Identifying structural phases of polymorphic HfO₂ by vibrational spectroscopy

Hafnia (HfO₂) is a promising material for emerging chip technology, mainly due to its robust ferroelectricity, high-κ dielectric behavior, compatibility with complementary metal-oxide-semiconductor (CMOS) technology, and suitability for negative capacitance heterostructures [1-4]. The polymorphic nature of hafnia makes the identification of its different phases challenging [4]. By means of first-principles lattice dynamics calculations combined with infrared and Raman vibrational spectroscopies, we investigate the signature vibrational fingerprints of five known phases of bulk hafnia (i.e., cubic, tetragonal, orthorhombic polar, orthorhombic antipolar, and monoclinic). We test and validate our theoretical predictions against the experimental observations and identify the vibrational spectroscopic fingerprints for each of the studied phases [5]. We especially focus on the ferroelectric phase and uncover the key polar phonon mode responsible for ferroelectric polarization in the ferroelectric hafnia.

References:

[1] Böscke et al., Appl. Phys. Lett. 99, 102903 (2011).

[2] Qi et al., Phys. Rev. Lett. 125, 257603 (2020).

[3] Xu et al., Nat. Mater. 20, 826-832 (2021).

[4] Jung et al. Nano Convergence 9:44 (2022).

[5] Fan et al., npj Quantum Materials 7, 32 (2022).