Electroless
deposition of noble metals on silicon has applications
in a wide range of fields including electronic circuitry, metal plating
industry, lithography, and other fabrication techniques. In addition,
studies using self-assembled monolayers (SAMs) as resists for electroless
deposition for controlled deposition have significant potential for
aiding advancement in the fields of nanoelectronics, sensing applications,
and fundamental studies. Herein, we discuss the development of appropriate
plating solutions for controlled deposition of metallic gold and silver
on Si(111) surfaces in the presence of an organic silane monolayer
acting as a resist film for directed metal deposition to produce metal-monolayer
hybrid surfaces while investigating microscopic plating trends. For
this, plating solutions were optimized to deposit metal on bare silicon
surfaces while avoiding deposition on the SAM protected areas. Trends
in the electroless deposition of gold and silver on a Si(111) surface
as a function of concentration of metal ions, NH4F, citric
acid, sodium citrate, polyvinylpyrrolidone (PVP), and deposition time
have been monitored under ambient conditions. The resulting surfaces
were characterized using atomic force microscopy (AFM), and the stability
of plating solutions was investigated by UV–vis spectroscopy.
For both gold and silver, we observed an increase in metal deposition
when the concentration of NH4F, citric acid, and deposition
time increased. The addition of PVP and the pH of the solution were
also shown to have a significant effect on the metal deposition. The
octadecyltrichlorosilane (OTS) SAM films act as effective nanoscale
resists when the NH4F concentration is reduced from typical
plating conditions. In particular, NH4F concentrations
from 0.02 to 0.50 M and metal ions concentrations from 0.001 to 0.020
M were found to allow deposition of metal nanostructures on a bare
Si surface while preserving OTS protected areas.