Fabrication of indium tin oxide whiskers by sputtering

Whisker crystals and whisker structures have many possibilities for industrial applications because of their unique shape with high aspect ratios. However, their fabrication methods need a high-temperature process and a limited substrate, thereby limiting their applications. Therefore, a new fabrication method that can prepare whiskers at low cost and directly on a versatile substrate, Such as a glass substrate, is required. We found that indium tin oxide coatings with well-developed whisker structures could be prepared on glass substrates heated at 300 degrees C using conventional DC magnetron sputtering. These whisker coatings consist of continuous underlayer and upper structures with many whiskers. Each whisker is 500 nm to 1 mu m in length and 10 to 20 nm in diameter. We revealed that the whisker structures were well grown under low-oxygen sputtering conditions and these whisker coatings could be categorized into three types of whisker morphology by scanning electron microscopy (SEM) observation and X-ray diffraction analysis (XRD). Whisker coatings of the first type have many needle structures and are strongly oriented along the (222) axis normal to the substrate. Whisker coating of the second type are increasingly oriented along the (400) axis and show a structure consisting of many trunks with side branches like similar to fir tree. Whisker coatings of the last type are equally oriented along (222) and (400) axes and have many fish-bone-like whisker structures. These whisker coatings may offer many possibilities for industrial applications, for example, emitter material for field-emission displays, and Surface structures for super-hydrophilic or super-hydrophobic surfaces.