Formation of Periodic Arrays of O Vacancy Clusters on Monolayer FeO Islands Grown on Pt(111)

The structural evolution of a Pt surface with 0 4 monolayer (ML) subsurface Fe on annealing in 11 x 10(-7) kPa O-2 was studied by scanning tunnel mu microscopy and X-ray photoelectron spectroscopy When the annealing temperature was 600 K. only dissociative adsorption of O-2 occurred, which induced the local restructuring of surface legions At 750 K, subsurface Fe atoms segregated onto the sin face and were oxidized When the annealing temperature was increased to 850 K. well defined monolayer FeO islands with periodic arrays of defects were formed The defects were located at the hexagonal closest packed sites (fcc) of FeO Moire unit cells and were either single oxygen vacancies of multiple oxygen vacancies consisting of six missing O atoms The formation of periodic defects On monolayer FeO islands may be a way to construct active sites on Pt-Fe model catalysts