Preparation of high transmittance ZnO: Al film by pulsed filtered cathodic arc technology and rapid thermal annealing

Approximately 200 nm thick ZnO:Al films with high visible and infrared transmittance properties were prepared on glass substrates by the pulsed filtered cathodic arc technique and rapid thermal annealing. The as-deposited and annealed films have a poly-crystalline hexagonal wurtzite type structure. As the annealing temperature increases from 500 °C to 650 °C, the visible transmittance remains nearly constant (∼85%) while the infrared (780-2500 nm) transmittance considerably improves from 22% for the as-deposited film to 58% at 600 °C and 71% at 650 °C at 2500 nm for the annealed films. However, the electrical properties of the films worsen after high-temperature annealing, and resistivity increases from 2.5 × 10^-4 Ω cm for the as-deposited film to 3.6 × 10^-3 Ω cm and 1.2 × 10^-2 Ω cm for the films annealed at 600 and 650 °C, respectively. The high-temperature annealing improved the crystallinity and transmittance of the films. Nevertheless, these improvements may lead to the segregation and oxidation of aluminum atoms, as well as the reduction of oxygen vacancies, thereby degrading the electrical properties of the films. © 2011 Elsevier B.V. All rights reserved.