Control of Gold Surface Diffusion on Si Nanowires

• Published in: Nano letters 2008-05, Vol.8 (5), p.1544-1550
• Main Authors: den Hertog, Martien I, Rouviere, Jean-Luc, Dhalluin, Florian, Desré, Pierre J, Gentile, Pascal, Ferret, Pierre, Oehler, Fabrice, Baron, Thiery
• Format: Article
• Language: English
• Subjects: Adsorption; Catalytic methods; Chemical and Process Engineering; Computer Simulation; Condensed Matter; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallization - methods; Diffusion; Diffusion in nanoscale solids; Diffusion in solids; Diffusion; interface formation; Engineering Sciences; Exact sciences and technology; Macromolecular Substances - chemistry; Materials; Materials Science; Materials Testing; Methods of nanofabrication; Models, Chemical; Molecular Conformation; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanotechnology - methods; Nanotubes - chemistry; Nanotubes - ultrastructure; Particle Size; Physics; Silanes - chemistry; Silicon - chemistry; Solid surfaces and solid-solid interfaces; Surface Properties; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Transport properties of condensed matter (nonelectronic)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl073356i

Silicon nanowires (NW) were grown by the vapor−liquid−solid mechanism using gold as the catalyst and silane as the precursor. Gold from the catalyst particle can diffuse over the wire sidewalls, resulting in gold clusters decorating the wire sidewalls. The presence or absence of gold clusters was observed either by high angle annular darkfield scanning transmission electron microscopy images or by scanning electron microscopy. We find that the gold surface diffusion can be controlled by two growth parameters, the silane partial pressure and the growth temperature, and that the wire diameter also affects gold diffusion. Gold clusters are not present on the NW side walls for high silane partial pressure, low temperature, and small NW diameters. The absence or presence of gold on the NW sidewall has an effect on the sidewall morphology. Different models are qualitatively discussed. The main physical effect governing gold diffusion seems to be the adsorption of silane on the NW sidewalls.