Henri I. BoudinovInstituto de Física, Universidade Federal do Rio Grande do Sul

Porto Alegre, RS, Brazil

henry@if.ufrgs.br

26_10_2009 NanoSYD, MCI, SDU, Sønderborg , Denmark

Ion Beam AnalysisPart 1

• The Porto Alegre Ion Beam Centre• Interaction of ions with matter• Stopping power• Rutherford Backskattering Spectrometry (RBS)• Channeling• Compositional and defect depth profiles• Proton Induced X-ray emission (PIXE)• Nuclear Reaction Analysis (NRA)• Microbeam analysis

Outline

Porto Alegre Ion Beam Centreestablished in 1981• Controllable Materials Modification

• Facilities• 0.2-3MV Tandetron• 30-500kV Single Ended Implanter• 10-250kV Medium Current Implanter• Implantation 10keV ~15MeV (up to 1mA)• Sample size up to 10cmx10cm• Hot (800oC) or cold (~LN)

• Applications• Ion Beam Synthesis

• Buried and surface oxides and silicides• Nanocristals

• Ion Implantation• Defect Engineering• Proton beam lithography

• potentially 1m resolution to 10m depths

• Advanced Materials Analysis• Facilities

• 3MV Tandem• Techniques include RBS, MEIS, ERDA, PIXE,

NRA• Channelling Spectroscopy for damage

analysis• Fully automated collection and analysis• Micro-beam with full scanning• External Beam for vacuum sensitive samples

• Applications• Thin Film Depth Profiling• Compositional Analysis• Disorder Profiling of Crystals• 3-D elemental composition and mapping

Porto Alegre Ion Beam Centre

• Ion Beam Modification of Materials

• Ion Beam Analyses

• Basic Physics

Ion Beam for:

• Material Science• Solid State Physics• Atomic and Molecular Physics

• Charged Particles• Electrons: e-, e+, b-, b+ 10m• Ions: p+, He++ (a), etc.. 1m

• Uncharged Particles• X-rays and g-rays 10cm• neutrons 10cm

Penetration of the Radiations in Solids

Ion Implanter

3MV Tandetron accelerator

E. Rutherford, 1911N.Bohr, 1913-54, 1948E. Fermi, 1924-H.A. Bethe, 1930-F. Bloch, 1933-L. Landau, 1944-

....

Penetration of charged particles through matter

Experimental ingredients

Ions : Z1=-1,1,2,...~100, electrons, muons, clusters,...

energies ~1eV – 1011 eV

Target : Z2 = 1,2,.. ~100, solids, gases, liquids, plasma,...

Bohr, Bethe,...

Stopping Power

dE/dx = N.SdE/dx – energy loss [eV/nm]

N – atomic density [nm-3]

S – stopping power [eV.nm2]

dE/dx : two types

vion << ve : the electrons shield (passive)

Elastic Collisions

Low energies

The ion lose energy to move the target atoms

Nuclear Stopping Power

Classic

vion ~ ve : active electrons (ionization/excitation, plasmons,...)

Inelastic Collisions

High energies

The ion lose energy to the electrons of the target

Electronic Stopping Power

Quantum

Electronic Energy loss (high energies)

Classical theory

dE/dx ~Z12 ln (|Z1|)

for Z1/v >> 1

Quantum theory

dE/dx ~Z12

First-order : for Z1/v <<1

Results from

Coupled-Channel Calculations

proton (b=1) on H(1s)

Results from

Coupled-Channel Calculations

anti-proton (b=1) on H(1s)

Transition from electronic to nuclear stopping power

Penetration of Ions in Silicon

10-3 10-2 10-1 100 101 102 103 104 10510-3

10-2

10-1

100

101

(dE/dx)e

(dE/dx)n

E3

E2E1

dE/d

x (e

V/io

n/A)

E(keV)

Target Si

ion mass E1 E2 E3 He 4 0,5 keV 2 keV 0,5 MeV B 11 3 keV 17 keV 3 MeV As 75 73 keV 800 keV 200 MeV Bi 209 530 keV 6000 keV 2000 MeV

• Energy Loss

The Stopping and Range of Ions in Matter

Software SRIM

Materials Radiation Analysis Concept

• AES (electron in and out)• RBS, MEIS, LEIS, ISS (ion in and out)• XRF (X-ray, in and out)

• XPS (X-ray in, electron out)• SEM/EDS (electron in, X-ray out)• SIMS and ERDA(ion in, target out)• PIXE (ion in, X-Ray out)

• PIGE, NRA, ...

