Evaluations of the hopping growth characteristics on three-dimensional nanostructure fabrication using focused ion beam

Hopping growth characteristics were examined to clarify the growth mechanism of three-dimensional nanostructures fabricated using focused-ion-beam chemical-vapor deposition (FIB-CVD). In this study, the gas density distribution of FIB-CVD was examined. As a result, a gas density has a large distribution on the vertical direction. However, the growth mechanism of a hopping nanostructure could not be explained completely. Therefore, sequential scanning ion microscope images of a hopping growth process were captured. It was found that the gap distance between the growth edges of the upper and lower structures changed during the hopping structure growth. This indicated the positional relationship between the Ga+ FIB and the growth structure. The change in this relationship induced the formation of a bridge bent structure and the change in the growth direction of the upper structure. To confirm the cause of the lower structure growth, the relationship between the Ga+ penetration depth into diamondlike carbon and the thickness of the upper structure was examined. The deposition onto the substrate was caused by the Ga+ FIB’s tail (directly irradiated beam). A hopping growth structure was formed by the repetition of these growth processes.