Scanning tunnelling microscopy observations at initial stage of Cs adsorption on Si(III)-√3x√3-Ag surface

The growth and ordering behaviour of Cs adatoms at the initial stage of adsorption on the Si(111)-root3 x root3-Ag surface have been investigated using low-temperature scanning tunnelling microscopy (STM). It was revealed that the Cs overlayer conducts two-dimensional gas-liquid-solid phase transitions by changing the Cs coverage below 0.143 monolayer. The STM images show that the Cs adatoms adsorb on a specific site in the unit cell of Si(111)-root3 x root3-Ag structure and move around by hopping among the equivalent sites in the liquid state. As the coverage increases, the Cs adatoms condense into the solid state, forming the surface superstructure Si(111)-root21 x root21-(Ag + Cs). Its atomic structure model was proposed based on STM observations. Copyright (C) 2005 John Wiley Sons, Ltd.