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Experimental techniques  sem Experimental techniques sem Presentation Transcript

  • ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMABulk Materials – Experimental TechniquesMain Outcome: Evaluation of properties of bulk nanostructured materials Mohammad Omar Abuelnaga AMT–506 Bulk Materials – Experimental Techniques 1
  • ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMAScanning Electron Microscope (SEM) AMT–506 Bulk Materials – Experimental 2 Techniques
  • ADVANCED MATERIALS & TECHNOLOGY Contents POSTGRADUATE DIPLOMA1. Electron Beam Energy2. Advantages of Electron Microscope (Wave length–Resolving power–Depth of focus)3. SEM Sample Preparation4. What can we use a SEM for?5. How do we get an image?6. Electron beam-sample interactions7. Components of the SEM AMT–506 Bulk Materials – Experimental Techniques 3
  • 1. Electron Beam Energy e- beam energy ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA SEM TEM synchrotron 0.2 keV to 40 keV ›100 KeV 1 GeV Microstructure Crystal structure Particle Physics ResearchSynchrotron Images http://www.xente.mundo-r.com/rcid/pages/phy_9.html http://www.desy.de/news/news/archive_before_2010/2007/photon_219/index_eng.html AMT–506 Bulk Materials – Experimental Techniques 4
  • 2. Adv. of Electron Microscope ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA•Wavelength: Visible light: 400-700 nm Electron Beam: 0.001-0.01 nm•Resolving power: The closest spacing of two points clearly as separate entities. http://www.olympusmicro.com/primer/anatomy/numaperture.html AMT–506 Bulk Materials – Experimental Techniques 5
  • 2. Adv. of Electron Microscope ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA •Resolving power: AMT–506 Bulk Materials – Experimental Techniques 6
  • 2. Adv. of Electron Microscope ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA •Resolving power:In practice:Magnification of LOM ≈ 1000 X Magnification of TEM ≈ 2,000,000 X Magnification of SEM ≈ 500,000 X AMT–506 Bulk Materials – Experimental Techniques 7
  • 2. Adv. of Electron Microscope ADVANCED MATERIALS & TECHNOLOGY Depth of focus POSTGRADUATE DIPLOMA http://www.emal.engin.umich.edu/courses/sem_lecturecw/SEM_DepthofFocus.html•At some distance D/2 above and below the focus plane the diameter of the beambecomes twice the pixel diameter for the magnification being used, whereuponthe signals from adjacent pixels overlap enough to cause the image to appearblurred.•Over the distance D between these limits, however, the image will appear to be inacceptably sharp focus, and so this distance is called the depth of field or thedepth of focus. AMT–506 Bulk Materials – Experimental Techniques 8
  • 2. Adv. of Electron Microscope ADVANCED MATERIALS & TECHNOLOGY Depth of focus POSTGRADUATE DIPLOMA Optical microscopy vs SEM Depth of focus Magnification Optical SEM 10 60 μm 1000 μm 100 8 μm 100 μm 1000 0.2 μm 10 μm 10000 --- μm 1 μm Screw length: ~ 0.6 cm Images: the A to Z of Materials• A SEM typically has orders of magnitude better depth of focus than a optical microscope making SEM suitable for studying rough surfaces.• The higher magnification, the lower depth of focus. AMT–506 Bulk Materials – Experimental Techniques 9
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA• General characteristics for sample preparation:– Must be conductive to prevent charging– Must be vacuum compatible– Dependent on material properties (beam sensitivity,hardness, etc.) AMT–506 Bulk Materials – Experimental Techniques 10
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 1. Cutting•Conventional SamplePreparation procedures:1. Cutting2. Mounting(Conductive mounting material for SEM)3. Grinding 2. Mounting Hot Mounting4. Polishing Machine5. Etching Hot Mount Cold Mounts AMT–506 Bulk Materials – Experimental Techniques 11
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA AMT–506 Bulk Materials – Experimental Techniques 12
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY 3. Grinding POSTGRADUATE DIPLOMA Grinder/Polisher preparation machine Polishing Paper Grinding Paper AMT–506 Bulk Materials – Experimental Techniques 13
  • 3. SEM Sample Preparation 4. Polishing ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA Colloidal Silica for sample polishing•Abrasive Powders in a colloidal suspension /slurry / Paste.•Commonly used polishing Materials are:1. Alumina2. Silica3. Diamond paste DIAMOND PASTE with different particle sizes AMT–506 Bulk Materials – Experimental Techniques 14
  • 5. Etching ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA• The purpose of etching is to optically enhance microstructural features such as grain size and phase features.[Metallography & Ceramography]1. Chemical etching.(e.g.: Nital [95 % Alcohol + 5 % Nitric Acid] for 30 seconds is used for steel etching)2. Molten salt etching.(e.g.: Al2SiO5 in Potassium hydrogen fluoride melt in a Platinum crucible for 5-10 minutes)3. Electrolytic etching.4. thermal etching . (e.g.: heating Si3N4 in vacuum at 1250 ⁰C for 15 minutes)5. plasma etching.• For difficult to etch specimens, the etching rate can be enhanced with temperature, ultrasonic, electrolytic or microwave energy. AMT–506 Bulk Materials – Experimental Techniques 15
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMASEM Gold Sputtering System A spider coated in gold to prepare it as a specimen for Scanning electron microscopy. http://en.wikipedia.org/wiki/Scanning_electron_microscope Silver Paint AMT–506 Bulk Materials – Experimental Techniques 16
