Sequential sputtering technology was developed for the formation of transparent and conductive very thin films of ZnO doped by Al (AZO) with a nanocolumnar polycrystalline structure. The characterization of their properties, including structural (scanning electron microscopy, X-ray diffractometry), electrical (Hall measurements) and optical (visible spectrometry, ellipsometry), was performed. AZO thin films with thicknesses of approximately 100 nm were prepared with a pronounced nanocolumnar and (002) textured crystalline structure, sufficient low resistivity (approximate to 10(-1) Omega cm), satisfactory optical transparency (approximate to 90%) and adequate refractive index (approximate to 2.0) for future applications in biochemical sensors. (C) 2015 Elsevier B.V. All rights reserved.