Transcript 1. dia

N R A
School of Ion Beam Analysis and Accelerator Applications
Nuclear Reaction Analysis
Resonances
Gábor Battistig
Research Institute for Technical Physics
and
Materials Science
(MTA - MFA)
Budapest, Hungary
[email protected]
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
Inelastic nuclear collision with nuclear excitation
Nuclear reaction in general
A(a,b)B
Isotope specific!
Projectile energy must be higher than
Coulomb barrier
AA  Aa  Ab  AB
Z A  Z a  Zb  Z B
Ea  E A  Eb  EB  Q
Q  ( M a  M A  M b  M B )c 2
Q  0  Exoterm
Q  0  Endoterm
13-24 March, 2006, ICTP, Trieste, Italy
1

Z AZ ae2
Ec 
 Z A Z a AA 3 [ MeV ]
R
M B  Mb
Eth  Q
M B  Mb  Ma
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N R A
School of Ion Beam Analysis and Accelerator Applications
Ion-Gamma reaction :
Ion-Ion reaction :
19F(p,g)20Ne
19F(p,a)16O
Ion-Neutron reaction :
Q=12.845 MeV
Q=8.115 MeV
19F(p,n)19Ne
Q=-4.020 MeV
Particle Induced Activation Analysis (PAA) :
19F(p,n)19Ne
19F
b
Energy levels and
cross sections
in nuclear reactions
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Natural abundance of stable sotopes















