Energy transfer in the photoexcitation of Sm3+-implanted TiO2 thin films

High-quality nanocrystalline TiO2 thin films of anatase phase were prepared by using the atomic layer deposition technique and implanted with Sm3+ ions. After the annealing of the films a band-to-band optical excitation of TiO2 at low temperatures led to a broadband excitonic emission superposed by a Sm3+-specific emission series of a well-pronounced fine structure. At higher temperatures (>250 K) only the Sm3+ emission dominates. The fine structure of Sm3+ ions indicates that the Sm3+ ions occupy regular sites in the host material. rect and indirect (retarded) channels of formation of the excitonic states were concluded from the decay kinetics of the emission spectra of Sm3+-doped TiO2. The energy transfer from the host matrix to the Sm3+ ions is demonstrated and the participation of bound excitonic states in the energy transfer process discussed.