Excitation Mechanisms of Green Emission from Terbium Ions Embedded Inside the Sol-Gel Films Deposited onto Nanoporous Substrates

In this work we investigate the excitation mechanism of Tb3+ ions in different inorganic sol-gel matrices (composite film of YAlO3 and Al2O3; Ba0,6Sr0,3Ca0,1:TiO3) in porous anodic alumina films. The interest in synthesis of light-emitting materials in porous anodic alumina arises from its unique tailor-made honey-comb structure, strongly enhanced Tb luminescence and great photonic density of states at direction along the channels of the anisotropic light scattering. All discussed sol-gel films were synthesized by spin-on deposition on porous anodic alumina grown on a silicon wafer and annealed at different temperatures. An influence of the annealing temperature on the terbium PL was studied using XRD, 2D photoluminescence excitation and time-resolved spectroscopy. Further, the comparison of thermal quenching data for the most intensive 5D4 →7F5 luminescence band and excitation band of Tb 3+ ions was performed for the temperature range of 10 - 300 K. From the resultant data, mechanisms of Tb excitation and its dependence on the annealing conditions are proposed and discussed.