The Role of Zr on Monoclinic and Orthorhombic Hf(x)Zr(y)O(2) Systems: A First-Principles Study

HfO(2) shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO(2) is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P2(1)/c and the orthorhombic Pca2(1) polymorphs of HfO(2), Hf(0.75)Zr(0.25)O(2), and Hf(0.5)Zr(0.5)O(2) 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 Pca2(1) polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of Hf(x)Zr(y)O(2) 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(x)Zr(y)O(2), identifying the effects of doping phenomena.