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

2 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) –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/TiO 2 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 TiO 2 ) –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 Conductive Si MgO Material With Large Backscatter Yield

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 Al 2 O 3 samples to compare Will anneal some samples and reexamine results

7 CO 2 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 Transfer Chamber Mass Spectrometer Chamber XPS/UPS/SEY Chamber

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

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13 Prism for Transmission Photocathodes Photocathode Holder

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