Leakage currents in high-permittivity thin films

Quite often leakage current data through high-permittivity thin films exhibit straight lines in the Schottky plot, i.e., log (current density j) versus sqrt (mean applied field), which suggests an electrode-limited current by field-enhanced thermionic emission. Unfortunately, the extracted permittivity at optical frequencies seldom is in agreement with experimental values and often is unacceptably small, i.e., <1. We suggest a model demonstrating that the leakage current in high-permittivity thin films is bulk-limited, but still is showing the characteristic dependence of thermionic emission. This is due to a combination of boundary conditions of the model, low-permittivity thin layers (dead layer) at the electrodes and current injection/recombination terms at the injecting/collecting electrodes, respectively. (C) 2003 American Institute of Physics.