Abstract
The three-dimensional (3D) morphology of a nanometer-sized object can be obtained using electron tomography. Variations in composition or density of the object cause variations in the reconstructed intensity. When imaging homogeneous objects, variations in reconstructed intensity are caused by the imaging technique, imaging conditions, and reconstruction. In this paper, we describe data acquisition, image processing, and 3D reconstruction to obtain and compare tomograms of magnetite crystals from bright field (BF) transmission electron microscopy (TEM), annular dark-field (ADF) scanning transmission electron microscopy (STEM), and high-angle annular dark field (HAADF) STEM tilt series. We use histograms, which plot the number of volume elements (voxels) at a given intensity vs. the intensity, to measure and quantitatively compare intensity distributions among different tomograms. In combination with numerical simulations, we determine the influence of maximum tilt angle, tilt increment, contrast changes with tilt (diffraction contrast), and the signal-to-noise ratio (SNR) as well as the choice of the reconstruction approach (weighted backprojection (WB) and sequential iterative reconstruction technique (SIRT)) on the histogram. We conclude that because ADF and HAADF STEM techniques are less affected by diffraction, and because they have a higher SNR than BF TEM, they are better suited for tomography of nanometer-sized crystals.
| Original language | English |
|---|---|
| Pages (from-to) | 18-27 |
| Number of pages | 10 |
| Journal | Ultramicroscopy |
| Volume | 106 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Dec 2005 |
| Externally published | Yes |
Funding
We thank Matthew Weyland and Paul Midgley for their help with the tomography and Dennis Bazylinski for the samples of MV-1. We also thank Karl Weiss and Rick Flubacher for valuable discussions concerning the design of the high-tilt holder. Microscopy was performed at the John M. Cowley Center for High Resolution Electron Microscopy at ASU. Funding was provided by NASA through ASU Astrobiology Grant no. NCC2-1051 and NSF Grant EAR-0003533.
Keywords
- Bright-field TEM imaging
- Electron tomography
- HAADF STEM imaging
- Histogram analysis
- Magnetite crystals
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