SAFIR : Un accélérateur Van de Graaff pour l’analyse de couches minces et ultra-minces

Equipe Couches Nanométriques : Formation, Interfaces, Défauts

SAFIR

2.5 MV Van de Graaff• 1H, 2H, 3He, 4He, C,N,O etc• Stable operation down to < 150keV• Beam energy resolution 50-100eV• Several A in 2mm at target

The SAFIR Laboratory General purpose IBA chambers

•10-7 mbar•RBS, NRA, NRP, ERDA•Fast opening and pumping•Large sample holder•Goniometer chamber for channeling

UHV goniometer chamber•10-11 mbar•LEED/Auger•Channeling/Blocking•Evaoprators•Sample heating and cooling•Rare gas handling

MEIS

~10 permanent research/teaching staff3 1/3 dedicated technical staff

M eV ion beam

D etector

2 2,M Z2E

1E

0E

S am ple

of so l id ang le

1 1,M Z

1 1,M Z

2 2,M Z

• Energy loss

• PIXE

• Elastic Scattering

• Nuclear Reactions

• Narrow resonance profiling

Energy range0.1-10 MeV

Projectilesprotons, deuterons,alphas, 3He

Ion Beam Analysis (IBA)

0.0 0.5 1.0 1.5 2.0 2.5 3.01x10-9

1x10-7

1x10-5

1x10-3

1x10-1

1x101

1x103

1x105

1x107

1x109

15N(d,)13CRutherford

Experimentale28Si(p,p)28Si

18O(p,)15N

Ionisation en couche k

Evenement de perte d'énergie dans un choc p - Si

(ba

rn)

Energie (MeV)

1x10-15

1x10-13

1x10-11

1x10-9

1x10-7

1x10-5

1x10-3

1x10-1

Eve

nem

ents

(nm

-1)

Quelques sections efficaces Pour un proton dans le silicium

0.0 0.5 1.0 1.5 2.0 2.5 3.01x10-9

1x10-7

1x10-5

1x10-3

1x10-1

1x101

1x103

1x105

1x107

1x109

15N(d,)13C

Rutherford

Experimental28Si(p,p)28Si

18O(p,)15N

k-shell ionisation

energy loss event in p-Si collision

(b

arn)

Energy (MeV)

1x10-15

1x10-13

1x10-11

1x10-9

1x10-7

1x10-5

1x10-3

1x10-1

Eve

nts

(nm

-1)

The stopping power

The stopping power

x

E E-E

0limx

E dES

x dx

Units : eV cm2 atom-1

eV cm2 g-1 eV nm-1

N atoms cm-3

Density g cm-3

0 2 4 6 8 100

100

200

300

400

500

600

700

Bethe (high energy)region

velocity proportional(low energy) region

Stopping Power of 4He in Ni

-dE

/dx

(eV

/nm

)

Energy (MeV)

0

10

20

30

40

50

60

70

80

Emax

(eV

/10

15 a

tom

s.cm

-2)

0 5000 10000 150000

200

400

600

800

1000

1200

1 MeV protons in Siliconfrom SRIM2003

Ene

rgy

(keV

)

Depth (nm)

0

5

10

15

20

25

dE

/dx

(eV

/10

15 a

tom

cm

-2)

0.0 0.5 1.0 1.5 2.0 2.5 3.01x10-9

1x10-7

1x10-5

1x10-3

1x10-1

1x101

1x103

1x105

1x107

1x109

15N(d,)13C

Rutherford

Experimental28Si(p,p)28Si

18O(p,)15N

k-shell ionisation

energy loss event in p-Si collision

(b

arn)

Energy (MeV)

1x10-15

1x10-13

1x10-11

1x10-9

1x10-7

1x10-5

1x10-3

1x10-1

Eve

nts

(nm

-1)

Rutherford Backscattering Spectrometry RBS

Bague isolante

4He+ Détecteur particules

Porte échantillon

K1E0

EE

K2E0

Détecteur particules

x

xx

Atome d’Or

Atome d’Aluminium

Nombre de coups

E

RBS - principle

4He+

Energy ETrace of heavy element in a light substrate - eg Au in Si

0 E1 E2

Yie

ld

Detector

E1 = k1 EE2 = k2 E

Energy gives mass scale

Ausurface

Sisurface Au

Depth

Si Depth

Beam loses energy

Energy

Energy loss givesdepth scale

Intensity givesconcentration

21 22 22 2 4

1 21 2

1 22 4 2 2

1 2

1 ( / ) sin cos1

4 sin 1 ( / ) sin

M MZ Z ed

d E M M

Analytique !

