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Characterization Plans

Characterization Plans. Slade J. Jokela, I. Veryovkin, A. Zinovev. Secondary Emission Materials. We have mainly focused on MgO and Al 2 O 3 We should examine other materials as well as structures (primarily layered materials)

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Characterization Plans

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  1. Characterization Plans Slade J. Jokela, I. Veryovkin, A. Zinovev

  2. Secondary Emission Materials • We have mainly focused on MgO and Al2O3 • We should examine other materials as well as structures (primarily layered materials) • Looking for non-conducting materials with high electron backscatter. • Find optimal thickness for MgO (or other material) then place an electron ‘reflecting’ layer just underneath • This would essentially make use of primary electrons that penetrate further than the maximum escape depth for secondary electrons

  3. Examine ‘New’ Materials/Structures • While it appears that MgO provides excellent emission capabilities, there are other materials/structures to try • MgO/TiO2 or MgO/CaO mix • Shows an increase in emission over MgO alone • Suspected that band structure change due to increased oxygen to cation ratio is responsible (for TiO2) • Diamond • First strike material (can’t be deposited deep in channel)

  4. Electron Backscatter • High Z materials • Tungsten is a candidate • Will take a survey of samples and see if there are MgO samples on W that aren’t too thick • Thickness of backscatter layer will certainly play a role Material With Large Backscatter Yield MgO Conductive Si

  5. Electron Beam Pulsing • I’m confident that I have figured out how to properly pulse electron beam with current equipment • Need a Trigger-Link cable for Keithley Meters (proprietary?) • Still need to write a Labview VI, but this can’t be tested until I get the trigger cable

  6. Continued Thickness Series • Need to repeat MgO thickness series on new LEED system (reproducibility) • Will need to repeat again once pulsing is enabled (accuracy) • Need Al2O3 samples to compare • Will anneal some samples and reexamine results

  7. CO2 Snow Cleaning • Will begin this experiment in the next two weeks • Comparing microscopic images between cleaned and uncleaned MCPs (looking for clogged pores) • Eventually will test MCPs after ALD coating to determine if cleaning will improve the final product

  8. Photocathodes • Sample carousel (4 position) designed • Photocathode position • Rotation axis of carousel contains a prism that will direct light from a chamber window to the back side of the transmission photocathode • Heater position • 20 Watt quartz lamp will be directed to heat the sample • Remaining positions are open • One may contain a faraday cup • Other may just be for high voltage applications

  9. Mass Spectrometry • Still pursuing a mass spectrometer • Necessary for accurate studies of scrubbing (electron stimulated desorption) • Temperature-programmed desorption (20 W quartz heater) • What does heat-treating samples actually do? • What temperature is necessary to treat the sample and why? • What material is removed that improves the sample? • Secondary Neutral Mass Spectrometry (SNMS) • Post-sputter ionization of material using electron impact • Useful for depth profiling where material isn’t easily ionized by ion beam • Should be better at depth profiling photocathodes

  10. XPS/UPS/SEY Chamber Transfer Chamber Mass Spectrometer Chamber

  11. 4-Position Sample Carousel Additional 20W Heater in this holder

  12. Photocathode Holder Prism for Transmission Photocathodes

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