The Role of Zr on Monoclinic and Orthorhombic HfxZryO2 Systems: A First-Principles Study

Eleonora Pavoni; Elaheh Mohebbi; Pierluigi Stipa; Davide Mencarelli; Luca Pierantoni; Emiliano Laudadio

doi:10.3390/ma15124175

The Role of Zr on Monoclinic and Orthorhombic Hf_xZr_yO₂ Systems: A First-Principles Study

Materials (Basel). 2022 Jun 13;15(12):4175. doi: 10.3390/ma15124175.

Authors

Eleonora Pavoni¹, Elaheh Mohebbi¹, Pierluigi Stipa¹, Davide Mencarelli², Luca Pierantoni², Emiliano Laudadio¹

Affiliations

¹ Department of Materials, Environmental Sciences and Urban Planning, Marche Polytechnic University, 60131 Ancona, Italy.
² Information Engineering Department, Marche Polytechnic University, 60131 Ancona, Italy.

Abstract

HfO₂ shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO₂ is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P2₁/c and the orthorhombic Pca2₁ polymorphs of HfO₂, Hf_0.75Zr_0.25O₂, and Hf_0.5Zr_0.5O₂ is reported. For all six systems, density functional theory (DFT) methods based on generalized gradient approximations (GGAs) were first used; then the GGA + U method was settled and calibrated to describe the electrical and optical properties of polymorphs and the responses to the oxygen vacancies. Zr had different effects in relation to the polymorph; moreover, the amount of Zr led to important differences in the optical properties of the Pca2₁ polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of Hf_xZr_yO₂ nanostructures. The combined GGA and GGA + U methods adopted in this work generate a reasonable prediction of the physicochemical properties of o- and m-Hf_xZr_yO₂, identifying the effects of doping phenomena.

Keywords: HfO2; Hubbard; Zr doping; optical properties; oxygen vacancies.

Grants and funding

951761/European Commission