C-Axis-Oriented Ru Thin Films Prepared by Sputtering in Ar and O2 Gas Mixture

C-axis-oriented Ru thin films were deposited on glass substrates by sputtering a Ru target in Ar and O2 gas mixture with O2 flow ratios which were lower than that required for RuO2 formation. A minimum value of 3.5° was obtained for the full-width at half maximum (FWHM) of the rocking curve of a Ru (002) peak for the Ru film deposited at a substrate temperature of 500°C and O2 flow ratio of 4%. The c-axis-oriented Ru films were observed to be formed from the initial stage of crystal growth and became continuous even at a film thickness of 3 nm. Two-dimensional crystal growth of the single-axis-oriented Ru films was suggested.