edx energy dispersive x-ray...
TRANSCRIPT
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX
Energy Dispersive X-ray analysis
Mats Halvarsson
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Image information
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX spectrum
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
K lines
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
L lines
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
X-ray production
EK
EL
EM
K
L
Mvacuum
energy shell
12 E(Ka) = EK-EL
X-ray
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0Note E>EK neededE> E(Ka) not enough
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Over voltage
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Over voltage
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
K, L, M lines
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Nomenclature
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Transitions
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Fluorescence yield of X-rays
• w+a=1
• w - X-rays• a - Auger electrons
• light elementsfew X-rays
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Auger electrons
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Auger spectroscopy
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Cupper
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
K line ratios
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Bremsstrahlung
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Dysprosium
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
SEM / EDX
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX system
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX system
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Si detector
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Instrumentation
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Window transmission
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Oil
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Low-energy tailing
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Artefacts
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Ice build-up
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Backscattering artefact
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Absorption
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Electron trap
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX spectrum
• Characteristic peaks– For identification and quantification– 3.8 eV/electron-hole pair
• Bremsstrahlung• Escape peaks
– E-1.74 keV• Si extra peak
– From detector
• Sum peaks– 2 photons
• Low energy tailing– Dead layer
• Illumination artefacts
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Generation and emission
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Copper generated
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Copper detected
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Absorption
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Spectrum absorption
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Generation and detection - summary
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
10 and 20 kV
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
30 kV
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
EDX
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Acceleration voltage
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Acceleration voltage
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Electron range
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Different materials
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Interaction volume
3 g/cm3 10 g/cm3
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Different materials
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
X-rays in Cu-Al
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
X-ray generation and emission
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Quantification - 1st approximation
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
ZAF correction
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
ZAF correction
• Z - atomic number– Stopping power dE/(ρ dx)– Backscattering η
• A - absorption– I = Io exp{- C (µ/r) (rz)}
• F - fluorescence– ∆E ≤ 5 keV
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Stopping power 20 kV
SP =1ρ
dEdx
ρ densityx depth
SP higher for low Z
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Quantification - ZAF
• Remove background• Measure peak areas• Compare with standard• Calculate apparent concentration• Calculate ZAF factor• Calculate concentration with ZAF• Iterate until stable
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Background
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Top hat filter
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Filtering
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Example: Au-Cu
Cu+Au Cu
Too high Cu is measured
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
ZAF correction
• Z– Stopping power is higher in standard– Backscattering higher in specimen
- less x-rays produced
• A– Abs of CuK is less in standard
I(CuK(std)) > I(CuK(spec))• F
– CuK can be generated by AuLI(CuK(std)) < I(CuK(spec))
Cu+Au Cu
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
ZAF correction
• Z(Cu) = 0.893Z(Au) = 1.24
• A(i), F(i) < 2%
• In this case Z correctionhighest
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
WDX – Wavelength Dispersive X-ray spectroscopy
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
WDX spectrum
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Peak overlaps
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
WDX features
• Micro-analysis approximately 10x more sensitive than EDS– trace element analysis (down to below 0.1%)
• Spectral resolution ~ 10 eV– separation of overlapping peaks– accurate peak ID
• High sensitivity for light element detection
• Improved P/B X-ray mapping
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
The main components of a WDX spectrometer are:
– Diffracting Crystal– Entrance Slit– Detector or Counter
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Theory
• Technique measures wavelength of characteristic X-ray emission to identify constituent elements
• From the number of X-rays collected the amounts of these elements can be determined (quant)
• X-rays characteristic of different elements are separated by X-ray diffraction using a crystal of known lattice spacing d
• The angle of diffraction needed to collect X-rays of a particular wavelength is predicted using Bragg’s Law
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Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
Theory
n: a whole number multiple that indicates the diffraction orderl: the wavelength of the X-ray that will be diffractedd: the interatomic spacing for the diffracting crystalq: the angle at which diffraction is occurring; i.e., the angle between the
crystal planes and the diffracted X-ray
d
q
l
nl=2d sinq
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
OperationDue to limitations in achievable movement a number of diffracting crystals is needed to cover element range
Crystal Crystal Crystal 2d A Analyzing Analyzingdesignation type focusing spacing range A, range, K-lines
LIF(200) Lithium fully 4.0267 1.1436-3.7202 Ca-AsFluoride
PET Pentaerythritol fully 8.74 2.4827-8.0765 Si-V
TAP Thallium acid fully 25.75 7.3130-23.79 O-Alphthalate
LSM-060 W-Si multilayer semi ~61 ~17- ~56 C-F
LSM-080 Ni-C multilayer semi ~78 ~22- ~72 B-O
LSM-200 Mo-B4C multilayer semi ~204 ~58- ~90 Be-B
Mats Halvarsson Materials Microstructure • Dept. of Physics
Chalmers University of Technology
WDX detector