Hydrogen annealing of arrays of planar and vertically stacked Si nanowires

Four level matrices of round, 35nm in diameter Si nanowires (NWs) are obtained thanks to a top-down approach. In particular, we report optimized H2 annealing conditions (800to900°C) in order to reconstruct the plasma-etched surfaces of the suspended nanowires. The nanowire shape evolution has been studied in scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The side roughness decrease and the rounding of the NWs have been quantified. The instability of the anchors of the NWs to the contact regions has been evidenced and confirmed by surface diffusion simulations.