Thermally decomposed (110) surface of RuO2 single crystal

RuO2 single crystal is thermally reduced to generate a surface of coexisting Ru and RuO2 (Ru/RuO2) on its (110) facet, which is investigated using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The reduced RuO2 (110) facet exhibits longitudinal fissures parallel to stripes of Ru nuclei in the c -axis of the rutile structure, suggesting that the anisotropic lattice degradation commences at the weak links between the infinite chains of RuO6 octahedrons. Raman spectra of Ru/RuO2 surfaces reveal an additional feature at ∼190 cm−1 of the Ru phase among the RuO2 modes. The red-shifts and the asymmetric line width broadening of E g mode of RuO2 features are analyzed by a spatial correlation model. The fitted correlation length estimates the size of RuO2 grains which remained on the partially decomposed surface. The XPS O 1s line of the Ru/RuO2 surface provides a sensitive indication of crystal decomposition, especially at high take-off angles.