Amorphous-nanocrystalline Al doped ZnO transparent conducting thin films

Al-doped ZnO films have been deposited at room temperature by means of RF sputtering under different conditions and subjected to annealing treatments looking for amorphous Transparent Conducting Oxide (TCO) films in the search for their integration into the emerging area of the flexible electronics. Structural studies have been performed as well as optical and electrical characterization. Spectroscopic ellipsometry has been used for the determination of the optical gap for films grown on Si and the films thickness. The amorphous fraction of the films (up to 86%) depends on the substrate and RF power but not on the annealing temperature up to 600 °C for glass substrates. The resistivity is found to be independent of the amorphous degree and correlates to the optical bandgap which presents three regimes depending on the annealing temperature.

► Al- doped ZnO films by RF- sputtering as amorphous TCO. ► Structural characterization confirms amorphous-nanocrystalline nature of samples. ► Optical gap dependence on substrate and grain size. ► Resistivity correlates to the optical bandgap.