LAYER GROWTH OF CS ON SI(100)C(4X2) STUDIED WITH PHOTOELECTRON-SPECTROSCOPY

Different coverages of Cs on the cold Si(100)c(4x2) surface were studi ed by photoelectron spectroscopy. Valence-band spectra were recorded t ogether with Si 2p and Cs 4d core-level spectra at a sample temperatur e of similar to 100 K for increasing Cs coverage. Emission from Ca ato ms at the Si-Cs interface and from the bulk and surface of the Cs over layer is readily identified in the Cs 4d spectra. Three different kind s of plasmon losses contribute to the photoemission background. The pl asmons originate from the Si-Cs interface, Cs surface and Cs bulk with energies of around 1.0, 2.2, and 3.2 eV, respectively. The Si 2p emis sion becomes attenuated for increasing Cs coverage and is not detectab le at a coverage of similar to 4.4 times the room temperature saturati on coverage. From the results of a systematic and quantitative analysi s of the spectra combined with low-energy electron diffraction results , we conclude that Cs grows in a layer-by-layer fashion on the cold Si (100)c(4x2) surface.