1
Materials research with ion beamsMaterials research with ion beamsbeam-induced material modifications
• track formation• damage analysis• threshold• sputtering
5 nm
single ion track irradiated epoxy foilssurface tracks
nanotechnology
nanowiresnanopores biosensors
Christina Trautmann, Materialforschung, GSI
2
targetarea
irradiation sites 100 m
ESRexperimentalstorage ring
SISheavy ion synchrotron
80 - 2000 MeV/uion range ~ 10 cm
FRSfragment-separator
UNILACuniversal linear ion accelerator
3.6 - 13 MeV/uion range ~ 100 µm
HLIhigh charge state injector
1.4 MeV/uion range ~ 10 µm
GSI Accelerator Facilities
beamline XO & microprobeE = 11.4 MeV/u
R ~ 100 µm
Irradiation Experiments forMaterials Research
ion species ..C…Xe...Ufluence 1 ...109... 1013 ions/cm2
Irradiation Experiments forMaterials Research
ion species ..C…Xe...Ufluence 1 ...109... 1013 ions/cm2
cave AE = 1-2 GeV/u
Range: mm-cm
3
ion beamsion beamskinetic energy: kinetic energy: MeVMeV-- GeVGeV
10% of velocity of light10% of velocity of light
10 nm
4
Single ion tracks produced in amorphisable insulators@ ~ 10 MeV/u heavy ions
Au-ion trajectory in high Tc superconductor cross section of Pb-ion track in mica
10 nm
J. Vetter et al., NIMB 141 (1998) 747
range ~100 µm
J. Wiesner et al., Physica C 268 (1996) 161
5
5 100
1 101
1.5 101
2 101
2.5 101
3 101
3.5 101
4 101
10-4 10-3 10-2 10-1 100 101 102 103
ener
gy lo
ss (k
eV/n
m)
specific energy (MeV/u)
energy (MeV)10-2 10-1 100 101 102 103 104
energy depositionelectronic stopping
nuclear stopping~ 1 keV/u
~MeV/u
SRIM-code
trackdefect clusters - amorphisation
target atoms
atomic collision cascade
defects
target electrons
electron cascade
coupling to lattice
10-17 - 10-16 s
10-15 - 10-14 s
10-13 - 10-11 s
6
5 100
1 101
1.5 101
2 101
2.5 101
3 101
3.5 101
4 101
10-4 10-3 10-2 10-1 100 101 102 103
ener
gy lo
ss (k
eV/n
m)
specific energy (MeV/u)
energy (MeV)10-2 10-1 100 101 102 103 104
energy depositionelectronic stopping
nuclear stopping~ 1 keV/u
~MeV/u
SRIM-code
elastic collisions
vacancies & interstitials
important material parameter =displacement energy
target atoms
atomic collision cascade
defects
7
5 100
1 101
1.5 101
2 101
2.5 101
3 101
3.5 101
4 101
10-4 10-3 10-2 10-1 100 101 102 103
ener
gy lo
ss (k
eV/n
m)
specific energy (MeV/u)
energy (MeV)10-2 10-1 100 101 102 103 104
energy depositionelectronic stopping
nuclear stopping~ 1 keV/u
~MeV/u
SRIM-code
electroncascade
trackdefect clusters - amorphisation
target electrons
electron cascade
coupling to lattice
10-17 - 10-16 s
10-15 - 10-14 s
10-13 - 10-11 s
8
linear energy loss of different ionslinear energy loss of different ions
0
5
10
15
20
0 5 10 15
elec
troni
c en
ergy
loss
(keV
/nm
)
spezific energy (MeV/nucleon)
polycarbonate
A
A
dE/dx ~ Z2eff (ion) . Z(target)
X
U
Xe
Au
Kr
Ar
SRIM code
UNILAC high energy
0.0
0.5
1.0
1.5
0 20 40 60 80 100
Ar PC 1000MeV/u data 17:35:56 Uhr 21.01.
