Selective Growth of Metal Tips onto Semiconductor Quantum Rods and Tetrapods

Mokari, Taleb; Rothenberg, Eli; Popov, Inna; Costi, Ronny; Banin, Uri

doi:10.1126/science.1097830

Cited by 1,072 publications

(1,293 citation statements)

References 26 publications

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“…It is possible that the extra spots on Si(100)/gold result from the presence of crystalline gold silicides (summarized in Table 1, Supporting Information). In Figure 5a for gold on Si(111), there are seven additional spots (in green), of which four can be indexed against the Au 2 Si, Au 5 Si, Au 7 Si intermetallics. In Figure 5b for gold on Si(100), 11 additional spots are observed of which 9 can be indexed for intermetallics, and in Figure 5c, for a different region of gold on Si(100), 12 extra spots are observed of which 7 can be indexed for intermetallics.…”

Section: Resultsmentioning

confidence: 99%

“…In Figure 5b for gold on Si(100), 11 additional spots are observed of which 9 can be indexed for intermetallics, and in Figure 5c, for a different region of gold on Si(100), 12 extra spots are observed of which 7 can be indexed for intermetallics. The spots in the Si(100) case correspond to the following intermetallics: Au 7 Si, Au 4 Si, Au 5 Si, Au 5 Si 2 ,Au 3 Si 2 ,Au 3 Si, and Au 2 Si. Similarly, six extra spots are observed in the diffraction pattern for a gold nanoparticle on a silicon nanowire (Figure 5d), three of which can be indexed to the Au 2 Si, Au 5 Si, and Au 7 Si intermetallics.…”

Section: Resultsmentioning

confidence: 99%

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Heteroepitaxial Growth of Gold Nanostructures on Silicon by Galvanic Displacement

et al. 2009

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This work focuses on the synthesis and interfacial characterization of gold nanostructures on silicon surfaces, including Si(111), Si(100), and Si nanowires. The synthetic approach uses galvanic displacement, a type of electroless deposition that takes place in an efficient manner under aqueous, room-temperature conditions. The case of gold-on-silicon has been widely studied and used for several applications and yet, a number of important, fundamental questions remain as to the nature of the interface. Some studies are suggestive of heteroepitaxial growth of gold on the silicon surface, whereas others point to the existence of a silicon؊gold intermetallic sandwiched between the metallic gold and the underlying silicon substrate. Through detailed high resolution transmission electron microscopy (TEM), combined with selected area electron diffraction (SAED) and nanobeam diffraction (NBD), heteroepitaxial gold that is grown by galvanic displacement is confirmed on both Si(100) and Si(111), as well as silicon nanowires. The coincident site lattice (CSL) of gold-on-silicon results in a very small 0.2% lattice mismatch due to the coincidence of four gold lattices to three of silicon. The presence of gold؊silicon intermetallics is suggested by the appearance of additional spots in the electron diffraction data. The gold؊silicon interfaces appear heterogeneous with distinct areas of heteroepitaxial gold on silicon, and others, less well-defined, where intermetallics may reside. The high resolution cross-sectional TEM images reveal a roughened silicon interface under these aqueous galvanic displacement conditions, which most likely promotes nucleation of metallic gold islands that merge over time: a Volmer؊Weber growth mechanism in the initial stages.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Heteroepitaxial Growth of Gold Nanostructures on Silicon by Galvanic Displacement

et al. 2009

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“…Integrating different metallic NCs into a HMNC can introduce new and enhanced properties, or multi-functionality not found in the parent metal NCs [1][2][3][4][5][6][7] . The properties of a HMNC are clearly architecture dependent [7][8][9][10][11][12][13][14][15][16][17] .…”

Section: Spatial Arrangement Edge Satellitementioning

confidence: 99%

Engineering the architectural diversity of heterogeneous metallic nanocrystals

et al. 2013

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Similar to molecular engineering where structural diversity is used to create more property variations for application explorations, the architectural engineering of heterogeneous metallic nanocrystals (HMNCs) can likewise increase the versatility of metallic nanocrystals (NCs). Here we present a synthesis strategy capable of engineering the architectural diversity of HMNCs through rational and independent programming of every architecture-determining element, that is, the shape and size of the component NCs and their spatial arrangement. The strategy is based on the galvanic replacement reaction of a self-sustaining layer formed by underpotential deposition on a polyhedral NC. The selective deposition of satellite NCs on specific site of the central NC is realized by creating a geometry-dependent heterogeneous electron distribution. This site-selective deposition approach is applicable to central NCs in various polyhedral shapes and sizes. The satellite NCs can further develop their own shape and size through crystal growth kinetics control.

