Coalescence driven size-controlled synthesis of ITO nanospheres

A well-controlled yet simple process to synthesize indium tin oxide (ITO) nanospheres of various sizes has been proposed and described. The process was also extended to grow multi-layers of ITO nanospheres stacked one on top of another. To obtain nanospheres, e-beam evaporated ITO films wee selectively wet-etched using a dilute HCl acid solution. Size of the ITO nanospheres was controlled by varying the thickness of the ITO film. This simple process is accomplished in only a few seconds during which ITO nanosphere formation takes place via coalescence. To understand the mechanism of nanospheres formation, variation of etching time, etchant concentration and ITO film thickness were employed. A model based on etching-reaction and coalescence is suggested to reproduce the evolution of the size of nanospheres with etching time and etchant concentration. A possible application of ITO nanospheres to enhance light output from a blue GaN based light-emitting diode is also demonstrated.