Epitaxial growth of Yb/Er co-doped HfO₂ films with coexisting ferroelectric and luminescent properties

We report on the fabrication of high-quality Yb³⁺ and Er³⁺ co-doped HfO₂ epitaxial films using pulsed laser deposition. The host material HfO₂ has relatively low phonon energy, which is desirable to inhibit the nonradiative relaxation. The dopant Yb³⁺ is used to stabilize the ferroelectric o-phase and also acts as the sensitizer to enhance the optical absorption cross section, while Er³⁺ is the luminescence activator. The films exhibit robust ferroelectricity with a remanent polarization of 12 μC/cm² and comparable endurance performance to HfO₂-based epitaxial films reported before. The up- and downconversion luminescence properties were ascertained by photoluminescence spectroscopy. The Yb³⁺/Er³⁺ co-doped HfO₂ films with coexisting ferroelectric and luminescent functionalities may suggest a promising approach toward electric field tunable phosphors.