Growth mechanism of indium tin oxide whiskers prepared by sputtering

Whisker structures of indium tin oxide were prepared on a glass substrate by conventional sputtering using an indium-tin alloy target. Whisker structures grew well at higher temperatures than the crystallization temperature of In2O3 and the melting temperature of the In-Sn alloy, and also under the sputtering conditions of comparatively scarce oxygen and a high sputtering rate. These sputtering conditions correspond to the transition mode of reactive sputtering. The whisker structures were categorized into a structure consisting of many needles and a structure consisting of many trunks with side branches. Each whisker was a bcc single crystal growing along the (222) direction and had a spherical droplet-like structure on the tip. Consequently, it was revealed that In-Sn droplets acted as important cores of whisker growth. The indium tin oxide (ITO) whiskers were grown by a self-catalytic vapor-liquid-solid mechanism promoted by the supersaturation of indium vapor.