TEM ED-Map:TEM Electron Diffraction Mapping
Features
This method uses the electron diffraction results from TEM to analyse the distribution of the crystal lattice orientations. A high spatial resolution can be obtained by measuring the electron diffraction pattern at each point while scanning the electron probe.
This technique, which also is called Automated Crystal Orientation Mapping in TEM (ACOM-TEM), enables analysis of smaller grains compared to the electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM).It can be used to obtain the following:
- Grain size
- Orientation of the crystal lattice planes
- Observation of twin (coincidence) grain boundaries
- Specific crystal orientation
- Azimuth of neighbouring grains
- Nanometer-sized crystal grains evaluation
Application Examples
- Evaluation of crystal grain size of polycrystalline thin films
- Size evaluation of crystals embedded in amorphous structure
- Crystal orientation evaluation
Principle
When a TEM sample is irradiated by an electron beam, diffraction occurs in the transmission direction due to periodic structures in the sample. The diffraction forms a pattern that is captured by an imaging device. By continuously acquiring and analysing this pattern, information on the orientation of each crystal grain can be obtained.
Note: Smaller grains can be evaluated by thinning the TEM sample.
Device configuration
- A high-sensitivity CCD camera captures the electron diffraction pattern formed by the transmitted electrons.
- Image processors process the acquired image with respect to background elimination, noise reduction, contrast enhancement, and spatial filtering.
- To collect mapping data, an external controller controls the electron beam of the TEM with respect to beam position.
- The image acquisition system captures images of the electron diffraction patterns and stores the raw data for crystal orientation mapping.
- The data analysis system processes the raw image data and creates orientation maps, crystal particle size distributions, lattice deformation distribution.
Data examples
Fig. 3 and Fig. 4 show examples of ED-mapping of Au nanoparticles. A crystal orientation map (inverse pole figure map) and pole figures were constructed from the collected electron diffraction pattern dataset.
Grain map (Fig. 5) and particle size distribution (histogram) (Fig. 6) extracted from ED-Map dataset of Au nanoparticles. As shown in Fig. 6, it is possible to detect nano-sized crystals.
Specifications
Items for enquiries
- Purpose and content of measurement
- Sample information
・Number of samples, and availability of preliminary samples
・Mterials and crystal structures at the analytical sites and surrounding areas
・Precautions for handling samples
- Details on delivery
・Preferred due date for preliminary analysis report
・Due date for delivery of final report
- Any other issues
Caution
- Like TEM, thinning of the sample by focused ion beam etching or milling is necessary. In some cases, however, thinning may prove difficult.
- Sample processing and observation may alter or deform the sample.
- Hydrocarbon and other substances may adsorb to the sample during analysis.
- Crystal grains of a few nanometres or less may not be detected.
- Analysis may not be possible for some materials and/or when multiple grains overlap spatially.