Temperature-dependent photoemission on Al(001)

CH. SØNDERGAARD; PH. HOFMANN; CH. SCHULTZ; S.V. HOFFMAN; M. S. MORENO; J. E. GAYONE; M. A. VICENTE ALVAREZ; G. ZAMPIERI; S. LIZZIT; A. BARALDI

Polonia

Conferencia; 20th European Conference on Surface Science; 2001

We have measured angle-resolved photoemission spectra from bulk and surface states of Al(001) over a large range of temperatures and photon energies. The bulk data were analyzed using a model that allows to calculate the photoemission intensity for transitions with the simultaneous excitation/absorption of 0, 1, 2, etc. phonons. The model gives a good description of the data but only if phonon-assisted contributions to the photoemission peak are considered. We show that the so-called direct transition photoemission peaks contain strong contributions from transitions which are actually indirect and that this can influence the photoemission lineshape. The surface state at the centre of the surface Brillouin zone can be observed at high photon energies and appears to be more stable towards an increase of the sample temperature than the bulk photoemission peaks, although the surface Debye temperature on Al(001) is lower than its bulk counterpart. We try to explain this by considering the different nature of photoemission from the surface and the bulk and, in particular, the different role of phonon scattering.