Similarity of the laser- and thermally annealed Si(111) surfaces

Photoemission studies using synchrotron radiation show that laser-annealed Si(111)-(1×1) and Si(111)-(7×7) surfaces have very similar electronic structures; namely, both show (i) the same two surface states (each with a characteristic angular emission pattern), (ii) similar surface core-level spectra, and (iii) the same Fermi-level pinning. We observe that the (1×1) and cleaved (2×1) surfaces are not related as recently reported. Low-energy-electron-diffraction studies conclude that the (1×1) surface has a compressed ideal (1×1) geometry; this is inconsistent with a band-theory interpretation of our results. © 1981 The American Physical Society.