edx ebsd msc engl
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Analytics with
Scanning Electron Microscopy
A. Danilewsky
Energy Dispersive X-Ray Analysis EDX
Electron Back Scatter Diffraction EBSD
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Depth of Signals
Auger - elektrons
Secondary electrons SE
Back scatter electrons BSE
X rays:
- Characteristic X - rays
- Continuum X- rays
Sample surface
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Topographic contrast
Electron beam
Electron beam
Many
secondary
electrons
leave the
sampleFew
secondary
electrons
leave thesample
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Characteristic X - Rays
k 1: LIII Kk 2: LII K
k : MIII K
keV
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Relative Intensity of Characteristic X - Rays
L shell consists of 3 subshells with quantum numbers n, l, j and spin m:
lI: 2s orbital n = 2, l = 0, j = , m = max. 2 electrons
=> forbidden transition
lII: 2p orbital n =2, l = 1, j = , m = => max. 2 electrons=> k2 line
lII: 2p orbitals n = 2, l = 1, j = 3/2, m = , 3/2 max. 4 electrons=> k1 - line
Intensity k
1
: k
2
= 2 : 1
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Characteristic X - Rays
Characteristic X rays Continuum X- rays
k : L K
k : M K
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X Ray Detector
Si crystal drifted by Li with
FET (field effect transistor)
Be window
collimator
cooling by liquid N2 (77 K)
dewar
liq. N2
Be - window
collimator
Si - crystal
cold finger
distance
adjustment
preamplifier
sensor
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X Ray Detector: Si crystal drifted by Li
X-ray photons generate
electron hole pairs
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Semiconductor X Ray Detector
Valence band of an intrinsic semiconductor is fully occupied Conduction band of an intrinsic semiconductor is largely unoccupied
X-rays raise electrons from valence to conduction band (photo- and
Auger electrons)
Electron hole pairs move free in the crystal during their lifetime
Bias voltage across the detector moves charge carriers to opposite
electrodes
=> signal/pulse
The number of electron hole pairs is proportional to the energy of
X-ray photons
Minimum energy is the energy gap of the semiconductor (Si: 1.1 eV)
+ energy of lattice vibrations + other physical effects => about 3.8 eV
Multi-channel analyser: 1024 channels set to 10 eV/channel
=> 0.5 10 keV
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Semiconductor X Ray Detector:
Silicon drifted by Li
Low leakage current => high resistivity Si (ultra pure)
Li as a donor compensates p-type conduction of Si at low temperature
Li stabilises the Si structure against X- ray radiation damage
p n - junction from undoped to Li doped area
Only one pulse is is processed at a time. To many X-ray photons during the
anlyser is busy:
=> dead time: no other photons are counted ! Timescale: nano seconds
e.g. 30 seconds counting time at 10% dead time needs
33 seconds real time measurement
X-rays generated in the Si detector crystal it-self: escape peak
Ti Si = 2.77.keV
Si = 1.74 keV
Ti = 4.51 keV
keV
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L - linesK 1 K 2
X Ray Spectra
Energy of of photons: Characteristic X-ray lines
Number of photons: Concentration of element
M -lines
L -lines
K lines at 80.8. keV
keV
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X Rays:
Absorption and Fluorescence
e.g. Fe - Mn
electron beam
Fek
Mnk
SE
SE
ZAF Correction:
Z = atomic numberA = absorption
F = fluorescence
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X Rays: Background Corrections
Continuum spectrum:
Calculation from elements
Subtraction
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Energy dispersive X-ray analysis (EDX)
Oxford - Link System ISISat Zeiss DSM 960
Acceleration voltage: 20 kV
Magnification: x200 x1000
Detector: Si:Li
Qualitative mapping of elements:
Al, Si, Ti, Ca, Fe, Mn
BSE
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Energy dispersive X-ray analysis (EDX)
200 m
200 m
Si
200 m
200 m 200 m
AlFe
Ti
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Geometrie EBSD
Bragg: n = 2d sin
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Electron Backscatter Diffraction EBSDOxford - Link System
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Crystal
Homogenous, anisotropic discontinuum with three-dimensional
periodical arrangement of lattice elements
Crystal Lattice
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Crystal Lattice
br
cr
231
r
straight line through the points 000 and 231: [231]
c1b3a2cwbvaur
r
rr
r
rr
++=++=
ar
[231]
,,Angles
,,sBasevector cba r
r
r
Atomic Plane
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Atomic Plane
ar
br
cr
Indices to Wei reciprocal Miller
plane I 111 111 (111)
plane II 122 1 (211)
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Zone and Zone Axis
Zone axis
Plain of the
surface normal
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Crystal Structure
Gitter
Basis
Lattice
Base
Crystal
structure
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Crystal Systems
Cubic
Hexagonal
Tetragonal
Rhombohedral
Orthorhombic
Monoclinic
Triclinic
C b i
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14 Bravais
Lattices
C u b i c
H e x a g o n a l T e t r a g o n a l
O r t h o r h o m b i c
M o n o c l i n i c T r i c l i n i c
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Unit CellSmallest assembly, which expresses the metric and includes all
symmetry elements
z.B.: F 4 3 m,
Zinkblende structure
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Symmetry
Deckoperationen
im
Kontinuum
Diskontinuum
Symmetry elements in two-dimensions
Mirror plane m
Rotation axis
2-fold 4-fold
3-fold6-fold
Glide reflection
Translation
Symmetry
Transformations:
Continuum
and
Discontinuum
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Space Groups
Tabulated in:
International Tables
for
Crystallography, Vol A
Asymmetric unit:
Smallest portion of a crystal
structure to which crystallo-
graphic symmetry can be
applied to generate one unit cell.By application of all symmetry
operations of the space group,
the whole space is filled.
