Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

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 degrees 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 degrees C and decreased between 350 and 850 degrees C, while creeping up again at 850 degrees 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 degrees 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 degrees C. The ZnO: Zr film-coated glass substrates show good optical and electrical performance up to 550 degrees C during superstrate thin film solar cell deposition.