Younes Sina & Uk Huh/ Poster for TEM Class
1
Comparison between SAD and CBED YOUNES SINA AND UK HUH MATERIAL SCIENCE AND ENGINEERING DEPARTMENT, THE UNIVERSIT Y OF TENNESSEE, KNOXVILLE, TN In TEM, there are many methods such as Kikuchi, Fresnel, CTEM, HRTEM, Lorentz, SE, BE, BF, DF, HAADF, CBED, SAD, EELS, etc. Among them, SAD & CBED are two major methods to obtain crystal structure. CBED is easier and more useful method than SAD to obtain CBED is easier and more useful method than SAD to obtain crystal structure information in crystal structure information in TEM. If you want to: TEM. If you want to: Check for the presence of weak reflections; look for Check for the presence of weak reflections; look for structure in the diffuse scattering; get structure in the diffuse scattering; get diffraction from a polycrystalline region, amorphous samples, diffraction from a polycrystalline region, amorphous samples, or a region with more than one or a region with more than one grain use SAD. In the other cases, use CBED. grain use SAD. In the other cases, use CBED. Illumination of the sample in SAD is parallel beam and in Illumination of the sample in SAD is parallel beam and in CBED is focused beam. If we CBED is focused beam. If we remove our specimen in SAD, we see a single bright spot and in remove our specimen in SAD, we see a single bright spot and in CBED, a single disc. CBED, a single disc. In CBED, we can focus the beam on a small area (30 - 100 In CBED, we can focus the beam on a small area (30 - 100 nm). The smallest area in case nm). The smallest area in case of SAD is about 0.5 of SAD is about 0.5 μ μ m. Therefore SAD is more desirable for a m. Therefore SAD is more desirable for a region contains more than region contains more than one grain. one grain. Although position of the spots in SAD has a clear meaning Although position of the spots in SAD has a clear meaning but intensities of the spot has a but intensities of the spot has a Little information. Intensities of discs in CBED contain about Little information. Intensities of discs in CBED contain about the sample such as: 3D the sample such as: 3D information about the lattice, symmetry details, lattice information about the lattice, symmetry details, lattice parameter & thickness changes. parameter & thickness changes. If the specimen is polycrystalline, SAD is to be preferred If the specimen is polycrystalline, SAD is to be preferred because SAD will produce a because SAD will produce a sharp ring pattern. If the specimen is an amorphous material, sharp ring pattern. If the specimen is an amorphous material, SAD pattern has preference than SAD pattern has preference than CBED. CBED. CBED has preference for tilting and aligning the sample in CBED has preference for tilting and aligning the sample in order to navigation in order to navigation in reciprocal space, because Kikuchi lines in CBED are more reciprocal space, because Kikuchi lines in CBED are more clearly visible. clearly visible. 1. 1. D. B. Williams and C. B. Carter (1996), D. B. Williams and C. B. Carter (1996), Transmission Electron Transmission Electron Microscopy, Microscopy, Plemun, New York, U.S.A. Plemun, New York, U.S.A. 2. 2. J.A.Eades, educational article: J.A.Eades, educational article: When to use selected-area diffraction When to use selected-area diffraction and when to use convergent-beam diffraction and when to use convergent-beam diffraction , , Acta Microscopica Acta Microscopica Vol. 17, Vol. 17, No. 1, 2008, pp.101-105 No. 1, 2008, pp.101-105 3. 3. Reimer. Transmission Electron Microscopy. Springer, Berlin, Reimer. Transmission Electron Microscopy. Springer, Berlin, 1993 (3rd edition). 1993 (3rd edition). Left) Kikuchi lines can be observed in CBED. Right) Kikuchi lines are har * Kikuchi line have very valuable information about determining the orien Diffraction pattern types: • Spot (Selected area diffraction) • Ring (Polycrystals) • Amorphous (Diffuse rings) • CBED (Convergent beam) • Kikuchi (Inelastic scattering) • HOLZ (Higher Order Laue Zones) From diffraction patterns we can: measure the average spacing between layers or rows of atoms determine the orientation of a single crystal or grain find the crystal structure of an unknown material measure the size, shape and internal stress of small crystalline regions This poster presents the strengths and weaknesses of SAD and CBED. CBED is the most useful method and should be generally used. SAD should be used only in certain specific cases which are discussed. INTRODUCTION GOAL COMPARISON RESULTS AND SUMMARY DIFFRACTION PATTERN TYPES AND USES REFERENCES LOGO • • Parallel beams are focused at the back focal plane Parallel beams are focused at the back focal plane • • Parallel illumination results sharp spots at the plane Parallel illumination results sharp spots at the plane • • Conical illumination results discs at the plane Conical illumination results discs at the plane CBED patterns of five fold, three fold, and two fold respectively CBED patterns of five fold, three fold, and two fold respectively SAD patterns of polycrystalline, texture, amorphous SAD patterns of polycrystalline, texture, amorphous SAD and CBED; Two major techniques in TEM SAD and CBED; Two major techniques in TEM
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Younes Sina & Uk Huh Poster for TEM class, Dr. Duscher CBED vs. SAD University of Tennessee,MSE
Transcript of Younes Sina & Uk Huh/ Poster for TEM Class
Comparison between SAD and CBEDYOUNES SINA AND UK HUH
MATERIAL SCIENCE AND ENGINEERING DEPARTMENT, THE UNIVERSIT Y OF TENNESSEE, KNOXVILLE, TN
In TEM, there are many methods such as Kikuchi, Fresnel, CTEM,
HRTEM, Lorentz, SE, BE, BF, DF, HAADF, CBED, SAD, EELS, etc.
