Abstract
The 4 at. % zirconium-doped zinc oxide (ZnO:Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO:Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 °C and decreased between 350 and 850 °C, while creeping up again at 850 °C. UV–vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 °C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350–550 °C. The ZnO:Zr film-coated glass substrates show good optical and electrical performance up to 550 °C during superstrate thin film solar cell deposition.
Highlights
zinc oxide (ZnO) is believed to be a promising indium tin oxide (ITO) substitute material due to its abundance and large optical band gap, and because it can be doped to degeneracy
The structural properties of the annealed ZnO:Zr films were investigated by X-ray diffraction (XRD)
ZrO2 phases were formed at the non-crystalline region in the grain boundary. It indicated that the replacement and occupation of Zr4+ does not change the hexagonal wurtzite structure of the ZnO
Summary
ZnO is believed to be a promising indium tin oxide (ITO) substitute material due to its abundance and large optical band gap, and because it can be doped to degeneracy. The high carrier density in the impurity-doped ZnO film will slightly increase the band gap due to the Burstein–Moss effect [1]. N-type dopants that are commonly used in ZnO are Al [2,3,4] and Ga [5,6,7,8], while trials on. Zirconium ion dopant attracts worldwide attention due to its physical nature. Zirconium-doped zinc oxide (ZnO:Zr) films are stable at high temperature (
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