SEM study of site-specific thermal behavior of Au@SiO2 core–shell nanostructures under inert and air atmospheres

Abstract

Study of Metal–SiO2-Si interfaces is of great technical as well as fundamental interest. The presence of gold in contact with the SiO2-Si system at higher temperatures is known to have a major impact on the dynamics of interaction between the interfaces involved. In this work, we are offering a rare combination of interfaces wherein the interfacial binding forces are vastly different between Au–SiO2 (Shell), SiO2 (shell)-SiO2 (native), and the usual SiO2 (native)-Si(100). Au@SiO2 core–shell nanoparticles have been prepared by a standard solvothermal method and are dispersed on Si(100) substrates by drop cast technique. Site-specific thermal behavior of resulting interfaces has been analyzed using Scanning Electron Microscopy (SEM) and X-ray Diffraction technique (XRD), before and after annealing at 900 ∘C in N2 and air atmospheres separately. Appropriate locations were identified for the as-prepared specimens in both cases so that morphological changes accurate to each nanoparticle could be studied post-annealing. The number of gold particles reduce drastically post-annealing under N2 atmosphere and has been argued to be as a result of thermal decomposition of both shell and native SiO2, aided by the presence of gold. In the specimen annealed in air, a constant supply of oxygen seems to have suppressed the decomposition reaction to a great extent.