Dielectric properties of high-k oxides: Theory and experiment for Lu2O3

The quest for a dielectric for the replacement of silica in Si-based devices has focused the attention of the scientific community on the class of high dielectric constant ($\kappa )$ insulators. In this work we unfold the physical origin of $\kappa $ and its direct connection with lattice dynamics and polarizability in these materials, analyzing the specific case of Lu$_{2}$O$_{3}$ in its ground-state bixbyite structure with a combined experimental and theoretical analysis. The vibrational dielectric function of Lu$_{2}$O$_{3}$ thin films grown by atomic-layer deposition was studied by infrared transmission and reflection-absorption spectroscopies, selectively accessing transverse and longitudinal optical frequencies. The static dielectric constant was extracted analyzing the infrared response. We also present first-principles density-functional linear-response calculations, which are in close agreement with experiment, and provide insight into the microscopic nature of vibrational spectra and dielectric properties.