Embedded Co nanostructures on Au(0 0 1) substrate studied by scanning tunneling microscopy

Surface structures and morphology of Co deposited on Au(0 0 1) surface have been studied by scanning tunneling microscopy (STM) up to nominal Co thickness dn of 2.4 monolayers (ML). The room-temperature (RT) growth shows pseudomorphic bcc Co growth with island structures. The structure and morphology of the samples change markedly after post-annealing at 230 °C. STM images have revealed two kinds of regular nanostructure aligned to the 〈1 0 0〉 direction. They are composed of Au(0 0 1) surface with a characteristic reconstruction modulation and the buried Co nano islands with a surfactant Au layer. It is clarified from the height profiles in STM that the core (rim) of the buried Co islands consists of 5 (4) ML Co with 1 (2) ML for Au surfactant for 2.4 ML Co deposition.