Quantum efficiency enhancement in CsI/metal photocathodes

Abstract

a b s t r a c tHigh quantum efficiency enhancement is found for hybrid metal-insulator photocathodes consisting of thin films of CsI deposited on Cu(1 0 0), Ag(1 0 0), Au(1 1 1) and Au films irradiated by 266 nm laser pulses. Low work functions (near or below 2 eV) are observed following ultraviolet laser activation. Work functions are reduced by roughly 3 eV from that of clean metal surfaces. We discuss various mechanisms of quantum efficiency enhancement for alkali halide/metal photocathode systems and conclude that the large change in work function, due to Cs accumulation of Cs metal at the metal-alkali halide interface, is the dominant mechanism for quantum efficiency enhancement.

A mechanism of Cu work function reduction in CsBr/Cu photocathodes

“…9 The large work function reduction has been ascribed to the formation of Cs metal at the interface. 14 A further insight into the large variation in estimated work function reduction and LA mechanisms can be gained by modelling techniques. Thin insulating films are known to lower the metal work function predominantly due to compression of metal electronic wavefunctions at the interface, charge transfer between insulating film and metal, and interface roughness.…”