Supervisor: Dr. Alexander Kobzev Students: Given Madiba Sithenkosi - - PowerPoint PPT Presentation

Supervisor: Dr. Alexander Kobzev Students: Given Madiba Sithenkosi Mlala Phuti Ngoepe

Frank Laboratory of Neutron Physics (FLNP)

11 October 2012

To investigate the element content and depth distribution of different elements in various samples using the following methods:

} Rutherford Backscattering Spectroscopy (RBS) } Elastic Recoil Detection (ERD) } Nuclear Reaction Analysis (NRA) } Particle Induced X- ray Spectroscopy (PIXE)

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} Accelerator principles

• Van de Graaff (parameters)

} Theoretical background } Results

• Rutherford backscattering spectroscopy (RBS)
• Elastic recoil detection (ERD)
• Nuclear reaction analysis (NRA)
• Particle induced X- ray emission (PIXE)

} Conclusion

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Van de Graaff accelerator schematic Van de Graaff accelerator schematic

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EG EG-

• 5 accelerator

5 accelerator

• Helium ion and proton energy:

0.9 – 3.5 M eV

• Accelerator belt velocity:

20 m/ s

• Beam at target: 1.5 mm
• Tank pressure: 10 atm
• EG-5 has six beam lines

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Inside experimental chamber Inside experimental chamber

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Experimental setup Experimental setup

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Kinematic factor Kinematic factor

K – Kinematic factor E1 – Energy after scattering E0 – Initial energy M1 – Mass of accelerated particle M2 – Mass of target atoms θ – Scattering angle

1

2 1 2 2 2 2 1 1 2 1

( sin ) cos M M M E K E M M θ θ   − +   = =   +    

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Kinematic factor at 170 Kinematic factor at 170o

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Rutherford formula Rutherford formula

σ1 – Scattering cross section Z1 – Atomic number (beam) Zi – Atomic number (target) E – Energy of accelerated particle θ – Scattering angle

2 1 2 2 2 1 2 2 1 1 1 2 2 2 2 1

cos 1 sin 2 sin 1 sin

i i i

M M Z Z e E M M θ θ σ θ θ           + −                 =           −       

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Rutherford Backscattering Spectroscopy Rutherford Backscattering Spectroscopy

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Channel

200 400 600 800

Counts

500 1000 1500 2000 2500 3000

Experimental Simulated

Ti Mo Si substrate

E = 2.035 M eV

α = 15o β = 5o θ = 170o

Experimental Simulated

RBS RBS

Layers Thickness Element Concentrations (%) (1015 atoms/ cm2) (nm) Ti M o Si 1 2450 140.5 1.0 2 909 80.3 1.0 3 90000 1.0

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RBS RBS

Channel

200 300 400 500 600 700 800

Counts

200 400 600 800 1000 1200 1400 1600 1800

Experimental Simulated

Si Ge Si substrate

E = 1.0 M eV

α = 30o β = 20o θ = 170o

Experimental Simulated

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RBS RBS

Layers Thickness Element Concentrations (%) (1015 atoms/ cm2) (nm) Si Ge 1 170 37.3 1.0 2 150 30.1 1.0 3 160 38.4 1.0 4 150 28.1 1.0 5 165 38.4 1.0 6 140 28.1 1.0 7 175 39.6 1.0 8 135 27.1 1.0 9 60 18.1 1.0 10 150 26.4 0.2 0.8 11 3500 1.0

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Elastic Recoil Detection Elastic Recoil Detection

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Channel

200 400 600 800

Counts

50 100 150 200 250 300

Experimental Simulated

Proton Deuterium E = 2.297 M eV

α = 75o β = 75o θ = 30o

ERD ERD

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Layers Thickness Element Concentrations (%) (1015 atoms/ cm2) (nm) H D C Ni 1 200 26 0.46 0.04 0.44 0.06 2 300 38.1 0.41 0.03 0.4 0.16 3 300 37.6 0.37 0.02 0.33 0.28 4 300 35.7 0.23 0.05 0.19 0.575 5 300 35.1 0.16 0.005 0.1 0.735 6 300 33.8 0.05 0.004 0.946 7 1000 0.03 0.002 0.968

NRA and RBS NRA and RBS

Nuclear Reaction Analysis H+ RBS 4He+

Channel

200 400 600 800 1000

Counts

500 1000 1500 2000 2500 3000

Experimental Simulated

Nb Si

E = 2.012 M eV

α = 10o β = 0o θ = 170o

Channel

400 600 800 1000

Counts

500 1000 1500 2000

Experimental Simulated

Si Nb O Li

E = 2.012 M eV

α = 10o β = 0o θ = 170o

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NRA (H NRA (H+

+) and RBS (4He

) and RBS (4He+

+)

)

Layers Thickness Element Concentrations (%) (1015 atoms/ cm2) (nm) Li O Nb Si 1 8000 777.5 0.25 0.55 0.2 2 600 85.9 0.2 0.4 0.2 0.2 3 350 104.7 0.3 0.5 0.1 0.1 4 700 122.5 0.2 0.2 0.05 0.55 5 90000 1.0

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Particle Induced X Particle Induced X-

• ray Emission

ray Emission

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M oseley M oseley’ ’s law s law

• ν – frequency of X-ray quantum
• Rc – Rydberg constant
• Z – atomic element
• Sn – Screening constant
• n – main quantum number

n c

Z S R n − ν =

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Calibration: PIXE Calibration: PIXE

200 400 600 800 1000 1200 1400 1600 10 20 30 40 50 60 70 80 90

26.35 16.84 20.12 17.75 13.94 11.89 3.35 Intensity Channel number

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Aerosol: PIXE Aerosol: PIXE

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Aerosol: RBS Aerosol: RBS

600 650 700 750 800 1000 2000 3000 4000

Aerosol Ep= 2.005 MeV

Θ = 135

Si Al Na F O N C Ca S Fe Backscattering yield Channel number

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Table of concentrations Table of concentrations

Element

• Concen. At.

% Method Element Concen. At. % Method C 41 RBS K 0.1 PIXE N 20.5 RBS Ca 0.53 RBS O 28 RBS Mn 0.007 PIXE F 2.6 RBS Fe 0.14 RBS Na 2.5 RBS Cu 0.002 PIXE Mg 1.3 RBS Zn 0.01 PIXE Al 1.3 RBS As 0.001 PIXE Si 1.8 PIXE Sr 0.0006 PIXE S 0.2 RBS Zr 0.005 PIXE Cl 0.01 PIXE Ba 0.01 PIXE

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Conclusion Conclusion

• Depth distribution
• M ethods are non-destructive
• Investigate depth resolution near 10 nm

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Acknowledgements Acknowledgements

• Dr. Jacobs
• Prof. Lekala
• M r. M alaza
• National Research Foundation
• Department of Science and Technology
• Joint Institute for Nuclear Research

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THANK YOU!

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