Photoemission study of Cs–NF3 activated GaAs(100) negative electron affinity photocathodes

Abstract

GaAs based negative electron affinity photocathodes activated with Cs and NF3 are used as polarized electron sources for linear accelerators. It is generally believed that the activation layer consists of CsF. The activation layers of Cs–NF3 on GaAs photocathodes are herein investigated using synchrotron radiation photoelectron spectroscopy. F1s, N1s, and other core levels are recorded at photon energies ranging from 70to820eV. Surprisingly, a significant amount of nitrogen is observed in the activation layers. Two distinct species of nitrogen are observed, one of which decreases along with the fluorine signal as the yield of the photocathode decays with time.

The surface activation layer of GaAs negative electron affinity photocathode activated by Cs, Li, and NF3

“…Instead, N and F are still bonded together as N-F clusters. 12 We observed the same thing for Cs+NF 3 activated samples. Although we believe that the N-F cluster is simply the NF 3 molecular form because NF 3 is inert at room temperature, 13 we decided not to draw such a conclusion at this point simply based on the atomic ratio between N and F (0.3±0.1) alone.…”

A density functional theory research on Cs–O activation process of GaAlAs photocathodes

“…With high quantum efficiency, low energy spread and high spin polarization, Negative Electron Affinity (NEA) GaAs photocathodes have been widely used in night vision image intensifiers and are potential electron sources for the next-generation electron accelerators [1][2][3][4]. In ocean environment, GaAs photocathodes would produce more noise and could not be used all-weather; therefore, they are not suitable for ocean detection.…”

Comparative research for GaAs photocathodes with graded compositional Al x Ga 1−x As buffer layer

“…For the sensitive photocathodes on short wavelength band near 400 nm have wide applications in many areas such as under water observations and communications, multispectral systems, microscopy remote control systems, sandy or desert conditions. So the research on increasing quantum efficiency for GaAs photocathodes at short wavelength band becomes very much [1][2][3]. Graded Al compositional design on the band gap of Al x Ga 1 À x As material has been already used in solar cells, which can enhance the power conversion efficiency by reducing the surface recombination losses.…”