Ru and RuO2 Thin Films by XPS

Ru and RuO2 thin films are considered to be new electrode materials for dynamic random access memories (DRAMs) and ferroelectric nonvolatile memories because of their low resistivity and good thermal and chemical stabilities. In this study these thin films were pepared by reactively sputtering a Ru metal target (99.9% purity) in an argon and oxygen atmosphere. XPS spectra were collected with a PHI 1600 spectrometer equipped with a monochromatic Al Kα x-ray source and a multichannel detector. This report includes XPS spectra of Ru 3d and O 1s core regions for these samples. The binding energy of Ru 3d5/2 is determined as 280.0 and 280.8 eV for Ru and RuO2 films, respectively. The presence of a small amount of Ru with higher oxidation states, such as Ru6+ and Ru8+, is shown at the surface of the RuO2 thin film.