Ba and BaOx surface structures on Au(111)

Scanning tunneling microscopy (STM) is used to investigate surface structures of barium and barium oxide grown on (22 × 3 )-reconstructed Au(111) surfaces. Evaporated Ba attaches to the Au herringbones after ultrahigh vacuum (UHV) annealing, forming a stripe pattern. Oxidation of the Ba stripes gives rise to a BaOx structure pinned to the Au herringbones. Conversely, well-ordered epitaxial BaOx structures can be obtained with oxidation of the deposited Ba by residual oxygen and subsequent UHV annealing. The two ordered BaOx phases, a (6 × 6) and a (2 3 × 2 3 )-R30° structure, coexist on the surface and lift the Au reconstruction.