Focused-Ion-Beam-Induced Folding of 3D Structures

The 3D structures were experimentally fabricated on self-supporting Au films by employing a focused-ion-beam (FIB) irradiation-induced folding technique^{26 (link), 30 (link)}. Specifically, the pre-designed patterns were firstly cut by utilizing a dual beam FIB/SEM system (FEI Helios 600i). Subsequently, the FIB was continuously scanned using the line scan mode along the bottom edge of the patterned structures, which folded the structures naturally by utilizing the ion-implantation induced stress. During fabrications, the acceleration voltage of Ga⁺ was set to 30 kV and an ion-beam current of 40 or 80 pA was used, with which a maximum folding angle of 90° could be achieved with an accumulated ion dose of ~3.2 × 10⁷ ions/μm^{26 (link)}. Due to the large scale of the structure, the fabrication resolution is about 20 nm.