2023
07/21
OPEN
Date
2023/07/21(Fri.) 14:00～15:00
Venue
1Room-1, Bldg#1 1F +Teams
Speaker
Gaoxue Wang (Los Alamos National Laboratory, Theoretical Division)
Language
English
URL
Contact
M. Yamamoto (PHS 4912)
Overview
Photocathodes are crucial electron sources for X-ray free electron laser (XFEL) and X-ray energy recovery linacs (XERL), which produce high-resolution and coherent X-rays for studying materials. Quantum efficiency (QE) and operational lifetimes are two of the key figures of merit of photocathodes performance. Alkali-based semiconducting photocathodes display high QE in the visible light spectrum, while their lifetimes are shorter than their metallic counterparts due to the sensitivity to residual gases. Coating alkali-based photocathodes with two dimensional (2D) materials is an effective approach to improve the lifetimes of photocathodes. During my presentation, I will discuss our investigation of the interfaces between 2D materials with photocathodes using ab-initio electronic structure calculations. We have discovered that the induced dipole moments at the interfaces play a key role in influencing the work function of coated photocathodes and subsequently their QE. Building on this understanding, we have conducted a computational screening in 2D material database to identify those that could enhance the performance of photocathodes. We have identified several promising candidates, including a monolayer of BN, which can maintain the QE of semiconducting photocathodes while also protecting their surfaces.