AbstractThe effects of Cs on oxygenated epitaxial diamond (100) films are studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). The epitaxial diamond (100) films are grown on synthetic diamond substrates using chemical vapor deposition and are boron doped. Before Cs deposition and oxygenation, UHV STM imaging of the epitaxial (100) films reveals a (2×l) dimer reconstruction. After Cs deposition and oxygenation, steps with relatively smooth surfaces are observed using positive tip voltages. Using negative tip voltages, many round bright structures approximately 20 Å in diameter are observed on the surface. We propose that these bright structures are Cs atoms or clusters of Cs atoms. Since these structures are only observed for negative tip voltages, they have a large number of empty states. Our observations are compared with recent theoretical predictions for Cs adsorbed on oxygenated diamond (100).