Ion Beam Analysis Part 1 Henri I. Boudinov Instituto 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

Outline 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

Porto Alegre Ion Beam Centre established 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 1m resolution to 10m depths

Porto Alegre Ion Beam Centre 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

Ion Beam for: Ion Beam Modification of Materials Ion Beam Analyses Material Science Solid State Physics Atomic and Molecular Physics Ion Beam Modification of Materials Ion Beam Analyses Basic Physics

Penetration of the Radiations in Solids Charged Particles Electrons: e-, e+, b-, b+ 10m Ions: p+, He++ (a), etc.. 1m Uncharged Particles X-rays and g-rays 10cm neutrons 10cm

Ion Implanter

3MV Tandetron accelerator

Penetration of charged particles through matter E. Rutherford, 1911 N.Bohr, 1913-54, 1948 E. Fermi, 1924- H.A. Bethe, 1930- F. Bloch, 1933- L. Landau, 1944- .... 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,...

dE/dx = N.S Stopping Power dE/dx – energy loss [eV/nm] N – atomic density [nm-3] S – stopping power [eV.nm2]

dE/dx : two types

Low energies vion << ve : the electrons shield (passive) Elastic Collisions The ion lose energy to move the target atoms Nuclear Stopping Power Classic

High energies vion ~ ve : active electrons (ionization/excitation, plasmons,...) Inelastic Collisions 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

Coupled-Channel Calculations Results from Coupled-Channel Calculations proton (b=1) on H(1s)

Coupled-Channel Calculations Results from Coupled-Channel Calculations anti-proton (b=1) on H(1s)

Transition from electronic to nuclear stopping power

Penetration of Ions in Silicon 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, ... Auger electron spectroscopy (AES) Secondary ion mass spectroscopy (SIMS) X-ray fluorescence spectroscopy (XRF) Electron microprobe analysis (EMA)

Ion Beam Analysis (IBA) RBS Energy of recoiling protons give element composition and elemental depth profiles STIM Measure the energy loss of transmitted ions to map density variations Sample 1 – 3 MeV proton beam PIGE Nuclear reactions give characteristic gamma rays from light nuclei (e.g. Li, B, F) PIXE Characteristic X-ray emission Simultaneous part-per-million detection of trace elements from Na to U

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 Incident Ion Sample To detector C O Na Cl RBS Spectrum of 2mm 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)

K = E1 /E0 E1 E0

E1 = K E - dE/dx(out) x / cos q2 E = E0 – dE/dx(in) x / cos q1 E1 = K E - dE/dx(out) x / cos q2 K E0 - E1 x = K dE/dx(in) / cos q1 + dE/dx(out) / cos q2

RBS profiling

Fluctuations 1 Physics 2 3 Dx number of collisions impact parameter charge state ... 1 Physics 2 3 roughness detector parameters beam spot .... Forte dependencia nas condições iniciais. Part. 1 sofre mais colisões que a part. 3. Mas isto não significa que a primeira perderá mais energia. Uma única colisão violenta (tipo head on) pode afetar muito mais a trajetória que milhares de colisões tipo soft. Dx

Energy straggling Beam spot Multiple scattering Detector aceptance

monocrystal

Thin Film Analysis Structural information (near surface region) Increased sensitivity to light impurities

Surface Peak A aplicação de feixes de íons para estudar a estrutura de superfícies depende 1) medida acurada do pico de superfície 2) capacidade de prever (simular) esta estrutura para uma dada superfície. RBS MEIS

MEIS Si peaks: SIMOX better than Si As+ 20keV, 5E14 cm-2 + annealing: RTA better than FA As+ 20keV, 5E14 cm-2 + annealing: RTA 1000C/10s or FA 950C/15min

Rutherford backscattering spectrometry (RBS) 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

Elastic Recoil Detection Analysis

Proton Induced X-ray Emission Analogous to EDS using MeV protons No primary bremsstrahlung, so low detection limits (1-10ppm) Can be made quantitative Fe Cu Zn K Ca PIXE

PIXE Target (Ca) Beam Detector Counts Electronics K K Energy

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) ^0 ^1 ^2 ^3 100 300 500 700 900 1100 1300 1500 1700 f:\pc_users\jpn\971118\490001g4._ : Tourmaline std: GRR573 F B10 Al Li Na Tourmaline standard GRR573 PIGE

Nuclear Reaction Analysis (NRA) p + 18O 15N + 4He

Nuclear Microscopy All types of data can be collected simultaneously

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 30m). (No chemical information) STIM STIM image of the leg and claw of a wasp showing internal detail