Unveiling the double-well energy landscape in a ferroelectric layer.

The properties of ferroelectric materials, which were discovered almost a century ago, have led to a huge range of applications, such as digital information storage, pyroelectric energy conversion and neuromorphic computing. Recently, it was shown that ferroelectrics can have negative capacitance, which could improve the energy efficiency of conventional electronics beyond fundamental limits. In Landau-Ginzburg-Devonshire theory, this negative capacitance is directly related to the double-well shape of the ferroelectric polarization-energy landscape, which was thought for more than 70 years to be inaccessible to experiments. Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric HfZrO. To achieve this, we integrated the ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has its origin in the energy barrier in a double-well landscape. Furthermore, we demonstrate that ferroelectric negative capacitance can be fast and hysteresis-free, which is important for prospective applications. In addition, the HfZrO used in this work is currently the most industry-relevant ferroelectric material, because both HfO and ZrO thin films are already used in everyday electronics. This could lead to fast adoption of negative capacitance effects in future products with markedly improved energy efficiency.