Cu-O atomic chains observed on an ultrathin film of Cu(110)

The fringe contrast observed in a copper film with its Cu[110] parallel to the incident electron beam has been investigated by high-resolution electron microscopy (HREM). According to a geometrical analysis for these fringes, it was assumed that they originated from the Cu-O chains adsorbed on a Cu(110) surface. This assumption was confirmed by a multislice image simulation on the basis of the electron diffraction and imaging theory using an added-row reconstruction model. Our calculation indicates that an added-Cu-O-chain surface reconstruction can generate a regular fringe pattern with sufficient contrast in a thin copper film with a thickness of several nanometers. The present study demonstrates the potential of HREM to investigate surface structures and surface reaction of ultrathin films at the atomic level.