Electronic structure of Si(111)-B(√3 × √3 )R30° studied by Si 2pand B 1score-level photoelectron spectroscopy

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Abstract
An investigation of the Si(111)-B(√3 × √3 )R30° system has been performed using high-resolution photoelectron spectroscopy of the Si 2p core level and polarization-dependent studies of the B 1s absorption edge. Least-squares analysis of the Si 2p core-level line shape reveals that it comprises a bulk component and a surface component shifted by 0.40±0.02 eV to higher binding energy. The exceptionally large surface-to-bulk ratio that is observed in this system suggests that the range of influence of the B atoms extends to more than 1 monolayer of Si atoms. The magnitude of the surface-to-bulk ratio is consistent with a model in which B occupies a subsurface site below a Si adatom. The B 1s edge contains a feature which is excited by the component of the electric field vector perpendicular to the surface. We argue that this arises from an electronic transition from the B 1s level into an empty surface orbital, orientated perpendicularly to the surface. We also study the change of the electronic structure as the surface is covered with Si, thereby producing a buried δ-doping layer.