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 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. PACS  73.61.Ng; 73.50.Lw; 77.55.+f