1H
- 99.985%
3He - 0.0001%
6Li - 7.56%
9Be - 100%
10B - 19.8%
12C - 98.89%
14N - 99.64%
16O - 99.76%
19F - 100%
23Na - 100%
24Mg - 78.99%
27Al - 100%
28Si - 92.23%
31P – 100%
50Cr – 4.35%
2H
- 0.015%
4He - 99.999%
7Li - 92.44%
11B
- 80.2%
13C - 1.11%
15N - 0.36%
17O - 0.04%
18O
25Mg
26Mg
- 10.0 %
- 0.20%
- 11.01%
29Si
- 4.67%
30Si
- 3.10%
52Cr
– 83.79%
53Cr
– 9.5%
13-24 March, 2006, ICTP, Trieste, Italy
54Cr
– 2.36%
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N R A
School of Ion Beam Analysis and Accelerator Applications
Most used particle induced nuclear reactions of light elements
Proton induced
reactions Q [MeV]
3He induced
Deuteron induced
reactions Q [MeV] reactions Q [MeV]
4He
6Li(p,a)3He
2H(d,p)3He
10B(a,p)13C
4.02
7Li(p,a)4He
17.35
9Be(p,a)6Li
2.13
10B(p,a)7Be
1.15
11B(p,a)8Be
8.58
15N(p,ag)12C
4.97
18O(p,ag)15N
3.98
19F(p,ag)16O
8.11
23Na(p,ag)24Mg 11.69
27Al(p,g)28Si
11.59
29Si(p,ag)30P
5.59
52Cr(p,ag)53Mn 7.56
3He(d,a)1H
12C(d,p)13C
13C(d,p)14C
14N(d,p)15N
14N(d,a)12C
16O(d,p)17O
16O(d,a)14N
19F(d,a)17O
13-24 March, 2006, ICTP, Trieste, Italy
4.03
18.35
2.72
5.95
8.61
13.57
1.92
3.11
10.03
2H(3He,p)4He
18.35
6Li(3He,p)8Be
6.79
9Be (3He,p)11B
0.32
9Be(3He,a)8Be
18.91
12C(3He,p)14N
4.78
12C(3He,a)11C
1.86
18O(3He,p)20F
6.87
18O(3He,d)19F
2.50
18O(3He,a)19O
12.51
induced
reactions Q [MeV]
4.06
11B(a,p)14C
0.78
14N(a,p)17O
-1.19
19F(a,p)22Ne 1.67
31P(a,p)34S
0.63
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N R A
School of Ion Beam Analysis and Accelerator Applications
Principle
100
12 C(d,p )13 C
0
150°lab
Q=2.77 MeV
Sample
4He+, 3He+, 2H+, 1H+,
etc
Absorber
foil
s(mb sr-1)
80
40
20
0
Detector
16O(d,p )17O
1
60
0
200
400
600
800 1000 1200
Energie (keV)
14
16O(d,p )17O
0
12
Energy
13-24 March, 2006, ICTP, Trieste, Italy
10
s (mb sr -1)
Counts
12C(d,p )13O
0
16O(d,p )17O
1
150°lab
Q=1.05 MeV
8
6
4
2
0
0
200
400
600
800
Energie (keV)
G. Battistig, MTA – MFA Budapest, Hungary
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1000
1200
N R A
School of Ion Beam Analysis and Accelerator Applications
Experimental setup
Vacuum chamber
Vacuum chamber
LN2
trap
Surface barrier
detector
LN2
trap
Sample
Filter foil
Ion
beam
Sample
Ion
beam
Anular surface
barrier
detector
13-24 March, 2006, ICTP, Trieste, Italy
g detector
Filter foil
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N R A
School of Ion Beam Analysis and Accelerator Applications
Experimental results
600 nm SiO2 layer; 900 keV, Deuteron beam
Yield:
Nb
NA 
ds ( )
N a 
d
Well known reference sample is needed for quantification !!!
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Experimental results
170 nm AlxN layer, 1.7 MeV d beam
Many reactions, many, sometimes overlapping peaks.
Total amount of the given isotope can be determined.
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Thin sample : interferences
900 keV 2H+ on TiOxNy film
Numerous overlapping peaks from
14N(d,p
0-7) and
14N(d,a ) reactions.
0,1
2500
2000
Counts
1500
Reaction Q-values are known
In principle, interferences can be
accounted for.
In practice we avoid having to.
16
O reference
16
14
film containing O and N
1000
500
0
100
200
300
400
Channels
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Reference samples
YU
NU 
NR
YR
Anodic isotopic Ta2O5 thin films for
Certified
sources.
16O
16O
and
18O
and 18O films available from different
For thin targets, the cross section ratios of 12C(d,p)13C, D(3He,p)4He, 14N(d,a)12C,
14N(d,p)15N, 15N(d,a )13C and 15N(p,a )12C to that of 16O(d,p )17O have been obtained by
0
0
1
using stoichiometric frozen gas targets of CO2, NO and D2O.
This enables the reliable and robust Ta2O5 reference targets to be used as a
reference for NRA determinations of D, 12C, 14N and 15N.
Davies, J. A., T. E. Jackman, et al. (1983). "Absolute calibration of 14N(d,a) and 14N(d,p)
reactions for surface adsorption studies." Nucl. Instr. and Meth. 218: 141-146.
Sawicki, J. A., J. A. Davies, et al. (1986). "Absolute cross sections of the 15N(d,a0)13C and
15N(p, a )12C reaction cross sections." Nucl. Instr. and Meth. B15: 530-534.
0
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Depth Profiling : Principle
x
dx
E inc
q
C(x)
• A channel of width dEc at energy Ec in
the spectrum corresponds to a slice
of width dx at depth x in the sample,
with Ec and dEc being inversely
related to x and dx through a linear
combination of the stopping powers
for the incident and outgoing particle
• The number of particles accumulated
into that histogram bin is proportional
to C(x), dx, and s(Ex), where Ex is the
energy of the incident beam when it
gets to depth x;
s (x)
E
Area A
dE
Y  Ns ( E )
 Cxs ( E )
  C ( x)s ( E )dx
x
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Cross section
ds/d (mb. sr-1)
Depth profiling
Depth profiling nitrogen
in titanium via
14N(d,a )12C
1
1.5
1.0
0.5
0.0
600
800
1000
1400
1200
Energy (keV)
Spectra
Concentration profile
d)
b)
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Ion implantation of SiC
RBS + channeling = lattice disorder
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
RBS + NRA = More information
W. Jiang et al. / Nucl. Instr. and Meth. in Phys. Res. B 161±163 (2000) 501
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Thin sample : summary
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