stop
ping
pow
er (k
eV/Å
)
Energy (MeV/nucleon)
Ar
U
Xe
9
linear energy loss of different ionslinear energy loss of different ions
0
5
10
15
20
0 5 10 15
elec
troni
c en
ergy
loss
(keV
/nm
)
spezific energy (MeV/nucleon)
polycarbonate
A
A
dE/dx ~ Z2eff (ion) . Z(target)
X
U
Xe
Au
Kr
Ar
SRIM code
UNILAC
10-1
100
101
102
10-1 100 101 102 103
ener
gy d
ensit
y (e
V/a
tom
)
specific energy (MeV/u)
×
energy density
Track formation models
microscopic
molecular dynamic calculations: ab initio lattice calculations
• electron subsystem not included• interatomic potential?• large computing times!
macroscopic
Coulomb explosion: screening time by electronsfew quantitative calculations
++
++ +
+
+
++
[Fleischer et al., J. Appl. Phys. 36 (1965) 3645][Lesueur et al., Rad. Eff. Def. Sol. 126 (1993) 135]
thermal spike: local melting and quenchingtransient thermodynamics?
[Desauer, Z. Physik 38 (1923) 12][Seitz and Köhler Sol. St. Phys. 2 (1956) 305][Lifshitz et al. J. Nucl. Ener. A12 (1960) 69]
[Beuve et al.PRB 68 (2003) 125423 ][Bringa NIMB 203 (2003) 1]
Scheme of two-step process for track formationenergy deposition
electronic excitation & ionization‘hot’ electrons10-17 - 10-16 s
electron cascade
energy diffusion in electronic subsystemcooling of hot electrons
'cold' lattice10-15 - 10-14 s
10-13 - 10-12 s
electron-phonon interaction Coulomb explosion
energy diffusion to atomslattice heating
melting
thermal spikequenching of atomic disordermetals ~ 10-12 sinsulators ~ 10-10 s fast cooling of atoms
defect formation
Scheme of two-step process for track formationenergy deposition
10-17 - 10-16 s
10-15 - 10-14 s
10-13 - 10-12 s
electronic excitation & ionization‘hot’ electrons
electron-phonon interaction
thermal spikequenching of atomic disordermetals ~ 10-12 sinsulators ~ 10-10 s
electron cascade
energy diffusion in electronic subsystemcooling of hot electrons
'cold' lattice
energy diffusion to atomslattice heating
melting
fast cooling of atomsdefect formation
Coulomb explosion
electronic energy loss regime
important material properties:
• electric (number & mobility of electrons)
• thermal conductivity
• electron – phonon coupling
Inelastic Thermal Spike Model
electron-phonon coupling
),()()(1)( trATTgrTTrK
rrtTTC ae
eee
eee +−−⎥⎦
⎤⎢⎣⎡=
∂∂
∂∂
∂∂
)()(1)( aea
aaa
aa TTgrTTrK
rrtTTC −+⎥⎦
⎤⎢⎣⎡=
∂∂
∂∂
∂∂
Electrons
Atoms
two-temperature model~ ion energy loss
C = specific heat capacityK = thermal conductivity
metals: Wang et al., J. Phys. : Condens. Matter 6 (1994) 6733Dufour et al. Bull. Mater. Sci. 22 (1999) 671
insulators: Toulemonde et al., Nucl. Instr. Meth. B166-167 (2000) 903
Thermal Spike Code available: Toulemonde (CIMAP, Caen) or Stoquert (PHASE, Strasbourg)
Diffusion & Transfer of Energy - Thermal Spike
102
103
104
10-16 10-15 10-14 10-13 10-12 10-11
