Nanostructured zinc oxide films grown from microwave activated aqueous solutions

ZnO films have been obtained by a modification of the chemical bath deposition (CBD) procedure in which crystal growth is activated using microwave (MW) radiation. ZnO films has been grown on F-doped SnO2-covered glass substrates immersed in an aqueous solution which contains a soluble zinc oxide precursor (zinc nitrate or zinc acetate) and urea or hexamethylenetetraamine to promote the formation of the oxide. This new method, MW-CBD, produces well-adhered films at low temperatures, in an open atmosphere and in short times. The deposited material is crystalline and, thus, no additional heat treatment is necessary. The degree of coverage and the shape of the ZnO nanocrystallites are determined by the composition of the chemical bath and by the MW radiation power and irradiation time. A suitable selection of these parameters allows attaining complete substrate coverage with ZnO nanorods, mainly oriented perpendicularly to the substrate, in only 12 min.