STM study of surface restructuring of oxidized Cu(100)

The Cu(100) surface offers a model platform for the investigation of the copper oxidation process. Starting from clean Cu(100), we characterized oxidized surfaces with varying oxygen exposure, sample temperature, and post-oxidation annealing conditions. Scanning tunneling microscopy was used to characterize the surfaces with atomic resolution imaging at 78 K. Annealing in O-2 (P similar to 5<middle dot>10(-6) mbar) at 80-260 degrees C led to the (2 root 2 x root 2) R45 degrees Cu(100)-O missing row reconstruction (MRR), which self-limited at monolayer coverage and was relatively insensitive to exposure or temperature in this range. Further annealing of the MRR surface in UHV (P-O2 < 10(-9) mbar) at 160 degrees C resulted in large scale reorganization of the surface into MRR areas with a higher degree of step-bunching, coexisting with facet-like hills. The facets are decorated by terraces with a quasi-hexagonal lattice that we attribute to a Cu(110) c(6 x 2) oxygen induced reconstruction.