Combined experimental setup for spin- and angle-resolved direct and inverse photoemission

Abstract

We present a combined experimental setup for spin- and angle-resolved direct and inverse photoemission in the vacuum ultraviolet energy range for measurements of the electronic structure below and above the Fermi level. Both techniques are installed in one ultrahigh-vacuum chamber and, as a consequence, allow quasisimultaneous measurements on one and the same sample preparation. The photoemission experiment consists of a gas discharge lamp and an electron energy analyzer equipped with a spin polarization detector based on spin-polarized low-energy electron diffraction. Our homemade inverse-photoemission spectrometer comprises a GaAs photocathode as spin-polarized electron source and Geiger-Muller counters for photon detection at a fixed energy of 9.9 eV. The total energy resolution of the experiment is better than 50 meV for photoemission and better than 200 meV for inverse photoemission. The performance of our combined direct and inverse-photoemission experiment with respect to angular and energy resolutions is exemplified by the Fermi-level crossing of the Cu(111) L-gap surface state. Spin-resolved measurements of Co films on Cu(001) are used to characterize the Sherman function of the spin polarization detector as well as the spin polarization of our electron source.