Dependence of the electrical and optical properties of sputter-deposited ZnO:Ga films on the annealing temperature, time, and atmosphere

Article

Abstract

Effects of annealing process parameters such as annealing temperature, time, and atmosphere on the electrical resistivity and transmittance properties of Ga-doped ZnO (ZnO:Ga) thin films deposited on glass by rf magnetron sputtering were investigated. The electrical resistivity of a ZnO:Ga thin film is effectively decreased with increasing annealing temperature and time in a reducing atmosphere such as N2 + 5%H2. This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. Also the resistivity of 4.9 × 10−4Ω cm was obtained by annealing at 200°C for 15 h in the same atmosphere, which is not bad for a transparent conductor for solar cell applications. However, annealing at a temperature higher than 400°C is less effective. The lowest resistivity of 2.3 × 10−4Ω cm was obtained by annealing at 400°C for 1 h in an N2 + 5%H2 atmosphere. The optical transmittance of the ZnO:Ga film is improved by annealing regardless of the annealing atmosphere. Annealing in N2 + 5%H2 atmosphere widens the optical band gap, while annealing in an O2 atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.

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Copyright information

© Springer Science+Business Media, LLC 2006

Authors and Affiliations

  1. 1.Department of Materials Science and EngineeringInha UniversityIncheonKorea

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