Effects of visible and synchrotron x-ray radiation on the growth of silver nanoplates on n-GaAs wafers: A comparative study

Abstract

Thermal effect on the oxides on Nb(100) studied by synchrotron-radiation x-ray photoelectron spectroscopy High resolution synchrotron radiation-based x-ray photoemission spectroscopy study of the Si-rich β-SiC(100) 3×2 surface oxidation

Metal Nanoplates on Semiconductor Substrates

“…Figure summarizes the major reactions involved in the synthesis of Ag nanoplates on n‐type GaAs wafers through this simple strategy. In a typical synthesis, a droplet of AgNO 3 solution is delivered to the surface of an n‐type GaAs wafer, which has been soaked in a dilute (2%) hydrofluoric acid (HF) solution for 5 min to remove the native oxide followed by being rinsed with water and dried with nitrogen blowing 68–70. Contacting the GaAs wafer with AgNO 3 solution immediately initiates the rapid reduction of Ag + ions by surface electrons, resulting in the formation of small Ag nanocrystals (i.e., nuclei) on the nucleation sites (e.g., surface defects) of the GaAs surface (Figure 3a).…”

“…When the crystalline structure of the Ag nuclei and kinetics of the hole injection process are appropriate, Ag nanostructures with well‐defined shapes can be obtained. For example, reactions between clean n‐type GaAs wafers and aqueous solutions of AgNO 3 with concentrations higher than 0.3 M at room temperatures lead to deposition of flat Ag nanoplates on the GaAs substrates 68–70. Figure 4a presents a typical scanning electron microscopy (SEM) image of a sample formed through reaction of a 1 M AgNO 3 solution with a GaAs wafer (doped with Si at a concentration of 1.5 × 10 18 cm −3 ).…”

Nanophase Evolution at Semiconductor/Electrolyte Interface in Situ Probed by Time-Resolved High-Energy Synchrotron X-ray Diffraction

“…All diffraction peaks recorded in the course of 0−200 s can be well indexed to fcc Ag, fcc Ag 7 NO 11 , and simple cubic (sc) Ag 3 AsO 4 with the cubic groups of Fm 3̅ m , Fm 3̅ m , and P 4̅3 n , respectively (Supporting Information Figure S2). Previous studies show that X-ray irradiation can create charge separation in an n-type GaAs substrate although the mechanism is different from absorption of visible light . In general, X-ray photons with high energies excite deep core levels of elements in the GaAs lattice followed by relaxation through Auger process or secondary photon emission, which creates a cascade of secondary electrons, holes, and photons. , These secondary electrons and holes eventually thermalize to the band edges of the GaAs wafer (i.e., electrons in the conduction bands and holes in the valence bands).…”

In Situ Synchrotron X‐Ray Techniques for Real‐Time Probing of Colloidal Nanoparticle Synthesis

“…For example, the reaction of an aqueous solution of AgNO 3 with an n‐type GaAs wafer in dark forms pure Ag nanoplates on the surface of the GaAs wafer . The redox reaction between GaAs and AgNO 3 is prevented when the GaAs surface wetted with the AgNO 3 solution is illuminated with a 12‐keV synchrotron X‐ray beam . When the wetted surface is illuminated with an X‐ray beam of 65.02 keV, the growth of Ag nanoplates is barely influenced and nanoparticles made of new compounds including Ag 7 NO 11 (silver oxy salt) and Ag 3 AsO 4 (silver arsenate) are formed only at long illumination time .…”

“…[ 153,154 ] The redox reaction between GaAs and AgNO 3 is prevented when the GaAs surface wetted with the AgNO 3 solution is illuminated with a 12-keV synchrotron X-ray beam. [ 155 ] When the wetted surface is illuminated with an X-ray beam of 65.02 keV, the growth of Ag nanoplates is barely infl uenced and nanoparticles made of new compounds including Ag 7 NO 11 (silver oxy salt) and Ag 3 AsO 4 (silver arsenate) are formed only at long illumination time. [ 156 ] Moreover, high intensity X-rays can induce radiolysis of solvent molecules to break their chemical bonds in solution-phase reactions, [ 157,158 ] leading to the formation of very reactive radicals that can react with precursors to change the reaction pathways for the formation of colloidal nanoparticles.…”