dE/dx not needed
Shape of s(E,q) much more important than absolute value.
Precision standards are used rather than precision cross
sections (Standardless NRA?)
Approximate relative cross sections are needed to help in
experimental design (isotopes …)
Reaction Q values are needed - these are easily accessible
and well known.
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Resonances
cross section [mb/sr]
Differential
Differenciális Hatáskeresztmetszet
[µb/sr]
18O(p,a)15N
cross section
Cross section in
the resonance:
Breit-Wigner (Lorenz)
function
6
10
5
10
4
10
334 keV
152 keV
3
10
629 keV
216 keV
s R (E)  K
2
10
10
18
0
10
-1
10
-2
10
-3
10
-4
10
-5
2
( E  ER ) 
4
2
1
10
2
O(p,a) N
15
Q = 3.9804 MeV
 = 135°
100
200
300
400
500
600
Proton Energy
Energia [keV]
Proton
[keV]
13-24 March, 2006, ICTP, Trieste, Italy
700
800
900
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School of Ion Beam Analysis and Accelerator Applications
Most used Narrow Resonances in Depth Profiling
Reaction
Resonance energy
Resonance width

18O(p,a)15N
100 eV

29Si(p,g)30P

15N(p,a)12C

30Si(p,g)31P

18O(p,a)15N

27Al(p,g)28Si

23Na(p,g)24Mg

27Al(p,g) 28Si

52Cr(p,g)53Mn

13C(p,g)13N
152 keV
413.9 keV
429 keV
620.4 keV
629 keV
632.23 keV
676.7 keV
991.86 keV
1005 keV
1748 keV
13-24 March, 2006, ICTP, Trieste, Italy
120 eV
68 eV
2000 eV
6.7 eV
<70 eV
70 eV
50 eV
135 eV
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N R A
School of Ion Beam Analysis and Accelerator Applications
Depth Profiling by Resonance
The resonance is scanned through the
target depth by scanning the incident
beam energy.
Resonance samples the given isotope at depth
E0  E R
x
dE
dx
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Principle of depth profiling with narrow resonances
18
O(p,a)15N resonance at 152 keV
Sample
energy loss
E
in the sample
Beam
energy
ER + E
The resonance occurs
at depth xin the sample
154
13-24 March, 2006, ICTP, Trieste, Italy
The resonance samples
the
18
O at depth
x =E/dE/dx
FWHM ~ 100 eV
153
152
151
average beam energy in sample [keV]
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150
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N R A
School of Ion Beam Analysis and Accelerator Applications
An excitation curve
Yield
Concentration profile C(x)
Corresponding
excitation curve N(E)
Beam Energy [keV]
N ( E )  G ( E ) * ( E ) * T ( E ) * S C ( x)
n 
S C ( x)   k n f (u )
*n
n 0
13-24 March, 2006, ICTP, Trieste, Italy
G(E)
(E)
T(E)
S<C(x)>
beam + Doppler energy spread
rersonance lineshape
beam energy straggling
„straggling” of C(x)
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21
N R A
School of Ion Beam Analysis and Accelerator Applications
Excitation curve
G(E)
beam - Gaussian,
+ Doppler energy spread due to the thermal vibration of the target atoms
s D (E ) 
2
(E)
2MAE
Ma
kT
rersonance lineshape - Lorantzian
s R (E )  K
2
2
(E  E R ) 
4
13-24 March, 2006, ICTP, Trieste, Italy
2
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N R A
School of Ion Beam Analysis and Accelerator Applications
T(E)
beam energy straggling
E
f(u)
Energy loss u
f(u;x) tends towards a Gaussian
for large x
s (f (u ))  S
2Z
A
2
0.2 mg/cm
protonok
152 152
keVkeV-os
protons
in CH2
stragglingje CH2-ben
2
"
Tetszoleges
egység
The charged particles lose their
energy in independent collisions
with electrons.
0.3 mg/cm
2
0.4 mg/cm
2
0.6 mg/cm
2
0.8 mg/cm
2
1 mg/cm
x
0.0
13-24 March, 2006, ICTP, Trieste, Italy
0.5
1.0
1.5
2.0
Energyveszteség
loss [keV]
Energia
[keV]
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23
N R A
School of Ion Beam Analysis and Accelerator Applications
„Straggling”
*
S<C(x)> ‘ straggling ’ of C(x)
On average, m energy-loss events per
unit length
*
*
f(u)
*
f(u)
f(u)
f(u)
For thickness x mx events on average
f(u)*f(u)
g(u;x)
0
g u ; x  
n 
*n
P
(
mx
)
f
(u )
n
n 0
Pn mx   e mx
13-24 March, 2006, ICTP, Trieste, Italy
u
(mx )n
n!
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24
N R A
School of Ion Beam Analysis and Accelerator Applications
Experimental excitation curves
Si18O2 /Si sample,
thermally grown, 20 mC /point
Beam energy spred + Doppler
broadening: 100 eV
Resonance width: 100 eV
Ta218O5 /Ta sample, anodically
oxidised, 20 mC /point
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Tilting the sample – increases the
virtual thickness of the layer

