Facile fabrication of functional 3D micro-nano architectures with focused ion beam implantation and selective chemical etching

Abstract

In this work, a facile nanofabrication approach for functional 3D micro-nano architectures is developed. Freestanding silicon 3D micro-nanostructures are fabricated by precisely controlling and selective chemical etching of ion implanted patterns written by a focused ion beam (FIB). The etch-stop mechanism of gallium implanted silicon is investigated, with threshold ion dose determined between implanted and non-implanted surface. Computational Monte Carlo simulations reveal the spatial-distribution of implanted-ions, dislocated-atoms, and effects of ion energy, which contribute to the etching resistance in silicon and fabrication of suspended nanostructures. The precise nature, tuning of ion beam in a FIB enable complex pattern writing and the application of the proposed approach is further utilized towards realization of suspended and delicate 3D micro-nanostructures such as nanomesh, pyramids, nanotrumpets etc. in addition to nanowires with a high aspect ratio (≈625) and small diameter (~31 nm). Microscopic characterizations reveal the near-amorphous nature of the fabricated nanostructures, arising from the ion implantation during pattern generation. The fabricated nanostructures exhibit potential for unique optical properties and pyramids, nanotrumpet structures are further engineered for antireflection, color filtering applications respectively. The developed approach provides fabrication of 3D micro-nano architectures, with an outlook towards realization of Si based photonics devices, resonators, sensors etc.