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Imaging individual atoms

A rough estimation of the magnification M can be obtained from a heuristic geometrical argument to yield [Pg.40]

Typically, L = 10 cm, R = 100 A, and M = 10 . An atom at the tip end, with a typical diameter 3 A, creates a 3-mm-size spot on the screen. A deviation up to a factor of 3 from the prediction of Eq. (1.30) was observed experimentally (Muller and Tsong, 1969). Nevertheless, it gives the correct order of magnitude. [Pg.40]

To obtain sharper images, the tip is usually cooled below liquid nitrogen temperature. However, atomic features can be observed at room temperature without cooling, which is more convenient for in situ characterization of the STM tip. [Pg.41]

The most frequently studied samples with FIM are refractory metal tips, such as W, Mo, Pt, Ir, etc. The field evaporation threshold for refractory metals is appreciably higher than the field to ionize helium atoms, which is 4.5 V/A. Field evaporation is also used for forming and cleaning the FIM sample, which is the tip end, to make it a sharp end and to remove adsorbed exotic atoms. A typical FIM image is shown in Fig. 1.34. [Pg.41]

Tsong (1987) made an extensive comparison between FIM and STM. The major points are as follows  [Pg.41]


The results for the apparent radius of STM images for individual states can be used to interpret experimental images directly. For surfaces with complex periodic structures, such as Si(lll)-7 X 7 and Si(lll)-5 X 5, the concept of imaging individual atomic states is a much better description than surface Bloch functions. For adatoms and defects, the individual state description is the only possible one. [Pg.155]

It is increasingly important to understand nature on a scale in between the quantum and classical worlds. Technological methods have moved into this transitional realm with dramatic results. Scanning tunneling microscopes can image individual atoms and reveal the atomic character of surfaces of solids. Individual atoms can be moved about and materials tailored for specific purposes. Electronic circuit elements have been reduced to dimensions of molecules. As scientists come to understand how the quantum domain gives way to the classical domain, these technologies will... [Pg.250]

That is, an AFM probe responds to the average force between the sample surface and a group of tip atoms that are in close proximity to the surface. In order to image individual atoms by SPM, the surface-tip interactions must be limited to the nearest atom(s) on the tip periphery. Hence, an AFM image will not show individual atoms, but rather an average surface, with its ultimate resolution dependent on the sharpness of the tip structure. In contrast, STM is capable of atomic resolution since the tunneling current passes only through the tip atom that is nearest the sample surface. Named after Bmnauer, Emmett, and Teller. [Pg.430]

The laws of chemical combination provided indirect evidence for the existence of atoms. The experiments of Thomson, Wien, and Rutherford provided direct physical evidence for the existence of the elementary particles that make up the atom. We conclude this chapter by describing an experimental method that allows us not only to image individual atoms and molecules but also to observe and control a chemical reaction at the single molecule level—a feat only dreamed of as recently as the mid-1980s. [Pg.22]

Today, the evidence for the atomic theory is overwhelming. Recent advances in microscopy have allowed scientists not only to image individual atoms but also to pick them up and move them ( Figure 4.2). Matter is indeed composed of atoms. [Pg.94]


See other pages where Imaging individual atoms is mentioned: [Pg.283]    [Pg.810]    [Pg.811]    [Pg.46]    [Pg.39]    [Pg.39]    [Pg.42]    [Pg.157]    [Pg.70]    [Pg.173]    [Pg.100]    [Pg.354]    [Pg.134]    [Pg.283]    [Pg.271]    [Pg.283]    [Pg.464]    [Pg.728]    [Pg.50]   


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