Using Raman spectroscopy and x-ray diffraction for phase determination in ferroelectric mixed Hf1−xZrxO2-based layers

The discovery of ferroelectric properties in the doped HfO2 and mixed Hf1−xZrxO2 systems made precise phase determination very important. However, due to the similarities of the diffraction peaks between the tetragonal and the orthorhombic phases, the discrimination of these two critical phases by x-ray diffraction remains challenging. This work introduces Raman spectroscopy as a structural characterization method to unambiguously identify phases by comparing experimental data with density functional simulation results for the mixed hafnia–zirconia system in the complete composition range. Raman modes for the non-polar monoclinic and tetragonal phases are presented in comparison to those of the polar orthorhombic phase. Changes in phonon mode frequencies in the hafnia–zirconia system with Hf/Zr composition are related to the appearance of ferroelectric properties.