Atomic force microscopy AFM probe

The ability to control the position of a fine tip in order to scan surfaces with subatomic resolution has brought scanning probe microscopies to the forefront in surface imaging techniques. We discuss the two primary techniques, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interested reader is referred to comprehensive reviews [9, 17, 18]. 

Friction can now be probed at the atomic scale by means of atomic force microscopy (AFM) (see Section VIII-2) and the surface forces apparatus (see Section VI-4) these approaches are leading to new interpretations of friction [1,1 a,lb]. The subject of friction and its related aspects are known as tribology, the study of surfaces in relative motion, from the Greek root tribos meaning mbbing. 

We confine ourselves here to scanning probe microscopies (see Section VIII-2B) scanning tunneling microscopy (STM) and atomic force microscopy (AFM), in which successive profiles of a surface (see Fig. VIII-1) are combined to provide a contour map of a surface. It is conventional to display a map in terms of dark to light areas, in order of increasing height above the surface ordinary contour maps would be confusing to the eye. 

The most popular of the scanning probe tecimiques are STM and atomic force microscopy (AFM). STM and AFM provide images of the outemiost layer of a surface with atomic resolution. STM measures the spatial distribution of the surface electronic density by monitoring the tiumelling of electrons either from the sample to the tip or from the tip to the sample. This provides a map of the density of filled or empty electronic states, respectively. The variations in surface electron density are generally correlated with the atomic positions. 

Experimental techniques based on the application of mechanical forces to single molecules in small assemblies have been applied to study the binding properties of biomolecules and their response to external mechanical manipulations. Among such techniques are atomic force microscopy (AFM), optical tweezers, biomembrane force probe, and surface force apparatus experiments (Binning et al., 1986 Block and Svoboda, 1994 Evans et ah, 1995 Israelachvili, 1992). These techniques have inspired us and others (see also the chapters by Eichinger et al. and by Hermans et al. in this volume) to adopt a similar approach for the study of biomolecules by means of computer simulations. 

The objective of this book is to highlight the important strides being made toward a molecular understanding of the processes that occur at surfaces through the unique information provided by the proximal scanning probe family of techniques this principally involves scanning tunneling microscopy (STM) but some atomic force microscopy (AFM) experiments are also included. 

The success of STM has resulted in the development of a whole variety of related scanning probe microscopes, the most important of which is atomic force microscopy, AFM, also known as scanning force microscopy. AFM was first reported in 1986 by Binnig, Quate and Gerber. 

Atomic force microscopy (AFM) is a variant of STM and was introduced in 1986 by Binnig et al. (11). AFM belongs to a family of near-field microscopies and is capable of imaging a wide variety of specimens surface down to an atomic scale. The technique employs a probe (pyramidal tip) mounted at the end of a sensitive but rigid cantilever (see Fig. 2). The probe is drawn across the specimen under very light mechanical loading (1). Measurements of the probe s interaction with the sample s surface are accomplished with a laser beam reflected from the cantilever. 

Atomic force microscopy (AFM) or, as it is also called, scanning force microscopy (SFM) is the most generally applicable member of the scanning probe family. It is based on the minute but detectable forces - order of magnitude nano-Newtons -between a sharp tip and atoms in the surface [39]. The tip is mounted on a flexible arm called a cantilever, and is positioned at a subnanometer distance from the surface. If the sample is scanned under the tip in the x-y plane, it feels the attractive or repulsive force from the surface atoms and hence is deflected in the z direction. Various methods exist to measure the deflection, as described by Sarid [40]. Before we describe equipment and applications to catalysts, we will briefly look at the theory behind AFM. 

Microscopic techniques, 70 428 Microscopists, role of, 76 467 Microscopy, 76 464-509, See also Atomic force microscopy (AFM) Electron microscopy Light microscopy Microscopes Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) acronyms related to, 76 506-507 atomic force, 76 499-501 atom probe, 76 503 cathodoluminescence, 76 484 confocal, 76 483-484 electron, 76 487-495 in examining trace evidence, 72 99 field emission, 76 503 field ion, 76 503 fluorescence, 76 483 near-held scanning optical,... 

The most popular tools for the visualization of engineered nanoparticles are electron and scanning probe microscopes. The visualization, the state of aggregation, dispersion sorption, size, structure, and shape can be observed by means of atomic force microscopy (AFM), scanning electron (SEM), and transmission electron microscopy (TEM). Analytical tools (mostly spectroscopic) can be coupled to... 

Among the many microscopy-based techniques for the study of biomolecular interactions on surfaces, scanning probe microscopies, and especially the atomic force microscopies (AFM), are the most used because of their molecular and sub-molecular level resolution and in situ imaging capability. Apart from the high resolution mapping of siuface nanotopographies, AFM can be used for the quantification and visualisation of the distribution of chemistry, hydrophobicity and local mechanical properties on surfaces, and for the fabrication of nanostructmes on surfaces. 

In more recent studies, the double layer of a pc-Au electrode has been probed by atomic force microscopy (AFM) measurements [7]. The properties of the Au/solution interface were changed by variations in pH, salt concentration, and electrode potential. 

Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) These methodologies for probing the morphological details of a surface down to... 

STM was the first of a class of techniqnes known as scanning probe microscopy. Atomic force microscopy (AFM), invented later in the 1980s, is currently the most widely used of these techniques. Both STM and AFM depend on probes with atomically sharp tips these probes are manenvred over the snrface of the sample to be imaged, maintaining atom-scale distances between the probe and sample. Both techniques are capable of picking np atoms individnally and placing them precisely on surfaces (7). 

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