Raman spectroscopy and high-resolution luminescence spectroscopy of Ce3+ doped Tb3Al5O12 single crystalline film phosphors grown onto Gd3Al2.5Ga2.5O12 and Y3Al5O12 substrates

Abstract

We present the results of a study on Raman and high-resolution luminescence spectroscopy of Ce³⁺-doped Tb₃Al₅O₁₂ single crystalline films (SCFs) grown by the liquid phase epitaxy (LPE) method onto Y₃Al₅O₁₂ and Gd₃Al_2.5Ga_2.5O₁₂ single crystal (SC) substrates. The Ce³⁺-doped Tb₃Al₅O₁₂ films exhibit a strong Ce³⁺ 5d–4f emission band centred at 560 nm when excited around 488 nm in the vicinity of the 4f–5d absorption band of Ce³⁺ and the 4f–4f absorption bands of Tb³⁺ ions in the visible range. To avoid overlapping with this luminescence, Raman spectra were recorded using a 785 nm excitation wavelength. The lattice mismatch between the Tb₃Al₅O₁₂:Ce films and the Y₃Al₅O₁₂ and Gd₃Al_2.5Ga_2.5O₁₂ substrates was found to be +0.53% and −1.32%, respectively. The film grown on the Gd₃Al_2.5Ga_2.5O₁₂ substrate exhibits negative and higher residual stress compared to its counterpart grown onto the Y₃Al₅O₁₂ substrate. The observed shifts in the positions of the Raman modes for the two epitaxial structures correlate with the differences in lattice constants between the films and their respective substrates. High-resolution luminescence spectra recorded at 488 nm and 785 nm excitation wavelengths reveal 5d–4f and 4f–4f electronic transitions of Ce³⁺ ions and lanthanide trace impurities, respectively.