SPIN-POLARIZED ELECTRON-GUN FOR ELECTRON SPECTROSCOPIES

A spin-polarized electron gun for electron spectroscopies is described in detail. The gun consists of an electron source based on a negative electron affinity GaAs photocathode coupled to an appropriate transport electron optics. The gun has been designed with the aid of ray-tracing analysis and then accurately tested. It produces a transversely polarized (P0 approximately 27%) electron beam at variable energy with a small spot size and angular spread (less than 2 mm and 5-degrees, respectively). Such performances are attained up to sample currents as high as 10-mu-A for the whole beam energy range (8-50 eV). As an application we present data on spin-dependent absorbed current spectroscopy from bcc Fe films epitaxially grown on Ag(100).