Photoluminescence of Lu3Al5O12:Bi and Y3Al5O12:Bi single crystalline films

Abstract

a b s t r a c tSingle crystalline films of Lu 3 Al 5 O 12 :Bi and Y 3 Al 5 O 12 :Bi have been studied at 4.2-450 K by the timeresolved luminescence spectroscopy method. Their emission spectrum consists of two types of bands with strongly different characteristics. The ultraviolet band consists of two components, arising from the electronic transitions which correspond to the 3 P 1 / 1 S 0 and 3 P 0 / 1 S 0 transitions in a free Bi 3þ ion. At T < 80 K, mainly the lower-energy component with the decay time w10 À3 s is observed, arising from the metastable 3 P 0 level. At T > 150 K, the higher-energy component prevails, arising from the thermally populated emitting 3 P 1 level. The visible emission spectrum consists of two dominant strongly overlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are w10 À5 s and w10 À4 s and decrease with increasing temperature. Both of the visible emission bands are assumed to be of an exciton origin. The lower-energy band is ascribed to an exciton, localized near a single Bi 3þ ion. The higherenergy band, showing a stronger intensity dependence on the Bi 3þ content, is assumed to arise from an exciton, localized near a dimer Bi 3þ center. The structure of the corresponding excited states is considered, and the processes, taking place in these states, are discussed.

Origin of Bi3+‐related luminescence centres in Lu3Al5O12:Bi and Y3Al5O12:Bi single crystalline films and the structure of their relaxed excited states

“…As previously observed, the decay time of both VIS emissions in LuAG:Bi and YAG:Bi increases as the temperature decreases down to 4.2 K [6][7]. Therefore, to more reliably determine the quantitative characteristics of the corresponding RESs, the investigated temperature range was extended down to 1.7 K. Temperature dependences of the decay times of the UV and VIS emissions of LuAG:Bi and YAG:Bi are shown in Figs.…”

“…As was already shown in [6][7], the decay kinetics of the visible emissions of LuAG:Bi and YAG:Bi are rather complicated. In the present work, it was found that at T<4.2 K, the decay times of the VIS emissions remain constant.…”

“…3a, curves 1, 1'), one observes mainly a slow component. The intensity of the fast component reported in [6][7] is negligible, and its very short decay time (0.1-0.6 ns) origin of a very weak fast (0.1-0.6 ns) component reported in [6][7][8] is not clear and needs further investigations. indicates that it cannot arise from the spin forbidden transitions of the triplet state of Bi 3+ .…”

“…The VIS emission was assigned to the Bi 3+ -related bound excitons [5] or to complex Bi 3+ -based centers [2][3][4]. Recently, we have carried out the study of the emission and excitation spectra and the luminescence decay kinetics of Bi 3+ -related centers in SCFs of Lu 3 Al 5 O 12 :Bi (LuAG:Bi) [6] and Y 3 Al 5 O 12 :Bi (YAG:Bi) [7] at 4.2-400 K. It was found that their emission spectrum consists of two types of bands with much different properties. Two UV emission bands were assigned to the decay of the radiative and metastable minima of the triplet RES of a Bi 3+ centre.…”

“…Despite the suggestion that the 2.75 eV emission is connected with the dimer Bi 3+ -Bi 3+ centers, no luminescence from such centers was found in [6][7]. However, later [8] it was concluded that the 3.995 eV emission band and the corresponding very narrow 4.32 eV excitation band of YAG:Bi arise from the dimer centers.…”