Extending an Asymmetric Double Well Potential Model to HfO2

Previously an asymmetric double well potential model was successfully applied to interpret the nonlinear relaxational polarization of Al
₂
O
₃
. Here we extend this model to HfO
₂
. The capacitance measurements on HfO
₂
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 HfO
₂
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 Al
₂
O
₃
and it has the ability to explain the nonlinearity of other metal oxides.