Thermal oxidation of Ru(0001) to RuO₂(110) studied with ambient pressure x-ray photoelectron spectroscopy

Abstract

The thermal oxidation of Ru(0001) has been extensively studied in the surface science community to determine the oxidation pathway towards ruthenium dioxide (RuO 2 (110)), improving the knowledge of Ru(0001) surface chemistry. Using time-lapsed ambient-pressure x-ray photoelectron spectroscopy (APXPS), we investigate the thermal oxidation of single-crystalline Ru(0001) films toward rutile RuO 2 (110) in situ. APXPS spectra were continuously collected while the Ru(0001) films were exposed to a fixed O 2 partial pressure of 10 −2 mbar and the sample temperature was increased stepwise from room temperature to 400 • C. We initially observe the removal of adventitious carbon and subsequent formation of a chemisorbed oxygen overlayer at 250 • C. Further annealing to 300 • C leads to an increase in thickness of the oxide layer and a shift in the Ru-O component of the Ru 3d spectra, indicating the presence of a metastable O-Ru-O trilayer structure. A rapid formation of the RuO 2 rutile phase with an approximate thickness of at least 2.6 nm is formed about four minutes after stabilizing the temperature at 350 • C and subsequent annealing to 400 • C, signaled by a distinct binding energy shift in both the Ru 3d and O 1s spectra, as well as quantitative analysis of XPS intensities. This observed autocatalytic oxidation process agrees well with previous theoretical models and experimental studies, and the data provide the unambiguous spectral identification of one proposed metastable precursor required for full oxidation to rutile RuO 2 (110). Further ex situ characterization of the grown oxide with x-ray photoelectron diffraction confirms the presence of three rotated domains of rutile RuO 2 (110) and reveals their orientation relative to the substrate lattice.

Mn-Doped Highly Dispersed RuO2 Catalyst with Abundant Oxygen Vacancies for Efficient Decarboxylation of l-Lysine to Cadaverine

“…Generally, the small peak locating at 530.0 eV corresponded to the crystal lattice oxygen (metal−oxygen bonds) in RuO 2 crystals. 14,48,49 Unlike the uniform assignment of the lattice oxygen around 530.0 eV, there was a little divergence in the accurate assignment of oxygen vacancies. For example, in a study, 50 the peak at the binding energy of 530.5 eV was assigned to the surface oxygen vacancies.…”

Femtosecond Laser-Induced Emission of Coherent Terahertz Pulses from Ruthenium Thin Films

“…From the literature and from our XPS measurements, we know that a native oxide forms on the as-deposited Ru thin films upon contact with ambient air, 32,34 a so-called O−Ru−O trilayer. Thermal annealing above a threshold temperature causes the formation of the RuO 2 rutile phase, which grows with the annealing time and temperature.…”

Activation mechanism of ruthenium etching by Cl-based radicals in O2/Cl2 plasma

“…It has been reported that a Ru(0001) surface oxidizes to RuO 2 (110) due to irradiation with O 2 gas or O radicals. [26][27][28][29][30] We thus identified the Ru oxide as an RuO 2 layer. Figure 4(c) also shows that O and Cl atoms were major fragments on the Ru oxide layer.…”