A team of researchers at Los Alamos National Laboratory has developed a new Hyperspectral X-ray Imaging (HXI) detector that provides ultra-sensitive elemental and chemical composition analysis for a variety of materials.
“HXI represents a generational leap forward in energy resolution and efficiency for material analysis in scanning electron microscopes,” said Matt Carpenter of Los Alamos’ Safeguards Science and Technology group. “This allows researchers to measure detailed composition at the nanoscale in ways never before possible.”
Material composition microanalysis using X-ray spectroscopy in scanning electron microscopes (SEMs) is common practice in many fields, including the semiconductor fabrication industry, geology, environmental science, forensics and materials engineering. However, standard commercial detectors that measure X-ray spectra require users to choose between high-energy resolution or high detection efficiency. As a result, detailed chemical and elemental composition mapping of material at the nanoscale level has never before been possible — until now. Such microanalysis is especially important for samples that vary in composition on very small length scales, and where macroscopic properties depend on microscopic features.
Los Alamos National Laboratory, National Institute of Standards and Technology, and the University of Colorado developed the Hyperspectral X-ray Imaging detector, or HXI, to meet this analytical challenge.
The team’s detector can deliver energy resolution 20 times better than current commercially available technology. This will allow manufacturers to see very fine details on a silicon microchip during quality assurance to detect important defects before mass production. It also provides the ability to identify material defects at the nanoscale before building airplanes and bridges, for example.
Another important field that utilizes SEMs is nuclear safeguards, which are technical measures used to ensure that countries are using nuclear material according to international treaties. Nuclear safeguard techniques include destructive and non-destructive analysis; destructive techniques alter the sample while non-destructive techniques can analyze samples without disturbing them. HXI is a non-destructive tool that can be readily combined with other analyses.
Electron microscopes are crucial tools in all these areas of study. Adding the HXI detector to a standard scanning electron microscope reveals details about materials and objects on the nanoscale, many thousands of times smaller than a light-based optical microscope can see.
When the electron beam in the microscope interacts with the sample, X-rays are emitted at energies characteristic to each element. The elemental composition of a sample can be determined from the X-ray spectrum and combined with the spatial information from the electron beam to make a map down to the nanometer level. This has broad application to many scientific and industrial fields, from measuring nanometer-sized chip features for semiconductor fabrication, to alloy nanoscale structure for materials science, to small scale mineral structure and distribution for geology and mineral exploration.
The HXI detector is operated in a manner similar to commercial energy dispersive X-ray spectrometers, or EDS, with high efficiency over the full X-ray energy range. HXI’s energy resolution matches or exceeds that of a wavelength dispersive spectrometer, or WDS. HXI combines the strengths of both into a single advanced instrument, something that has never been accomplished before. The more you can see in a material, the more you can understand and improve its properties. The HXI detector provides crucial insight to enable next generation technologies around the world.