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SEM (SCANNING ELECTRON MICROSCOPE)

SEM (SCANNING ELECTRON MICROSCOPE). 20823856 Özgen Buğdaycı 20824336 Elif Topçuoğlu 20823985 Yavuz Duran. Hacettepe University 12.04.2012. OUTLINE. Definiton of scanning electron microscope History Usage Area Instrumentation Sample preparation Working principles Limitations

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SEM (SCANNING ELECTRON MICROSCOPE)

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  1. SEM(SCANNING ELECTRON MICROSCOPE) 20823856 Özgen Buğdaycı 20824336 Elif Topçuoğlu 20823985 Yavuz Duran Hacettepe University 12.04.2012

  2. OUTLINE • Definiton of scanning electron microscope • History • Usage Area • Instrumentation • Sample preparation • Working principles • Limitations • Advantages & disadvantages • Conclusion

  3. What is SEM? • SEM = Scanning Electron Microscope • Is a type of electron microscope. • Uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. Scanning electron microscope - www.directindustry.com

  4. HISTORY • The first SEM image was obtained by Max Knoll in 1935. • Further pioneering work on SEM was performed by Manfred von Ardenne (1937) • Further developed by Prof. Sir Charles Oatley and his student Gary Stewart and first time marketed by Cambridge Scientific Instrument Company in 1965.  first successful SEM – www.science.howstuffworks.com

  5. USAGE AREA • Morphology • Topology • Microstructure studies • Solid state physic • Geology • Biology diamond-crystal structure - worldscheaper.com microstructureof a 15Mo3 steel - emeraldinsight.com

  6. SEM ELECTRONIC CONSOLE • focus • magnification • brightness • contrast Console of SEM - www.chems.msu.edu

  7. SEM ELECTRONIC COLUMN • generated under vacuum • focused to a small diameter • scanned across the surface of a specimen . Electronic column of SEM - www.chems.msu.edu

  8. INSTRUMENTATION COMPONENTS • Electron gun • Electromagnetic lenses • Scanning • Detectors • Sample stage • Vacuum system Components of SEM - www.purdue.edu

  9. INSTRUMENTATION ELECTRON GUN; • is used for producing an intense beam of electron • Thermionic gun  thermal energy • Field emission gun  electric field ANODE; accelarates the free electrons Electron gun - academic.udayton.edu

  10. INSTRUMENTATION LENSES; • is used to produce clear and detail images • Condenser lens  reduces the diameter of the electron beam • Objective lens  focuses electron beam Lens - ammrf.org.au Working principle of the lens - ammrf.org.au

  11. INSTRUMENTATION SCANNING COILS • are used to raster the beam across the sample surface • are able to move the beam Scanning coils - freudlabs.com

  12. INSTRUMENTATION SAMPLE CHAMBER • is where the sample is placed • can manipulate and move the • sample DETECTORS • is used the detect the secondary and backscattered electrons Sample chamber - jenkins.ucdavis.edu Detector - www.geos.ed.ac.uk

  13. INSTRUMENTATION VACUUM CHAMBER Absence of vacuum chamber; • electron gun’s filament would be damaged • other gas molecules would cause collisions with electrons • sample would react with gases Electron column - iaszoology.com

  14. SAMPLE PREPARATION For organic materials; • fixation  to preserve structure • drying  moisture must be removed • coating  to conductive the sample A spider coated with Au - thenallyblog.com • For metals; • no need for preparation • For non-metallics; • need to be coated Preparation - www.mos.org

  15. SAMPLE PREPARATION SPUTTER COATING; • Makes non metallic samples conductive • Uses Ar and electric field to tear off metal from cathode • Metal fall onto sample and coat the material Sputter coating device - microscopy.ca

  16. SAMPLE PREPARATION The coating material; • commonly carbon, gold, or some other metal or alloy • carbon  elemental analysis • metal coatings  high resolution imaging applications • must be vacuum compatible • dependent on material properties (beam sensitivity, hardness, etc.) • must be appropriate thickness

  17. WORKING PRINCIPLE Beam is; • generated by electron gun • collimated and focused by lenses • rastered across the sample surface Secondary or backscattered electrons are; • collected by detector • formed the specimen image in the microscope Working principle - ammrf.org.au

  18. LIMITATIONS • Samples must be solid • Size of analyte • vertically  <40mm • horizontally  <100mm • Stable in a vacuum • Designed to prevent any electrical and magnetic interference • Can not detect low elements (Lighter than Na-11) like most of analys microscopy

  19. ADVANTAGES • High resolution and magnification • 3-D Topographical imaging • Compatible with PC technologies and softwares • Fast Analysing • Store data in digital form • Easier sample preparation techniques A peacock’s head front wiev - www.nanosmo.com SEM adapted with pc equipments - www.lnnano.org

  20. DISADVANTAGES • Can not analys fluid or gas compounds • Expensive Instrumentation • Wasting time on sample preparation • Constant voltage during analysing

  21. RESULT • SEM uses electrons instead of light to form an image. • developed new areas of study & still helping. • popular among researchers due to their wide range of applications

  22. CONCLUSION SEM; • provides detailed surface data of solid samples • informs external morphology, chemical composition, crystalline structure • SAMPLE; • must be prepared before placed

  23. REFERENCES • www.iaszoology.com/sem • www.phy.cuhk.edu.hk • www.fy.chalmers.se/microscopy • www.materials.ac.uk • www.microscopemaster.com

  24. Thanks for your attention Any Questions?

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