Münster 1999 – scientific programme

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DS: Dünne Schichten

DS 2: Ionenimplantation II

DS 2.1: Fachvortrag

Monday, March 22, 1999, 11:00–11:15, PC 7

Electrical conductivity in ion implanted TiO₂ single crystals — •R. Fromknecht¹, O. Meyer¹, I. Khubeis², and S. Massing¹ — ¹FZ Karlsruhe, INFP — ²Fac. of Appl. Science, Al-Balqa Univ., Jordan

Single crystals of TiO₂ (rutile) were implanted with In, W and Xe ions at room temperature applying fluences between 10¹⁴/cm² and 10¹⁷/cm² at 150 and 300 keV. The lattice site location together with ion range and damage distribution was measured with Rutherford Backscattering and Channeling (RBS-C). The electrical conductivity was measured as a function of the implanted ion fluence as well as a function of the temperature. A maximum value for the electrical conductivity of σ=120 Ω⁻¹cm⁻¹ was reached for the amorphized TiO₂ single crystal at an implantation dose of 2·10¹⁷ W/cm². The functional behaviour of the conductance, G on the temperature in the region between 5 K and 300 K varies with ion dose. For low doses ℓnG is proportional T⁻¹, for medium doses proportional to T^−1/2, and for high doses proportional T^−1/4. The T⁻¹ dependence implies localized defect states at low doses with fixed activation energies in the region between 30 and 90 meV. With increasing defect density, states with different energy levels are localized in the gap and the electron transport is due to variable range hopping as indicated by the T^−1/4 dependence. The T^−1/2 dependence is attributed to variable range hopping but with a pseudogap near the Fermi energy due to long range Coulomb interaction between carriers. The activation energies were found in the region of 8 and 12 meV.