Transparent zinc oxide thin films were grown by reactive pulsed laser deposition on glass substrates. The substrates were kept at 200 degrees C constant temperature. Post-deposition heat treatment, applied to further promote crystallization and overcome any oxygen deficiency, yielded transparent thin films. Structural investigations carried out by atomic force microscopy (AFM) and X-ray diffraction (XRD), have shown a strong influence of deposition technique parameters and post-annealing on the crystallinity of the zinc oxide films. The gas sensing characteristics of these films were investigated towards different hydrogen concentrations (5000-30,000 ppm) at a selected operating temperature within the 150-230 degrees C range. (C) 2009 Elsevier B.V. All rights reserved.