time (s)
103
104
105
106
g = 2/λ2 =1.4 1013 W cm-3 K-1
tem
pera
ture
(K)
tem
pera
ture
(K)
Xe (1.1 MeV/u) → LiF, dE/dx =15 keV/nm
electrons
atoms
10 nm
15 nm
6 nm
3 nm
1 nm
Tmelt
Tvap
1 nm
3 nm
6 nm
10 nm
15 nm
electronic subsystem
( ) ( ) ( ) ( )trATTgrTTKr
rrtTTC e
eee
eee ,1
+−⋅−⎟⎠⎞
⎜⎝⎛=
∂∂
∂∂
∂∂
electron-phonon interaction
( ) ( ) ( )TTgrTTKr
rrtTTC e −⋅+⎟
⎠⎞
⎜⎝⎛=
∂∂
∂∂
∂∂ 1
atomic subsystem
Toulemonde et al. NIMB 167-167 (2000) 903
15
Electron-phonon coupling: λ
0
5
10
0 5 10 15
amorphisablenon amorphisable
λ (n
m)
Band gap energy (eV)
SiO2
Y3Fe5O12
high TC
GeS
LiF
High Tc
BaFe12O19
GeSY3Fe5O12
SnO2
LiNbO3
Gd3Ga5O12
UO2
Y2O3
Y3Al5O12
SiO2
CaF2
LiF
Toulemonde, Dufour, Paumier, Meftah, NIM B166-167 (2000) 903
16
Track formation and defectsin different materials
• metals• semiconductors• insulators
17
Material sensitivityMaterial sensitivity(phenomenological)
high sensitivity low sensitivity
~1 keV/nm ~20 keV/nm ~50 keV/nmdE/dxthreshold
semi-conductors metalsinsulators
☺ amorphous Si
☺ GeS, InP, Si1-xGex
Si, Ge
☺ amorphous alloys
Fe, Bi, Ti, Co, Zr
Au, Cu, Ag…
☺ polymers
☺ oxides, spinels
☺ ionic crystals
diamond
18
track size and energy loss thresholdtrack size and energy loss threshold
0
20
40
60
80
100
0 10 20 30 40
dam
age
cros
s se
ctio
n (n
m2 )
energy loss (keV/nm)
SiO2mica
LiFAl2O3
CaF2
19
Damage morphologyDamage morphology
inhomogeneous
discontinuous
homogeneous cylinder(R ≥ 3 nm)
spherical1
2
3
4
5
6
0 10 20 30
Tra
ck r
adiu
s R
e (n
m)
dE/dx (keV/nm)
Y3Fe5O12
Jensen, NIMB (1998)
20 nm
Si50Ge50
Gaiduk PRB (2003)
CaF2
Toulemonde et al., Sol. State Phen. 30/31 (1993) 477
20
discontinuous tracks in Ti
Dunlop et al. NIM B 112 (1996) 23
850 MeV Pb Ti
50 nm
30 MeV C60 Ni3Bamorphous tracks
Dunlop et al. NIM B 146 (1998) 222
structural changes in intermetallic compound NiTi
Barbu et al., NIMB 145 (1998) 354
Tracks in metals
sensitive metalspure metals: Fe, Ti, Co, Zr, Bimetallic compounds: NiB, FeCrNi, TiNi, etcmetallic glasses: PdSi, FeB, etc
insensitive metalsNb, Cu, Ni, Pt,W, Ag, Pd, Au
21
Tracks in semiconductors
22
no tracks in Si by monoatomic ions (up to U ions)but amorphous tracks by C60 clusters
30 MeV C60 clusters (111) Si
Dunlop et al., NIMB 146 (1998) 302Canut et al., NIMB 146 (1998) 296
23
discontinuous tracks in semiconducting compounds
Gaiduk et al, PRB 66 (2002) 045316Physica B 340 (2003) 808 L. Chadderton
InP
100 nm
SixGe1-x
0
1000
2000 (b)
Mob
ility
(cm
2 /V s
)
0
5
10
15
0 20 40 60 80 100
(c)
Ge content in alloy (at%)
1/k
(cm
K/ W
)
108
109
1010
1011
rows
single dots
(a)
Sur
face
Den
sity
(cm
-2)
Ge content
elec
tron
mob
ility
de
fect
den
sity
ther
mal
res
istiv
ity
Si50Ge50
24
amorphous tracks in narrow bandgap GeS
(0 1 0) plane
layered structure, Eg = 1.65 eV
lattice constants: a = 0.429 nmc = 0.365 nm 2.7 GeV U GeS