x ' x
13-24 March, 2006, ICTP, Trieste, Italy
1
cos 
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N R A
School of Ion Beam Analysis and Accelerator Applications
Depth resolution
0.5
10 A
+


Narrow resonance width
Large dE/dx (~ 100 keV)
„negligible cross section outside
the resonance – Background-free


20 A
30 A
0.3
Yield
Beütés

0.4
40 A
0.2
SiO 2
x
0.1
Straggling – beam broadens by
depth
Multiple Scattering at tilted
sample
0.0
152
153
ProtonEnergy
Energia[keV]
[keV]
Proton
Depth resolution
vs Depth
: tilt angle
line: straggling
circles: MS
crosses: overall
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Depth Profiling by Resonance - Summary

As for thin samples, plus need for accurate S(E)

low energy – large stopping – high depth resolution


Stronger requirement for shape accurate s(E,q) for accurate depth
profiling
Straggling and Multiple scattering gradually decreases resolution
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
Typical experimental results
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
Isotopic tracing study of the microscopic mechanisms of oxygen
transport in the oxide growing
during dry oxidation of silicon.
18O depth profile
SiO2
Silicon
16 O
2
then
18
88 O2
88
88
8
exchange
exchange
18O
depth profile
Experimental
excitation curve
growth
800
600
400
200
0
150
155
160
165
Energy [keV]
170
175
180
Interpretation of the spectra in terms of 18O depth profile, demonstrating
surface exchange and that the growth takes place at the SiO2/Si interface
through interstitial oxygen movement: direct confirmation of the Deal and Grove
model for growth x > 10 nm.
No isotopic exchange in the matrix (natural abundance, 0.2%) except near the surface.
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
depth profile
Coups
(u.a)
Yield
18O
150
160
170
180
190
200
210
Energy [keV]
Energie
(keV)
Sequential oxidations in 100 mb 16O2 (40 h) at 1100°C, yielding 1600 Å Si16O2 then in 18O2 (5
h, 10 h and 24 h: additional 100, 285 and 405 Å). Excitation curve registration with target
tilted to 60°.
I. Trimaille et al. GPS, Paris
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
Isotopic tracing by sequential oxydation of SiC
(40 h) then 18O2 (5 h, 10 h and 24 h)
6H-SiC
C terminated
surface
1,0
0,8
CoupsYield
(u.a)
Coups(u.a)
Yield
6H-SiC
Si terminated
surface
18
2
[ O](%)
16O
0,6
0,4
0,2
0,0
0
150 152 154 156 158 160 162 164
Energy
[keV]
Energie(keV
)
150 155 160 165 170 175 180 185
Energy
[keV]
Energie(ke
V)
100
200
Epaisseur (Å)
Thickness
[Å]
300
Sequential 16O2/18O2 oxidations, same conditions as for Si. SiC is a polar crystal: silica grows
on both faces, similarly to the Si case, but the Si and C faces produce slow and fast growth.
Isotopic tracing measurements of this type allow one to investigate with great sensitivity the
near surface and interface properties of the silica produced by oxidation of SiC.
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
32
N R A
School of Ion Beam Analysis and Accelerator Applications
Hydrogen profiling with a nuclear resonance
1H(15N,ag)12C
Hydrogen implantation
profile in silicon
(1016 cm-2, 40 keV)
from W.A. Lanford, NIMB66(1992),68
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
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N R A
School of Ion Beam Analysis and Accelerator Applications
Study of thin hafnium oxides deposited by atomic layer deposition
J.-J. Ganem, NIM B 219–220 (2004) 856
Excitation curves measured using the 151 keV 18O(p;ac)15N resonance on 3.5 nm (a) and 7.5 nm (b) HfO2
samples oxidized in 18O2 atmosphere at 425 C just after: deposition (black circles), post-deposition N2
anneal at 425 C (open circles) and post-deposition N2 anneal at 800 C (open squares).
After deposition the films present chlorine contamination and a lack of oxygen. They are unstable toward
thermal oxidation since a high oxygen transport and exchange mechanisms occur during the process.
