Nano-Structures & Nano-Objects 23 (2020) 100521 Contents lists available at ScienceDirect Nano-Structures & Nano-Objects journal homepage: www.elsevier.com/locate/nanoso SEM study of site-specific thermal behavior of Au@SiO 2 core–shell nanostructures under inert and air atmospheres Susheel Kumar Gundanna a , Arijit Mitra b , Lakshminarayana K.G. Bhatta a , Umananda M. Bhatta a,∗ a Centre for Incubation, Innovation, Research and Consultancy, Jyothy Institute of Technology, Visvesvaraya Technological University, Bengaluru 560082, India b Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India article info Article history: Received 12 April 2020 Received in revised form 12 June 2020 Accepted 28 June 2020 Keywords: Core–shell nanostructure Metal–Oxide–Semiconductor SiOx thermal decomposition Au@SiO 2 abstract Study of Metal–SiO 2 -Si interfaces is of great technical as well as fundamental interest. The presence of gold in contact with the SiO 2 -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–SiO 2 (Shell), SiO 2 (shell)-SiO 2 (native), and the usual SiO 2 (native)-Si(100). Au@SiO 2 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 N 2 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 N 2 atmosphere and has been argued to be as a result of thermal decomposition of both shell and native SiO 2 , 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. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Silicon is the most commonly used semiconductor in the current microelectronic industry. Crystalline silicon has a dia- mond FCC structure wherein each Si atom is covalently bonded to one another with a valency of 4. As a result, the surface of a typical silicon crystal has a series of dangling bonds which makes the surface highly reactive to the presence of oxygen [1– 4]. So, every clean silicon surface is prone to oxidation upon cleaving and possesses an ultra-thin layer of SiO x . For a variety of applications, it is also desirable to thermally grow SiO 2 of specific thicknesses [5–7]. Consequently, it is very important to fabricate, process, and manipulate the resulting Si–SiO 2 interfaces as a matter of fundamental and technological interests, especially in Metal–Oxide–Semiconductor technology (MOS). Possibility of any metallic impurity being able to diffuse through thermally grown SiO 2 will have an effect on its performance as MOS device and hence it is extremely important to study such systems from all possible criteria involved including fabrication, processing, temperature, surrounding atmosphere, etc. [8–14] ∗ Corresponding author. E-mail address: umananda.b@ciirc.jyothyit.ac.in (U.M. Bhatta). Specifically, the effect of the presence of gold on the in- terfacial electrical, electronic characteristics of a metal–oxide– semiconductor structure has been studied for several decades now [15–20]. There are several theoretical and experimental studies on the influence of gold at the SiO 2 surface and interface of SiO 2 –Si, on the interface states, etc. [9,15–22]. It has long been established that gold diffuses through native as well as thermal SiO 2 grown on Si substrates at high enough temperatures to preferably reach the Si–SiO 2 interface. Under suitable conditions, Au makes contact with Si substrate to form various phases of gold silicides at the interface [15,16,23,24]. It is also well known by now that gold acts as a catalyst in increasing the rate of thermal decomposition of SiO 2 through the reaction, SiO 2 +Si→2SiO↑ [25– 30]. Au–SiO 2 –Si interfaces have been fabricated and studied in var- ious forms appropriate to specific applications. It usually involves two steps. The first and most popular step has been to thermally grow SiO 2 on oriented substrates. Thickness, quality depends on time, purity, and availability of oxygen and also the orientation of the substrate. The second step is basically the introduction of gold by a variety of techniques like PVD, CVD, ion implantation. Some of the procedures may require post-processing by anneal- ing in UHV/HV/inert/oxidizing environments [20–22,26,31–34]. https://doi.org/10.1016/j.nanoso.2020.100521 2352-507X/© 2020 Elsevier B.V. All rights reserved.