Excitation process and photoluminescence properties of Tb3+ and Eu3+ ions in SnO2 and in SnO2: Porous silicon hosts

Tin oxide (SnO2)-layers-doped terbium and europium ions are elaborated by the sol-gel method on silicon substrates. After annealing at 500 deg. C, the transmission electron microscopy revealed a crystallization of tin oxide. The emission properties of rare-earth in SnO2 are studied systematically against temperature annealing and Tb3+ concentration. The PL spectrum is optimal after annealing at 900 deg. C and the corresponding photoluminescence (PL) decay is nearly exponential, showing that the sample is homogenous and the PL process can be described by two levels system. The concentration effect shows a quenching of the PL intensity for Tb3+ concentration above 4%. From the investigation of the decay rate from the 7F5 state within terbium concentration, we show that self-quenching is insured by dipole - dipole interaction. The evolutions of both PL intensity and PL lifetime versus temperature are studied. The PL intensity and PL lifetime are enhanced by deposing SnO2:Tb3+ and SnO2:Eu3+ in porous silicon. We show that an efficient excitation transfer from Si nanocrystallites to RE ions can occur