Thin films (7 nm layers) of CsBr and KBr were deposited on Cu(100) to investigate photoemission properties of these potential photocathode materials. After thin film deposition and prolonged laser ultraviolet (UV) irradiation (266 nm picosecond laser) photoemission quantum efficiency increases by factors of 26 and 77 for KBr/Cu(100) and CsBr/Cu(100) photocathodes, respectively. Immediately following thin film deposition, a decrease in work function is observed, compared to bare Cu, in both cases. Quantum efficiency enhancements are attributed to the decrease in photocathode work function, due to the deposition of alkali halide thin films, and photo-induced processes, that introduce defect states into the alkali halide bandgap, induced by UV laser irradiation. It is possible that alkali metal formation occurs during UV irradiation and that this further contributes to photoemission enhancement. Our results suggest that KBr, a relatively stable alkali-halide, has potential for photocathode applications.
Revised: August 18, 2014 |
Published: February 20, 2013
Citation
He W., S. VilayurGanapathy, A.G. Joly, T.C. Droubay, S.A. Chambers, J.R. Maldonado, and W.P. Hess. 2013.Comparison of CsBr and KBr coated Cu photocathodes: Effects of laser irradiation and work function changes.Applied Physics Letters 102, no. 7:Article No. 071604.PNNL-SA-92864.doi:10.1063/1.4793214