Improved conductivity and flatness of solution-processed transparent multilayer ZnO conductive films by stacking method

ZnO stacked films are prepared by a wet process under various conditions. Al and Ga are co-doped as dopants, i.e., producing AGZO films. The doping density dependence of the film resistivity shows that the best doping condition is 1.0 wt% of Ga-doping density and 0.1 wt% of Al-doping density, where the minimum sheet resistance of 1.2 × 105 Ω/□ and the best orientation of (002) surface are observed. The stacked AGZO films are prepared by two different methods to improve film properties: Method A is repeated provisional annealing, spin coating, and main annealing, where the maximum number of repetitions is three. On the other hand, method B is repeated provisional annealing and spin coating followed by annealing the stacked films only one time. As a result, the AGZO films produced by method B reveal a minimum surface roughness of about 3.2 nm. In addition, with an increase of the stacked layers, the sheet resistance is decreased.