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 8.01x10(-4) Omega cm. However, after annealing at 450 degrees C in air, the electrical resistivity of the AZO films increased to 1.97x10(-1) Omega cm because of a decrease in the carrier concentration. Subsequent annealing of the air-annealed AZO films in H-2 recovered the electrical conductivity of the AZO films. In addition, the conductivity change was reversible upon repeated air and H-2 annealing. 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. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2987472]