microscopic (AFM) studies to follow the course of spherulite development and the internal lamellar structures as the spherulite evolves [206-209]. The major steps in spherulite formation were followed by AFM for poly(bisphenol) A octane ether [210,211] and more recently, as seen in the example of Figure 12 for a propylene 1-hexene copolymer [212] with 20 mol% comonomer. Accommodation of significant content of 1-hexene in the lattice allows formation and propagation of sheaf-like lamellar structure in this copolymer. The onset of sheave formation is clearly discerned in the micrographs of Figure 12 after crystallization for 10 h. Branching and development of the sheave are shown at later times. The direct observation of sheave and spherulitic formation by AFM supports the major features that have been deduced from transmission electron and optical microscopy. The fibrous internal spherulite structure could be directly observed by AFM. 

Fig. 9 Preparation of PIC-coated polymeric micelles and their atomic force microscope (AFM) images. Reprinted from [201] with permission...

FIGURE 15.21 Atomic force microscope (AFM) image of a carbon nanotube contacted by two metal electrodes and Raman spectra taken from the nanotube. (Reprinted from web http //www-rcf.usc. edu/ scronin with permission from Dr S.B. Cronin.)... 

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