1 / 10

Characterization of Ageing in Photocathodes: Insights from SSL Studies

This study examines the multiple causes of ageing in photocathodes, highlighting the fast and slow components of gain decrease due to surface effects, such as water and oxygen species. Detailed discussions focus on the significant factors contributing to ageing, including surface composition and electron stimulation. Utilizing advanced tools like UHV AFM/STM and scanning tunneling spectroscopy, this research aims to improve our understanding of material properties and enhance the performance of photocathodes, aiming for better structural and chemical characterization to facilitate treatment and optimization.

zytka
Télécharger la présentation

Characterization of Ageing in Photocathodes: Insights from SSL Studies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Characterization UpdateAgeing Studies Slade J. Jokela

  2. Discussion on Ageing • Multiple causes of ageing are apparent • Fast component (decreased gain, short-lived) • I think this is most likely water, hydroxyls • Maybe some other surface-adsorbed species containing oxygen Plot of work done at SSL (O. Siegmund, J. McPhate, A. Tremsin) • Two slower components • Increase in gain after the initial rapid decrease • Overall decrease in gain that wins out

  3. Discussion on Ageing • Fast component is “revived” upon air exposure • Studies from SSL • Indicates to me that it is plentiful, but weakly adsorbed • H2O, CO2 • OH¯ or CO

  4. What could cause Ageing? • Surface composition • Electron stimulated desorption • Electron stimulated migration • Interstitial atoms or atoms in grain boundaries • Surface morphology • Electrons could also induce changes in structure • I know high energy electrons can, not sure about electrons in the 100eV or less range.

  5. What tools are available • Center for Nanoscale Materials (CNM) • Two Potentially Useful Instruments • Variable-temperature, UHV, AFM/STM • In High Demand • Scanning Tunneling Spectroscopy • Resistive and e-beam heating • Gas dosing (may be useful for photocathode tests) • LEED/Auger Module

  6. What tools are available • Scanning probe/scanning electron microscopy • Four-point contact measurement • Very little demand for this instrument • May be useful for electrical characterization • Has limited functionality as STM • Vibration is the limiting factor • SEM – Normally used for 4-point probe positioning • Gemini column for scanning Auger microscopy • Additional LEED/Auger module • Resistive heater

  7. Details • LEED module on each instrument • Can be configured to emit low-energy electron beam for sample exposure in small area • Used to test SEY • STM/AFM/SEM/LEED may be used to detect differences in morphology • Scanning Auger can be used to measure surface composition across electron-exposed region.

  8. Details • What could we study? • Initial studies will be on sample coupons • Non-reactive photocathodes • Later studies may include cleaved MCPs • Vacuum transfer system would allow activated photocathodes • The 2nd system mentioned may have its sample prep. module moved to another system, giving us the opportunity to add vacuum transfer capabilities at that time

  9. Details • Full details of these systems can be found at: http://nano.anl.gov/facilities/proximal_probes.html • What to do with the information we learn • Structural and chemical/compositional changes may be able to be induced in order to accelerate the scrubbing treatment • Annealing schedule • Examine other processes available in ALD to eliminate remnant precursor molecules

  10. CNM Proposal • CNM Proposal is due Friday, March 4th • Have discussed some of these details with Anton at SSL • Have discussed scope of project with Nathan Guisinger at CNM

More Related