The granulated gold-film-based semitransparent photocathodes in the visible spectrum range for femtosecond time-resolution experiments

Abstract

Developed is the granulated, Au film-based, semitransparent photocathode consisting of spherical Au nanoparticles. The granulated Au films are activated by a thin layer of cesium and oxygen of about two monolayer thicknesses to decrease the work function down to about 1 eV and gain the photoemission effect in the visible spectrum range. The sensitivity maximum equal to about one mA/W is located in the green spectrum range. The nanoparticles formation and photocathode surface structure are studied with the use of the X-ray photoelectron spectroscopy technique. Those studies have shown that the photoemission effect in the wavelength range λ > 450 nm is conditioned by excitation of the surface plasmons in quasi-spherical Au nanoparticles. This has allowed manufacturing of a streak tube with the introducible, Au nanoparticles-based photocathode, stability of which has been remaining invariant.