Si(100) and Ge(100) core-level shifts: A reevaluation

High resolution core level photoemission was used to study the Si 2p core levels of the clean Si(100) surface and other related surfaces, and the Ge 3d core level of the clean Ge(100) surface and other related surfaces. Two surface components S and S′ for the Si 2p core level from the clean Si(100) surface have been resolved. The S and S′ components were resolved for the Ge 3d core level from clean Ge(100) surface for the first time. On both surfaces, S and S′ components are identified to be the contribution from surface dimer atoms and the subsurface layer, respectively.