0.2 0.4 0.6 0.80

50

Si

O

Al Cu

Cou

nts

(C

-1 m

sr-1

keV

-1)

Energy (MeV)

0.5 0.6 0.7 0.80

20

40

60

80

Al Cu

Experiment

SimulationC

ount

s ( C

-1 m

sr-1

keV

-1)

Energy (MeV)

Taken from work with R. Serna et al, Instituto de Optica, Madrid

Structure supposed for RBS simulation

Composite formed by alternate pulsed laser deposition of Cu and Al2O3.

Non-linear optical properties – amplification …

Real RBS - Cu/Al2O3

Surfaces layers, plus 7 times90x1015 cm-2 Al2O3 (10nm)45 Al2O3+30%Cu

plus120x1015 cm-2 Al2O3

32 Al2O3+70%Cu

Artificially nanostructured Cu: Al2O3 films produced by pulsed laser ablation. R. Serna, C.N. Afonso, C. Ricolleau, Y. Wang, Y. Zheng, M. Gandais, I. Vickridge. Appl. Phys. A. 71 (2000), 583-586.

From P. Skeldon et al, Corrosion Centre,University of Manchester

RBS – Anodisation of Au/Al alloy

Au/Al alloy (4.5%Au)Anodicoxide

H. Habazaki, K. Shimizu, P. Skeldon, G.E. Thompson, G.C. Wood, and X. Zhou,J. Phys. D: Appl. Phys. 30, 1833 (1997).

RBS : Performances

Sensibilité : 1014 at/cm2

Résolution en profondeur : 10 nm

Résolution en masse : 1 amu jusqu'à ~40 amu

Durée d'analyse : 5 minutes

Nécessite vide : <10-5 mbar

(conditions favorables)

0.0 0.5 1.0 1.5 2.0 2.5 3.01x10-9

1x10-7

1x10-5

1x10-3

1x10-1

1x101

1x103

1x105

1x107

1x109

15N(d,)13C

Rutherford

Experimental28Si(p,p)28Si

18O(p,)15N

k-shell ionisation

energy loss event in p-Si collision

(b

arn)

Energy (MeV)

1x10-15

1x10-13

1x10-11

1x10-9

1x10-7

1x10-5

1x10-3

1x10-1

Eve

nts

(nm

-1)

Nuclear Reactions

Nuclear Reactions

M eV ion beam

D etector

2 2,M Z2E

1E

0E

S am ple

of so l id ang le

1 1,M Z

3 3,M Z

4 4,M Z

A b so rb e r fo i l

Charged particle induced reactions : NRA Nuclear Reaction AnalysisInteraction is inelastic : internal energy needs to be included in the kinematics. NRA is isotope-sensitive

20 1 2 3 4Q M M M M c

Reaction Q (MeV)

12C(d,p0)13C 2.72

12C(d,p1)13C -0.34

16O(d,p0)17O 1.92

16O(d,p1)17O 1.05

(residual nucleus in ground state)

0n nQ Q E (residual nucleus in nth excited state, of energy En)

NRA Kinematicslab=150°, Ed=1.4 MeV, mylar foil 12m

stops 0.9 MeV 2H2.8 MeV 4He

E.g. (d,p) reactionson light nuclei

H He 6Li 7Li 9Be 10B 11B 12C 13C 14N 15N 16O 17O 18O 19F Ne Na Mg 27Al 28Si 29Si

0

1

2

3

4

5

6

7

8

9

10

Pro

ton

En

erg

ies

Target Isotope

NRACross sections

See http://www-nds.iaea.org/ibandl/, and R33 files distributed with SimNRA

• Strong variation with E0

• Strong variation with • Few reliable nuclear models

see SigmaCalc

1 2 3 40

500

1000

1500

2000

12Cp016Op

0

16Op1

Deuterons incident on anodic Ta2O

5 thin film,

with carbon contamination.

Detector at 150°, 12m mylar absorber.

