Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 3, Issue 5, Pages 1581-1584Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am200144k
Keywords
galvanic displacement; gold; ultrasmooth; thin films; X-ray photoelectron spectroscopy; self-limiting
Funding
- National Science Foundation (through the Center of Integrated Nanomechanical Systems) [EEC-0832819]
- Comissionat per a Universitats i Recerca (CUR) del Departament d'Innovacio, Universitat i Empresa de la Generalitat de Catalunya
- [DMR-0804646]
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Galvanic displacement (GD), a type of electroless deposition, has been used to obtain ultrasmooth gold thin films on silicon < 111 >. The novel aspect of the method presented herein is the absence of fluoride ions in the liquid phase, and its principal advantage when compared to previous efforts is that the process is inherently self-limiting. The self-limiting factor is due to the fact that in the absence of fluorinated species, no silicon oxide is removed during the process. Thus, the maximum gold film thickness is achieved when elemental silicon is no longer available once the surface is oxidized completely during the galvanic displacement process. X-ray photoelectron spectroscopy has been used as a tool for thickness measurement, using the gold to silicon ratio as an analytical signal. Three gold plating solutions with different concentrations of KAuCl4 (2, 0.2, and 0.02 mM) have been used to obtain information about the formation rate of the gold film. This XPS analysis demonstrates the formation of gold films to a maximum thickness of similar to 3.5 angstrom. Atomic force microscopy is used to confirm surface smoothness, suggesting that the monolayer growth does not follow the Volmer-Weber growth mode, in contrast to the GD process from aqueous conditions with fluorinated species.
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