Vetter et al., NIMB 91(1994) 129
25
Tracks in carbon-based materials
26
Graphite (highly oriented pyrolytic, HOPG)
a=2.46Åc=6.70Å
30 nm x 30 nm5 nm
U (2710 MeV)
15 nm x 15 nm
Xe (475 MeV)
50 nm x 50 nm
U (2640 MeV)
Pt-Ir
bias ~250 mV
const I~1 nA
Scanning tunneling microscopy(STM)
Liu et al, PRB 64 (2001) 184115NIMB 212 (2003) 303
27
track diameter in HOPG
0 5 10 15 20 25 300
1
2
3
4
diam
eter
(nm
)
energy loss (keV/nm)
22Ne 58Ni 70Zn 132Xe 136Xe 238U 238U
track formation efficiency
0 5 10 15 20 25 30
10-2
10-1
100
yiel
denergy loss (keV/nm)
22Ne 58Ni 70Zn 132Xe 136Xe 238U 238U
• extremely small track diameters• 100% track efficiency only above ~18 keV/nm
AFM measurements
Ion tracks diameter in DLC
sp3-bonds: 70 - 80 %
n++-SiDLC 100 nm
ions
1 GeV U-ions (5x109 cm-2) DLC
topography current mapping
U = 150 mV
(U = 0.35 V (AFM tip – substrate)max. current = 98 nAcurrent density ~ 1x105 A/cm2
conductivity ~ 2.8 S/cm.
I-V diagram of single track and off-track regions
0,0 0,2
0,1
1
10
100
curre
nt /
nA
bias voltage / V
on track off track
A
off track
-1,0 -0,5 0,0 0,5 1,0-0,10
-0,05
0,00
0,05
0,10
curr
ent /
A
bias voltage / V
I-V diagram (1011 ions/cm2)
30
possible field emitting device
31
N
O
O
N
O
O
O
noutgassing of small molecules (COn, CnHm,...)
creation of unsaturated bonds (e.g. -C ≡ C, -C=C)
graphitization
Polymers• chain scission• cross linking• formation of radicals• amorphisation etc
graphitization of Kapton increasing as a function of ion fluence
32
Infrared spectroscopy: unsaturated bonds
Kr (720 MeV) Kapton
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
22002400260028003000320034003600
wavenumber [cm-1]
abso
rban
ce
virgin1012 ions/cm2
3x1012 ions/cm2
6x1012 ions/cm2
(-C ≡ C)
(-C ≡ N)-
Steckenreiter et al. J. Polym. Sci. A37 (1999) 4318
Defect creation in ionic crystalsDefect creation in ionic crystalsLiF, NaCl, KCl, MgF2, CaF2, BaF2
lithium fluoride non-amorphisable !!
fcc lattice, Eg=14.6 eVcleaving along (100) plane
F Li4.03 Å
- ++ - ++-
++ -++- ++
-++ ++ - ++
- ++ - ++ ++ -++- ++ - ++ - ++ ++
- ++ ++ - ++ -++- ++
-++ - ++ ++
- ++ - ++ ++ -++- ++ - ++ - ++ - ++
e-e-
e-
F-center
F2-center
H-centerVK-center
electron centers
hole centers
color centers
Frenkel pair
Spectroscopy of color centersSpectroscopy of color centers
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
200 300 400 500 600
optic
al a
bsor
banc
e
wavelength [nm]
2 x 1011 Bi/cm2
6 x 109 Bi/cm2
F3
F4F4
F3F
F2
LiF crystalLiF crystalirradiated with Bi ions
virgin
2 6 MeV/u
overlappingeffects
single tracks
Schwartz et al. Phys. Rev. B 58 (1998) 11232
Aggregation of single defectsAggregation of single defects
nF-clusters +metal colloids
electron center (F-centers )
Fn -centers Vn -centers
hole center (H- or V-centers )
nX0-clusters +halogen molecules
!! temperature !!
