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Optical properties of ZnN thin films fabricated by rf-sputtering from ZnN target

Maria G. Androulidaki 1Sotiris Dounis 1,3Popi Voulgaropoulou 1,3Vicky Kambilafka 1,5Michal Ružinský 2Vladimir Šály 1,2Patrik Prokein 2Zacharias Viskadourakis 4Elias Aperathitis 1

1. Microelectronics Research Group, Institute of Electronic Structure and Laser, Foundation for Research and Technology – Hellas, P.O. Box 1527, 71110 Heraklion, Crete, Greece, P.O. Box 1527, Heraklion 71110, Greece
2. Slovak University of Technology, Faculty of Electrical Engineering and Information Technology, Bratislava 81219, Slovakia (Slovak Rep.)
3. Materials Science and Technology Department, University of Crete, Heraklion 71003, Greece
4. Institute of Electronic Structure and Laser, FORTH,, P.O. Box 1527, Vassilika Vouton, Heraklion 71110, Greece
5. Physics Dpt, Univ. of Crete, PO Box 1527, Heraklion 71409, Greece


ZnN is a relatively new material, and even though its physical properties are not well studied and there is a controversy concerning its optical band gap, it has been used for the fabrication of p-type ZnO:N films through oxidation at temperatures ≥400oC and recently as electrode in Li-ion batteries. Oxygen contamination has been considered donor for ZnN leading to higher carrier concentration and larger band gap energy due to Moss-Burstein effect. Intentional oxygen doping can create oxynitride phases (ZnON) but annealing in oxygen environment can covert n-ZnN into p-ZnO:N.

In this investigation, ZnN thin films were deposited by magnetron sputtering from ZnN target in plasma consisting of mixture of Ar-N2 gases on silica and Si substrates. The ZnN films were n-type semiconductors having around 1020cm-3 carrier concentration, resistivity between 10-2-10-3Ωcm and low transmittance. The amount of nitrogen in plasma affected more the optical properties than the electrical properties of the films. Annealing, in N2 environment, at temperatures below 400oC improved the electrical properties but above 400oC the carrier concentration was reduced (1015cm-3) and the resistivity increased (102Ωcm). The transmittance of the films was ~85% in the near UV-VIS region regardless the annealing temperature. X-Ray Diffraction was used for monitoring the phases in the structure of the films. Low temperature photoluminescence (PL) was employed to study the bound exciton states in the range 3.326 to 3.365eV. Films deposited in pure Ar or N2 and after high temperature annealing, exhibited a sharp emission peak at 3.360eV and another one at 3.306eV. These PL peaks were shifted to higher energies for films deposited in a mixture of Ar-N2 plasma. Green PL, associated with defect states in the band gap, appeared at around 2.5eV. PL assignments were achieved by monitoring the temperature evolution of the peaks.

(*) Presenting Author: M. Androulidaki

(**) Corresponding author: E. Aperathitis


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Related papers

Presentation: Oral at E-MRS Fall Meeting 2007, Symposium H, by Elias Aperathitis
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-11 16:51
Revised:   2009-06-07 00:44