Lecture-9 SIMS & NDT

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

2. 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). Instrumentation • 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 Vacuum < 10−6 torr Ion detectors Mass Analyzers Ip Is Ion sources SIMS CAMECA 6F Mass analyzers http://www.youtube.com/watch?v=IO-KCjxznLs to~1:50

3. 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

4. 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. Energy Analyzer and Mass Spectrometer E Mass Analyzer (MA) Degree (r) of deflection of ions by the magnetic filed depends on m/q ratio. V - ion acceleration voltage Magnet Sector Electrostatic Sector r - radius of curvature of an ion Energy Focal plane https://www.youtube.com/watch?v=NuIH9-6Fm6U at~3:40-5:16 https://www.youtube.com/watch?v=EzvQzImBuq8 to~2:06 http://www.youtube.com/watch?v=lxAfw1rftIA at~1:00-4:12

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

6. MA ESA MA

7. http://www.eaglabs.com/mc/sims-secondary-ion-detectors.html#nexthttp://www.eaglabs.com/mc/sims-secondary-ion-detectors.html#next Ion Detectors 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 of108 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. Faraday Cup Secondary electron Multiplier 20 dynodes Current gain 107 https://www.youtube.com/watch?v=NuIH9-6Fm6U at~5:18-6:50 and to~9:25

8. M/z

10. http://www.youtube.com/watch?v=ZoAUxsEBUnk TOF-SIMS http://www.youtube.com/watch?v=KAWu6SmvHjc Time of Flight (TOF) SIMS - Reflectron 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. • (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. Schematic of time of flight (TOF) spectrometer - reflectron

11. Time of Flight (TOF) Spectrometer TOF operates in a pulse mode. During a short pulse of E, ions are accelerated and acquire a constant kinetic energy: kinetic energy = mv2/2 but have different m/q and Vs. Thus they arrive to the detector in time sequence after travel the same distance. Time required to travel distance l from the ion origin to the detector is: The light ions with higher Vs arrive to the detector first. pulse width Schematic of TOF spectrometer with a spectrum In order to provide higher resolution the pulse should be as narrow as 1-10 ns. The pulse repetition frequency is usually in a kHz range.

13. SIMS can do trace element analysis WDS ~100ppm EDS ~1000ppm Detection limit is affected by

14. 1 and 2 Static SIMS 3 Dynamic SIMS

18. Dynamic Secondary Ion Mass Spectrometry Dynamic SIMS involves the use of a much higher energy primary beam (larger amp beam current). It is used to generate sample depth profiles.The higher ion flux eats away at the surface of the sample, burying the beam steadily deeper into the sample and generating secondary ions that characterize the composition at varying depths. The beam typically consists of O2+ or Cs+ ions and has a diameter of less than 10 μm. The experiment time is typically less than a second. Ion yield changes with time as primary particles build up on the material effecting the ejection and path of secondary ions.

19. Dynamic SIMS – Depth Profiling Factors affecting depth resolution http://www.youtube.com/watch?v=-7gSbaslRCU&feature=related

21. Crater Effect (a) (b) (a) Ions sputtered from a selected central area (using a physical aperture or electronic gating) of the crater are passed into the mass spectrometer. (b) The beam is usually swept over a large area of the sample and signal detected from the central portion of the sweep. This avoids crater edge effects. The analyzed area is usually required to be at least a factor of 3  3 smaller than the scanned area.

22. Sample Rotation Effect

23. Gate Oxide Breakdown http://www.youtube.com/watch?v=IO-KCjxznLs&NR=1&feature=endscreen 2:08-2:40

24. Dynamic SIMS vs Static SIMS

25. http://www.youtube.com/watch?v=IO-KCjxznLs at~2:45-3:18

27. Some instruments simultaneously produce high mass resolution and high lateral resolution. However, the SIMS analyst must trade high sensitivity for high lateral resolution because focusing the primary beam to smaller diameters also reduces beam intensity. High lateral resolution is required for mapping chemical elements. Mapping Chemical Elements • The example (microbeam) images show a pyrite (FeS2) grain from a sample of gold ore with gold located in the rims of the pyrite grains. The image numerical scales and associated colors represent different ranges of secondary ion intensities per pixel. 34 S 197 AU