11 Laue - Groups
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11 Laue - Groups
Due to the phase problem, all diffraction patterns include an inversion center.
=> Centro- and noncentrosymmetric groups can not be distinguished
Crystal system Laue - Group Acentric subgroups
triclinic 1
monoclinic 2/m 2, m
orthorhombic mmm 222, mm2
tetragonal 4/m
4/mmm
4, 4
4mm, 4m2, 422
trigonal
m
3
3m, 32hexagonal 6/m
6/mmm
6, 6
6mm, 6m2, 622
cubic m
m m
23
43m, 432
1
3
3
3
3
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Structure Data
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Information of EBSD Pattern
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Information of EBSD - Pattern
EBSD of Ge
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EBSD of Ge
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Demonstration of Sample Orientation
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Demonstration of Sample Orientation
Projection of the
surface normal in atwo-dimensional
plain occurs analog-
ous to the stereo-
graphic projection:
=> Pole Figure
Pole Figure Corresponding to ~ [111]
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Pole Figure Corresponding to [111]
with Slightly Tilt and Rotation
Inverse Pole Figure
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Polycrystalline Sample
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y y pFew Alignment of Crystallites
Polycrystalline SampleAli t f C t llit C di t [101]
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Alignment of Crystallites Corresponding to [101],
Inverse Pole Figure
Polycrystalline Sample
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Alignment of Crystallites, Inverse Pole Figure
Reference System
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Reference System
Demonstration of Orientation
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Euler angleOrientation:
Rotation of the sample-fixed coordinate system (Cartesian!) into the crystal-
fixed system of the discrete crystallite.
a) Sample orientation
1 - Rotation on perpendicular direction
- Rotation on longitudinal direction
2 - Rotation on transversal direction
b) Crystal orientation
1 - Rotation in (001)
- Rotation on [100]
2 - Rotation in (001)
Convention according to Bunge:
Mechanical Sample Preparation
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Mechanical Sample Preparation
Mechanochemical Sample Preparation
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Sample Preparation
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Sample Preparation
Depth of penetration 10 - 100 nm
Good polish Bad polish
Sample Preparation by Ion Abrasion
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Polycrystalline Si
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rolling directionback scatter electrons (BSE)quality pattern
transverse directionnormal direction
x 200 pixel size 24 m
Polycrystalline Si:
Preferential growth direction
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Preferential growth direction
5 - 7 deviation from [110]
Literature to Scanning Electron Microscopy
L. Reimer, G. Pfefferkorn: "Rasterelektronenmikroskopie", Springer 1977
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H. R. Wenk (Ed.): "Electron Microscopy in Mineralogy", Springer Verlag 1976
L. Reimer: "Scanning Electron Microscopy", Springer 1983
L. Reimer: "Elektronenmikroskopische Untersuchungs- und Prparationsmethoden",
Springer 1967
Schmidt, Peter FritzPraxis der Rasterelektronenmikroskopie und Mikrobereichsanalyse / Peter
Fritz Schmidt - Renningen-Malmsheim : Expert-Verlag, 1994 (Kontakt &
Studium ; 444 : Metechnik)
Joy et al.: "Electron Channeling Pattern in the Scanning Electron Microscope",J. Appl. Phys. Vol 53, No 8 (1982) 439 - 461
U. Holzhuser: "Charakterisierung von Einkristallen mittels Electron Channeling
Pattern", Diplomarbeit Universit@t Freiburg 1992 Flegler, Heckmann, Klomparens, Elektronenmikroskopie, Spektrum
Akademischer Verlag Berlin und Heidelberg, 1993
Humphreys, "Reviw: Grain and subgrain characterisation by electron backscatter
diffraction, J. of Mat. Sci. 36 (2001), 3833 3854
Literature to Scanning Electron Microscopy
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and online:
"Grundlagen der Raster-Elektronenmikroskopie" http://www.reclot.de
by Alexander Fels
"SEM Electron Backscattered Diffraction" by Dr Geoff Lloyd
"Crash Kurs Textur" http://www.texture.de/Multex-Dateien/crash.htm
by Kurt Helming
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