A model of the microstructure of S-1 photocathodes is presented that explains the variation of the quantum yield from 300 to 1200 nm. This model, a refinement of an earlier one, is a three-layered structure, consisting of a base layer ≥30 nm thick with Cs<sub>11</sub>O<sub>3</sub> -coated (1- to 2-nm thickness) Ag microparticles in a matrix of Cs<sub>2</sub>O, a transition layer with Cs<sub>11</sub>O<sub>3</sub>-coated Ag microparticles partly immersed in the Cs<sub>2</sub>O and partly protruding into the vacuum, and an upper layer of Cs<sub>11</sub>O<sub>3</sub>-coated Ag microparticles completely in vacuum. This microstructure satisfactorily explains the additional silvering process and superficial oxidation performed on these surfaces. A theoretical calculation of the quantum yield based on a recently reformulated theory of optical absorption of inhomogeneous composite materials by us gives excellent agreement with the experimental data.
© 1985 Optical Society of America
C. W. Bates, Jr. and N. Alexander, "Microstructure of S-1 photoemitting surfaces," J. Opt. Soc. Am. A 2, 1848-1851 (1985)