Effect of oxygen on the electrical transport in RuO₂

Abstract

The electrical resistivity of RuO2 films formed by reactive sputtering, with oxygen contents in the sputtering chamber varying from 25% to 100%, was measured in the 4.2-300 K temperature range. The resistivity ρ is metallic and linear in temperature above 150 K, indicating primarily phonon scattering. The resistivities vary by an order of magnitude with the amount of oxygen in the chamber, even though all films are, within 8%, stoichiometric RuO2. These variations are correlated with changes in microstructure. A minimum in ρ is observed at 50% O2, although the residual resistance ratio is monotonically decreasing with percentage O2 and increasing with the grain size. In the grain boundary scattering model this minimum is mirrored in the minimum in the reflection coefficient at the boundaries. However, there is some evidence of changing carrier concentration with oxygen and a simple boundary scattering picture may not be adequate.