Optical study of potassium growth on the Si(100) surface

The formation of the Si(100)/potassium interface has been studied by real-time surface reflectance spectroscopy, Auger electron spectroscopy and low energy electron diffraction. The changes of the Si optical reflectance have been followed as a function of the amount of K deposited at room temperature. The first step of adsorption gave rise to a phase transition which occurs at about 0.4 SML (where 1 SML corresponds to the saturation monolayer). The corresponding optical spectra displayed peculiar features which could be due to a symmetrization of the dimers at the silicon surface. Two growth processes could be distinguished, which yielded different equilibrium states: a 'dynamic' process observed during K evaporation (with a saturation larger than 1 SML) and a 'static' one which takes place after the evaporation has been stopped (saturation at 1 SML). The optical spectrum corresponding to the saturation of the dynamic process displays an absorption band which is interpreted as due to resonances in small K clusters, as observed in free K cluster experiments.