Atoms microscopic study

Chen C-FI, Washburn N and Gewirth A A 1993 In situ atomic force microscope study of Pb underpotential deposition on Au(111) Structural properties of the catalytically active phase J.Phys. Chem. 97 9754-60... 

Lantz, M.A., O Shea, S.J., Welland, M.E. and Johnson, K.L., Atomic-force-microscope study of contact area and friction on NbSc2. Phys. Rev. B Condens. Matter, 55(16), 10776-10785(1997). 

Antony, P., Kwon, Y., Fhiskas, J.E., Kovar, M., and Norton, P.R. Atomic force microscopic studies of polystyrene-polyisobutylene block copolymers, Eur. Polym, J., 40, 149-157, 2003. 

Tsong, T, T. (1979). Quantitative atom-probe and field ion microscope studies at atomic resolution. Direct Imaging of Atoms in Crystals and Molecules Nobel Symposium 47, The Royal Swedish Academy of Sciences, 7-15. 

Sahu, K., Bansal, H., Mukherjee, C., Sharma, M., and Gupta, P. K. (2009). Atomic force microscopic study on morphological alternations induced by photodjmamic action of Toluidine Blue O in Staphylococcus aureus and Escherichia coli.. Photochem. Photohiol. B Biol. 96(1), 9-16. 

X 1) to (1 X 5) surface reconstructions of the (Oil) and (001) surfaces of fee metals such as Au, Pt and Ir have also been successfully studied with the STM,19,20 with the transmission electron microscope (TEM)13,21 and with the field ion microscope.14,15,22 Some of the FIM surface atomic reconstruction studies will be described below. 

FTM and atom-probe studies of thin films of Ni, Au, Pt, a-Ge H, a-Si H and WO3, etc., on various substrates were reported by Krishna-swamy et a/.81 First, field ion tips each with a field evaporated surface were prepared. They are placed in an MRC model 8502 r.f. sputtering system. Tips were mounted on a recessed and shielded structure behind the sputtering surface which is bored with small holes about 1 to 2 mm in diameter. The very end of the tips came out of the holes to approximately the same level of the sputtering surface. Films were sputtered at about 20 mTorr Ar at an r.f. power of about 50 W. Thickness of a deposited thin film was controlled by both the r.f. power and the deposition time. Film thickness in the range of a few hundred to a few thousand A were studied. These tips were then imaged with Ne in the field ion microscope, or analyzed in the flight-time-focused ToF atom-probe. 

In a study of this type, data are composed of single atom events. Statistical fluctuations of the data have to be carefully considered and a careful statistical analysis of the data has to be done before the conclusions derived can be statistically meaningful and reliable. Although there are many precautions which have to be taken in experiments of this type, because of the very well defined nature of these experiments the technique has now been developed to a high degree of reliability and field ion microscope studies of the behavior of single atoms are among the best established of all field ion experiments. 

At a very low temperature where an adatom jumps only occasionally, about one atomic jump in every few seconds, field ion microscope studies conclude that the surface diffusion of adatoms is consistent with a discrete nearest neighbor random walk. However, in molecular dynamic simulations of diffusion phenomena, which are carried out only for high temperature diffusions where atomic jumps are very rapid, i.e. an atomic... 

Before we discuss some field ion microscope and atom-probe studies of partitioning in alloys, let us touch briefly here upon some of the methods commonly used for analyzing atom-probe data. Obviously if a precipitate or an alloy phase can be distinguished from the matrix from the field ion image, the size can easily be found. For the composition the probe-hole may be aimed at the precipitate, or the alloy phase, and analyze the composition of this volume. If the precipitate is very small and the probe-hole is large, matrix atoms will be detected concurrently regardless of where the probe-hole is aimed. Another problem is aiming... 

