Depth Profiling with Low-Energy Nuclear Resonances H.-W. Becker, IAEA May 2011 CRP: Reference...
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Transcript of Depth Profiling with Low-Energy Nuclear Resonances H.-W. Becker, IAEA May 2011 CRP: Reference...
![Page 1: Depth Profiling with Low-Energy Nuclear Resonances H.-W. Becker, IAEA May 2011 CRP: Reference Database for Particle Induced Gamma-ray Emission (PIGE) Ruhr-University.](https://reader034.fdocuments.in/reader034/viewer/2022051517/56649ebf5503460f94bc9291/html5/thumbnails/1.jpg)
Depth Profiling
with Low-Energy Nuclear Resonances
H.-W. Becker, IAEA May 2011CRP: Reference Database for Particle Induced Gamma-ray Emission (PIGE)
Ruhr-University of Bochum
first some information about:
Experimental background – the lab in Bochum
Scientific background – Ion Beam Analysis and Nuclear Astrophysics
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The Lab in Bochum
Ruhr-Uni-Bochum4 MV Dynamitron Tandem
500 keV – open air – single ended
100 kV – Implanter (not shown)
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The NRRA set-up in BochumP = 2x10-9 mbar
The 4 summing crystal12x12 inch NaI(TL) with borehole
high efficiency( 50% photopeak efficiency at 2 MeV)
integrating over angular distributions
summing cascades into one peak
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Ion Beam Analysis and Nuclear Astrophysics
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Nuclear Resonance Reaction Analysis example 15p12C
6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 710-1
100
101
102
103
104
105
E = ER
0 2 4 6 8 10 12
0
100
200
300
400
500
600
700
Beam Energy = 6.446 MeV
Co
un
ts
Gamma Ray Energy (MeV)
E > ER
samplee
Detektor
E = ERE > ER
sample 100.28
0
1000
2000
3000
4000
5000
6000
6.300 6.350 6.400 6.450 6.500 6.550 6.600 6.650 6.700 6.750 6.800 6.850
energy [MeV]
co
un
ts
Strahlenergie [MeV]
Wirk
un
gsq
ue
rsch
nitt
[re
l.]
detector resolution for identifing the -ray only
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6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 710-1
100
101
102
103
104
105
What determines the depth resolution in NRRA ?
samplebeam
sample 100.28
0
1000
2000
3000
4000
5000
6000
6.300 6.350 6.400 6.450 6.500 6.550 6.600 6.650 6.700 6.750 6.800 6.850
energy [MeV]
co
un
ts
1.) resonance width Γ2.) beam energy resolution ΔEbeam
3.) Doppler broadening ΔED
stopping powerandtotal energy resolution:
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to get a feeling: 1nm requires 70 eV resolution at 400 keV
total energy resolution:
1.) resonance width Γ2.) beam energy resolution ΔEbeam
3.) Doppler broadening ΔED
by tilting the sample sub-nm resolution possible
t
ppD m
FTkEm2ln4E
e.g. for Si ~ 70 eV at room temperature
stopping power for protons
0
20
40
60
80
100
120
140
160
180
1 10 100 1000 10000 100000
proton energy [keV]
keV
/ µ
m Silicon
Carbon
stopping power:
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The 500 kV machine in Bochum:
0
500
1000
1500
2000
2500
3000
3500
4000
4500
415.8 416 416.2 416.4 416.6 416.8 417 417.2
proton energy
yiel
d
Lewis-peak
total resolution eV(mainly Doppler broadening)HV – ripple 30-40 eV
1 nm
Ep = 417 keVResonanz in 29Si
stability test
50
100
150
200
250
300
0 10 20 30 40 50 60 70
time [min]
gam
ma y
ield
at
50
% p
oin
t
20 eVstability:
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The ultimate resolution:
Phys. Rev. B 58 1103 (1998)
21Ne(p,)22Na, Ep = 272 keV Resonance
21Ne solid target (at 8 K !)
resonance width 1 eVbeam resolution 10 eVDopplerbroadening 17 eV
normal thick target yield
Lewis peak
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Nuclear Resonance Reaction Analysiswith Proton Induced Low Energy Resonances
0,0001 0,001 0,01 0,1 1 10 100
18O(p,a)11B(p,3a)24Mg(p,g)27Al(p,g)
21Ne(p,g)14N(p,g)
26Mg(p,g)27Al(p,g)
23Na(p,g)25Mg(p,g)29Si(p,g)27Al(p,g)
26Mg(p,g)19F(p,ag)28Si(p,g)
25Mg(p,g)27Al(p,g)29Si(p,g)
24Mg(p,g)15N(p,ag)25Mg(p,g)27Al(p,g)13C(p,g)
26Mg(p,g)
resonance strength ( *abundance)
some proton induced resonances between 150 keV and 500 keV:
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One example – Diffusion studies in Olivin(making use of the isotope sensitivity of NRRA)
There is a correlationbetween diffusionand plastic flow
mechanical properties
microscopic properties
Knowledge of the diffusion parameters necessary !
pinning down temperature, pressure and time-scales from observation
Motivation:
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100 m
100000 years
BA AB
ExperimentNatur
BA AB
e.g.: A + B -> AB
~ 8 days 10 nm
Measurement of diffusion processes in the laboratory:
kT
QDD exp0
time scale
temperature scale
Chemical potentialproduction of layerswith well defined stoichiometry
, Q = activation energy
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Investigation of Si diffusion in Olivin
nativesample
artificial Olivin layerenriched in 29Si(PLD)
Olivin(Fe,Mg)2SiO4
Testfall: Si Diffusion in Olivin
(Diffusionskonstanten aus SIMS Messungen bekannt)
R. Dohmen, S. Chakraborty, H.-W. Becker Geophys. Res. Lett. 29 (2002) 261-264
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results:
-50
50
150
250
350
450
550
650
750
850
950
410 415 420 425 430 435 440
proton energy [keV]
gam
ma
yiel
d
diffusion constant in good agreementwith our earlier data
reference layer, ~ 35 nm dick
first temperature process
second temperature process
40 20 0 20 40 60 80 100 120 140
0
0.2
0.4
0.6
0.8
1
1.2
dis tanc e from the surface (nm )
norm
aliz
ed c
once
ntar
tion
1 .15442
0.05
B j
ampi 0 83
650 83
initialj 0 83
750 83
Dliter
150hr 20
0
xj ampi 1 hr 15 initialj 1 hr y liter
depth [nm]
conc
entr
atio
n
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Handbook of Modern Ion Beam Material Analysis (1995)
information appears to be poor ….
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but lot of data are available from Nuclear Astrophysicsand increasingly from Material sciencea first attempt to collect the data (~ 1995)
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… but a lot of data available and still coming
It would be nice to evaluate, extract and bring in a comprehensive form for material analysis:
• The reaction and the abundance of the isotope
• Resonance energy ER
• Q-value or excitation energy• Resonance strength or cross section • Resonance width • Non resonant cross section, next resonance - ray energies, plots of spectra would be useful• Meaning of the values for practical purposes
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summary:
• Nuclear Reaction Analysis with low energy resonances can be a powerfull tool for depth profiling in the nm range
• There are quite a few reonances between 150 kV und 500 kV offering various opportunities for applications
• Sensitivity for isotopes offers special applications
• Probably most if not all necessary data are available
• Data evaluation collection and translation into material science lenguage desirable …