SIMS & NDT

Lecture- 9 simS Ndt SIMS Basic principles Instrumentation 令 Mass resolution Modes of analysis 令 Applications Non-Destructive AnalysiS (NDa) or Non-Destructive Testing(NDT)

Lecture-9 SIMS & NDT • SIMS ❖ Basic Principles ❖ Instrumentation ❖ Mass Resolution ❖ Modes of Analysis ❖ Applications • Non-Destructive Analysis (NDA) or Non-Destructive Testing (NDT)

Instrumentation Bombardment of a sample surface with a primary ion beam followed by mass spectrometry of the emitted secondary ions constitutes secondary ion mass spectrometry (sims). Ion Sources lon sources with electron impact ionization -Duoplasmatron: Ar, O2, o- Ion sources with surface ionization- Cst ion sources lon sources with field emission -Gat liquid metal ion sources Mass Analyzers Vacuum<10-6 torr Magnetic sector analyzer Quadrupole mass analyzer · Time of flight analyzer Ion Detectors Fa p araday cu Dynode electron multiplier Ion detectors Mass analyzers lon sources SIMS CAMECA 6F Mass analyzers http://www.youtube.com/watch?v=i0-kcjxznlstow1:50

Instrumentation SIMS CAMECA 6F Ion Sources • Ion sources with electron impact ionization - Duoplasmatron: Ar+ , O2 + , O- • Ion sources with surface ionization - Cs+ ion sources • Ion sources with field emission - Ga+ liquid metal ion sources Mass Analyzers • Magnetic sector analyzer • Quadrupole mass analyzer • Time of flight analyzer Ion Detectors • Faraday cup • Dynode electron multiplier Ip Is Ion sources Ion detectors Mass Analyzers Mass analyzers Vacuum < 10−6 torr http://www.youtube.com/watch?v=IO-KCjxznLs to~1:50 Bombardment of a sample surface with a primary ion beam followed by mass spectrometry of the emitted secondary ions constitutes secondary ion mass spectrometry (SIMS)

Cs ion source Duoplasmatron ion source 23456789 Primary beam mass filter Cameca Sims Immersion lens Sample 1011-12 Dynamic emittance matching A Transfer lens system B Liquid metal source Entrance slit s 9 Ga 10. 900 electrostatic analyzer 8 11. Energy slit S 12. Intermediate lens 1 7 13. 900 magnetic sector 14. Exit slit S3 15. Projection lenses 16. Projection deflector 17. Channelplate Accelerating voltage 19 18. Fluorescence screen Secondary ions have low kinetic 18 19. Electron multiplier energies from zero to a few 20. Faraday cup hundred ev. 1, L2 and L3-electromagnetic lens vww. eaglabs com/mc/sims-instrumentation html

Cameca SIMS Accelerating voltage Secondary ions have low kinetic energies from zero to a few hundred eV. L1 , L2 and L3 - electromagnetic lens http://www.eaglabs.com/mc/sims-instrumentation.html

Energy Analyzer and Mass spectrometer esa bends lower energy ions more strongly than higher energy ions. The sputtering process produces a range of ion energies. An energy slit can be set to intercept the higl energy ions. Sweeping the magnetic field in Ma provides the separation of ions according to mass-to-charge ratios in time sequence 2 B4.2 m/q et ESA 2V Electrostatic slit Mass Analyzer (MA) analyzer(ESa) Select the Ke B Select the m/e of ions Degree(r)of deflection of ions by the magnetic filed Magnet Sector Electrostatic depends on m/g ratio Sector V- ion acceleration voltage exit Point of radius of curvature of an ion slit d ouble focus Direction Ion focal plane Energy llector Focal plane Source exit https://www.youtube.com/watch?v=nuih9-6fm6uatn3:40-5:16 https://www.youtube.com/watch?v=ezvqzimbuq8tow2:06 http://www.youtube.com/watch?v=lxafw1rftiaatw1:00-4:12

Energy Analyzer and Mass Spectrometer ESA bends lower energy ions more strongly than higher energy ions. The sputtering process produces a range of ion energies. An energy slit can be set to intercept the high energy ions. Sweeping the magnetic field in MA provides the separation of ions according to mass-to-charge ratios in time sequence. Mass Analyzer (MA) Magnet Sector Electrostatic Sector E r - radius of curvature of an ion http://www.youtube.com/watch?v=lxAfw1rftIA at~1:00-4:12 Energy Focal plane Degree (r) of deflection of ions by the magnetic filed depends on m/q ratio. V - ion acceleration voltage https://www.youtube.com/watch?v=EzvQzImBuq8 to~2:06 https://www.youtube.com/watch?v=NuIH9-6Fm6U at~3:40-5:16

Basic equations of Mass spectrometry Ions kinetic e function of mv=zv accelerating voltage(v)and charge(z V ball centrifugal F=my/ r Centrifugal force force F=BEV L Applied magnetic field trimetal force rentz force Balance as ion goes mv/r=Bzv] through flight tube Combine equations to obtain m/z=br/2V Fundamental equation of mass spectrometry Change ' mass-to-charge(m/z)ratio by m/z =m/ changing V or changing B for singly charged ions NOTE: if B, v, z constant, then r-radius of circular ion path

