Luminescence spectra of chromium-doped LiGaO2 crystals as indicator of their phase heterogeneity

Meylman, Mikhail L.

doi:10.1016/j.optmat.2004.07.022

Cited by 3 publications

(4 citation statements)

References 28 publications

(50 reference statements)

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“…Following the earlier work on 3d 9 ions in tetrahedrally bonded ZnO, GaN, and AgGaSe 2 [19][20][21], we suggest that the unpaired spin in the Cu 2+ ion in LiGaO 2 occupies an xy-like orbital.…”

Section: Electron Paramagnetic Resonance (Epr)supporting

confidence: 73%

“…The successful development of solid-state dosimeters requires identifying appropriate dopants to serve as deep electron and hole traps. This can be readily accomplished in LiGaO 2 because large single crystals are easily grown [5] and the existence of monovalent (Li + ) and trivalent (Ga 3+ ) cation sites allows efficient doping with a variety of impurities (e.g., transition-metal and rare-earth ions) [8][9][10][11]. The presence of 6 Li nuclei with their large cross-section for thermal neutron absorption provides an added reason for interest in LiGaO 2 .…”

Section: Introductionmentioning

confidence: 99%

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Green luminescence from Cu-diffused LiGaO2 crystals

Holston

Ferguson

Giles

et al. 2016

Journal of Luminescence

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An intense green luminescence is observed from single crystals of LiGaO 2 doped with copper. Czochralski-grown undoped crystals are wrapped in thin copper foil and then held at 900 °C for 1 h in a flowing nitrogen atmosphere. Large concentrations of Cu + ions enter the crystals during this process and occupy Li + sites. These copper-diffused crystals are characterized with optical absorption, photoluminescence (PL), photoluminescence excitation (PLE), thermoluminescence (TL), and electron paramagnetic resonance (EPR). An optical absorption band peaking near 350 nm is assigned to the Cu + ions at Li + sites and represents an excitation from a 3d 10 ground state to a 3d 9 4s 1 excited state. A broad PL emission from these excited Cu + ions has a peak near 523 nm and the related PLE band has a peak near 356 nm (this PLE band links the emission to the optical absorption band). Illuminating a Cu-diffused crystal at room temperature with 325 nm laser light converts a portion of the Cu + ions to Cu 2+ ions. EPR spectra from these 3d 9 ions are easily seen at low temperatures and their angular dependence is used to determine the g matrix and the 63 Cu hyperfine matrix. Subsequent heating produces a TL peak near 122 °C with a maximum in its spectral dependence near 535 nm. Correlated EPR measurements show that this TL peak occurs when trapped electrons are thermally released from unintentionally present transition-metal ions (most likely Fe) and recombine with holes at the Cu 2+ ions.

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Section: Electron Paramagnetic Resonance (Epr)supporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Green luminescence from Cu-diffused LiGaO2 crystals

Holston

Ferguson

Giles

et al. 2016

Journal of Luminescence

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“…3), the only known transformation LiGa 5 O 8 undergoes is a reversible change into a high temperature polymorph, occurring at about 1410 K in bulk material. 40 Remarkably, no certain information is instead available, to the best of our knowledge, about the melting temperature of LiGa 5 O 8 , which anyways should be above 1720 K. 40,43 Actually, from 1410 K up to the melting point, the high temperature polymorph is not completely stable, and indications of decomposition with loss of lithium were reported after prolonged treatment above 1420 K. 44 In that temperature region, decomposition was observed to be accompanied by detection of weak b-Ga 2 O 3 XRD reflections. Incidentally, such a propensity to decompose is consistent with the indication of incongruent melting of LiGa 5 O 8 reported in an early study on the phase diagram of the Li 2 O-Ga 2 O 3 -B 2 O 3 system.…”

Section: The Endothermic Processmentioning

confidence: 99%

Diffusion-driven and size-dependent phase changes of gallium oxide nanocrystals in a glassy host

Golubev

Ignat’eva

Сигаев

et al. 2015

Phys. Chem. Chem. Phys.

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Phase transformations at the nanoscale represent a challenging field of research, mainly in the case of nanocrystals (NCs) in a solid host, with size-effects and interactions with the matrix. Here we report the study of the structural evolution of g-Ga 2 O 3 NCs in alkali-germanosilicate glass -a technologically relevant system for its light emission and UV-to-visible conversion -showing an evolution drastically different from the expected transformation of g-Ga 2 O 3 into b-Ga 2 O 3 . Differential scanning calorimetry registers an irreversible endothermic process at B1300 K, well above the exothermic peak of g-Ga 2 O 3 nano-crystallization (B960 K) and below the melting temperature (B1620 K). Transmission electron microscopy and X-ray diffraction data clarify that glass-embedded g-Ga 2 O 3 NCs transform into LiGa 5 O 8 via diffusion-driven kinetics of Li incorporation into NCs. At the endothermic peak, b-Ga 2 O 3 forms from LiGa 5 O 8 dissociation, following a nucleation-limited kinetics promoted by size-dependent order-disorder change between LiGa 5 O 8 polymorphs. As a result of the changes, modifications of UV-excited NC light emission are registered, with potential interest for applications.

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“…Though many potential applications of LiGaO2 imply use of its optical properties there are not many studies of its luminescence characteristics. As to our knowledge, there are some works devoted to luminescence of dopants in LiGaO2, such as ions of Cr 3 þ [18,19], Cu þ [11], V 3 þ [4], but very few studies deal with luminescence of pure crystals e among them the early work of Dirksen [15], where the observed emission band at 360 nm and its excitation band at 220 nm were explained by charge transfer transitions between Ga and O ions, and the recent work [20] on luminescence of LiGaO2 nanoflakes with the same interpretation of the emission and excitation bands, located at lower energies compared to bulk crystal.…”

Section: Introductionmentioning

confidence: 99%

Luminescence properties of LiGaO 2 crystal

et al. 2017

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The comprehensive spectral study of lithium metagallate LiGaO2 crystal has been done including methods of pump-probe techniques, optical absorption, photoluminescence, luminescence kinetics, thermoluminescence and polarised luminescence in broad temperature region. Luminescence spectrum of the crystal contains the main emission bands at 4.43, 3.76, 2.38 and 1.77 eV. The novel data on luminescence excitation spectra including VUV area, kinetics and polarization are presented. The correlation between pump-probe experiment results and luminescence properties is found. Conclusions are done about the recombination character of all the observed emission bands, implying tunnel recombi-nation of donor-acceptor pairs.

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Luminescence spectra of chromium-doped LiGaO2 crystals as indicator of their phase heterogeneity

Cited by 3 publications

References 28 publications

Green luminescence from Cu-diffused LiGaO2 crystals

Green luminescence from Cu-diffused LiGaO2 crystals

Diffusion-driven and size-dependent phase changes of gallium oxide nanocrystals in a glassy host

Luminescence properties of LiGaO 2 crystal

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