Breakdown mechanism in insulating zinc oxide film

A highly c-axis oriented and insulating zinc oxide (ZnO) thin film has been deposited by rf sputtering at room temperature. We have attempted to establish the mechanism of breakdown in insulating ZnO films in a metal-insulator-metal configuration using capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics. The C-V characteristics exhibit hysteresis during the retrace. The G-V characteristic was linear for both forward and reverse bias for small bias voltages. However, for a large bias strong directional behavior depending on the polarity of the applied bias was observed. The magnitude of the maximum value of conductance and the breakdown field were found to depend on the sweep rate indicating a thermal origin for the breakdown. The non-linearity is found to depend on the substrate metallization. The Influence of bottom electrodes on the dielectric properties is also discussed.