Regensburg 2000 – scientific programme

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DS: Dünne Schichten

DS 32: Ionenimplantation V

DS 32.2: Fachvortrag

Thursday, March 30, 2000, 16:00–16:15, H31

Diffusion Effects and Conductivity of Ge and Pb Implanted TiO₂ Single Crystals — •R. Fromknecht¹, T. Wiss², I. Khubeis³, and O. Meyer¹ — ¹Forschungszentrum Karlsruhe, IFP, 76021 Karlsruhe — ²European Commission, Institute of Transuranium Elements, 76021 Karlsruhe — ³Al-Balqa Appl. Univ., Al-Salt, Jordan

Single crystals of TiO₂ (rutile) were implanted with Ge and Pb ions. The damage distribution, the ion distribution and the lattice site location of the ions were determined as a function of the annealing temperature, using Rutherford Backscattering and Channeling (RBS-C).The electrical conductivity was measured as a function of temperature in the region between 5K and 300K. Upon annealing to 1100K a nearly complete recovery of the damage was observed. Ge and Pb atoms moved partly towards the surface, leading to precipitation at the surface in the case of high dose Pb implants. This was confirmed by EDX-analysis. Ions residing in the implanted region moved from coherent precipitates sites to perfect substitutional Ti lattice sites in the case of Ge and from displaced substitutional sites to perfect substitutional sites in the case of Pb. The resistivity at room-temperature as well as the temperature dependence of the resistivity, strongly depended on the treatment of the sample. For samples implanted at 300K, the resistivity was thermally activated over the whole temperature region, indicating carrier hopping. For samples implanted at high temperature (900K, 1000K) or annealed in vacuum, metallic behaviour was observed at low temperatures between about 30K and 100K. Oxygen vacancies seems to be the main defect causing this behaviour.