Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 12: Poster I

HL 12.51: Poster

Montag, 8. März 2004, 16:30–19:00, Poster A

Optical spectroscopy of perovskitic oxynitrides — •M. Güngerich¹, P.J. Klar¹, W. Heimbrodt¹, A. Jayakar², A. Weidenkaff², S. Ebbinghaus², and A. Reller² — ¹FB Physik und WZMW, Philipps-Universität, Marburg — ²Lehrstuhl für Festkörperchemie, Universität Augsburg, Augsburg

Substitution of O by N in mixed metal oxide perovskites are possible candidates for novel colour pigments. Several different oxynitrides with ABO₃ perovskite structure have been synthesized. Raman spectroscopy was employed to investigate structural changes taking place when annealing in air or nitrogen atmosphere. For samples annealed in air, Raman signals from different types of intermediate states occur in the transition from the oxynitrides to the corresponding oxides depending on the type of cations in the crystal. In all the investigated compounds N₂ entities in the crystal lattices were identified by a sharp Raman feature at 2330 cm⁻¹ after heating at temperatures ranging from 500 to 800 ^∘C. Raman spectra of the untreated and of the partially annealed oxynitrides show significantly broader signals than the oxides after annealing at approx. 900 ^∘C. A possible explanation is that the crystalline order is strongly increased after the full transition of the oxynitrides to the oxides. Reflectance measurements of single crystals were performed to gain insight into the correlations between band structure changes and visible colour changes during the transition from oxides to oxynitrides.