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) 2

} 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 3

Van de Graaff accelerator schematic Van de Graaff accelerator schematic 4

EG- -5 accelerator 5 accelerator EG • 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 5

Inside experimental chamber Inside experimental chamber 6

Experimental setup Experimental setup 7

Kinematic factor Kinematic factor 2   1 − θ + θ 2 2   2 ( M M sin ) M cos E = =  2 1 1 K 1  + E M M   0 2 1   K – Kinematic factor E 1 – Energy after scattering E 0 – Initial energy M 1 – Mass of accelerated particle M 2 – Mass of target atoms θ – Scattering angle 8

o Kinematic factor at 170 o Kinematic factor at 170 9

Rutherford formula Rutherford formula 2   1   2     2 M   θ + − θ  2   1  cos 1 sin     M     i 2    2  Z Z e σ =  1 i  θ 1 2 1   2 sin E   2   2 M  − θ  2  1 1 sin     M   i σ 1 – Scattering cross section Z 1 – Atomic number (beam) Z i – Atomic number (target) E – Energy of accelerated particle θ – Scattering angle 10

Rutherford Backscattering Spectroscopy Rutherford Backscattering Spectroscopy 3000 E = 2.035 M eV α = 15 o Experimental 2500 β = 5 o Simulated θ = 170 o Mo 2000 Experimental Simulated Counts 1500 Si substrate 1000 Ti 500 0 200 400 600 800 Channel 11

RBS RBS Layers Thickness Element Concentrations (%) (10 15 (nm) atoms/ cm 2 ) Ti M o Si 1 2450 140.5 1.0 2 909 80.3 1.0 3 90000 1.0 12

RBS RBS 1800 Ge E = 1.0 M eV 1600 Experimental α = 30 o Simulated β = 20 o 1400 θ = 170 o 1200 Experimental Counts Simulated 1000 Si substrate Si 800 600 400 200 0 200 300 400 500 600 700 800 Channel 13

RBS RBS Layers Thickness Element Concentrations (%) (10 15 atoms/ cm 2 ) (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 14

Elastic Recoil Detection Elastic Recoil Detection 300 Proton 250 Experimental Simulated 200 E = 2.297 M eV α = 75 o Counts β = 75 o 150 θ = 30 o Deuterium 100 50 0 200 400 600 800 Channel 15

ERD ERD Layers Thickness Element Concentrations (%) (10 15 atoms/ cm 2 ) (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 16

NRA and RBS NRA and RBS 3000 2000 Li O Nb Si Experimental Experimental Simulated Simulated 2500 1500 Nb 2000 Si Counts Counts 1500 1000 E = 2.012 M eV 1000 α = 10 o E = 2.012 M eV α = 10 o β = 0 o 500 β = 0 o θ = 170 o 500 θ = 170 o 0 0 200 400 600 800 1000 400 600 800 1000 Channel Channel RBS 4He + Nuclear Reaction Analysis H + 17

+ ) and RBS (4He + ) NRA (H + ) and RBS (4He + ) NRA (H Layers Thickness Element Concentrations (%) (10 15 atoms/ cm 2 ) (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 18

Particle Induced X- -ray Emission ray Emission Particle Induced X 19

M oseley’ ’s law s law M oseley − ν = Z S n R n c • ν – frequency of X-ray quantum • R c – Rydberg constant • Z – atomic element • S n – Screening constant • n – main quantum number 20

Calibration: PIXE Calibration: PIXE 90 80 13.94 17.75 70 60 50 Intensity 16.84 40 20.12 3.35 11.89 30 26.35 20 10 0 200 400 600 800 1000 1200 1400 1600 Channel number 21

Aerosol: PIXE Aerosol: PIXE 22

Aerosol: RBS Aerosol: RBS C 4000 N Aerosol O E p = 2.005 MeV Backscattering yield 3000 Θ = 135 0 2000 F Na Al Si S Ca 1000 Fe 0 600 650 700 750 800 Channel number 23

Table of concentrations Table of concentrations Concen. At. Method Element Concen. At. Method Element % % 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 24

Conclusion Conclusion • Depth distribution • M ethods are non-destructive • Investigate depth resolution near 10 nm 25

Acknowledgements Acknowledgements • Dr. Jacobs • Prof. Lekala • M r. M alaza • National Research Foundation • Department of Science and Technology • Joint Institute for Nuclear Research 26

THANK YOU! 27