Surface studies of group IV-VI layered crystals

Abstract

The surface structure of TiS2 has been investigated by low energy electron diffraction (LEED). No surface reconstruction was observed and comparison of LEED intensity data with theory suggests a slight outward relaxation of atomic planes at the surface. The LEED pattern for a crystal cleaved at a temperature below the charge density wave transition exhibited a 2ao x 2ao surface superlattice. The electronic band structures for TiS2e and TiS2 have been investigated by angle resolved photoemission spectroscopy. Excitation is provided by He I (21.2 eV) and He II (40.8 eV) ultraviolet radiation. The results indicate that TiSe2 a semimetal with a band overlap of less than 0.25 eV, while TiSi2 a semiconductor. These measured bands are in good agreement with recent theoretical band calculations.