Growth mechanism of vapor-liquid-solid (VLS) grown indium tin oxide (ITO) whiskers along the substrate

ITO films made of whiskers were prepared by electron shower PVD method. Two types of ITO whiskers having an In-Sn-O droplet on the tip were grown by VLS mechanism: lateral and normal whiskers. Whiskers grew along a glass substrate at t (deposition time) < 30 s, but whiskers perpendicular to the substrate appeared at t > 30 s. The growth rates of lateral and normal whiskers were 10 and, 0.6 nm/s, respectively. The deposition of Sn decreased with increasing growth time. This determines the two types of the whiskers. Sn is incorporated into a whisker during the VLS growth and the VLS growth is finally ceased by the exhaustion of Sn. As there is a lot of liquid Sn particles deposited on the substrate at t < 30 s, the VLS growth is continued to a lateral direction by the incorporation of the Sn particles in a droplet so that the whisker grows along the substrate. As the liquid Sn particles decrease at t > 30 s, the lateral VLS growth is ceased soon after the nucleation occurs in a droplet and the droplet mounts only on a basal plane. The whiskers grow perpendicular to the substrate. (C) 1999 Elsevier Science B.V. All rights reserved.