The initial growth behaviors of Au thin films on tin oxide substrates were investigated by in situ conductance measurement. The crystallinity of tin oxide films fabricated by ion-beam-assisted deposition was changed from amorphous to preferred oriented structure with ion beam energy. As the surface energy of tin oxide substrates increases with the irradiation of ion beams, an onset thickness of Au films is decreased. That means high surface energy of the substrate enhances surface mobility of Au adatoms so that it changes the growth mode of Au films from 3D to 2D growth. So the distance between islands where electron tunneling can occur is decreased with the surface energy of the substrate. Therefore, we conclude that different surface properties of tin oxide substrates play an important role in the early growth aspects of Au thin films. (C) 2004 The Electrochemical Society.