Phase Identification of 850 nm Thick 7%YO1.5–93%HfO₂ Films by Surface and Cross-Sectional Raman Spectroscopies

Phase identification of 850 nm thick 7%YO1.5–93%HfO2 films was carried out by analyzing both the surface and cross-sectional Raman spectra together with conventional X-ray diffraction (XRD). Preparation of 7%YO1.5–93%HfO2 films was conducted by deposition at room temperature on Pt-coated (100)Si substrates by pulsed laser deposition and postheat-treatment at 600–1100 °C under atmospheric N2 flow. The cross-sectional Raman spectra changed with the postheat-treatment temperature in accordance with the crystal structure determined by XRD measurements. Moreover, surface Raman analysis revealed that the crystalline phase transformed from the tetragonal phase (P42/nmc) to the orthorhombic phase (Pca21) when an electric field was applied. These data clearly show that Raman spectroscopy is a powerful tool for detecting the constituent phase with a spatial resolution on the order of several micrometers. In addition, a good signal-to-noise ratio was obtained from the cross-sectional Raman spectrum of 850 nm thick 7%YO1.5–93%HfO2 films, indicating promise for future measurements of the strain state and phase distribution along the thickness direction using this good spatial resolution.