【Substrate Papers】Physical and Multi-Stimuli Luminescence Properties with Defect Correlation in (100) and (010) Oriented Eu:β-Ga₂O₃ Single Crystals

      Researchers from the Anna University have published a dissertation titled "Physical and Multi-Stimuli Luminescence Properties with Defect Correlation in (100) and (010) Oriented Eu:β-Ga₂O₃ Single Crystals" in Materials Research Bulletin.

Abstract

      Rare-earth-doped gallium oxide single crystals possess a wide bandgap and tunable luminescence, yet their material performance optimization for scintillator and optoelectronic applications remains largely unexplored. The present study investigates the luminescence impact of Eu³⁺ doping (0.05, 0.1, 0.2, 0.3, and 0.5 mol%) on β-Ga₂O₃ single crystals oriented along the (100) and (010) planes. Microscopy analysis revealed the morphological changes with a roughness value below 2 nm, increasing at 0.2 mol.% of Eu³⁺. X-ray diffraction (XRD) and Raman analyses showed peak shifts and a 4 cm⁻¹ Raman shift, with reduced peak intensity, indicating lattice strain. X-ray photoelectron spectroscopy (XPS) confirmed the Eu³⁺ state, and elemental mapping revealed a uniform distribution of Eu. Optical studies demonstrated reduced transmission (40–60%) and bandgap narrowing, from 4.27 ± 0.02 to 4.12 ± 0.014 eV for the (100) orientation and from 4.18 ± 0.015 to 3.98 ± 0.021 eV for the (010) orientation. Photoluminescence exhibited broad emission (280 nm) and narrow hypersensitive ⁵D₀→⁷F₂ transitions at 611 nm (394 nm excitation) with the highest emission intensity at 0.5 mol.% Eu for (100) and 0.1 mol.% Eu for (010) yielding a quantum efficiency of 3.13%. The decay time was shortened, with τ₁ below 1 μs and τ₂ nearly 2 μs. Thermoluminescence glow peaks appeared at 135–170°C (shallow traps) and ∼200°C (deep traps). The first-order kinetic parameters revealed activation energies below 0.5 eV and a frequency factor of 10¹⁰ to 10¹⁴ s^-1 for Eu³⁺ doping. Radioluminescence exhibited defect-induced quenching and a visible emission shift after doping of Eu³⁺. CIE coordinates lie within the reddish-orange region with 90% color purity at 0.5 mol.%. These results demonstrate the potential of Eu:β-Ga₂O₃ for scintillators and optoelectronics.

DOI：

https://doi.org/10.1016/j.materresbull.2025.113888