Fluoride-target-assisted growth of Pb2OF2 oxyfluoride films with anion ordering and high dielectric constant

Abstract

Recent research increasingly focuses on mixed-anion compounds, wherein oxygen sites in the metal oxides are substituted with other anions. However, the synthesis of such compounds remains limited compared to conventional oxides, highlighting the need for new fabrication methods. In this study, oxyfluoride Pb₂OF₂ films are synthesized using pulsed laser deposition (PLD) with a PbF₂ target. The substrate temperature plays a crucial role in stabilizing the oxyfluoride phase, with an optimal temperature of approximately 200 °C. Furthermore, (110)-oriented growth on perovskite-type single-crystal oxide substrates was achieved, wherein oxygen and fluorine ions exhibited out-of-plane ordering. The (110)-oriented Pb₂OF₂ films demonstrated a relatively high dielectric constant (ε_r = 22)—four times larger than that of the polycrystalline films—likely due to enhanced ionic response resulting from improved structural ordering.