Different polymorphs of Y doped HfO2 epitaxial thin films: Insights into structural, electronic and optical properties.

We report the investigation of local structure, electronic and optical properties of different polymorphs of (YO 1.5) x (HfO 2) 1- x (x = 0, 0.05, 0.10, 0.15, and 0.20) epitaxial thin films on YSZ(100) substrate prepared by pulsed laser deposition technique. The X-ray diffraction results confirm that the deposited films are epitaxial and crystal structure changes from monoclinic to orthorhombic to cubic/tetragonal as Y concentration increases in HfO 2 thin films. Spectroscopic identification of phase transformation in these thin films was investigated using Fourier transform infrared and X-ray absorption spectroscopy (XAS). Effect of crystal structure on Hf-O & Hf-Hf bond distances and disorder were investigated by extended X-ray absorption fine structure. O K-edge XAS spectra show profound changes in e g and t 2g peaks for different HfO 2 polymorphs. X-ray photoelectron spectroscopic studies confirm that different chemical environments are present in different polymorphs of HfO 2 thin film. The photoluminescence measurements validate the wide band spectral emission in wavelength region of 400–550 nm for all polymorphs and photoluminescence areal intensity shows strong dependence on phase and local structure disorder. This work will be helpful in understanding the basic material properties and spectroscopic identification of different HfO 2 phases of high application relevance in semiconductor industry. [Display omitted] • The spectroscopic investigation of phase transformation in Y doped HfO2 epitaxial thin films by FTIR and XAS technique. • The crystal structure changes from monoclinic to orthorhombic to cubic as Y concentration increases in HfO 2 thin films. • The surface composition of thin films was calculated using XPS technique. • The photoluminescence areal intensity shows strong dependence on phase and local structure disorder. [ABSTRACT FROM AUTHOR]