Cou

nts

Energy (MeV)

NRA Thin Sample Principle

2H+

Energy (MeV)

Detector

Absorber foil

16O(d,p0)17O

16O(d,p1)17O

12C(d,p0)13O

400 500 600 700 800 900 1000 1100 12000

2

4

6

8

10

12

(m

b sr

-1)

Energy (keV)

16O(d,p1)17Olab=150°

Yie

ld

Cross section

Incident beam energy

0 50 100 150 200 250 3000

500

1000

1500

2000

2500

3000

3500

40000 1 2 3

NR

A Y

ield

(co

unts

)

Channel

12C(d,p0)

16O(d,p0)

16O(d,p1)

Energy (MeV)

Thin and Thick target NRA spectra

NRA Spectra from thin and thick Ta2O5 with small carbon contamination

NRA – isotopic profilingSimultaneous profiling of 14N and 15N via 14N(d,1)12C and

14N(d,0)13C respectively.

From I.C. Vickridge et al. Nucl. Instr. And Meth. B99 (1995) 454.

Strong nitrogen exchange between the gas and the nitride is observed.

Nitridation of a Ti6Al4V alloy : artificial hip, to improve biocompatibilty

NRA : Performances

Sensibilité : 1014 at/cm2, 0.1%

Résolution en profondeur : 100 nm

Spécificité isotopique : Elements légers (H-Si)

Durée d'analyse : 5 minutes

Nécessite vide : <10-5 mbar

(conditions favorables)

0.2 0.4 0.6 0.80

50

Si

O

Al Cu

Cou

nts

(C

-1 m

sr-1

keV

-1)

Energy (MeV)

0.5 0.6 0.7 0.80

20

40

60

80

Al Cu

Experiment

Simulation

Cou

nts

( C

-1 m

sr-1

keV

-1)

Energy (MeV)

High depth resolution IBA

2 2 2 2beam str foil detE E E E

xS

2MeV 4He in Ni x=16nm500 keV 4He in Si x=29nm

e.g. RBS, Edet= 10keV :

• Remove the detector Nuclear Resonance Profiling NRP

• Reduce Edet Electrostatic or Magnetic spectrometers MEIS

Reduce x?

0.0 0.5 1.0 1.5 2.0 2.5 3.01x10-9

1x10-7

1x10-5

1x10-3

1x10-1

1x101

1x103

1x105

1x107

1x109

15N(d,)13C

Rutherford

Experimental28Si(p,p)28Si

18O(p,)15N

k-shell ionisation

energy loss event in p-Si collision

(b

arn)

Energy (MeV)

1x10-15

1x10-13

1x10-11

1x10-9

1x10-7

1x10-5

1x10-3

1x10-1

Eve

nts

(nm

-1)

Narrow Resonance Profiling

153 152 151 150 149

FWHM ~ 100 eV

The resonance occurs at depth x in the sample

The resonance samples

the 18

O at depth x = E/dEdx

energy loss E

in the sample

energyEr + E

Beam

Sample

average beam energy in sample (keV)

18O(p,)15N resonance at 151 keV.

16O2

then

18O2

Si

exchange growth

SiO2

150 155 160 165 170 175 1800

200

400

600

800

0 200 400 600 800 1000 12000

10

20

30

40

50

60

150°lab

Q=3.98 MeV

18O(p,a0)15N

(m

b sr

-1)

Energie (keV)

149 150 151 152 153 154 155 156 157 158 159 160 161 1620.0

0.2

0.4

0.6

0.8

1.0

1.2

Ren

dem

ent

Energie du faisceau (keV)

Growth of SiC nanocrystals at the SiO2/SiC interface• Silicon with thermally grown SiO2

• 1100°C annealing under CO • Quartz furnace

SiO2

Si

13C180

SiC

SiO2

Si Epitaxial 3C - SiCCross sectional TEM image of a (100) Si/SiO2 system

annealed in 100% CO at 1 Bar at 1100oC for 2hrs

Moiré pattern

The use of 13C18O allows us to :

–observe the fate of C only from CO (13C) without being concerned with C contamination

–quantitatively determine the fate of 18O from the CO (Si16O2 matrix)

Typical excitation curve

150 152 154 156 158 160 162 1640

50

100

150

200

250

300

350 experimental excitation curve

Simulation of excitation curve

Overall 18O concentration profile Contribution of Process II Contribution of Process I Contribution of Interface

Co

un

ts

Ep (keV)

(a)

0 5 10 15 20 25 30 35 400.0

0.2

0.4

0.6

0.8

1.0

[18O

] n/[O] n

Depth (nm)

