AVS 56th International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF1-MoM

Paper TF1-MoM5
Influence of Nanostructure on Charge Transport in RuO2 Thin Films

Monday, November 9, 2009, 9:40 am, Room B3

Session: Thin Films: Growth and Characterization I
Presenter: M.M. Steeves, University of Maine
Authors: M.M. Steeves, University of Maine
R.J. Lad, University of Maine
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Ruthenium dioxide exhibits metallic electrical conductivity, and may have both electron and hole contributions to its charge transport. In this study, polycrystalline thin films of RuO2 were grown on fused quartz substrates by RF reactive magnetron sputtering, and a parametric study was carried out to probe the influence of film nanostructure on the four-point Van der Pauw resistivity and Hall coefficient. The films were grown via reactive RF magnetron sputtering of a Ru target in an Ar/O2 plasma using a range of deposition rates and with substrate temperatures ranging from 20-500oC. A wide variety of nanostructures and film textures were obtained as determined by high resolution x-ray diffraction for film thicknesses ranging from 40-180 nm as measured by x-ray reflectivity and profilometry. The films exhibited strains of the order of 0.5% and average crystallite sizes ranging from 20-70 nm. Room temperature resistivities varied between 200-400 μΩ cm and showed a relatively weak dependence on temperature. Hall coefficients ranged from +200 to -200 x10-5 cm3/C as a function of temperature, depending on exact nanostructure as well as the heating environment. The observation of both positive and negative Hall coefficients for different RuO2 films is in contrast to the reported single crystal value of -11 x10-5 cm3/C for which electrons are the majority carrier. Correlations between nanostructure and transport properties are given in terms of grain size, strain, film defects, and mobility of the majority carriers.