Münster 1999 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 1: Ionenimplantation I

DS 1.2: Fachvortrag

Montag, 22. März 1999, 09:45–10:00, PC 7

Oxidation state and lattice site occupation of ions implanted into TiO₂ — •R. Fromknecht¹, O. Meyer¹, and I. Khubeis² — ¹Forschungszentrum Karlsruhe, INFP, Postfach 3640, D-76021 Karlsruhe — ²Faculty of Applied Science, Al-Balqa Univ., Al-Salt, Jordan

Lattice site location studies of ions implanted into <001> and <100> oriented TiO₂ single crystals (rutile) have been performed in order to clarify electrical doping effects by applying Rutherford Backscattering and Channeling (RBS-C). 14 different ion species (Nb, In, Sb, Xe, La, Hf, W, Au, Hg, Pb, Bi, Ga, Ge, As) were implanted into TiO₂. At low concentrations (<0.1 at%) all ions (besides La and Xe) were located substitutional on Ti lattice sites or forms coherent, nanocrystalline precipitates (Ge). With increasing implanted ion concentration many ions (In,Sb,Hg,Pb,Bi) are displaced from their substitutional lattice sites, mainly along the c-axis whilst As was displaced perpendicular to the c-axis. It was noted that for ions with similar atomic radii but different oxidation states those with zero net charge reveal the highest substitutional concentrations. The increase of the maximum substitutional concentration with decreasing net charge is attributed to the formation of impurity-defect complexes. With increasing net charge it is electrostatically favourable for different defects to associate for charge compensation. Non-directed displacements indicate nearby oxygen vacancies, while directed displacements along <001> may be due to nearby Ti vacancies or Schottky trios.