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“…1,2 The literature now contains several cases with chemical transformations being accompanied by varying degrees of modification of properties, including crystal structure and particle shape. [3][4][5] As a recent example, we demonstrated that as-synthesized metallic nanocrystals yield, upon oxidation, nanostructures with modified morphologies such as hollow particles. 6 This morphological change derives from directional material flows due to differing diffusivities for the reacting atomic species, in a nanoscale version of the well-known Kirkendall Effect.…”

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confidence: 91%

Faceting of Nanocrystals during Chemical Transformation: From Solid Silver Spheres to Hollow Gold Octahedra

et al. 2006

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Sustained progress in nanocrystal synthesis has enabled recent use of these materials as inorganic, macromolecular precursors that can be chemically transformed into new nanostructures. 1, 2 The literature now contains several cases with chemical transformations being accompanied by varying degrees of modification of properties, including crystal structure and particle shape. [3][4][5] As a recent example, we demonstrated that as-synthesized metallic nanocrystals yield, upon oxidation, nanostructures with modified morphologies such as hollow particles. 6 This morphological change derives from directional material flows due to differing diffusivities for the reacting atomic species, in a nanoscale version of the well-known Kirkendall Effect. This general methodology has since been extended by other groups to produce nanostructures with various compositions and shapes. [7][8][9][10] Galvanic replacement reactions have been demonstrated to also produce hollow nanostructures. Xia et al. reported cases where a replacement reaction took place uniformly around Ag cubes of ~100 nm size, leading to formation of Au nanoboxes. The exterior shape of the nanoboxes tends to largely reproduce that of the sacrificial Ag counterparts. 11-15 Here, we report that performing the same replacement reaction on silver nanocrystals that are an order of magnitude smaller leads to significant changes in the external morphology of the Au shells as the reaction proceeds, while still creating a central void in each particle. Specifically, single crystalline silver nanoscrystals with a spherical shape act in the presence of Au 3+ as precursors for formation of hollow Au nanocrystals with truncated octahedral shape. The growth of significantly faceted particles from spherical precursors is made possible by the enhanced role of surface effects in our smaller nanocrystals. Production of hollow Au nanocrystals with faceted geometry allows increased tunability of optical properties as the surface plasmon resonance spectra of a hollow metallic nanocrystal depends strongly not only on the shell thickness, but also on the detailed shape. 16,17 To produce Ag nanocrystals with reduced sizes and improved monodispersity, we performed the synthesis using a modification of the polyol process in an organic solvent and at high temperature. 6,18 The silver salt AgNO 3 was reduced by a long chain polyol such as 1,2-hexadecanediol using an organic solvent, o-dichlorobenzene (DCB). Oleylamine was present as a surfactant. Near instant formation of silver nanocrystals upon reaction was indicated by the originally colorless solution turning dark brown. The transformation of solid nanocrystals into hollow ones was performed through galvanic replacement by dropwise addition of gold (III) chloride solution to diluted silver colloidal solution until the solution changed in color from dark yellow to blue. In this reaction, oleylamine likely serves two purposes. First, it solubilizes the precursors AgNO 3 and AuCl 3 in DCB. Second, it acts as a surfactant that controls t...

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Selective Growth of Metal Tips onto Semiconductor Quantum Rods and Tetrapods

Cited by 1,072 publications

References 26 publications

Heteroepitaxial Growth of Gold Nanostructures on Silicon by Galvanic Displacement

Heteroepitaxial Growth of Gold Nanostructures on Silicon by Galvanic Displacement

Engineering the architectural diversity of heterogeneous metallic nanocrystals

Faceting of Nanocrystals during Chemical Transformation: From Solid Silver Spheres to Hollow Gold Octahedra

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