Analytical techniques available
Secondary Electron Imaging
Secondary electron imaging provides information on the sample surface. The spatial resolution for SE imaging is approximately 100 to 200 nm, depending on the accelerating voltage, beam current, and other operating conditions. Common applications include studies of grain morphology, precipitates on a mineral surface, microfossils (for instance, ancient diatoms), and other materials too small for visible light microscopy.
Backscatter-electron images show atomic number differences within a sample. A certain fraction of the electrons in the beam are scattered "backward" out of the sample as a result of interactions with its nuclei, and these "backscattered" electrons can be used to form images. The number of electrons are backscattered increases with increasing mean atomic number of the material. In a BSE image, the brighter the area, the heavier the mean atomic mass of that material.
Cathodoluminescence (also known as CL) is the emission of photons as light, when a material is stimulated by high energy electrons. Cathodoluminescence emission in a material is a complex function of composition, lattice structure and superimposed strain or damage on the structure of the material.
- Semiconductors – purity, alloy composition, intrinsic stress/strain
- Geology – mineral identification and distribution, fluid inclusions and phase transitions
- Art and archaeology – characterization of pigments, ceramics and gemstones
- Pharmaceutics – content uniformity and component distribution
Energy-dispersive Spectrometry (EDS)
The EDS system can be used for quantitative analysis (one simply counts the X-rays received in the channels that correspond with a peak of interest), phase identification, rapid particle analysis etc. For many combinations of elements, however, the EDS system is less desirable than WDS because of its limited spectral resolution (overlapping peaks) and limited sensitivity. Still, if one wants to determine quickly what elements are present in a sample, EDS is the way to go!
Wavelength-dispersive Spectrometry (WDS)
WDS analysis results in a spectral resolution and sensitivity an order of magnitude better than is possible with EDS analysis; the detection limits of WDS ordinarily varies between 300 and 3 parts per million (ppm). Also, in comparison to EDS, WDS offers more accurate quantitative analyses, particularly for light elements, and better resolution of overlapping X-rays peaks for improved element identification and quantification.
Soft X-ray Emission Spectrometry (SXES)
The SXES spectrometer uses X-ray focusing optics, variable line-spacing gratings and a solid-state X-ray CCD detector to collect a low energy X-ray spectrum. It provides higher spectral resolution and higher sensitivity for soft X-rays (<1 keV) relative to traditional WDS, yielding information on electronic structure and bonding [1-2]. The grating and CCD detector are rigidly fixed, with no moving parts, resulting in spectra that are extremely reproducible.
Our facility is ideally suited to support a variety of innovative research and educational activities.