Raman scattering from monoalkali (Na-Sb and K-Sb), bialkali (Na-K-Sb) and multialkali (Na-K-Sb-Cs) photocathodes

Abstract

The Raman spectra of monoalkali (Na-Sb and K-Sb), bialkali (Na-K-Sb) and multialkali (Na-K-Sb-Cs) photocathodes were measured at room temperature. Three Raman lines were detected in Na-Sb at 45 cm -1, 128 cm -1 and 187 cm -1. The latter line was assigned to A 1g vibrations of sodium atoms at the (f) sites of the hexagonal ( D 4 6h) lattice of Na 3Sb. The only Raman-active mode ( F 2g) in cubic ( O 5 h) K 3Sb was found at 145 cm -1. The Raman line at 180–185 cm -1 in the spectra of the bialkali and multialkali photocathodes was assigned to the F 2g vibration of sodium atoms at the (c) sites of the cubic Na 2KSb lattice. It was established that in the latter type of photocathode a definite amount of the cubic K 3Sb phase is also present.