Extending an Asymmetric Double Well Potential Model to Hfo2

摘要

Previously an asymmetric double well potential model was successfully applied to interpret the nonlinear relaxational polarization of Al2O3. Here we extend this model to HfO2. The capacitance measurements on HfO2 based metal-insulator-metal MIM capacitors were performed. To study this relaxational polarization the thickness of the dielectric, device temperature, frequency and electric field were varied systematically. It was revealed that at lower temperatures T ≤ 180 K the relaxation happens via proton tunneling transition in asymmetric double wells. Incorporation of protons in HfO2 is illustrated by monitoring the mass spectra during oxide evaporation. Above 180 K the thermal activation transition comes in a play but the relaxation process is also found to be influenced by electrode space charges. One of our goals here was to show that our model is not specific to Al2O3 and it has the ability to explain the nonlinearity of other metal oxides.