Three-Dimensional Nanostructure Fabrication by Controlling Downward Growth on Focused-Ion-Beam Chemical Vapor Deposition

Focused-ion-beam chemical vapor deposition (FIB-CVD) is a key technology to achieve the arbitrary three-dimensional (3D) nano- and microstructure fabrication. However, most of 3D nanostructure fabrications have focused on upward or lateral growth whereas few of them focused on downward growth. The downward growth characteristics of air nanowires were investigated in order to achieve the fabrication of more arbitrary 3D nanostructures. As a result, it was not able to fabricate a 1 µm long downward growth nanowire with an angle lower than -10°. Also, we found that a nanowire with an angle lower than -18° cannot be fabricated. Furthermore, we demonstrated the fabrication of 3D nanostructure including downward growth by changing the scan speeds of Ga + FIB during fabrication. With controlling the downward growth, the fabrication of more various 3D nanostructures can be achieved.