EXCITATION TRANSFER IN CAF2-EU2+, SM2+ MULTILAYERED STRUCTURES GROWN BY MBE ON SI(111)

Multilayer CaF2 epitaxial structures, selectively doped with EU2+ and Sm2+ were grown on Si(1 1 1) by molecular-beam epitaxy. We investigate excitation transfer both within a single codoped layer and between tw o separated layers doped with EU2+ and Sm2+, respectively. We use the tripled output of a Q-switched YAG:Nd3+ laser to selectively excite th e lowest 4f --> 5d transition of EU2+. The Strokes shifted Eu2+ emissi on overlaps the absorption of Sm2+ at 420 nm. The time-resolved emissi on from Sm2+ at 706 nm is then monitored to provide an indication of e xcitation transfer to this ion. The buildup on Sm2+ emission is correl ated to the quenching of the time-resolved EU2+ emission. In addition, all measurements in the codoped structures are compared with similar measurements in singly doped materials. (C) 1998 Elsevier Science B.V. All rights reserved.