Weak-beam images

Figure 7. Weak beam images of a)octahedral and b)cubo-octahedral particles.

The new TEM techniques can provide a full characterization of small particles. The combination of weak beam images and microdiffraction information can render a very complete picture of the particle structure. In addition, refracted electron images can be... 

Pt-Ir Coimpregnating on A1203. / - / - High resolution weak beam images. 

Figure 1. Cross-section weak-beam images of the same area of a MOVPE-grown ZnO layer on Al203(0001) with a 40 nm GaN buffer layer taken with (a) g = 0002 under g,3g conditions and (b) g = 11-20 under g,3g conditions.

Cockayne (1973) has given a detailed account of the principles and practice of the WBDF technique, including weak beam image profiles of dislocations calculated using a six-beam dynamical theory. The diffracting conditions that optimize the capabilities of the microscope are the following ... 

Ishida, Y., Ishida, H., Kohra, K., Ichinose, H. (1980). Determination of the Burgers vector of a dislocation by weak-beam imaging in a HVEM. Phil. Mag., A42, 453-62. 

Fig. 4.7 a Dislocation wall dislocations are parallel and positioned in different basal planes one under another, b Same area as white square in (a), but at higher magnification (imaged in g (3360)). c Weak beam image of the same area as in (b), but tilted and imaged in g of (3300). Dislocations that become invisible in (c) are perfect edge dislocation those that remain visible are mixed dislocations [14]. With kind permission of Springer and Professor Barsoum... 

Fig. 5.26 a Bright field TEM image of 14 (111) dislocations in MoSi2 + 2.5 at% Re alloys in compression at 1400 °C. Weak beam images of dislocations labeled x in (a) are shown in (b) and (c) respectively. The electron beam direction is 5-10° Ifom [100] [23]. With kind permission... 

Figure 10. TEM weak-beam images of APB tubes in Ni,Ga. (a) The reflection 202 is parallel to the tube axis and the tubes are out of contrast, (b) The reflection 020 is perpendicular to the tube axis and strong tube contrast is observed...

Single-Particle Diffraction, Weak-Beam Dark-Field, and Topographic Images of Small Metallic Particles in Supported Catalysts... 

Figure 10.15 Simulated image width as a function of deviation parameter in Bragg case weak beam topographs. Here, the specimen is set off the Bragg peak and an image of the defect occurs only when the lattice planes are locally rotated or dilated back into the Bragg condition. As this occurs only close to the dislocation core, the images are narrowed from those under strong beam conditions...

Fig. 7.7. TEM images and SAD patterns (insets) of a poly crystalline ZnO film on silicon (111) PLD grown at 1 x 10 3mbar O2 and about 540°C (a) Bright field Si(lll) plane view observation, grain size is about 70 nm, (b) cross-section HRTEM lattice image with intermediate SiO layer, and (c) weak beam Si(110) TEM cross-section. The area from which the SAD patterns were taken are within the white circles. Reprinted with permission from [49]...

The TEM investigations were performed in a 200 keV Philips CM 200 FEG/ST microscope which is equipped with a field emission gun. Dislocation Burgers vectors b were analyzed on the basis of the b g = 0 extinction criterion using different imaging vectors g. The weak-beam... 

This equation is particularly useful when setting up for weak-beam dark field imaging, to be discussed in Chapter S. 

Kinematical and weak beam dark field (WBDF) images of dislocations... 

Figure 5.19. Ewald sphere diagrams and corresponding diffraction patterns illustrating the procedures for setting up the conditions for weak beam dark field imaging using the first-order diffracted beam g. Continued, p. 160)...

Figure 2. Amplifying a beam containing an image. Using a photorefractive material, the energy from a poor-quality, uniform pump beam can be coupled into the high-quality, weak beam containing an image. The beam is amplified and the image is retained.

Fig. 15.3 Preparation of epitaxial thin film model catalysts, (a) Electron micrograph of a Pt-AljOj model catalyst with a mean particle size of 5 nm the insets show the corresponding electron diffraction pattern and the (200) weak-beam dark-field image of a pyramidal Pt nanocrystal (b) an atomically resolved TEM micrograph of a slightly rectangular Pt particle. A structural model of a pyramidal Pt particle is presented in (c). To illustrate the epitaxial growth the NaCl substrate is also included...

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