Exploring the optical properties of Vernier phase yttrium oxyfluoride thin films grown by pulsed liquid injection MOCVD

In this work, we report on the first successful deposition of Vernier phase yttrium oxyfluoride (V-YOF) thin films on Si (100) wafers using pulsed liquid injection metal organic chemical vapor deposition (PLI-MOCVD). The formation of V-YOF has been confirmed by X-ray diffraction measurements and electron probe microanalysis. The infrared phonon modes of V-YOF thin films and their corresponding optical constants as inferred from spectroscopic ellipsometry are reported here for the first time. The V-YOF thin films are featured by a broad absorption band centering around 370-373 cm^-1; their refractive index is located between those of YF₃ and Y₂O₃, and which shows an intimate relationship with the oxygen content in the film. The luminescence properties of Er³⁺ doped V-YOF thin films are finally examined and compared with that of YF₃. Our results highlight that the as-deposited V-YOF thin films by PLI-MOCVD serve as promising candidates as efficient host material for spectral conversion for photovoltaic applications.