Energy dispersive spectrometry (EDS) is a technique used to determine the elemental composition of materials. EDS relies on detecting X-rays emitted from a sample when it is exposed to an electron beam. The X-ray energies are characteristic of elements present in the sample. EDS systems consist of a detector that converts X-ray energies to voltage pulses, a pulse processor that amplifies the signals, and a multi-channel analyzer that sorts the pulses by energy and displays the results as an X-ray spectrum or elemental maps. EDS allows elemental analysis of micrometer-scale sample volumes and provides both qualitative and quantitative chemical information.

1. Presentation Topic:
Energy Dispersive Spectrometry
(EDS)

2. Energy Dispersive Spectrometry
➢Function
➢Introduction
➢working of EDS
➢Principle
➢Basic components
➢Results

3. Energy Dispersive Spectrometry:
Energy-dispersive X-ray spectroscopy (EDS, EDX, EDXS or XEDS), sometimes called
energy dispersive X-ray analysis (EDXA or EDAX) or energy dispersive X-ray microanalysis
(EDXMA)
Function:
EDS is a technique used for the elemental analysis or chemical characterization of a
sample. It relies on an interaction of some source of X-ray excitation and a sample.
EDS can be used to find the chemical composition of materials down to a spot size of
a few microns, and to create element composition maps over a much broader raster
area.

4. Energy Dispersive Spectrometry:
Introduction:
➢Energy Dispersive Spectrometry (EDS) was first introduced in the late
1960s.
➢ Before that time, the wavelength-dispersive spectrometer (WDS) was used
for x-ray characterization.
➢In the late 1960s, Fitzgerald, Keil, and Heinrich first used the solid state
detector as an electron beam micro analyzer.

5. Diagram:
The basic design of an energy dispersive spectrometer is shown in Figure.

6. Basic Principle:
Principle of EDS.

7. Basic Principle:
➢The incident beam may excite an electron in an inner shell, ejecting it from the shell
while creating an electron hole where the electron was.
➢An electron from an outer, higher-energy shell then fills the hole, and the difference
in energy between the higher-energy shell and the lower energy shell may be
released in the form of an X-ray.
➢The number and energy of the X-rays emitted from a specimen can be measured by
an energy-dispersive spectrometer. the energy of the X-rays are characteristic of the
difference in energy between the two shells, and of the atomic structure of the
element from which they were emitted, this allows the elemental composition of the
specimen to be measured.

8. Working:
➢The detector generates a charge pulse proportional to the X-ray energy
➢This pulse is first converted to a voltage.
➢ Then the signal is amplified through a field effect transistor (FET)
,isolated from other pulses , further amplified ,then identified electronically
as resulting from an X-ray of specific energy
➢Finally, a digitized signal is stored in a channel assigned to that energy in the
MCA (Multi Channel Analyzer).

9. Basic Components:
Detector
• Window
• Cryostat
Pulse
Processor
• Amplifier
Multi-
Chanel
Analyzer
• MCA

10. Detector:
Window:
➢The window is made up of Beryllium.
➢The window provides a barrier to maintain vacuum within the detector
whilst being as transparent as possible to low energy X-rays.

11. Cryostat:
➢- The charge signals generated by the detector are small and can only be
separated from the electronic noise of the detector if the noise is reduced
by cooling the crystal and FET.
➢The Field Effect Transistor is the first stage of the amplification process that
measures the charge liberated in the crystal by an incident X-ray and
converts it to a voltage output.
➢- The natural width (FWHM) of an X-ray peak is on the order of 2-10 eV .

12. Pulse Processor:
➢The signal (voltage step) from the preamplifier is transformed into a voltage pulse
that is suitable for the multi channel analyzer.
➢The time over which the waveform is averaged is called the process time (Tp).
➢Tp is under control of the operator. The longer the Tp, the lower the noise but
more time is spent measuring each X- ray, and the fewer events that can be
measured.
➢If noise is minimized, the resolution of the peak displayed in the spectrum is
improved, and it becomes easier to separate or resolve, from another peak that is
close in energy.

13. Graph:

14. Multi-Chanel Analyzer (MCA)
➢ The MCA takes the data from the pulse processor and displays it as a
histogram of intensity (number of counts) vs voltage.
➢ The voltage range (for ex., 20 keV) displayed on the x- axis is divided into a
number (1024, 2048 etc.) of channels each corresponding to a given energy
range (for example, 5,280 eV –5,300 eV).
➢ The MCA takes the peak height of each voltage pulse, converts it into a
digital value, and puts it into the appropriate channel.
➢Thus a count is registered at that energy level.

15. Output forms of EDS:
Spectrum
• Spectrum: a plot of the number of
X-rays detected versus their
energies.
• The Characteristic X-rays allow the
elements present in the sample to
be identified.

16. Conti…
Map:
Map: an image showing how the
concentration of one element varies
over an area of a sample. In this
example, red colors indicate higher
concentrations and blue colors reflect
lower concentrations.