Microstructures and electrical resistivities of the RuO2 electrode on SiO2/Si annealed in the oxygen ambient

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Abstract
The electrical resistivity property of RuO2 thin films grown on the SiO2/Si substrate by reactive dc sputtering was examined in terms of microstructure using x-ray diffraction and cross-sectional transmission electron microscopy. As the samples were annealed in the oxygen ambient over the temperature range 300–700 °C, the resistivity decreased from 270 to 90 μΩcm with increasing annealing temperature. When heat treatment was performed below 500 °C, the strain which accumulated in the RuO2 layer during deposition was released without significant increase in grain size. It is thought that below 500 °C improvement in the crystallinity plays an important role in the variation of the resistivity. Although a considerable amount of growth of RuO2 grains was achieved, the columnar structure of the RuO2 layer in the as-deposited sample remained unchanged even after annealing at 700 °C. The resistivity improvement above 500 °C was driven mainly by the grain boundary annihilation.