MICROSTRUCTURE OF RUTHENIUM DIOXIDE FILMS GROWN ON ALPHA-AL2O3(0001),ALPHA-AL2O3 (1(1)OVER-BAR02), AND SRTIO3 (100) USING REACTIVE SPUTTERING

A quantitative study was made of the composition and microstructure of RuO2 films deposited on three different substrates using reactive spu ttering. Most of the films had a composition within 2.5 wt. % of the c orrect stoichiometry; the only exceptions were films grown on Al2O3 (0 001) at 150 degrees C, which had an oxygen-to-ruthenium ratio of 1:2.2 4. The excess oxygen was attributed to a thin oxygen-rich layer that e ncapsulated the grains. Hydrogen concentrations for the films deposite d on Al2O3 (0001) were 14, 6, 6, and <0.5 at. % for room, 150, 300, an d 450 degrees C growth temperatures respectively. The films deposited at room temperature were amorphous on Al2O3 (0001) and SrTiO3 (100), b ut weakly crystalline on Al2O3 (<1(1)over bar 02>). Highly oriented Ru O2 (100) films were produced on Al2O3 (0001) at deposition temperature s greater than or equal to 150 degrees C. The in-plane alignment was [ 010](RuO2)//[<(2)over bar 110>](Al2O3) and a threefold mosaic microstr ucture was observed. The grain boundaries in these films were disconti nuous until the substrate temperature was raised to 450 degrees C, whe re coherent grain boundaries were formed. The films grown on Al2O3 (<( 1)over bar 102>) at 450 degrees C exhibited the epitaxial relationship : RuO2(101)//Al2O3 (<(1)over bar 102>). The in-plane alignment was RuO 2[101]//Al2O3[<(1)over bar 101>], and the lattice parameters were the same as found in bulk RuO2. Transmission electron microscopy indicated a large degree of imperfection in the region between coalescing grain s. The RuO2 films grown on SrTiO3 (100) at room temperature were amorp hous. The film grown at 450 degrees C showed a preferential orientatio n with RuO2 (100)//SrTiO3 (100), but without in-plane orientation.