RATHERFORD SCATTERING-CHANNELING-PIXE AND PIGE

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10. Semiconductor materials
Solar cells
Glasses
Metals
Special and compound materials
Coatings
Biomedical materials
Arts and cultural heritage
Geological samples
Archaeometry
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15. 1. X-ray detector
2. Micro-camera
3. Exit nozzle with a
100 nm thick Si3N4
4. RBS detector with
He flux
5. Two lasers
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16. Question:
is it pure gold or a coating?

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18. What is Rutherford
Backscattering
Spectrometry?
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20. • 1911: Rutherford’s scattering experiments:
He on Au
⇒ Atomic nucleus, nature of the atom
• 1957: S. Rubin, T.O. Passell, E. Bailey,
“Chemical Analysis of Surfaces by Nuclear
Methods”, Analytical Chemistry 29 (1957)
736
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22. →(conservation of momentum
and energies)
Kinematic factor: E1 = K E0
•Is independent of the ion initial energy
• Is monotonicaly increasing with M 2
•Allows the best mass resolution for Q=P
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23. Sensitivity increases with
• increasing Z1
• increasing Z2
• decreasing E
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24. The stopping cross section allows to calculate the film
thicknesses and the depth-profiles of the various elements
•Lightly depends on energy
• Is in general monotonically increasing with the target atomic number,
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26. 2000 keV He, θ = 165°
backscattered from C, O, Fe, Mo, Au
3×1016 Atoms/cm2 each on Si substrate
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30.  well adapted to the analysis of heavy elements on light substrates
 It consists in observing the elastic diffusion of incident particles
(typically 2 MeV a) on target nuclei
•No dissipative processes
•Target nucleus and incident particle remain in the fundamental state
•The energetic balance is neutral: Q elast = 0
 Analysing depth: ~ micrometers
 High resolution RBS as special application --> depth resolution <
1 nm
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31. •It consists in observing nuclear collisions occuring between incident
particles and target nuclei and in detecting the reaction products (charged
particles or hu)


Selective detection of light elements
Isotope sensitive
Depth resolution:
~ 8 nm (in Si)
1 nm (grazing incidence)
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32. B
A:RBS spectrum with He ions (2.274 MEV) B:NRAspectrum with d ions (1 MEV)
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34. When a set of planes or axes in
a single crystal is aligned
along the incident ion beam
direction. ions undergo a
process called .
During this process, ions are
steered by atomic planes or
rows close to the center of
planar or axial channels
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35. A crystal is a regular arrangement of atoms located at lattice positions in
the form of strings and planes.
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36. e+
e-

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38. The general foundations of channeling were established by
j. lindhard in 1965 .
 The base of lindhard s theory was on classical collision
model.
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40. The most important are two
Critical Angel
Minimum yield
And also
 Beam Energy
 Beam Divergence
 Incident Angel
 Debye temperature of the material ,etc
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41. Shielding effect(shadow cone)
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43. c
If  >  c ions stuffer small impact collisions which finally turn into the
dechanneling of ions .if  <  c ions are steered by continuum
potential.
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44. The most important are two
Critical Angel
Minimum yield
And also
 Beam Energy
 Beam Divergence
 Incident Angel
 Debye temperature of the material ,etc
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45. Fraction of the channel area which is forbidden by the
vibrating strings of atoms.
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46. The total available area is given by 1/ND
,where N is the atomic density and d is
atomic spacing .
Thus the minimum yield is:
*
* Is independent of beam parameters and determined solely by the
properties of the crystals
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47. occurs even in a perfect single crystal and
effect is enhanced due to presence of defects in a crystal
occurs when the distortion of the channel
walls become significant relative to the channeling critical
angel
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49. Point Defects
Dislocations
Stacking Faults
Twins
Impurity ,cte….
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58. The crystal lattice constants
Examine the crystal lattice structure
Determine the atom location
Determine the impurities position
Examine dislocation of lattice
Emamine the depth of layers
Study of amorphous layers
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