Inverse photoemission spectrometer for interface studies

An inverse photoemission spectrometer is described which combines momentum resolution for measurements done with low energy incident electrons (photon energy range 12-44 eV) and momentum integration for high energy studies in the isochromat mode (photon energy 14896.6 eV). This unique combination makes it possible to maximise surface sensitivity, enhance bulk sensitivity, and identify the orbital angular momentum character of specific unoccupied states through variations in photoionisation cross section. Experimental capabilities are included for characterisation of ordered, disordered and reactive overlayers deposited in situ on metal and semiconductor surfaces. Representative results are presented for interfaces formed by depositing Fe onto cleaved surfaces of the high temperature superconductor La1.85Sr0.15CuO4.