Al-doped ZnO (AZO) films were deposited on a fused silica glass substrate by reactive dc unbalanced magnetron sputtering using a Zn-Al (Al: 3.6 at.%) alloy target with an impedance control system. A very thin slightly reduced AZO buffer layer was inserted between the glass substrate and AZO films. For the AZO films deposited at 200 degrees C, the lowest resistivity in the absence of the buffer layer was 8.0 x 10(-4) Omega cm, whereas this was reduced to 5.9 x 10(-4) Omega cm after introducing a 5-nm-thick buffer layer. The transmittance for all the films was above 80% in the visible region. The effects of the buffer layer were analysed and discussed in detail. It is found that the insertion of the buffer layer can improve the crystallinity of the AZO film. (C) 2013 Elsevier B.V. All rights reserved.