Electronic Structure of Si(100) Surfaces Studied by Two-Photon Photoemission

C. Kentsch, M. Kutschera, M. Weinelt, Th. Fauster, and M. Rohlfing

The electronic structure of the valence and conduction bands at the Si(100) surface has been studied by two-photon photoemission over a wide photon-energy range. The ionization energy was determined to 5.41±0.03 eV. The occupied surface state at is placed 0.14±0.06 below the valence band maximum. Several other spectral features are assigned to transitions involving surface states and between bulk bands including backfolded bands due to the surface reconstruction. The moderate agreement between experimental data and band structure calculations calls for an improved theoretical description of the two-photon photoemission process at semiconductor surfaces incorporating, e.g., a one-step model and excitonic effects.