Surface-disorder effects in angle-resolved photoemission spectra

We report for the first time the evidence of a strong correlation between angle-resolved photoemission spectra and surface disorder. This was observed for the case of cleaved GaAs(110). While for well-ordered surfaces a direct-transition model is clearly the dominant process, in the case of surfaces with a high density of random steps the photoemission process switches to a one-dimensional density-of-states regime. In both cases the spectra are still interpretable in terms of bulk band emission along the crystal normal. These results may explain the behavior of some materials, such as the IV-VI compounds, whose spectra do not seem to follow the direct-transition model.