Energy Dispersive X-ray Spectroscopy (EDS or EDX) is the most widely used analytical technique in electron microscopy. By detecting the characteristic X-rays emitted when the electron beam interacts with your sample, EDS identifies which elements are present and quantifies their concentrations.

How EDS Works

When high-energy electrons from the SEM beam strike atoms in the sample, they can eject inner-shell electrons (typically from K, L, or M shells). This leaves the atom in an excited state. When an outer-shell electron drops down to fill the vacancy, the energy difference is released as an X-ray photon.

Each element has a unique atomic structure, so it emits X-rays at specific, characteristic energies. By measuring the energy of detected X-rays, we can identify which elements produced them—creating an elemental fingerprint of the sample.

EDS Detector Technology

Analysis Modes

Point Analysis

Position the beam on a feature of interest and acquire a spectrum. Identify elements present and calculate composition at that specific location. Ideal for analyzing particles, inclusions, or phases.

Line Scan

Acquire spectra at regular intervals along a line. Generates composition profiles across interfaces, gradients, or layered structures. Reveals how composition changes with position.

Element Mapping

Collect X-ray data at every pixel while scanning the image area. Generate color-coded maps showing the spatial distribution of each element. Visualize compositional variations, phase distributions, and segregation patterns.

Spectrum Imaging (HyperMap)

Store a complete spectrum at every pixel, creating a datacube. Extract maps of any element or peak after acquisition. Reprocess data without re-acquiring. The most flexible and powerful analysis mode.

Quantitative Analysis

EDS can calculate element concentrations as weight percent (wt%) or atomic percent (at%). Quantification methods include:

• Standardless: Uses theoretical models to calculate composition without reference materials. Convenient but less accurate (typically ±5-10% relative).
• Standard-based: Compares unknown spectra to measured standards of known composition. More accurate (±1-2% relative) but requires appropriate standards.
• ZAF Correction: Corrects for atomic number (Z), absorption (A), and fluorescence (F) effects that influence X-ray generation and detection.

Elemental Range

Modern EDS systems detect elements from Boron (Z=5) to Uranium (Z=92). Detection limits depend on the element, matrix, and acquisition conditions, but typically range from 0.1% to 1% by weight. Some considerations:

• Light Elements (B-F): Low energy X-rays are easily absorbed. Require thin-window or windowless detectors and careful sample preparation.
• Heavy Elements: Produce multiple peak families (K, L, M lines). May have overlapping peaks requiring careful peak deconvolution.
• Peak Overlaps: Some element pairs have overlapping peaks (e.g., Mn Kα/Fe Kβ, Ti K/Ba L). Software peak fitting algorithms help resolve these.

Applications

Materials Science

• Alloy Composition: Verify alloy chemistry and detect impurities
• Phase Identification: Distinguish phases by compositional differences
• Failure Analysis: Identify contaminants, corrosion products, and inclusions
• Coating Analysis: Measure coating composition and layer structure

Electronics

• Solder Analysis: Verify lead-free solder composition
• Contamination Detection: Find conductive particles and ionic residues
• Wire Bonding: Analyze intermetallic formation at bond interfaces

Geology & Mining

• Mineral Identification: Rapidly identify mineral phases by composition
• Ore Characterization: Assess grade and mineral associations
• Elemental Deportment: Map where valuable elements occur

Life Sciences

• Biomineralization: Analyze bone, teeth, and shell composition
• Particle Identification: Identify inhaled or ingested particulates
• Trace Elements: Detect metal accumulation in tissues

Optimizing EDS Analysis

Accelerating Voltage

Choose voltage to efficiently excite the X-ray lines of interest. A general rule: use 1.5-2× the highest energy peak you need to analyze. Too low voltage gives weak signal; too high increases background and sampling depth.

Count Rate and Dead Time

Balance count rate and dead time for optimal throughput. Dead times of 20-40% provide good statistics without excessive pulse pile-up. Higher count rates speed analysis; lower rates improve peak resolution.

Acquisition Time

Longer acquisition times improve statistics and detection limits. Point analysis may need only 30-60 seconds; element maps may require 10-30 minutes or more depending on desired quality.

Bruker ESPRIT Software

Our EDS systems use Bruker ESPRIT software for data acquisition and analysis. Features include:

• Automatic element identification and spectrum labeling
• Advanced peak deconvolution for overlapping peaks
• Quantitative analysis with standardless or standard-based methods
• Element mapping with adjustable color schemes
• HyperMap spectrum imaging with post-acquisition processing
• Phase analysis and compositional classification
• Report generation and data export