Aluminium doped zinc oxide (ZnO:AI) films were deposited on amorphous substrates heated up to 200 degreesC with a radio frequency (rf) power of 100 W by rf magnetron sputtering from a ZnO target mixed with Al2O3 Of 2 Wt.%. Argon gas pressure during deposition was in the range 0.08-2.7 Pa. As argon gas pressure was increased, the deposition rate and the grain size were decreased and the surface roughness was increased. Furthermore, the carrier concentration and the Hall mobility were decreased and thus the electrical resistivity was increased. However, the optical transmittance of about 90% was maintained over the argon pressure range. The resistivity of the film deposited at argon gas pressure of 0.13 Pa was about 2.5 x 10(-4)Ohm cm, a value comparable to that for indium tin oxide film presently used as a transparent electrode.