Dielectric constant and current transport for HfO2 thin films on ITO

The dielectric constant and leakage current mechanisms for HfO2 thin films deposited on indium-tin-oxide using reactive rf sputtering deposition were examined. Indium-tin-oxide was selected as the bottom metal as it is of interest as an electrode in transparent field-effect transistor development. The dielectric constant of HfO2 films was approximately 20 and did not vary significantly with deposition conditions. Temperature-dependent leakage current measurements indicate that Schottky emission is the dominant transport mechanism in films deposited at low temperature and/or low oxygen pressure. The HfO2/indium-tin-oxide barrier height was extracted to be similar to 1.1 +/- 0.2 eV. Films deposited at high temperature and/or oxygen pressure deviate from the Schottky emission model, presumably due to the formation of polycrystalline material with grain boundary conduction.