Kinetic Analysis of Au deposition from Aqueous HF onto Si(111) by Surface Second Harmonic Generation

Abstract

Deposition of Au from aqueous HF onto Si(111) has been studied by Rutherford backscattering (RBS) and surface second harmonic generation (SHG), which at 532 nm is nearly resonant with the surface plasmon of Au nanoclusters. The RBS measurements indicate that Au deposition is rate-limited by diffusion, while the SHG measurements indicate that Au cluster growth is rate-limited by either a surface reaction involving a fluoride-containing species or electron transfer. This apparent contradiction can be reconciled by proposing that initial deposition in the form of AuCN is followed by a slow electroless reduction of Au(I) accompanied by Si oxidation. By addition of HCl and KF, the solution phase equilibria can be separately manipulated, motivating further SHG experiments which indicate that HF and not HF 2Ϫ is the kinetically active fluoride-containing species. The apparent reaction order for Au cluster growth with respect to HF is approximately 1/2, and the reaction order for Au cluster growth with respect to Au(CN) 2Ϫ is near zero in the concentration range 10 Ϫ4 to 10 Ϫ5 M.

Hyper-Rayleigh scattering studies of silver, copper, and platinum nanoparticle suspensions

“…For macroscopic samples/interfaces, coherent SHG has proven to be sensitive to metal-based plasmon resonance [18,19]. We reinforce here that HRS is an effective probe of nonlinear optical behavior on an interface size regime essentially inaccessible by coherent SHG.…”

Heteroepitaxial Growth of Gold Nanostructures on Silicon by Galvanic Displacement

“…73,74 A threedimensional (3D), island or VolmerϪWeber (VW) growth mode has also been reported for the deposition of gold on silicon surfaces by galvanic displacement. 37,38,46,47 VW growth mode involves the nucleation of small clusters directly on the substrate surface followed by their subsequent growth into islands. 61 For galvanically displaced gold on silicon, AFM studies along with surface X-ray diffraction 46 and surface second harmonic generation 37,38,47 surface analyses reveal Au cluster formation which would be suggestive of a 3D or VW growth mechanism.…”

A SERS investigation of the electrodeposition of Ag–Au alloys from free-cyanide solutions

“…This peak can be related to the peculiar inhibited Au deposition mechanism active at low current densities [39], where a peculiar crystallographic structure was assessed and explained with the intercalation of CN À -related species in the crystal lattice. In the literature a chemical-electrochemical mechanism with an adsorbed AuCN species has been proposed for the reduction of the Au(I) cyanocomplex at low negative potentials [3,4,40]. At high negative polarisations, Au electrodeposition has been reported to take place according to a different mechanism, which can be interpreted as the direct reduction of Au(CN) À 2 to metallic Au [40].…”

“…In the literature a chemical-electrochemical mechanism with an adsorbed AuCN species has been proposed for the reduction of the Au(I) cyanocomplex at low negative potentials [3,4,40]. At high negative polarisations, Au electrodeposition has been reported to take place according to a different mechanism, which can be interpreted as the direct reduction of Au(CN) À 2 to metallic Au [40]. Also this kind of mechanism gives rise to negative passivation starting around )1000 mV in accord with thermodynamic data [41].…”