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This work outlines conditions suitable for the heteroepitaxial growth of Cr2O3(0001) films (1.5–20 nm thick) on a Ru(0001)-terminated substrate. Optimized growth is achieved by sputter deposition of Cr within a 4 mTorr Ar/O2 20% ambient at Ru temperatures ranging from 450 to 600 °C. The Cr2O3 film adopts a 30° rotated honeycomb configuration with respect to the underlying Ru(0001) substrate and exhibits a hexagonal lattice parameter consistent with that for bulk Cr2O3(0001). Heating to 700 °C within the same environment during film preparation leads to Ru oxidation. Exposure to temperatures at or above 400 °C in a vacuum, Ar, or Ar/H2 3% leads to chromia film degradation characterized by increased Ru 3d XPS intensity coupled with concomitant Cr 2p and O 1s peak attenuations when compared to data collected from unannealed films. An ill-defined but hexagonally well-ordered RuxCryOz surface structure is noted after heating the film in this manner. Heating within a wet Ar/H2 3% environment preserves the Cr2O3(0001)/Ru(0001) heterolayer structure to temperatures of at least 950 °C. Heating an Ru–Cr2O3–Ru heterostacked film to 950 °C within this environment is shown by cross-sectional scanning/transmission electron microscopy (S/TEM) to provide clear evidence of retained epitaxial bicrystalline oxide interlayer structure, interlayer immiscibility, and epitaxial registry between the top and bottom Ru layers. Subtle effects marked by O enrichment and O 1s and Cr 2p shifts to increased binding energies are noted by XPS in the near-Ru regions of Cr2O3(0001)/Ru(0001) and Ru(0001)/Cr2O3(0001)/Ru(0001) films after annealing to different temperatures in different sets of environmental conditions. 

The electrodeposition of Ru was investigated from solutions of ruthenium(III) nitrosyl sulfate and ruthenium(III) chloride onto seed layers of epitaxial and polycrystalline Ru and epitaxial Au. Using both galvanostatic and potentiostatic deposition modes, metallic Ru was found to electrodeposit as a porous layer comprised of (0001) oriented Ru crystallites, the presence of which was discovered and confirmed by X-ray and scanning transmission and transmission electron microscope (S/TEM) analyses. This finding was independent of the Ru salt and seed layer used. Using X-ray reflectivity (XRR), the average film density ${\rho }_{eff}$of the porous electrodeposited Ru layer was measured as less than the density of bulk Ru ${\rho }_{Ru,bulk}$(14.414 g cm⁻³). Increasing the magnitude of the applied current density from −100μA cm⁻²to −10 mA cm⁻²in solutions of Ru nitrosyl sulfate increased the ${\rho }_{eff}$from 7.4 g cm⁻³to 9.7 g cm⁻²while the current efficiency decreased from 9.4% to 4.3%.