Reactively sputtered Ru–Si–O films

Abstract

Films of Ru–Si–O were synthesized by reactively sputtering a Ru1Si1 target in an Ar/O2 gas mixture. They were characterized in terms of their composition by 2.0 MeV He++4 backscattering spectrometry, their atomic density by thickness measurements combined with backscattering data, their microstructure by x-ray diffraction and transmission electron microscopy, and their electrical resistivity by four-point-probe measurements. The compositions indicate preferential sputtering with ruthenium enrichment of the films, and a saturation level of oxygen is determined at 67 at. % corresponding to the formation of SiO2 and RuO2. X-ray diffraction spectra reveal an amorphous structure for oxygen-saturated and nanocrystals for unsaturated as-deposited films. The crystallization temperature clearly increases with the oxygen concentration of the films, from 500 °C for oxygen-free films to 1000 °C for oxygen-saturated films, when annealed in vacuum for 30 min. Transmission electron micrographs of as-deposited oxygen-saturated films show few nanocrystals of 1–2 nm in diameter in an otherwise amorphous matrix. The atomic density is roughly 8×1022 atom/cm3 for all compositions. The resistivity of the ternary alloys scales with the terminal phases in the ternary phase diagram and reaches a maximum value when the Ru–SiO2 tie line is crossed near 50 at. % oxygen. The films are stable in vacuum up to thermal stressing at 800 °C for 5 h, and their decomposition starts near 1000 °C.