STIMMeasure the energy

loss of transmitted ions to map density

variations

PIGENuclear reactions give characteristic gamma rays from light nuclei (e.g. Li, B, F)

RBSEnergy of recoiling protons give element composition and elemental depth profiles

Ion Beam Analysis (IBA)

PIXECharacteristic X-ray emissionSimultaneous part-per-million detection of trace elements from Na to U

Sample

1 – 3 MeV proton beam

Rutherford BackScattering

• Energy of ions recoiling from nuclear collisions depends on mass and depth

• Measure light elements (C,N,O) and thickness or depth profiles

• MDL around 0.1%, but can be used to help quantify PIXE

Sample

Incident Ion

To detector

C

ONa

Cl

RBSSpectrum of 2m diameter marine aerosol particle showing sodium and chlorine and carbon and oxygen from the plastic support film

Backscattering Spectrometry

Yield • Concentration

Energy • Element (K)• Depth (dE/dx)

E1

E0

K = E1 /E0

x

KE

E

E1

E0

2

1

E = E0 – dE/dx(in) x / cos 1

E1 = K E - dE/dx(out) x / cos 2

K E0 - E1x =K dE/dx(in) / cos 1 + dE/dx(out) / cos 2

RBS profiling

Fluctuations

Dx

1

2

3

i. number of collisions

ii. impact parameter

iii. charge state

iv. ...

i. roughness

ii. detector parameters

iii. beam spot

iv. ....

Phys

ics

Multiple scattering

Detector aceptance

Energy straggling

Beam spot

0 2 4 6 8 100

2

4

6

8

10

E1 KE0

Cou

nts

Energy0 2 4 6 8 10

0

2

4

6

8

10

E1 KE0

Cou

nts

Energy0 2 4 6 8 10

0

2

4

6

8

10

E1 KE0

Cou

nts

Energy0 2 4 6 8 10

0

2

4

6

8

10

E1 KE0

Cou

nts

Energy

monocrystal

Thin Film Analysis1. Structural information (near surface region)

2. Increased sensitivity to light impurities

Surface Peak

240 260 280 300 3200

5000

10000

15000

20000

random channeling <100>

He+(1.2 MeV) SIMOX

Cou

nts

Channel55 60 65 70 75 80 85 90

0

100

200

300

400

500

600

H+ (100keV) + SIMOX

High resolution

Cou

nts

keV

RBS MEIS

MEIS

0.0

0.5

1.0

1.5

2.0

2.5

75 80 85 90 95 1000.0

0.5

1.0

1.5

2.0

2.5

O

Si

As

RTA 1000ºC/10s

SIMOX Si

Cou

nts

FA 950ºC/15min

SIMOX Si

Energy (keV)Si peaks: • SIMOX better than Si• RTA better than FA

As+ 20keV, 5E14 cm-2 + annealing:

RTA 1000C/10s or FA 950C/15min

• Nondestructive and multielemental analysis technique • Elemental composition (stoichiometry) without a standard (1-5%

accuracy). • Elemental depth profiles with a depth resolution of 5 - 50

nanometers and a maximum depth of 2 - 20 microns. • Surface impurities and impurity distribution in depth (sensitivity

up to sub-ppm range). • Elemental areal density and thus thickness (or density) of thin

films if the film density (or thickness) is known. • Diffusion depth profiles between interfaces up to a few microns

below the surface. • Channeling-RBS is used to determine lattice location of impurities

and defect distribution depth profile in single crystalline samples

Rutherford backscattering spectrometry (RBS)

Elastic Recoil Detection Analysis

Characteristic X-rayphoton

Ejected electron

PIXE

Proton Induced X-ray Emission

• Analogous to EDS using MeV protons

• No primary bremsstrahlung, so low detection limits (1-10ppm)

• Can be made quantitative

FeCu Zn

K

Ca

Beam

Target(Ca)

Detector

Electronics

Counts

EnergyKa Kb

PIXE

0 2 4 6 8 10 12 14 161

10

100

1000

10000

100000

1000000

Sr

RbKb

RbKa

PbLb

ZnKbPbLa

ZnKaCu

Ni

FeKb

FeKa

Mn

Cr

TiKb

TiKa

CaKb

CaKaK

S

Si

Al

Mg

Na

Cou

nts/C

Energy (keV)

Buffalo River Sediment (NIST 8704)

Applications Microelectronics Environmental sciences Food processing Biological tissues Biotechnology Archaeology - Art Earth Sciences

Proton Induced Gamma Ray Emission

• MeV protons can tunnel through the Coulomb barrier of light nuclei to induce gamma emitting nuclear reactions

• Gamma energy is characteristic of specific isotopes

• Detection limits ~ 0.1 %• Useful for specific problems (e.g. F19,

B10/B11)

p F19

a

O16

IntermediateNe20 nucleus in

excited state

Decays to O16 + alphaparticle and emits

characteristic gamma raysg

Ne20

F19(p,ag)O16

^0

^1

^2

^3

100 300 500 700 900 1100 1300 1500 1700

f:\pc_users\jpn\971118\490001g4._ : Tourmaline std: GRR573

F F

B10 Al AlLi

Na

Tourmaline standard GRR573

PIGE

ERE ER

Nuclear Reaction Analysis (NRA)

p + 18O 15N + 4He

Nuclear Microscopy

LensBeam fromAccelerator

Scanningsystem

Map arrayY

X

Sample

Detectors

Image incomputermemory

• All types of data can be collected simultaneously

STIM

Scanning Transmission Ion Microscopy

• Energy loss of transmitted ions depends on thickness and density.

• Use energy loss mapping to image the structure of thin samples (up to 30m).

• (No chemical information)

EnergyHigh

Low

STIM image of the leg and claw of a wasp showing internal detail