【Others Papers】Enhanced Hypersensitive (⁵D₀→⁷F₂) Transition Characteristics of Eu³⁺ Doped β-Ga₂O₃ Microrods

      Researchers from the Anna University have published a dissertation titled "Enhanced Hypersensitive (⁵D₀→⁷F₂) Transition Characteristics of Eu³⁺ Doped β-Ga₂O₃ Microrods" in Journal of Molecular Structure.

Abstract

      Exploring and realizing the luminescence characteristics of rare earth metal (RE) ions doped gallium oxide (Ga₂O₃) is crucial for developing optoelectronic device applications. The current research used the solid-state reaction approach to synthesize Ga₂O₃ microrods doped with various europium (Eu³⁺) concentrations (0.1, 0.2, 0.3, 0.5, 0.75, and 1 mol). X-ray diffraction (XRD) and Raman spectral analyses confirm the monoclinic structure of β-Ga₂O₃. The intensity of the Raman phonon modes decreased and a peak shift was observed for Eu:β-Ga₂O₃. The electron microscopy (SEM, TEM) images depicted a nearly uniform distribution of microrods for undoped and Eu:β-Ga₂O₃ samples. The interplanar distance (d = 0.290 nm, 0.561 nm, and 0.433 nm), from HR-TEM images, corresponding to (0 0 4), (1 0 0), and (1 0 2) crystallographic orientations confirm the monoclinic structure of β-Ga₂O₃. The elemental mapping images showed a nearly homogeneous Ga, O, and Eu distribution. The UV-visible diffuse reflectance spectroscopy (UV-DRS) showed a notable reduction in the bandgap as the Eu³⁺ concentration increased. The emission spectra of Eu: β-Ga₂O₃ microrods showed a narrow red emission at 612 nm (⁵D₀ → ⁷F₂), which relates to the ⁵D₀ → ⁷F_j (j = 0, 1, 2, 3) energy level arising from an intra-4f transition of Eu³⁺ ions upon 394 and 465 nm excitation. The red emission was found to increase with Eu content up to 0.5 mol.%. A quenching of emission due to the multipole–multipole interactions was obtained beyond 0.5 mol.% of Eu. The absolute quantum yield (η) calculated for Eu: β-Ga₂O₃ (0.5 mol.%) was 3.82%. The luminescence decay curve using the bi-exponential fit and the average lifetime (τ) of the Eu: β-Ga₂O₃ (0.5 mol.%) was found to be ∼0.172 ms. CIE chromaticity and correlated color temperature analyses of Eu:β-Ga₂O₃ microrods yielded a red emission with a superior color purity (93%). The obtained results suggest that Eu:β-Ga₂O₃ (0.5 wt.%) microrods could be one of the potential candidates for red light sources.

DOI：

https://doi.org/10.1016/j.molstruc.2024.140144