Role of solvent in direct growth of gold nanostructures at the interface between focused ion beam-amorphized silicon and Au-ion-containing solution

Abstract

The direct growth of gold nanostructures at the interface between a focused ion beam (FIB)-amorphized silicon surface and a HAuCl4-dissolved solution is demonstrated, and its mechanism is discussed in terms of the solvent for HAuCl4. Gold nanostructures successfully grew when a protic solvent such as water or alcohol, which has a hydroxyl group, was used as the solvent for HAuCl4. In contrast, no gold nanostructures were observed in the case of dimethyl sulfoxide (DMSO), an aprotic solvent having no hydroxyl group. Each protic solvent deactivates the FIB-amorphized silicon surface in the absence of Au ions. The growth of gold was inhibited when the FIB-amorphized silicon was exposed to the solvent before exposure to HAuCl4(aq). Silicon dangling bonds, which commonly exist in amorphized silicon, seem to reduce Au ions with the participation of protic solvent molecules in the redox reaction, initiating the growth of gold. The results of time-of-flight secondary ion mass spectrometry (TOF-SIMS) also support our suggestion.

Area-Selective Electroless Deposition of Gold Nanostructures on SiC Using Focused-Ion-Beam Preprocessing

“…As in the case of silicon, the nucleation of gold on SiC is probably initiated by silicon dangling bonds as follows: We previously presented the following chemical equation for the nucleation of gold on silicon [2], 3Si• + Au 3+ + 3ROH → 3Si-OR + Au + 3H + (R = H or C n H 2n+1 ),…”

“…For these applications, area-selective fabrication of gold with a desired size on a substrate is a key technology. We recently reported a new option to area-selectively fabricate gold nanostructures on crystalline silicon [1,2]: A pure HAuCl 4 aqueous solution with no additives is dropped onto a silicon substrate preprocessed with, for instance, a focused ion beam (FIB). Gold nanostructures selectively grow on the preprocessed area.…”

Focused-ion-beam-enabled electroless growth of gold nanoparticles on silicon

“…Thus, we investigated the dependence of growth behavior of gold on the solvents used to dissolve chloroauric acid. 29) An undoped Si(100) wafer was cut into 5 mm squares and precleaned by sonication in ethanol for 5 min. A local area of 5¯m square was irradiated with a Ga + FIB (JEOL JIB-4600F) at an acceleration voltage of 30 kV, a current of 1000 pA, and an ion dose of 0.5 nC/¯m 2 .…”

“…For the measurement after gold growth, gold was removed in a similar manner described in Ref. 29) before the measurement. The result indicated that the FIB-irradiated silicon did not dissolve during the growth of gold.…”

“…SEM images of gold nanoparticles that grew areaselectively on the FIB-irradiated area of silicon substrates in response to exposure to a 5 mM chloroauric acid (a) aqueous, (b) ethanol, (c) 1-butanol, and (d) DMSO solution for 1 min 29). …”