Resolving the coverage puzzle of the Pb/Si(111)-[square root]7*[square root]3 phase

The dense Pb/Si(111)-[alpha]-[square root]3-[square root]3 is studied with scanning tunneling microscopy (STM) and surface diffraction to determine its structure and its phase transformations with temperature T and coverage [theta]. The studies have shown that there are two different [square root]7 * [square root]3 phases with the same unit cell symmetry but different stoichiometry.