Transcript Ion beam Analysis

Ion beam Analysis
Joele Mira
from UWC and iThemba LABS
Tinyiko Maluleke
from US
Supervisor:
Dr. Alexander Kobzev
Contents
Descriptions of Van de Graaf
Rutherford back-scattering (RBS)
RBS and Elastic recoil detection
(ERD)
RBS and Proton induced X-ray
emission (PIXE)
Conclusion
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VAN DE GRAAFF ACCELERATOR
 The EG-5 accelerator,
accelerate ions to energy
between 0.9-3.5 MeV
 Beam intensity of 30μA for
H and 10 μA for He.
 Energy spread of 0.5 keV.
 Energy precision of 2 keV.
 6 beam lines.
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Introduction to RBS
 The use of RBS is to provide information on
concentration vs depth for heavy element in
a light material.
+
 A beam of 2-3 MeV He ions are directed at
different angles on a sample surface.
 The ion loses energy due to collision with
electrons.
 The ion will scatter elastically with the atomic
nucleus and lead to a kinematic factor K,
 m2
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

2
2
2
E
( M 2  M 1 sin )  M 1 cos 
 1 

E0 
M 2  M1


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Experimental setup for RBS
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RBS spectrum
0
200
400
600
800
1000
Element
Conc.
At(%)
Pb
0.05
Ru
0.5
Br
0.05
Fe
0.59
Ca
0.26
P
0.5
Al
1.0
O
12.90
C
84.06
O
EHe = 2.3MeV
150
170
150

15
Backscattering Yield
Thickness = 12x10 Atoms/cm
2
Ru
100
100
Al
P
50
Fe
Ca
Pb
Br
50
0
0
400
600
800
1000
Channel
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Elastic Recoil Detection (ERD)
 ERD is a complimentary technique to RBS
 It is used to measure concentration of H atoms in
the thin layers, and in the near surface region of
material.
 The incident beam is directed at a grazing angle
onto the sample surface.
 The recoiling atoms are ejected and detected at
forward angle.
 A thin foil is placed in front of the detector to stop
elastically scattered incident ion beam and all
atoms with mass heavier than the beam.
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Experimental setup
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RBS spectrum
100
3000
200
300
400
500
600
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Thickness = 2.5X10 cm
H = 32%
C = 18%
O = 20%
Si = 30%
2500
C
RBS Yield
2000
700
3000
-2
2500
2000
O
1500
1500
Si
1000
1000
500
0
100
500
200
300
400
500
600
0
700
Channel number
RBS SPECTRUM
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ERDA spectrum
800
18
Thickness = 2.5X10 cm
H = 32%
C = 18%
O = 20%
Si = 30%
ERD Yield
600
-2
400
200
0
100
200
300
400
500
Channel
ERDA Spectrum
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Proton Induced X-ray Emission (PIXE)
 Occurs when a sample is bombarded with the
beam, the proton interact with the electrons in the
atoms of the sample, creating an inner shell
vacancy
 The X-ray is emitted when an electron from outer
shell fills the hole left by an electron.
 The energy of the X-rays emitted are
characteristic of the element from which they
originate.
 The number of emitted X-rays is proportional to
the amount of the corresponding element within
the sample.
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Experimental setup for RBS and PIXE
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RBS and PIXE
4000
C
3500
N
Backscattering yield
3000
Aerosol
Ep=2.005 MeV
O
2500
0
=135
2000
F
Na Al
Si
1500
1000
S Ca Fe
500
0
550
600
650
700
750
800
Channel number
RBS Spectrum
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PIXE
PIXE Spectrum
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PIXE
Concen. At.
Element %
C
41
N
O
20.5
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Method
Concen.
Element At. %
RBS
K
0.1
RBS
RBS
Ca
Mn
Method
PIXE
0.53
RBS
PIXE
0.14
RBS
PIXE
0.01
PIXE
0.007
F
Na
2.6
2.5
RBS
RBS
Fe
Cu
0.002
Mg
1.3
RBS
Zn
Al
1.3
RBS
As
Si
S
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PIXE
0.001
1.8
PIXE
Sr
0.0006
PIXE
Elements
in aerosol PIXE
0.2 content
RBS& concentrations
Zr
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0.005
Conclusion
 The use of ion beam analysis is non-destructive,
high accuracy and easy to interpret the
experimental results.
 The use of these models allow the determination
of different elements from Hydrogen to heavy
elements concentrated in samples.
 It also allow the analysis of very thin sample of
about 10 nm.
 Ion beam analysis is applied in various fields
such as microelectronics, environmental
monitoring etc.
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Thanks for your attention!!
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