Formation of Oxides and Their Role in the Growth of Ag Nanoplates on GaAs Substrates

Abstract

Simple galvanic reactions between highly doped n-type GaAs wafers and a pure aqueous solution of AgNO 3 at room temperature provide an easy and efficient protocol to directly deposit uniform Ag nanoplates with tunable dimensions on the GaAs substrates. The anisotropic growth of the Ag nanoplates in the absence of surfactant molecules might be partially ascribed to the codeposition of oxides of gallium and arsenic, which are revealed by extensive data from electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, during the growth of the Ag nanoplates. The electron microscopic characterization shows that each Ag nanoplate has a "necked" geometry, that is, it pins on the GaAs lattices through only a tiny neck (with sizes of <10 nm). In addition, the as-grown Ag nanoplates exhibit strong enhancement toward Raman scattering of materials on (or around) their surfaces.

Metal Nanoplates on Semiconductor Substrates

“…When the concentration of AgNO 3 solution is high enough, the growth rate of oxides becomes higher than the dissolution rate, resulting in deposition of an oxide layer on the GaAs surface. Transmission electron microscopy (TEM, Figure ), X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy provide direct evidence to confirm the existence of oxides in the fresh samples obtained through reacting n‐GaAs wafers with AgNO 3 solutions with concentrations higher than 0.1 M 71. The in situ formation of an oxide layer can eliminate progressive nucleation process to facilitate the anisotropic growth of the existing nuclei into larger particles.…”

“…This reaction leads to the formation of oxides (i.e., Ga 2 O 3 , As 2 O 3 and their corresponding hydrates) of GaAs over the surface of the wafer (Figure 3c). 71 The overall chemical change involved in the hole injection process can be summarized as: …”

“…The blue arrows indicate the flow of Ag + ions to the lateral surfaces with high indexes. Adapted with permission 71. Copyright 2008, American Chemical Society.…”

Reconstruction of Silver Nanoplates by UV Irradiation: Tailored Optical Properties and Enhanced Stability

“…Colloidal noble‐metal nanoparticles, especially of gold and silver, have proven to be good candidates for applications in catalysis,1, 2 surface‐enhanced Raman scattering (SERS),3, 4 biosensors,5 and plasmonics,6 of which chemical and biological sensing are the most promising. Most of these attractive applications are based on the particles’ surface plasmon resonance (SPR), which strongly depends on their specific composition, size, shape, local dielectric environment, and electromagnetic interactions with proximate particles 7–10.…”

Plasmon-assisted site-selective growth of Ag nanotriangles and Ag-Cu2O hybrids

“…Different metal nanocrystals with various morphologies, such as nanospheres, nanoplates, nanorods, have been used in many fields, such as surface-enhanced Raman scattering (SERS), optical sensing, near-field optical probing, and optical bio-imaging12345678. Among all, the morphologies are controlled by the overgrowth of nanoparticles which are reduced by metal precursors.…”