Peculiarities of excited state structure and photoluminescence inBi3+-dopedLu3Al5O12 single-crystalline films

Abstract

Single-crystalline films of Lu3Al5O12:Bi, prepared by the liquid phase epitaxy method from the melt-solution based onBi2O3 flux, have been studied at 4.2–400 K by time-resolved luminescence spectroscopy methods.Their emission spectra consist of two types of bands with strongly different characteristics.The ultraviolet emission band consists of two components, arising from the electronictransitions which correspond to the and transitions in a free Bi3+ ion. At low temperatures, mainly the lower-energy component of this emission is observed, having thedecay time∼10−3 s atT<100 K and arising fromthe metastable 3P0 level. At T>100 K, the higher-energy emission component appears, arising from the thermally populated emitting3P1 level. The visible emission spectrum consists of two dominant stronglyoverlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are∼10−5 s and decrease with increasing temperature. Both of the visible emission bands are assumed tohave an exciton origin. The lower-energy band is ascribed to an exciton, localized near a singleBi3+ ion. The higher-energy band shows a stronger intensity dependence on theBi3+ content and is assumed to arise from an exciton localized near a dimerBi3+ center. The origin and structure of the corresponding excited states is considered and theprocesses, taking place in the excited states, are discussed.