Contributions of the escape depth to the photoelectron intensity of a well-defined initial state

Abstract

Using the adsorbate-induced two-dimensional electron system on InAs(110) as an initial state, which provides rather small energy and k-space distribution, we measure the photoelectron intensity as a function of photoelectron energy. It oscillates twice between 3 eV and 23 eV having maxima at 5.5 eV and 19 eV. Comparison with calculations performed within the one-step model shows that the maximum at low energy is due to an overlap of a maximum in the photoelectron escape depth and a maximum of the matrix elements corresponding to the atomic wave functions. In contrast, the maximum at high energy is caused by final states crossing the Γ point exactly at this energy. The comparison confirms the theoretical prediction that the escape depth at low excitation energies can be significantly modified by band-structure effects.