18O concentration profiles supposed for Fig 1a

Overall 18O profile Process II Process I Interface

Process I dominant

Process II dominant

Interface region

(b)

18O Excitation curves after 1100°C treatment for 90 min at 350mbar

The three regions in the 18O concentration profile reflect 3 processes

CO diffusion with exchange in volume Process I Oxygen exchange at surface Process II

+ oxygen network diffusion Oxygen incorporation at interface Process III

Si

SiC

SiO2

Volume 16O-18O exchange

CO interstitiel diffusion

Interfacereaction

Process I

Process II

An 18O study of the interaction between carbon monoxide and dry thermal SiO2 at 1100°C. Catherine Deville Cavellin, Isabelle Trimaille, Jean-Jacques Ganem, Marie D’Angelo, Ian Vickridge, Anita Pongracz and Gabor Battistig. Journal of Applied Physics (2009), 105, 033501.

Isotopic tracing study of the growth of silicon carbide nano-crystals at the SiO2/Si interface by CO annealing. A. Pongracz, Y. Hoshino, M. D’Angelo, C. Deville Cavellin, J.-J. Ganem, I. Trimaille, G. Battistig, K.V. Josepovits, I. Vickridge. Journal of Applied Physics (2009) 106, 024302.

0 20 40 60 80 100 120 1400,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

18O

/13C

at

the

inte

rfac

e

Initial oxide thickness X0 (nm)

50mb 100mb 200mb 350mb

- Simulated (13C18O/13CO)

Ratio of O to C incorporated in the interface region

18 18 0,0

0

cosh(( ) / )O ( ) O

cosh( / )g cc

x xx L

x

0

13 18

130

coshC O

CO cosh

x x

xx

13 18

0130

C O 1

CO coshx x

x

We can now confidently conclude that

for each C atom incorporated in a SiC nano-crystal, an oxygen atom is incorprated in the SiO2/Si interfacial region.

90 min, 1100°C

Electrostatic detector

Medium Energy Ion Scattering

32 3 10E

E

Semiconductor detector

p-type silicon

undepletedregion

depletedregion

deposited energy

10 keVE

1 nmx 10 nmx

46ALa2Si2O7

13ASiO2

Si(100)

Détecteur électrostatique toroïdal

permettant une analyse simultanée

en énergie (profil de composition) en angle (structure)

des ions rétro-diffusés dans les premiers nm.

120 140 160 180 200 2200

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Cou

ps

Energie (keV)

simulated O Si La

La2O3 (high k) deposited on Si, then oxidised : chemical reaction …

RBS relatively classical200keV 4He+ dét. 15keV

Medium Energy Ion Scattering

(from M. Copel et al, IBM Almaden)

MEIS : Typical example

RBS MEIS

Résolution en profondeur 10 nm 0.3 nm

Profondeur explorable 1m 20 nm

Sensibilité (at.cm-2) 1014 qqs 1012

Comparaison MEIS – RBS

MAIS : temps d’acquisition des spectres (RBS = 101 minutes, MEIS = 102 minutesdégâts induits dans l’échantillonphysique sous-jacente +compliquée, moins bien maitrisée

One important topic we have not talked about : ion channelling

600 800 1000 1200 1400 16000

200

400

600

800

1000

1200

1400

1600

1800

2000

amorphized layer~ 2000 Å thick

Channelled Random

Coun

tsEnergy (keV)

Amorphisation of Si by implantation of 29Si

But, damage …

0 20 40 60 80 100 120 140 160

1.0

1.1

1.2

1.3

1.4

1.5

1015 at.cm-2

Yie

ld/Y

0

Current density increased by factor of 4

GaSb <100>

Channeling yield for 1.4 MeV D+ beam

0 50 100 150 200 250C/mm2

Augmenter l'angle solide des détecteurs de particules, sans perdre en résolution en énergie

Réduire dose nécessaire pour obtenir spectres utiles

(Aussi polymères, hydrogène …)

Design and build large area segmented particle detectors.

16 spectra collected simultaneously, at various angles

20 to 40 times greater solid angle for detection

Spectroscopic tests underway in Rossendorf. Installation at INSP at end 2010 probably…

Détecteurs pour tests

Matrice de 16 détecteurs pour RBS

Matrice de 16 détecteurs pour ERDA (détection H)