Brenner et al. reported an atom-probe field-ion microscope study of decomposition in an Fe-Cr-Co alloy (see Fig. 18.11) [23]. The atom probe allows direct compositional analysis of the peaks and valleys of the composition waves. It is probably the best tool for verifying a spinodal mechanism in metals, because the growth in amplitude of the composition waves can be studied as a function of aging time, with near-atomic resolution. In spinodal alloys, there is a continuous increase in the amplitude of the composition waves with aging time. On the other hand, for a transformation by nucleation and growth, the particles formed earliest generally exhibit a compositional discontinuity with the matrix. 

Gesang, T. Hoeper, R. Possart, W., Petermann, J. Hennemann, O. D. Adsorption and Growth of Dip-Coating Prepolymer Films on Silicon Wafers. An Atomic Force Microscope Study. Appl. Surf. Sci. 1997, 115, 10-22. 

Ai85,86 is discussed on p. 114. Agarwal et al.102 as well as Sharma et al.103 studied this reaction using silica-supported V2Os-alkali metal sulphate catalysts. A two-step oxidation-reduction mechanism gave the best description of the process. The activity increased with increasing atomic number of the added alkali metal for which no interpretation was offered. In an electron microscopic study of these catalysts Sharma et al.103 showed that K2 S04 and V2 05 are present as separate phases but that the sulphate causes the presence of a larger amount of V2 05 in the form of needle-like crystals which appear to be more active for the methanol oxidation. A similar result was obtained by these authors for catalytic oxidation of toluene over these catalysts.104... 

Browning-Kelley, M.E., Wadu-Mesthrige, K., Hari, V., and Liu, G.Y. 1997. Atomic force microscopic study of specific antigen/antibody binding. Langmuir, 13 343-350. 

M. Koinume and K. Uosaki, Electrochim. Acta 40 1345 (1995). Atomic force microscope studies of GaAs. 

W.R. Bowen, N. Hilal, R.W. Lovitt and C.J. Wright, Atomic force microscope studies of membrane surfaces, in Surface chemistry and electrochemistry of membrane surfaces, ed. T.S. Sorensen (Marcel Dekker, in press). 

Electron microscopic studies of the ribosome at increasingly high resolution provided views of the overall structure and revealed the positions of tRNA-binding sites. Astounding progress on the structure of the ribosome has been made by x-ray crystallographic methods, after the pioneering work by Ada Yonath. The structures of both the 30S and the 50S subunits have been determined at or close to atomic resolution, and the elucidation of the structure of intact 70S... 

The field emission microscope (FEM) and the field ion microscope (FIM) are in many respects complementary instruments. While the FIM can depict surface structure in atomic detail, study of field electron emission from the same specimen can yield information about the electronic structure of the surface layer. Field ion microscopy has been the subject of an earlier review and in this article more recent developments in field emission microscopy and its application to surface studies are reviewed. Earlier developments have been the subject of several reviews. 

It is probably true that the as formed na noparticles do not contain dislocations (see Waychunas, this volume). However, high-resolution transmission electron microscope studies show that nanocrystals (e g., 3 nm size) certainly do contain dislocations, twins, and stacking faults. These may arise due to mistakes during atom-by-atom coarsening of primary nanoparticles. However, a more obvious source is evident. 

Electron microscopic studies in the 1940s proved that supported catalysts possess a crystalline structure, dispelling earlier conjecture of amorphicity. However, practical catalysts are never uniform, exhibiting particle size distribution, lattice defects (Frenkel or Schottky), and dislocations. The following questions then arise Are all lattice surfaces equally active Do surface clusters of particles and surface atoms have comparable activity Does catalytic activity depend on particle size Is there an optimal particle size or distribution These questions remain, in general, still unanswered. However, in recent electrocatalytic studies concern about these effects is shown, following similar concern in conventional heterogeneous catalysis. 

C.M. Mate, Atomic-force-microscope study of polymer lubricants on silicon surface, Phys. Rev. Lett., 68, 3323-3326, 1992. 

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