Surface reduction of ruthenium compounds with long exposure to an X-ray beam in photoelectron spectroscopy

The reduction of Ru at the surface of commercial RuCl3 and RuO2 has been ob served during XPS analysis. The experiments have been performed with either a non-monochromatized (Mg K-alpha) or a monochromatized (Al K-alpha) X-ray beam. Ruthenium reduction is enhanced by increasing the X-ray dose, but th e residual pressure exerts only a weak influence. The initial composition o f commercial ruthenium (III) chloride hydrate is a complex mixture of chlor o or chlorohydroxo species rather than pure RuCl3. nH(2)O. RuCl3 is not sui table as a reference compound for ruthenium chloride compounds in XPS analy sis, because it contains mainly Ru(IV) which is reduced under X-ray. A simi lar reduction occurs at the surface of RuO2 samples (by reduction of RuO3 l ayers), and on the adventitious carbon. (C) 1999 Elsevier Science B.V. All rights reserved.