Highly oriented polycrystalline aluminium-doped (Al-doped) and ruthenium-aluminium (Ru-Al) co-doped zinc oxide are prepared on borosilicate glass and polycarbonate (PC) substrates by co-sputtering at room temperature. To investigate the effect of Ru doping, co-sputtering is achieved by varying the sputtering power of Ru target while keeping the sputtering target power of Al-doped zinc oxide unchanged. Atomic force microscopy (AFM) data shows that the root-mean-square roughness of all the films is less than similar to 2.5 nm. With Ru doping, the resistivity of the film improves by one order of magnitude as compared to pure Al-doped zinc oxide sample. The resistivity and carrier concentration values obtained correlated to the degree of crystallinity in the samples. High optical transmittance in the visible range are achieved (>90% for borosilicate glass and >80% for PC). (C) 2010 Elsevier B.V. All rights reserved.