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??)