Selective growth of gold nanostructures on locally amorphized silicon

Abstract

Locally selective formation of gold nanostructures on a silicon wafer without photolithography, electrolysis, or hydrofluoric acid was reported previously. With our previous method, gold nanostructures grow selectively on the locally amorphized surface on a silicon wafer when the silicon wafer is exposed to a customized Au ion-containing solution. The locally amorphized surface is produced by, for example, irradiation of a focused ion beam (FIB) or a femtosecond laser. The Au ion-containing solution is prepared by mixing (3-mercaptopropyl)trimethoxysilane (MPTMS) with an aqueous solution of HAuCl 4 . Here, the mechanism of selective growth of gold nanostructures on the amorphized silicon is explained. Au ions in the solution placed on the FIB-or laserprocessed silicon are reduced by the amorphized silicon. Silicon-dangling bond defects, which exist in the amorphized silicon, seem to reduce the Au ions. Finally, we find that the use of MPTMS is unnecessary and a simple HAuCl 4 aqueous solution produces desired results.

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

“…Since, in the case of silicon, the irradiation-induced amorphous phase has a positive effect on the growth of gold [1], Raman spectra were measured on the non-irradiated and the FIB-irradiated surfaces on a SiC substrate. Figure 4 shows Raman spectra on (a) the nonirradiated and (b) the FIB-irradiated areas on the Si face of a SiC substrate.…”

“…This partially explains that A gold on silicon is greater than those on SiC. We previously revealed that greater number of gold nanostructures grow on the spatter-deposited amorphous silicon surface than on the fractured surface of crystalline silicon because the amorphous silicon has much more dangling bonds [1]. Less-damaged crystalline structures of the FIB-irradiated SiC has smaller number of silicon dangling bonds than the FIB-amorphized silicon.…”

“…Before discussing the growth stage of gold, the total number of gold atoms expected by equation (1) was calculated both on SiC and silicon using an extremely overestimated number of silicon dangling bonds that is defined here as equal to the number of silicon atoms existing in the FIB-damaged volume. This volume is the product of the FIB-irradiated area, 5 m x 5 m and the penetration depth of a 30 keV Ga + ion into SiC or silicon.…”

“…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

“…Gold is deposited selectively on the indentation spot. In our method, 26) a silicon substrate, any type: intrinsic, n, p, is irradiated using a Ga + FIB, and is exposed to a pure chloroauric acid solution. Gold nanoparticles grow selectively on the FIB-irradiated area.…”