Abstract
Hollow-cone dark-field images from crystalline silicon were examined as a function of thickness and scattering angle. We find that both coherent scattering and multiple scattering can cause the intensity to depend non-linearly on thickness, even for high-angle scattering events. A simple method for estimating the effect of multiple elastic scattering in thick specimens is provided. We show theoretically, that a coherence volume exists around each scatterer whose dimensions depend inversely on scattering angle. The coherence volume has a narrow "cigar" shape, elongated along the optic axis. The narrowness ensures that inter-atomic-column interferences, such as zero-order Laue zone Bragg reflections, are suppressed, whereas the elongation permits intra-atomic-column interference (or columnar diffraction). In high-resolution "Z-contrast" images, this bias towards columnar diffraction acts to enhance the signal from atom columns.
Original language | English (US) |
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Pages (from-to) | 31-53 |
Number of pages | 23 |
Journal | Ultramicroscopy |
Volume | 52 |
Issue number | 1 |
DOIs | |
State | Published - Sep 1993 |
Externally published | Yes |
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Instrumentation