Interaction Volume
Definition
The pear-shaped region of specimen material within which the primary electron beam deposits energy and generates signals. At 20 kV in a medium-Z material, approximately 1-2 micrometres deep and 1-2 micrometres in diameter.
- Field
- Scanning electron microscopy
- Shape
- Pear-shaped
- Depth at 20 kV, medium-Z
- Approximately 1 to 2 micrometres
- Diameter at 20 kV, medium-Z
- Approximately 1 to 2 micrometres
Common questions
Why does the interaction volume matter for spatial resolution in EDS analysis?+
X-rays used for elemental analysis are generated throughout the interaction volume, not just at the beam's surface spot, so the effective analytical spot size for EDS is set by the volume's width, not the narrower diameter of the electron beam itself.
How does accelerating voltage change the size of the interaction volume?+
Raising the accelerating voltage drives electrons deeper into the specimen, enlarging the interaction volume, while lowering the voltage confines it closer to the surface, which is why low-voltage imaging is preferred when fine surface detail matters more than X-ray yield.
Related terms
- ASTM E1588
- ASTM International standard practice for gunshot residue analysis by scanning electron microscopy with energy-dispersive spectrometry. Defines particle classification (characteristic, consistent-with, indicative), morphology...
- Back-Scattered Electron (BSE)
- High-energy electron from the primary beam that has bounced elastically off a nucleus and exited the sample. BSE yield increases with atomic...
- Characteristic X-Ray
- An X-ray photon emitted when an outer-shell electron drops into an inner-shell vacancy created by ionisation. Energy is set by the difference...
- Energy-Dispersive X-Ray Spectroscopy (EDS)
- An X-ray detection method that simultaneously measures the energies of all characteristic X-ray photons emitted from the interaction volume, identifying all elements...
- FIB (Focused Ion Beam)
- A technique using a focused gallium ion beam to mill a specimen at a specific site-selected location, producing a TEM-quality cross-section with...
- Lead-Free GSR
- Gunshot residue produced by ammunition using non-lead primer formulations (SINTOX, Diazol, or other variants). Does not contain the conventional Pb-Sb-Ba three-element combination;...
- Secondary Electron (SE)
- Low-energy electron (below 50 eV) ejected from the top few nanometres of the sample when the primary beam knocks a loosely bound...
- Silicon Drift Detector (SDD)
- The current standard EDS detector type, using a reverse-biased silicon chip cooled by a Peltier element to achieve high count-rate capability (up...
- Sputter Coating
- Vacuum-deposition technique that lays a thin (5 to 15 nm) conductive layer of gold, gold-palladium or carbon onto a non-conductive sample (polymer,...
- Ultramicrotome
- A precision instrument for cutting sections of resin-embedded specimens to 60-100 nm thickness using a diamond knife, enabling TEM examination of the...
- ZAF Correction
- A software correction applied to raw EDS X-ray intensities to account for atomic number (Z), absorption (A), and fluorescence (F) effects within...