Dresden 2003 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 23: Elektrische und optische Eigenschaften II

DS 23.8: Vortrag

Donnerstag, 27. März 2003, 17:00–17:15, GER/38

Optical properties of Eu doped yttria thin films — •Lutz Rabisch, Philipp Burmester, Takugo Ishii, and Günter Huber — Institut für Laser-Physik, Universität Hamburg, Jungiusstraße 9A, D-20355 Hamburg, Germany

Yttria (Y₂O₃) is an attractive host material for optically active rare-earth ions. In combination with α-Al₂O₃ an interesting, lattice matched epitaxial system arises which has a wide variety of possible applications (crystalline coatings, compact passive and active waveguides).

We demonstrate epitaxial growth of Eu:Y₂O₃ [111] films on Al₂O₃ (0001) substrates using the Electron Beam Evaporation (EBE)- and the Pulsed Laser Deposition (PLD) technique. Optical properties of the Eu:Y₂O₃-films were investigated by spectroscipic characterization of the 4f - 4f transitions of the Eu³⁺ ion. Depending on the fabrication process an amorphous interface between the substrate and the Y₂O₃ (crystalline) film can exist. The spectra of Eu-ions in such an interfacial amorphous layer are inhomogeniously broadened whereas the crystalline films show the same local symmetry of the Eu³⁺-centers as in a bulk crystal.

VUV and UV investigations reveal spectroscopic features arising at the Y₂O₃/Al₂O₃ interface. On the one hand excitonic states can be excited in the Eu:Y₂O₃-films at reduced energies in comparison to a bulk crystal, on the other hand a strong, spectrally broad luminescence that does not exist in the bulk material can be observed at λ_ex = 205 nm. Both effects seem to be stronger in the PLD-films in comparison to the EBE-films. A model is presented, which explains this effect in terms of incorporated Eu²⁺ ions at the Y₂O₃/Al₂O₃ interface.