!! dose !!
defect aggregates
Scheme of track damage in Scheme of track damage in LiFLiF
×
ionizations
MC calculations by S. Bouffard
core (aggregates)
radius 1-2 nm
energy ~ 0.3 Etot
halo (single defects)
radius 10-40 nm
energy ~ 0.7 Etot
37
Ion-induced bulk modifications
volumeexpansionvolume
expansion
stressstress
dislocationsdislocationsfragmentationfragmentation
bondbreaking
bondbreaking
out-gassing
out-gassing
amorphisationamorphisationdefect
aggregatesdefect
aggregates
38
Ion-induced surface processesscanning force microscopy
amorphous metallic alloyFe85B15 ionic crystal CaF2
0
10 nm
50150
100200 nm
polymer (PMMA)10 nm
500 nm
α = 0º45º 79º 10 nm
300 nm
Audouard, NIMB 146 (1998)
Khalfaoui NIMB (2005)
ρmatrix ρtrack>
Papaléo, NIMB 206 (2001)
39
Swelling and stress due to phase change and/or defects
quartz (1 mm)
profilometryirradiation
Xe (450 MeV) → quartz (range = 30 µm)
-3
-2
-1
0
1
0 2 4 6 8 10
step
hei
ght (
µm)
1012 cm2
-8
-6
-4
-2
0
0 2 4 6 8 10
step
hei
ght (
µm)
scan length (mm)
1.2 1013 cm2
~ 4 µm
40
ion-induced swelling
0.0
0.2
0.4
0.6
0.8
1.0
0 2 1011 4 1011 6 1011 8 1011 1 1012 1.2 1012
step
heig
ht (µ
m)
fluence (ions/cm2)
Pb (4 MeV/u)
SiO2
LiF
CaF2
Y3Fe5O12
0.0
0.2
0.4
0.6
0.8
1.0
0 2 1011 4 1011 6 1011 8 1011 1 1012 1.2 1012
step
heig
ht (µ
m)
fluence (ions/cm2)
Pb (4 MeV/u)
SiO2
LiF
CaF2
Y3Fe5O12
threshold effect
10-17
10-16
10-15
10-14
0 5 10 15 20 25no
rmal
ized
step
per
ion
(cm
2 )mean energy loss (keV/nm)
LiF
scales with range of ionssaturates at high fluencesincreases with electronic energy lossoccurs above a dE/dx threshold Trautmann et al., PRB 62 (2000)13
41
before irradiation
Beam-induced grain breaking
0
10
20
30
40
0 5 1011 1 1012 1.5 1012 2 1012
grai
n si
ze (n
m)
Fluence (ions/cm2)
4 MeV/u Pb CaF2 powder
in-situ X-ray diffraction
evolution of (111) peak width
100 nm
1012 cm-2
40 nm 20 nm grainsBoccanfuso, thesis CIRIL
42
Use of diamonds in irradiation experiments
Solids under extreme conditions
simultaneous or sequential exposure
Motivation: Materials Science & Geosciences
Geo- and thermochronology
Minerals exposed to high pressure and temperature
Earth’s interior:
25 °C/km and 50 MPa/km
influence of pressure on fission track formation?(e.g. track length → dating)
can fission fragments induce specific phase transitions?
1 GPa = 10 kbar
45
diamond anvil cell (DAC)
diamondgasket(250 µm)
ruby(pressure reference)
pressuremedia
apply pressure
Bassett et al.,Rev. Sci. Instrum. 64 (1993)
5 cm
200 µm
Irradiation experiments with pressurized samples
relativistic ions (e.g., Au, Pb, U
relativistic ions (e.g., Au, Pb, U
PhysicsWeb 5/2006Phys. Rev. Lett. 96 (2006)
"Heavy ions feel the squeeze"
Irradiation experiments with samples pressurized in diamond anvil cells (DAC)
relativistic ions (e.g., Au, Pb, U
relativistic ions (e.g., Au, Pb, U
intense photoluminescence
pressure remained constant in cell(up to > 50 GPa and 5×1012 ions/cm2)
no instantaneous diamond failure
!!! but after several beamtimes:
coloration
risk of diamond fragmentation (stress??)
intense photoluminescence
pressure remained constant in cell(up to > 50 GPa and 5×1012 ions/cm2)
no instantaneous diamond failure
!!! but after several beamtimes:
coloration
risk of diamond fragmentation (stress??)