28. Summary • SIMS can be used to determine the composition of organic and inorganic solids at the outer 5 nm of a sample. • To determine the composition of the sample at varying spatial and depth resolutions depending on the method used. This can generate spatial or depth profiles of elemental or molecular concentrations. • These profiles can be used to generate element specific images of the sample that display the varying concentrations over the area of the sample. • To detect impurities or trace elements, especially in semi-conductors and thin filaments. • Secondary ion images have resolution on the order of 0.5 to 5 μm. • Detection limits for trace elements range between 1012 to 1016 atoms/cc. • Spatial resolution is determined by primary ion beam widths, which can be as small as 100 nm. SIMS is the most sensitive elemental and isotopic surface microanalysis technique (bulk concentrations of impurities of around 1 part-per-billion). However, very expensive. http://www.youtube.com/watch?v=QTjZutbLRu0 at~1:38-2:14 advantages and disadvantages of SIMS

29. Review Questions for SIMS • What are matrix effects? • What is the difference between ion yield and sputtering yield? • When are oxygen and cesium ions used as primary ions? • What is mass resolution? • How can depth resolution be improved? • Applications of SIMS • Advantages and disadvantages of SIMS

30. https://www.nde-ed.org/index_flash.php Non-destructive Analysis (NDA)Non-destructive Testing (NDT) Introduction to NDT Overview of Six Most Common NDT Methods Selected Applications https://www.youtube.com/watch?v=tlE3eK0g6vU NDT very good

31. Definition of NDT The use of noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object. i.e. Inspect or measure without doing harm.

32. What are Some Uses of NDT Methods? • Flaw Detection and Evaluation • Leak Detection • Location Determination • Dimensional Measurements • Structure and Microstructure Characterization • Estimation of Mechanical and Physical Properties • Material Sorting and Chemical Composition Determination Fluorescent penetrant indication

33. Why Nondestructive? • Test piece too precious to be destroyed • Test piece to be reused after inspection • Test piece is in service • For quality control purpose • Something you simply cannot do harm to, e.g. fetus in mother’s uterus

34. When are NDE Methods Used? There are NDE applications at almost any stage in the production or life cycle of a component. • To assist in product development • To screen or sort incoming materials • To monitor, improve or control manufacturing processes • To verify proper processing such as heat treating • To verify proper assembly • To inspect for in-service damage

35. Six Most Common NDT Methods Detection of surface flaws • Visual • Liquid Penetrant • Magnetic • Ultrasonic • Eddy Current • Radiography Detection of internal flaws

36. 1. Visual Inspection Most basic and common inspection method. Tools include fiberscopes, borescopes, magnifying glasses and mirrors. Portable video inspection unit with zoom allows inspection of large tanks and vessels, railroad tank cars, sewer lines. Robotic crawlers permit observation in hazardous or tight areas, such as air ducts, reactors, pipelines.

37. https://www.youtube.com/watch?v=xEK-c1pkTUI to~2:26 • A developer (powder) is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen. • Visual inspection is the final step in the process. The penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity. Liquid Penetrant Inspection Low surface wetting • A liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects. • The excess liquid is removed from the surface of the part. High surface wetting https://www.youtube.com/watch?v=tlE3eK0g6vU at~2:48-3:33 https://www.youtube.com/watch?v=bHTRmTQDZzg

38. Magnetic Particle Inspection (MPI) • A NDT method used for defect detection. Fast and relatively easy to apply and part surface preparation is not as critical as for some other NDT methods. – MPI one of the most widely utilized nondestructive testing methods. • MPI uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be effective. • The method is used to inspect a variety of product forms such as castings, forgings, and weldments. Many different industries use MPI for determining a component's fitness-for-use. Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test such things as offshore structures and underwater pipelines. https://www.youtube.com/watch?v=tlE3eK0g6vU at~1:10-2:48 MPI https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/cc_mpi_index.php

39. https://www.youtube.com/watch?v=qpgcD5k1494 to~3:03 Magnetic Particle Inspection The part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions. Flux leakage Cracks just below the surface can also be revealed. Relative direction between the magnetic field and the defect line is important. The magnetic particles form a ridge many times wider than the crack itself, thus making the otherwise invisible crack visible. https://www.youtube.com/watch?v=dQoB7jpxSe8 MPI testing procedure

40. Magnetic particles • Pulverized iron oxide (Fe3O4) or carbonyl iron powder can be used • Colored or even fluorescent magnetic powder can be used to increase visibility • Powder can either be used dry or suspended in liquid

41. Examples of visible dry magnetic particle indications Indication of a crack in a saw blade Indication of cracks in a weldment Before and after inspection pictures of cracks emanating from a hole Indication of cracks running between attachment holes in a hinge

