Speaker
Description
We present measurements of enhanced quantum efficiency (QE) in thin film photocathodes due to optical interference in the cathode-substrate multilayer. Modulations in the quantum efficiency of Cs$_{3}$Sb films grown on multilayer 3C-SiC substrates are observed over a range of visible wavelengths, and are shown to increase the QE by more than a factor of two at certain wavelengths. We derive a model to describe the modulations in QE based on a three step photoemission process incorporating cases of both constant density of states and density functional theory (DFT) derived density of states, which is shown to be in good agreement with the measurements. Predictions from the model show that the QE can be enhanced by more than a factor of four by optimizing the cathode and substrate layer thicknesses. We also find that by optimizing layer thicknesses of the cathode-substrate system in the calculation, optical interference can enhance the QE beyond optically dense films. Advantages of this interference effect for electron accelerator sources are discussed.
Funding Agency
The Center for Bright Beams, NSF
| Region represented | North America |
|---|---|
| Paper preparation format | LaTeX |
