Faceting of Re ($11\bar {2}1)$ induced by oxygen

The oxygen-induced nanoscale faceting of Re ($11\bar {2}1)$ has been studied by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES); the results are compared with recent STM and LEED studies of O-induced faceting of Re($12\bar {3}1)$. The evolution of surface morphology depends on oxygen exposures and deposition temperatures. Re($11\bar {2}1)$ remains planar after oxygen deposition at 300K. Annealing O-covered Re($11\bar {2}1)$ between 800K-1200K leads to the formation of ($01\bar {1}0)$ and ($10\bar {1}0)$ facets that coexist with the ($11\bar {2}1)$ surface. Under oxidation conditions, i.e. dosing a large amount of oxygen at high temperatures (900-1000K), the ($11\bar {2}1)$ surface is completely covered by 4-sided nanoscale pyramidal structures whose facets are identified as ($01\bar {1}0)$, ($10\bar {1}0)$, ($01\bar {1}1)$ and ($10\bar {1}1)$. The fact that the ($11\bar {2}1)$ surface becomes completely faceted only after oxidation is consistent with our previous data for O-induced faceting of Re($12\bar {3}1)$, where one facet has the ($11\bar {2}1)$ orientation and is unstable against oxidation. The faceted O/Re surfaces may be potential templates to grow nano-structures with narrow size distribution, and may also be substrates to study structural sensitivity in catalytic reactions.