Charge Transfer Luminescence of Yb3+
Charge Transfer Luminescence of Yb3+ Charge Transfer Luminescence of Yb3+
186L. van Pieterson et al. / Journal of Luminescence 91 (2000) 177–193Fig. 11. Decay time (*), on the left axis, and CT luminescenceintensity (&), on the right axis, of YAG doped with 2% Yb 3+as a function of temperature.Fig. 12. Emission (a, l exc ¼ 220 nm) and excitation (b,l em ¼ 350 nm) spectra of YAlO 3 doped with 2% Yb 3+ atT ¼ 10 K.Fig. 10. Emission (for l exc ¼ 160 nm) and excitation (forl em ¼ 255 nm) spectra of the YAG host lattice (a, b) andemission (for l exc ¼ 170 nm) and excitation (for l em ¼ 345 nm)spectra of YAG doped with 2% Yb 3+ (c, d). In Fig. 10 (c), thebroken line represents measurements performed with a SEYAmonochromator, the solid line represents measurements performedwith a SPEX monochromator equipped with aTektronics ccd-array.Fig. 13. Decay curves (at 10 K) of the Yb 3+ CT emissions at350 (dotted) and 516 nm (broken line) in YAlO 3 .
L. van Pieterson et al. / Journal of Luminescence 91 (2000) 177–193 187Fig. 15. Decay time (*), on the left axis, and CT luminescenceintensity at 420 nm (&) and at 822 nm (n), on the right axis, ofLa 2 O 2 S doped with Yb 3+ as a function of temperature.SPEX 1680 spectrofluorometer. Fig. 14 shows theemission and excitation spectra of Y 2 O 2 S:Yb 3+and La 2 O 2 S:Yb 3+ at 10 K. In Y 2 O 2 S, Yb 3+charge transfer luminescence is observed at 390and 612 nm. The energy difference between theCT bands is 9500 cm 1 , close to the expected10 000 cm 1 . The FWHM of the bands is about3500 cm 1 . In the excitation spectrum the chargetransfer band is observed at 309 nm so the Stokesshift is relatively small, about 6000 cm 1 . Thedecay time measured at 390 nm is about 250 ns.The Y 2 O 2 S host lattices luminesce at 318 nm whenexciting into the conduction band (l5260 nm).This emission quenches already below 50 K. Also abroad defect-related emission around 590 nm isobserved which quenches at about 275 K.In La 2 O 2 SYb 3+ CT luminescence is observed at439 and 759 nm, the energy difference betweenthese bands is 9500 cm 1 . The CT excitation bandis observed at 317 nm, giving a Stokes shift ofapproximately 8500 cm 1 . In Fig. 15, the intensityof the Yb 3+ CT luminescence in La 2 O 2 S and itsdecay time are given as a function of temperature.From this figure we can estimate the quenchingtemperature at 150 K. Table 7 summarizes theluminescence properties of the oxysulfide hostlattices and Yb 3+ -doped samples.Fig. 14. Emission (for l exc ¼ 240 nm) and excitation (forl em ¼ 393 nm) spectra of Y 2 O 2 S doped with 1% Yb 3+ (a, b)and emission (for l exc ¼ 270 nm) and excitation (for l em ¼460 nm) spectra of La 2 O 2 S (c, d) doped with 1% Yb 3+ ,T ¼ 10 K.3.5. FluoridesFig. 16 shows the emission and excitationspectrum of LiYF 4 doped with 3% Yb 3+ . Theemission spectrum has been recorded using gateddetection (delay 5 ns, gate 10 ns) and shows two
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186L. van Pieterson et al. / Journal <strong>of</strong> <strong>Luminescence</strong> 91 (2000) 177–193Fig. 11. Decay time (*), on the left axis, and CT luminescenceintensity (&), on the right axis, <strong>of</strong> YAG doped with 2% Yb 3+as a function <strong>of</strong> temperature.Fig. 12. Emission (a, l exc ¼ 220 nm) and excitation (b,l em ¼ 350 nm) spectra <strong>of</strong> YAlO 3 doped with 2% Yb 3+ atT ¼ 10 K.Fig. 10. Emission (for l exc ¼ 160 nm) and excitation (forl em ¼ 255 nm) spectra <strong>of</strong> the YAG host lattice (a, b) andemission (for l exc ¼ 170 nm) and excitation (for l em ¼ 345 nm)spectra <strong>of</strong> YAG doped with 2% Yb 3+ (c, d). In Fig. 10 (c), thebroken line represents measurements performed with a SEYAmonochromator, the solid line represents measurements performedwith a SPEX monochromator equipped with aTektronics ccd-array.Fig. 13. Decay curves (at 10 K) <strong>of</strong> the Yb 3+ CT emissions at350 (dotted) and 516 nm (broken line) in YAlO 3 .
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