Reversible change in electrical and optical properties in epitaxially grown Al-doped ZnO thin films

Aluminum-doped ZnO (AZO) films were epitaxially grown on sapphire (0001) substrates using pulsed laser deposition. As-deposited AZO films had a low resistivity of 8.01×10−4 Ω cm. However, after annealing at 450 °C in air, the electrical resistivity of the AZO films increased to 1.97×10−1 Ω cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H2 recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H2annealing. A photoluminescence study showed that oxygen interstitial(O′i) is a critical material parameter allowing for the reversible control of the electrical conducting properties of AZO films