Electron diffraction low angle

Fig. la. Brighl-field transmission electron micrograph (TEM) of typical craze microstructure in polytstyrenc-acrylonitriie) PSAN- b Low angle electron diffraction pattern from the fibrils of the craze in a. Note the main-fibril axis lies primarily along s,. the tensile axis direction and the direction norma] to the craze-bulk polymer interface... 

Figure 12.12 Bright-field TEM image of craze (A) formed in PMMA and its corresponding low-angle electron diffraction pattern (B) an idealized representation of the craze microstmc-ture is shown in C. (Reproduced with permission from Berger, Macromolecules, 22, 3162 (1989))...

Yang, A.C.-M. and Kramer, E.J. (1986) Craze microstructure characterization by low-angle electron-diffraction and Fourier-transforms of craze images. J. Mater. Sci., 21, 3601. 

Berger, L.L., Buckley, D.J., Kramer, E.J. et al. (1987) Low-angle electron-diffraction from high-temperature polystyrene crazes. J. Polym. Sci. Polym. Phys. Ed., 25, 1679. 

FIG. 9.15 Path of a diffracted electron beam in low-energy electron diffraction (LEED), and indexing of points in reciprocal space, (a) interaction of a diffracted beam with a photographic plate for small angles of incidence and (b) illustration of the indexing of points in reciprocal space relative to the primary beam, labeled 00. 

Fig. 2.4 Low-energy electron diffraction (LEED). (a) Apparatus, showing how electrons reflected from a surface are detected by a fluorescent screen, (b) LEED pattern obtained from the surface of a tungsten oxide crystal. The bright spots show reflected electron beams. Measurement of their angles and Intensities gives information about the positions of atoms on the surface.

Knupp (2005 this volume), is one of interpretation. Unlike X-ray crystallography, low-angle fiber diffraction does not lead directly to images of the diffracting object or to the generation of electron density maps. Setting up models with whatever prior knowledge is available is required, and then the unknowns must be set up as parameters and searched for the best values of these parameters to provide a model that satisfactorily accounts for the observed diffraction patterns. 

Diffraction techniques (low-energy electron diffraction [34, 35], helium diffraction [36, 37] and grazing incidence X-ray diffraction [38]), scanning tunneling microscopy (STM) [36, 39, 40] and atomic force microscopy (AFM) [41] served to solidify the conclusions inferred from the less direct spectroscopic methods and provide additional structural details. The sulfur atoms order epitaxially on the substrate in a (x/3 X V3) R30° structure [36-38, 40, 41]. The angle of the sulfur-carbon bond with respect to the substrate plane is approximately 104° for alkanethiol monolayers [38, 42] and 180° for arylthiol SAMs [42, 43]. Given the agreement between the results obtained from direct structural methods and indirect spectroscopic methods, one... 

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