Recent Progress in the Development of β-Ga2O3 Scintillator Crystals Grown by the Czochralski Method

A high-quality bulk single crystal of β-Ga2O3 has been grown by the Czochralski method and its basic scintillation characteristics (light yield, energy resolution, proportionality, and scintillation decay times) have been investigated. All the samples cut from the crystal show promising scintillation yields between 8400 and 8920 ph/MeV, which is a noticeable step forward compared to previous studies. The remaining parameters, i.e. the energy resolution slightly above 10% (at 662 keV) and the scintillation mean decay time just under 1 μs, are at the same level as we have formerly recognized for β-Ga2O3. The proportionality of yield seems not to deviate from standards determined by other commercial scintillators

Recent progress in the development of β-Ga2O3 scintillator crystals grown by the Czochralski method

A high-quality bulk single crystal of β-Ga2O3 has been grown by the Czochralski method and its basic scintillation characteristics (light yield, energy resolution, proportionality, and scintillation decay times) have been investigated. All the samples cut from the crystal show promising scintillation yields between 8400 and 8920 ph/MeV, which is a noticeable step forward compared to previous studies. The remaining parameters, i.e. the energy resolution slightly above 10% (at 662 keV) and the scintillation mean decay time just under 1 μs, are at the same level as we have formerly recognized for β-Ga2O3. The proportionality of yield seems not to deviate from standards determined by other commercial scintillators

Tailoring the Scintillation Properties of β-Ga2O3 by Doping with Ce and Codoping with Si

Measurements of pulse height spectra and scintillation time profiles performed on Czochralski-grown β-Ga2O3, β-Ga2O3:Ce, and β-Ga2O3:Ce,Si crystals are reported. The highest value of scintillation yield, 7040 ph/MeV, was achieved for pure β-Ga2O3 at a low free electron concentration, nevertheless Ce-doped crystals could also approach high values thereof. Si-codoping, however, decreases the scintillation yield. The presence of Ce, and the more of Ce and Si, in β-Ga2O3 significantly increases the contribution of the fastest components in scintillation time profiles, which makes β-Ga2O3 a very fast scintillator under γ-excitation

Low temperature thermoluminescence of β-Ga2O3 scintillator

Low temperature thermoluminescence of β-Ga2O3, β-Ga2O3:Al and β-Ga2O3:Ce has been investigated. Glow curves have been analyzed quantitatively using a rate equations model in order to determine the traps parameters, such as activation energies, capture cross-sections and probabilities of recombination and retrapping

Heading for brighter and faster β-Ga2O3 scintillator crystals

Czochralski-grown β-Ga2O3 and β-Ga2O3:Si crystals with the free electron concentrations between 2.5·1016 and 4.3·1018 cm−3 have been characterized by means of pulse height and scintillation time profile measurements in order to assess their basic scintillation properties. At room temperature, with increasing free electron concentration in the studied range, the scintillation yields decrease from 8920 to 1930 ph/MeV, while the mean scintillation decay times pare down from 989 to 61 ns. However, when the brightest β-Ga2O3 sample is cooled down below 100 K, its scintillation yield exceeds 20000 ph/MeV

Lithium-Doped Two-Dimensional Perovskite Scintillator for Wide-Range Radiation Detection

Two-dimensional lead halide perovskites have demonstrated their potential as high-performance scintillators for X- and gamma-ray detection, while also being low-cost. Here we adopt lithium chemical doping in two-dimensional phenethylammonium lead bromide (PEA)2PbBr4 perovskite crystals to improve the properties and add functionalities with other radiation detections. Li doping is confirmed by X-ray photoemission spectroscopy and the scintillation mechanisms are explored via temperature dependent X-ray and thermoluminescence measurements. Our 1:1 Li-doped (PEA)2PbBr4 demonstrates a fast decay time of 11 ns (80%), a clear photopeak with an energy resolution of 12.4%, and a scintillation yield of 11,000 photons per MeV under 662 keV gamma-ray radiation. Additionally, our Li-doped crystal shows a clear alpha particle/gamma-ray discrimination and promising thermal neutron detection through 6Li enrichment. X-ray imaging pictures with (PEA)2PbBr4 are also presented. All results demonstrate the potential of Li-doped (PEA)2PbBr4 as a versatile scintillator covering a wide radiation energy range for various applications

Effect of commensurate lithium doping on the scintillation of two-dimensional perovskite crystals

Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium (Li)-doping (1 : 1 Li : Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Li, e.g. light yield enhancement, is more prominent in PEA2PbBr4 compared to BA2PbBr4. Both perovskite crystals show a broadening of the radioluminescence spectrum and a slightly longer afterglow, with residual scintillation below 2% after 5 s for both materials. The effects of Li on the negative thermal quenching exhibited by the perovskites are also discussed. Li doping increases the light yield of PEA2PbBr4 by 78% and both perovskite materials show an improvement in their energy resolutions, with a record of 7.7% at 662 keV for the Li-doped PEA2PbBr4. Both perovskite crystals also show very fast gamma-ray excited scintillation decays, with average times of 12.9 ns and 8.0 ns for PEA2PbBr4 and BA2PbBr4, respectively. This work shows that Li doping brings a significant improvement of the perovskite performance, making the perovskites more competitive for fast, high light yield applications in the medical, security or industrial sectors.Ministry of Education (MOE)The authors acknowledge financial supports from the Singapore Ministry of Education (MOE2019-T1-002-087) and Thales-CINTRA Funding

Lattice expansion in Rb-doped hybrid organic-inorganic perovskite crystals resulting in smaller band-gap and higher light-yield scintillators

Two-dimensional hybrid-organic-inorganic perovskite (2D-HOIP) lead bromide perovskite crystals have demonstrated great potential as scintillators with high light yields and fast decay times while also being low cost with solution-processable materials for wide energy radiation detection. Ion doping has been also shown to be a very promising avenue for improvements of the scintillation properties of 2D-HOIP crystals. In this paper, we discuss the effect of rubidium (Rb) doping on two previously reported 2D-HOIP single crystals, BA2PbBr4 and PEA2PbBr4. We observe that doping the perovskite crystals with Rb ions leads to an expansion of the crystal lattices of the materials, which also leads to narrowing of band gaps down to 84% of the pure compounds. Rb doping of BA2PbBr4 and PEA2PbBr4 shows a broadening in the photoluminescence and scintillation emissions of both perovskite crystals. Rb doping also leads to faster γ-ray scintillation decay times, as fast as 4.4 ns, with average decay time decreases of 15% and 8% for Rb-doped BA2PbBr4 and PEA2PbBr4, respectively, compared to those of undoped crystals. The inclusion of Rb ions also leads to a slightly longer afterglow, with residual scintillation still being below 1% after 5 s at 10 K, for both undoped and Rb-doped perovskite crystals. The light yield of both perovskites is significantly increased by Rb doping with improvements of 58% and 25% for BA2PbBr4 and PEA2PbBr4, respectively. This work shows that Rb doping leads to a significant enhancement of the 2D-HOIP crystal performance, which is of particular significance for high light yield and fast timing applications, such as photon counting or positron emission tomography.Ministry of Education (MOE)Published versionF.M. and C.D. acknowledge financial support from the Singapore Ministry of Education(T2EP50121-0025) and the MERLION Project. M.H.M. and M.D.B. acknowledge research funds from the Institut Teknologi Bandung under the “Penelitian, Pengabdian Masyarakat, dan Inovasi (PPMI) 2022” scheme (6A/IT1.C07.2/TA.01/2022)and Lukasiewicz Research Network-PORT, respectively

Thermal Quenching and Dose Studies of X‑ray Luminescence in Single Crystals of Halide Perovskites

Temperature- and dose-dependent measurements of X-ray luminescence (XL) in various perovskite single crystals are reported. For methylammonium lead halide perovskites (MAPbX₃, MA = methylammonium, X = Cl, Br, or I), the quenching temperature of XL intensities shifts to lower temperatures in the sequence from Cl to I. This quenching is strongly affected by the decrease of the thermal activation energy Δ<i>E</i>_q from 53 ± 3 to 6 ± 1 meV. We replace MA in MAPbBr₃ with Cs and observe that the quenching temperature even shifts to lower temperature. But unlike the MAPbX₃ perovskites, the quenching in CsPbBr₃ is now affected by the increase of the ratio between the thermal quenching rate and the radiative transition rate (Γ₀/Γ_v) from 15 ± 1 to 66 ± 14. The same influence was observed if we dope MAPbBr₃ with Bi³⁺, Γ₀/Γ_v increases to 78 ± 18 for crystal with Bi/Pb ratio of 1:10 in precursor solution. For larger dose of X-ray, we observe that the XL intensities are still linear without saturation. Unlike temperature-dependent measurements, we do not observe the line width narrowing in dose-dependent XL spectra. Thus, this scintillator is still stable with the large X-ray dose in comparison with the variation in the temperature