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA SEM Sample Holders holding specimen and shorter screws with Allen wrench AMT–506 Bulk Materials – Experimental Techniques 17
  • 3. SEM Sample Preparation ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMAThis dovetail is on the bottom of all of the http://www.azonano.com/news.aspx?newsID=13399holders. It fits onto the SEM motorizedstage dovetail mount. http://www.efjeld.com/P_S-hold.htm AMT–506 Bulk Materials – Experimental Techniques 18
  • ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 4. What can we use a SEM for? What can we study in a SEM?1. Topography and morphology2. Chemistry3. Crystallographic Orientation of grains (EBSD- Kikuchi bands)4. In-situ experiments Effects of temperature (Hot Stage) AMT–506 Bulk Materials – Experimental Techniques 19
  • 1. Topography and morphology ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMAAMT–506 Bulk Materials – Experimental Techniques 20
  • 2. Chemistry (EDX Mapping) ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMACKline Pb L lines X-Ray Generation AMT–506 Bulk Materials – Experimental Techniques 21
  • 2. Chemistry (EDX Mapping) ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMACKline Pb L lines AMT–506 Bulk Materials – Experimental Techniques 22
  • 2. Chemistry (EDX Mapping) ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA Carbon Manganese Pb M Lead CK lines line Mn K lines Pb L lines 0 2 4 6 8 10 12 14 16 18 20Full Scale 143608 cts Cursor: 19.997 (142 cts) keV AMT–506 Bulk Materials – Experimental Techniques 23
  • 2. Chemistry (EDX Mapping) ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA CeFe Sr AMT–506 Bulk Materials – Experimental Techniques 24
  • 3. Crystallographic Orientation of grains ADVANCED MATERIALS & TECHNOLOGY (EBSD- Kikuchi bands) POSTGRADUATE DIPLOMAhttp://www.stanford.edu/group/snl/SEM/OIMIntro.htm AMT–506 Bulk Materials – Experimental Techniques 25
  • 3. Crystallographic Orientation of grains ADVANCED MATERIALS & TECHNOLOGY (EBSD- Kikuchi bands) POSTGRADUATE DIPLOMA OIM scan progress and data review AMT–506 Bulk Materials – Experimental Techniques 26
  • 3. Crystallographic Orientation of grains ADVANCED MATERIALS & TECHNOLOGY (EBSD- Kikuchi bands) POSTGRADUATE DIPLOMA EBSD detectorSEM System that provides simultaneous EDS,EBSD and WDS data collection detectors. AMT–506 Bulk Materials – Experimental Techniques 27
  • 4. In-situ experiments: Effects of temperature (Hot Stage) ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA• A modern SEM can be equipped with various accessories, e.g. a hot stage AMT–506 Bulk Materials – Experimental Techniques 28
  • 5. How do we get an image? ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA Electrons out Electrons in or: x-rays out• In brief: we shoot high-energy electrons and analyze the outcoming electrons/x-rays AMT–506 Bulk Materials – Experimental Techniques 29
  • 5. How do we get an image? ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMAThe instrument in brief AMT–506 Bulk Materials – Experimental Techniques 30
  • 5. How do we get an image? ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA Electron gun 288 electrons! 156 electrons! Detector Image AMT–506 Bulk Materials – Experimental Techniques 31
  • 5. How do we get an image? ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA AMT–506 Bulk Materials – Experimental Techniques 32
  • ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA6. Electron beam-sample interactions AMT–506 Bulk Materials – Experimental Techniques 33
  • ADVANCED MATERIALS & TECHNOLOGY6. Electron beam-sample interactions POSTGRADUATE DIPLOMA Auger elect rons Secondary elect rons Backscat t ered elect rons Charact erist ic X-rays Cont inuum X-rays Fluoresecent X-rays AMT–506 Bulk Materials – Experimental Techniques 34
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA AMT–506 Bulk Materials – Experimental Techniques 35
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 1. Electron Gun Types 2. Lenses 3. Detectors 4. Vacuum AMT–506 Bulk Materials – Experimental Techniques 36
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 1. Electron Gun Types With field emission guns we get a smaller spot and higher current densities compared to thermionic guns Vacuum requirements are tougher for a field emission gunsSingle crystal of LaB6 Tungsten wire Field emission tip AMT–506 Bulk Materials – Experimental Techniques 37
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 1. Electron Gun Types The Electron Gun -emitter -Wehnelt cap or grid -anode -first “lens” in the SEMEmitter/Wehnelt cap assembly Anode [Hitachi S2300][from Hitachi S2300] AMT–506 Bulk Materials – Experimental Techniques 38
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 2. Lenses Cross-section of Electromagnetic Lens from an SEM -note the copper wire turns & power leads AMT–506 Bulk Materials – Experimental Techniques 39
  • 7. Components of the SEM ADVANCED MATERIALS & TECHNOLOGY POSTGRADUATE DIPLOMA 3. DetectorsBackscattered electrondetector:(Solid-State Detector)Secondary electron detector:(Everhart-Thornley) Image: Anders W. B. Skilbred, UiO AMT–506 Bulk Materials – Experimental Techniques 40
  • 7. Components of the SEM 3. Vacuum SEM Vacuum System -multistage system: 1.) low-vac [“roughing”] 2.) high-vac [“diff pump”] Oil Diffusion pump -high-vac[Rotary] Mechanical pump-”roughing” or low-vac