Mechanism of Au nanowire growth by Au evaporation on Si substrates irradiated with Ar ions

Abstract

This study aims to clarify the mechanism of site-selective Au-nanowire (NW) growth on Si substrates irradiated with Ar ions. Au NWs are grown by Au evaporation at specific regions in the boundary zones between the ion-irradiated and unirradiated areas of Si substrates. The NW growth area are restricted by placing a grid mesh with a certain hole size within the boundary zone to limit the irradiation area. The length and diameter of the NWs can be controlled by controlling the hole size. Cross-sectional microscopic analyses reveal the presence of a thin Si-oxide layer as well as an Au–Si buried layer beneath the NWs. A site-selective Au NW growth model is developed by modifying the already-existence model. By fitting the Au NW length calculated using our model to the experimental data, the surface diffusion length of Au adatoms (λs) is estimated to be approximately 7 μm, close to the radius of the irradiated area Rw (6 μm). This validates our model that assumes that the NWs are grown at the bottom from the Au adatoms migrating onto the substrate. The Au-NW growth mechanism is discussed along with the role of the oxide layer and surface diffusion of Au adatoms.