Growth and electronic structure of some monovalent metals on TiS2(001)

The epitaxial growth of Ag on TiS2(001) is characterized using reflection high-energy electron diffraction (RHEED), low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Ag grows in the (111) orientation epitaxially on TiS2(001) with Ag[110BAR]parallel-toTiS2[100]. The growth mode belong to the Volmer-Weber type, which means that Ag forms three-dimensional clusters on top of TiS2(001). Ag also diffuses slowly into the substrate. The evolution of the electronic structure during this intercalation process is studied in detail with angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and x-ray photoelectron spectroscopy (XPS). We observed a striking difference between surface Ag and subsurface or intercalated Ag. We conclude that Ag atoms on TiS2(001) have little interaction with the substrate, while upon intercalation charge transfer takes place from Ag to TiS2. For comparison, we also studied Na and K at the TiS2(001) surface. At low temperature (-140-degrees-C), Na deposition results in an ordered (square-root 3 x square-root 3)R30-degrees superstructure. Na and K intercalation proceeds very rapidly. The Ti2p core-level spectra provide additional evidence that charge transfer has taken place after deposition and intercalation of Ag, Na and K.