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PL spectrum of OPSi (cw excitation at 325 nm) at 4 K. The Ph is also shown. It was normalized so that its long wavelength part matched that of the PL spectrum. The spectrum peaked at 3 eV with a FWHM of 0.36 eV (termed fast band) was obtained by subtracting the Ph from the PL.
Time dependence of Ph spectra at 4 K after excitation at 266 nm was turned off (delay time of 140 ms and gate time of 30 ms).
Temperature dependence of the Ph intensity at 2.68 eV (delay: 140 ms; gate time 30 ms). Its fit using the function , which assumes thermally activated escape of carriers from the phosphorescent level (Ref. 11) is also plotted. The PL intensity of (i) crystalline at 2.8 eV (excitation at 8.7 eV) adapted from Ref. 9, and (ii) Suprasil-W at 2.7 eV (excitation at 7.9 eV) (Ref. 10) are also plotted. The inset shows the time evolution of the Ph intensity at 2.68 eV at different temperatures.
Dependence of the Ph spectrum (delay: 140 ms; gate time 30 ms) upon excitation energy at 3.8 K.
Energy-level diagram illustrating the Ph process. Excitation Mode I: Excitation is above 4.4 eV. Relaxation brings excitons to state and triplet state . Mode II: Direct excitation of state occurs. Thermal equilibrium determines the respective populations of and .
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