Abstract
Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+) and tetravalent (Zr4+, Ti4+) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. Tunable laser excitation was applied for time-resolved experiments in order to obtain luminescence decay curves under excitations in Ce3+, Gd3+ and excitonic absorption bands. The influence of the co-dopant ions on the Ce3+ luminescence decay kinetics is elucidated. The fastest luminescence decay was observed for the Mg2+ co-doped crystals under any excitation below bandgap energy indicating the perturbation of the 5d states of Ce3+ by Mg2+ ions. Synchrotron radiation was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. Special attention was paid to the analysis of Ce3+ excitation spectra in VUV and XUV spectral range where multiplication of electronic excitation (MEE) processes occur. Our results demonstrated that GGAG:Ce single crystals co-doped by Mg2+ ions as well as the GGAG:Ce crystal annealed in vacuum reveal the most efficient excitation of Ce3+ emission in VUV-XUV excitation range. The role of intrinsic defects in MEE processes in the co-doped as well as in the annealed GGAG:Ce single crystals is discussed.
Highlights
Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+) and tetravalent (Zr4+, Ti4+) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range
The same could be said about the absorption band of 4f–5d1 transitions, which looks truncated for all co-doped crystals except the most thinner GGAG:Ce crystal
The luminescence properties of cerium doped as well as co-doped GGAG single crystals have been investigated by means of the vacuum ultraviolet (VUV) and soft X-ray (XUV) excitation spectroscopy utilizing synchrotron radiation and by means of time-resolved luminescence spectroscopy under tunable laser excitations
Summary
Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+) and tetravalent (Zr4+, Ti4+) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. To create a luminescence center in the form of an excited Ce3+ center, the C e4+ ion must capture an electron from the conduction band This means that the processes of energy transfer to emission centers do not include the hole trapping stage, which is necessary in the case of the Ce3+ ion. In current work we have applied the excitations produced by the tunable laser excitations (in 210–420 nm range) in order to compare time-resolved luminescence characteristics under excitations in C e3+, Gd3+, defect and excitonic absorption bands of GGAG:Ce single crystals co-doped by divalent and tetravalent ions. The GGAG compound belongs to the class of wide band gap materials having the band gap about 6.2 eV This energy and higher refers to the vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. Varying the excitation energy in VUV-XUV range one can manipulate the penetration depth of photons and can distinguish surface and bulk related relaxation processes
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