Characterization of Si nanowires fabricated by Ga+ FIB implantation and subsequent selective wet etching

Local gallium (Ga) ion implantation in silicon (Si) by focused ion beam (FIB) and subsequent anisotropic and selective wet etching has been used to fabricate freely suspended nanowires (NWs) with reproducible widths between 20 and 200 nm. The dependence of the resulting NW width on the implanted fluence has been investigated and is supported by a numerical model reproducing the experimental data and enabling an a priori estimation of the NW width as a function of the implanted fluence. Furthermore, the resistance of the NWs, its temperature response and the activation energy for electrical current flow were investigated before and after direct current (DC) annealing in air and in vacuum. Annealed NWs showed a decrease of their resistivity up to two orders of magnitude, indicating a partial re-crystallization of the NWs through self-heating and a change in the conduction. The assumption of recrystallization is supported by scanning electron microscopy (SEM) and Raman spectroscopy.