Paper SS+AS-TuM9
Growth of Oxide Nanowires on Vicinal Metal Surfaces: Atom Exchange Processes at Step Edges

Tuesday, October 29, 2013, 10:40 am, Room 201 A

Low-dimensional model systems are of fundamental importance to elucidate emergent phenomena in condensed matter physics and chemistry. Here we present 1-dimensional oxide-metal hybrid model systems, Co-oxide and Mn-oxide nanowires coupled to a Pd surface, which have been fabricated by the decoration of steps of a vicinal Pd(100) surface. We have studied the growth of Co-oxide and Mn-oxide nanostructures on a Pd(1 1 23) surface using LEED and STM, and have probed their electronic properties by STS in a low-T (5K) STM. At low oxide coverages and suitable kinetic conditions, the Pd step edges are decorated by oxide nanostripes, while the Pd(100)-like terraces are covered by a (2x2) layer of chemisorbed oxygen (as a result of the reactive metal oxide deposition procedure). However, there are significant structural differences between Co- and Mn-oxide nanowires: whereas Mn-oxide decorates the Pd steps by monoatomic MnO_x lines in a pseudomorphic (1x1) arrangement, Co-oxide grows in form of 2-4 atom-wide CoO_x nanostripes, with a strained hexagonal structure partially embedded into the outer terrace areas. In addition, rod-like structures attached to the CoO_x step edges are periodically observed, which have been identified by STS as rows consisting of 4±1 Pd atoms that have been ejected from the Pd steps. This indicates that Co-Pd atom exchange at the step edges is a dominant feature during oxide step decoration and growth. The absence of such structures on the MnO_x covered Pd(1 1 23) surface demonstrates that Mn-Pd atom exchange is much less pronounced, thus revealing a significant difference in growth behavior between MnO_x and CoO_x nanostructures and in their interactions with Pd surfaces.

Work supported by the ERC Advanced Grant SEPON.