Basic Equations of Mass Spectrometry 1 2 2 mv zV = 2 F mv R = / F Bzv = 2 mv R Bzv / = 2 2 m z B R V / / 2 = Ion’s kinetic E function of accelerating voltage (V) and charge (z). Centrifugal force Applied magnetic field Lorentz force Balance as ion goes through flight tube Fundamental equation of mass spectrometry Combine equations to obtain: Change ‘ mass-to-charge’ (m/z) ratio by changing V or changing B. NOTE: if B, V, z constant, then: r m  m/z = m/e for singly charged ions r- radius of circular ion path r r r

How Mass Spectrometry Works 2009 How stuf MWorks Stream of lon Positively Charged Stream C lon Stream A lons 00666 Stream B MA- Electromagnet ESA ESA Electrostatic MA analyzer(ESA) Select theKE B、 Select the m/e of ions Detector Energy focal plane Slit Direction Detector cal plane exIt Mass Spectrometer Layout

ESA MA MA

Ion detectors http://www.eaglabs.com/mc/sims-secondary-ion-detectors.html#next Ion Collector A Faraday cup measures the suppressor electrode Ion beam ion current hitting a metal T To amplifier cup, and is sometimes used Load for high current secondary ion Detector Faraday resistor signals. With an electron S cage multiplier an impact of a Faraday cup single ion starts off an Ion Detector electron cascade, resulting in beam slit Sucessivly higher voltage a pulse of10° electrons which is recorded directly Electrons To amplifier Usually it is combined with a Discrete dynode Dynode electron multiplier Be/Cu surface fluorescent screen, and Secondary electron Multiplier signals are recorded either 20 dynodes Current gain 107 with a CCD-camera or with a fluorescence detector https://www.youtube.com/watch?v=nuih9-6fm6uatm5:18-6:50andtow9:25

Ion Detectors Faraday Cup Secondary electron Multiplier 20 dynodes Current gain 107 A Faraday cup measures the ion current hitting a metal cup, and is sometimes used for high current secondary ion signals. With an electron multiplier an impact of a single ion starts off an electron cascade, resulting in a pulse of 108 electrons which is recorded directly. Usually it is combined with a fluorescent screen, and signals are recorded either with a CCD-camera or with a fluorescence detector. http://www.eaglabs.com/mc/sims-secondary-ion-detectors.html#next https://www.youtube.com/watch?v=NuIH9-6Fm6U at~5:18-6:50 and to~9:25

Mass resolution Several definitions of mass resolution(R) R- capability of a mass spectrometer to differentiate between masses If M=1000 and M=l, then R =1000 △M AM- mass difference between two adjacent peaks that are just resolved M-nominal mass of the first peak or mean mass of two peak Resolution is also defined as the full width at half maximum(FWHm) of a peak 28.0313 HN+ 280187 △M=0.0126 28.0061 M+△M CO+ 27.9949 28.0313+28.0187 R 2220 0.0126 Time M/ amu

M/z

High Mass resolution Pyrite〔FeS2) Grain 12 10 x0EoE Lineal 31.96 3197 31.98 31.99 32.00 Mass Mass spectrometers enables to resolve atomic ions from interfering molecular ions if the resolution is high enough Spectrum in both linear and semi-log scales

Time of Flight (TOF) SIMs-Reflectron http://www.youtube.com/watch?v=zoauxsebunkTof-sims http://www.youtube.com/watch?v=kawu6smvhjc 1. Ion source with a TOF SIMS is based on the fact that ions with the same energy but different masses travel pulsed a g0 deflector with different velocities. Basically, ions formed 2. Liquid metal by a short ionization event are accelerated by source an electrostatic field to a common energy and 3. target travel over a drift path to the detector. The 4. Single stage reflector lighter ones arrive before the heavier ones and 5. Detector a mass spectrum is recorded. Measuring the flight time for each ion allows the determination of its mass 日::日 5 (TOF) SIMS enables the analysis of an unlimited mass range with high sensitiv ity and quasi-simultaneous detection of all secondary Schematic of time of flight ( TOF) ions collected by the mass spectrometer

Time of Flight (TOF) SIMS - Reflectron (TOF) SIMS enables the analysis of an unlimited mass range with high sensitivity and quasi-simultaneous detection of all secondary ions collected by the mass spectrometer. TOF SIMS is based on the fact that ions with the same energy but different masses travel with different velocities. Basically, ions formed by a short ionization event are accelerated by an electrostatic field to a common energy and travel over a drift path to the detector. The lighter ones arrive before the heavier ones and a mass spectrum is recorded. Measuring the flight time for each ion allows the determination of its mass. Schematic of time of flight (TOF) spectrometer - reflectron http://www.youtube.com/watch?v=ZoAUxsEBUnk TOF-SIMS http://www.youtube.com/watch?v=KAWu6SmvHjc