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EBSD – Fundamentals

EBSD – Fundamentals. Pole piece. SEM based technique 70° tilted specimen 1-10 nA , ~20 kV Detector Phosphor + CCD camera EBSP Kikuchi bands (planes) Zones (directions) Orientation Sub-micron resolution ~0.5deg angular resolution Surface Effect Sampling upper 30-50nm

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EBSD – Fundamentals

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  1. EBSD – Fundamentals Pole piece • SEM based technique • 70° tilted specimen • 1-10 nA , ~20 kV • Detector • Phosphor + CCD camera • EBSP • Kikuchi bands (planes) • Zones (directions) • Orientation • Sub-micron resolution • ~0.5deg angular resolution • Surface Effect • Sampling upper 30-50nm • Surface prep important! Phosphor Screen Camera EBSP Phosphor Sample Forescatter Electron Detector HKL EBSD – CSEM 2003

  2. What does an EBSP look like? Silicon at 20kV HKL EBSD – CSEM 2003

  3. How it works - EBSP formation • The Electron beam strikes the specimen • Scattering produces electrons travelling in all directions in a small volume (the excitation volume) • Electrons that travel in a direction that satisfies the Bragg condition (nl=2dhkl.sinq) for a plane (hkl) are channeled Kikuchi bands • The electrons hit the imaging phosphor and produce light • The light is detected by a CCD camera and converted to an image • Which is indexed... Phosphor Spherical Kikuchi map HKL EBSD – CSEM 2003

  4. Indexing Cycle Collected EBSP Hough space Move beam or stage • Position electron beam • Capture EBSP • Perform Hough transform, find peaks (= band position & orientation) • Compare to possible peak positions and intensity heirarchy versus theoretical for potential match phases • If match is made within acceptable error limits, store data & repeat for next point Save data to file Phase and orientation Indexed EBSP Currently, our system can perform as many as 90 cycles per second! (sample/conditions dependent) HKL EBSD – CSEM 2003

  5. Visualization of Data General Micro-structure Deformed silica (quartz) Pixel map of pattern quality + crystal orientation + grain boundary location and character HKL EBSD – CSEM 2003

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