Origin of Pyroelectricity in Ferroelectric HfO₂

The emergent pyroelectricity in the ferroelectric (orthorhombic P00exc00exa2₁) phase of CMOS-compatible hafnia offers great potential for future infrared-sensing and energy-harvesting applications, but an understanding of the phenomenon in this particular compound is still lacking. The authors use first-principles calculations to show that pyroelectricity arises unexpectedly from the s00exe00exc00exo00exn00exd00exa00exr00exy effect in ferroelectric HfO₂, due to the peculiarity of its piezoelectricity. They also find an orthorhombic-to-tetragonal structural phase transition associated with a giant pyroelectric response, which can be further enhanced by doping with Si.