EDS
Overview
Energy dispersive x-ray spectroscopy (EDS) or (EDX) is an analytical technique allowing for precise elemental characterization of specimens in an electron microscope. Results are collected as spectra and typically presented as an elemental map or a quantitative distribution. Data may be collected from an entire image, a region, a single point or series of points, or a line drawn across an image. Signal for EDS analysis is generated when an incident electron beam displaces electrons in a specimen, causing higher energy electrons to fall and fill the lower energy vacancy, emitting a photon of a characteristic energy in the process. Signal may be generated from up to 1um beneath the specimen surface.
Techniques
When performing EDS, sufficient beam energy and electron dose must be supplied to the system to generate the appropriate characteristic x-ray lines. In general, high energy (20kV+) and a spot size or probe current sufficient to achieve 20-40% Dead Time (DT) yields the best results. For beam sensitive specimens, the voltage may be reduced so it is about 2-3x the energy of at least one line for each element in the specimen. Refer to a periodic table displaying these values, or the tables on this page to estimate the required voltage or the visible elements for a given voltage
External Resources
- MyScope Training Module from Microscopy Australia tips for identifying elements based on spectra
Equipment
Scanning Electron Microscopes
- JEOL 7500F HRSEM (EDAX - APEX)
- TFS Quanta 600 FEG ESEM (EDAX - TEAM)
Focused Ion Beam Microscopes
- TESCAN S8000X FIB/SEM (EDAX)