42. Magnetic particle wet fluorescent indication of a cracks at a fastener hole Examples of Fluorescent Wet Magnetic Particle Indications Magnetic particle wet fluorescent indication of a cracks in a drive shaft Magnetic particle wet fluorescent indication of a crack in a bearing

43. Advantages of MPI • One of the most dependable and sensitive methods for surface defects • fast, simple and inexpensive • direct, visible indication on surface • unaffected by possible deposits, e.g. oil, grease or other metals chips, in the cracks • can be used on painted objects • results readily documented with photo or tape impression

44. Limitations of MPI • Only good for ferromagnetic materials • sub-surface defects will not always be indicated • relative direction between the magnetic field and the defect line is important • objects must be demagnetized before and after the examination • the current magnetization may cause burn scars on the item examined

45. https://www.youtube.com/watch?v=gqJN8tyosDw to~0:42 Ultrasonic Inspection (Pulse-Echo) In ultrasonic testing, high-frequency sound waves are transmitted into a material to detect imperfections or to locate changes in material properties. The most commonly used ultrasonic testing technique is pulse echo, whereby sound is introduced into a test object and reflections (echoes) from internal imperfections or the part's geometrical surfaces are returned to a receiver.   The time interval between the transmission and reception of pulses give clues to the internal structure of the material. https://www.youtube.com/watch?v=tlE3eK0g6vU at~6:45-8:00 or to 11:35

46. Ultrasonic Inspection (Pulse-Echo) High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws. Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features that reflect sound. Principle of ultrasonic testing LEFT: A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo. RIGHT: A defect creates a third indication and simultaneously reduces the amplitude of the back wall indication. The depth of the defect is determined by the ratio D/Ep Ultrasonic Probe f Oscilloscope, or flaw detector screen Ultrasonic probe is made of piezoelectric transducers. https://www.youtube.com/watch?v=UM6XKvXWVFA at~1:18-3:08 http://www.doitpoms.ac.uk/tlplib/piezoelectrics/applications.php

47. How It Works? At a construction site, a technician tests a pipeline weld for defects using an ultrasonic instrument. The scanner, which consists of a frame with magnetic wheels, holds the probe in contact with the pipe by a spring. The wet area is the ultrasonic couplant (medium, such as water and oil) that allows the sound to pass into the pipe wall. Spline cracking Non-destructive testing of a swing shaft showing spline cracking. Backwall Spline – any of a series of projections on a shaft that fit into slots on a corresponding shaft, enabling both to rotate together. Lower end Upper end https://www.youtube.com/watch?v=UM6XKvXWVFA at~3:08-4:10

48. Images obtained by C-Scan High resolution scan can produce very detailed images. Both images were produced using a pulse-echo techniques with the transducer scanned over the head side in an immersion scanning system. Gray scale image produced using the sound reflected from the back surface of the coin (inspected from “heads” side) Gray scale image produced using the sound reflected from the front surface of the coin

49. Applications of Ultrasonic Inspection Ultrasonic inspection is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is used in many industries including steel and aluminium construction, metallurgy, manufacturing, aerospace, automotive and other transportation sectors. Limitations of Ultrasonic Inspection 1. Manual operation requires careful attention by experienced technicians. 2. Extensive technical knowledge is required for the development of inspection procedures. 3. Parts that are rough, irregular in shape, very small or thin, or not homogeneous are difficult to inspect. 4. Surface must be prepared by cleaning and removing loose scale, paint, etc. 5. Couplants are needed to provide effective transfer of ultrasonic wave energy between transducers and parts being inspected unless a non-contact technique is used.  6. Inspected items must be water resistant, when using water based couplants that do not contain rust inhibitors.

50. Eddy Current Testing (ECT) Electrical currents are generated in a conductive material by an induced alternating magnetic field. The electrical currents are called eddy currents because they flow in circles at and just below the surface of the material. Interruptions in the flow of eddy currents, caused by imperfections, dimensional changes, or changes in the material's conductive and permeability properties, can be detected with the proper equipment. • Eddy current testing can be used on all electrically conducting materials with a reasonably smooth surface. • The test equipment consists of a generator (AC power supply), a test coil and recording equipment, e.g. a galvanometer or an oscilloscope • Used for crack detection, material thickness measurement (corrosion detection), sorting materials, coating thickness measurement, metal detection, etc. https://www.youtube.com/watch?v=tlE3eK0g6vU at~11:36-12:38