Oxygen diffusion can be significantly reduced after a thermal anneal in N2 atmosphere.
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Ultrathin silicon oxynitride film formation
Experimental excitation curves of the 18O(p,a)15N reaction for samples with (a) deferent 15N areal
densities, sequentially oxidized in 16O2 (60 min) and in 18O2 (90 min). The arrows indicate the
energy position of the surface (dashed) and of the SiO2/Si interface (solid) in each sample; (b) no
N prior to oxidation, oxidized under the same conditions as samples in (a).
N amounts as low as 1/30 of a monolayer at the surface of Si wafers hamper the oxidation of
Si, and the higher the N concentration, the thinner the oxynitride films;
(ii)
(ii) during the film growth, N and O are responsible for the atomic transport, while Si remains
immobile;
(iii) N, which is initially present at the surface of the Si wafer, migrates during oxidation, remaining
at the near-surface and at the near-interface regions of the film.
(i)
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
35
N R A
School of Ion Beam Analysis and Accelerator Applications
Silicon isotopic tracing with the
415 keV
29Si(p,c)
narrow resonance near
29Si(p,
c)30P excitation curves from an enriched silicon single crystal before and after
thermal oxidation, showing loss of silicon during the oxidation process.
I.C. Vickridge et al, NIM B 161±163 (2000) 441
13-24 March, 2006, ICTP, Trieste, Italy
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N R A
School of Ion Beam Analysis and Accelerator Applications
Annealing of ZrAlxOy Ultrathin Films on Si in a Vacuum or in O2
E. B. O. da Rosa et al., Journal of The Electrochemical Society, 148 G695-G703 (2001)
ZrAlxOy films were deposited at a rate of 0.3 nm/min by reactive sputtering using a Zr80-Al20 atomic
composition target in an oxygen-containing plasma directly on Si(001) substrates. Postdeposition
annealings were performed ex situ at 600°C for 10 min, either in high vacuum (p10-5 Pa) or in 710-3
Pa of dry 98.5% 18O2.
Areal densities of Al and Si were estimated from the areas of the excitation curves of the
27Al(p,g)28Si and 29Si(p,g)30P nuclear reactions around the resonance energies at 404.9 and 414 keV.
The as-deposited film has an approximate composition Zr4AlO9.
Normalized excitation curves of the
18O(p,a)15N nuclear reaction around the
resonance at 151 keV before and after
thermal annealings and the used
experimental geometry.(b) Normalized 18O
concentration vs. normalized depth for
the as deposited and 18O2-annealed
samples.
Solid lines represent the as-deposited sample, empty
circles and triangles correspond to vacuum and 18Oannealed samples, respectively.
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
37
N R A
School of Ion Beam Analysis and Accelerator Applications
(a) Excitation curves of the 27Al(p,g)28Si nuclear reaction around the resonance at 404.9
keV before and after thermal annealings and the used experimental geometry.
(b) Normalized 27Al concentration vs. normalized depth for the as-deposited and vacuumannealed samples.
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
38
N R A
School of Ion Beam Analysis and Accelerator Applications
(a) Excitation curves of the 29Si(p,g)30P nuclear reaction around the resonance at 414 keV
before and after thermal annealings.
(b) Normalized 29Si concentration vs. normalized depth for the as-deposited, 18O2- and vacuumannealed samples.
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
39
N R A
School of Ion Beam Analysis and Accelerator Applications
Summary
• Isotope specific – unique tool for studying transport processes
• Absolute concentration by well-known reference samples (no
need of exact knowledge of cross section)
• Narrow resonances: almost atomic depth resolution at the
surface
13-24 March, 2006, ICTP, Trieste, Italy
G. Battistig, MTA – MFA Budapest, Hungary
40