Among them, SAD & CBED are two major methods to obtain crystal
structure.
CBED is easier and more useful method than SAD to obtain crystal structure information in CBED is easier and more useful method than SAD to obtain crystal structure information in
TEM. If you want to:TEM. If you want to:
Check for the presence of weak reflections; look for structure in the diffuse scattering; get Check for the presence of weak reflections; look for structure in the diffuse scattering; get
diffraction from a polycrystalline region, amorphous samples, or a region with more than onediffraction from a polycrystalline region, amorphous samples, or a region with more than one
grain use SAD. In the other cases, use CBED. grain use SAD. In the other cases, use CBED.
Illumination of the sample in SAD is parallel beam and in CBED is focused beam. If weIllumination of the sample in SAD is parallel beam and in CBED is focused beam. If we
remove our specimen in SAD, we see a single bright spot and in CBED, a single disc.remove our specimen in SAD, we see a single bright spot and in CBED, a single disc. In CBED, we can focus the beam on a small area (30 - 100 nm). The smallest area in caseIn CBED, we can focus the beam on a small area (30 - 100 nm). The smallest area in case
of SAD is about 0.5 of SAD is about 0.5 μμm. Therefore SAD is more desirable for a region contains more than m. Therefore SAD is more desirable for a region contains more than
one grain.one grain. Although position of the spots in SAD has a clear meaning but intensities of the spot has aAlthough position of the spots in SAD has a clear meaning but intensities of the spot has a
Little information. Intensities of discs in CBED contain about the sample such as: 3DLittle information. Intensities of discs in CBED contain about the sample such as: 3D
information about the lattice, symmetry details, lattice parameter & thickness changes.information about the lattice, symmetry details, lattice parameter & thickness changes. If the specimen is polycrystalline, SAD is to be preferred because SAD will produce aIf the specimen is polycrystalline, SAD is to be preferred because SAD will produce a
sharp ring pattern. If the specimen is an amorphous material, SAD pattern has preference sharp ring pattern. If the specimen is an amorphous material, SAD pattern has preference thanthan
CBED.CBED. CBED has preference for tilting and aligning the sample in order to navigation inCBED has preference for tilting and aligning the sample in order to navigation in
reciprocal space, because Kikuchi lines in CBED are more clearly visible.reciprocal space, because Kikuchi lines in CBED are more clearly visible.
1.1. D. B. Williams and C. B. Carter (1996), D. B. Williams and C. B. Carter (1996), Transmission Electron Microscopy, Transmission Electron Microscopy, Plemun, New Plemun, New York, U.S.A.York, U.S.A.
2.2. J.A.Eades, educational article: J.A.Eades, educational article: When to use selected-area diffraction and when to use When to use selected-area diffraction and when to use convergent-beam diffractionconvergent-beam diffraction,, Acta Microscopica Acta Microscopica Vol. 17, No. 1, 2008, pp.101-105Vol. 17, No. 1, 2008, pp.101-105
3.3. Reimer. Transmission Electron Microscopy. Springer, Berlin, 1993 (3rd edition).Reimer. Transmission Electron Microscopy. Springer, Berlin, 1993 (3rd edition).
Left) Kikuchi lines can be observed in CBED. Right) Kikuchi lines are hardly visible in SAD.
* Kikuchi line have very valuable information about determining the orientation of the sample.
Diffraction pattern types:
• Spot (Selected area diffraction)• Ring (Polycrystals)• Amorphous (Diffuse rings)• CBED (Convergent beam)• Kikuchi (Inelastic scattering)• HOLZ (Higher Order Laue Zones)
From diffraction patterns we can:
measure the average spacing between layers or rows of atoms
determine the orientation of a single crystal or grain
find the crystal structure of an unknown material
measure the size, shape and internal stress of small crystalline regions
This poster presents the strengths and weaknesses of SAD and CBED.
CBED is the most useful method and should be generally used. SAD
should be used only in certain specific cases which are discussed.
INTRODUCTION
GOAL
COMPARISON RESULTS AND SUMMARY
DIFFRACTION PATTERN TYPES AND USES
REFERENCES
LOGO
• • Parallel beams are focused at the back focal planeParallel beams are focused at the back focal plane• • Parallel illumination results sharp spots at the planeParallel illumination results sharp spots at the plane• • Conical illumination results discs at the planeConical illumination results discs at the plane
CBED patterns of five fold, three fold, and two fold respectivelyCBED patterns of five fold, three fold, and two fold respectively
SAD patterns of polycrystalline, texture, amorphous SAD patterns of polycrystalline, texture, amorphous
SAD and CBED; Two major techniques in TEMSAD and CBED; Two major techniques in TEM
