Oxygen-Driven Porous Film Formation of Single-Crystalline Ru Deposited on Au(111).

We examined the interaction of oxygen with ultrathin Ru layers deposited on a Au(111) substrate using scanning tunneling microscopy, X-ray photoelectron spectroscopy, and low-energy electron diffraction. The deposition of pure Ru below one monolayer (ML) at room temperature leads to the formation of clusters on the Au(111) surface, preferentially located at the elbow sites of the herringbone reconstruction. Subsequent exposure of molecular oxygen to such a Ru-covered Au(111) surface at 680 K results in the growth of two-layer-thick Ru islands that are embedded in the top Au(111) layer.

Nanoscale Origin of Mesoscale Roughening: Real-Time Tracking and Identification of Three Distinct Ruthenium Oxide Phases in Ruthenium Oxidation.

The structural modification of the Ru(0001) surface is followed in real-time using low-energy electron microscopy at elevated temperatures during exposure to molecular oxygen. We observe the nucleation and growth of three different RuO2 facets, which are unambiguously identified by single-domain microspot low-energy electron diffraction (μLEED) analysis from regions of 250 nm in diameter. Structural identification is then pushed to the true nanoscale by employing very-low-energy electron reflectivity spectra R(E) from regions down to 10 nm for structural fingerprinting of complex reactions such as the oxidation of metal surfaces.

Insights into the gas phase oxidation of Ru(0001) on the mesoscopic scale using molecular oxygen.

We present an extensive mesoscale study of the initial gas phase oxidation of Ru(0001), employing in situ low-energy electron microscopy (LEEM), micro low-energy electron diffraction (μ-LEED) and scanning tunneling microscopy (STM). The initial oxidation was investigated in a temperature range of 500-800 K at a constant oxygen pressure of p(O2) = 4 × 10(-5) mbar. Depending to the preparation temperature a dramatic change of the growth morphology of the RuO2 film was observed.