Reactive molecular dynamics simulations on SiO₂-coated ultra-small Si-nanowires

Abstract

The application of core-shell Si-SiO(2) nanowires as nanoelectronic devices strongly depends on their structure, which is difficult to tune precisely. In this work, we investigate the formation of the core-shell nanowires at the atomic scale, by reactive molecular dynamics simulations. The occurrence of two temperature-dependent oxidation mechanisms of ultra-small diameter Si-NWs is demonstrated. We found that control over the Si-core radius and the SiO(x) (x≤ 2) oxide shell is possible by tuning the growth temperature and the initial Si-NW diameter. Two different structures were obtained, i.e., ultrathin SiO(2) silica nanowires at high temperature and Si core|ultrathin SiO(2) silica nanowires at low temperature. The transition temperature is found to linearly decrease with the nanowire curvature. Finally, the interfacial stress is found to be responsible for self-limiting oxidation, depending on both the initial Si-NW radius and the oxide growth temperature. These novel insights allow us to gain control over the exact morphology and structure of the wires, as is needed for their application in nanoelectronics.

Silicon‐Based Dielectric Metamaterials: Focus on the Current Synthetic Challenges

“…[37] TheD eal-Grove model predicts that nanoparticles of smaller diameter will have at hinner oxide coating than larger nanoparticles because of the more significant volume expansion and thus the larger increase in compressive stress during the oxidation. Si spheres form apassivating coating of SiO 2 , that then protects the Si from further oxidation, referred to as self-limiting oxidation.…”

“…This is also true in air for native oxide layers which do not exceed an e = 2t o 3nm. [37] However,a no xide layer thicker than 3nm would only be grown if the particles were heated in the presence of oxygen.…”

“…It is safe to consider that a particle of outer radius R and oxide shell thickness e optically behaves like a bare Si sphere of radius ( R − e ) in water. This is also true in air for native oxide layers which do not exceed an e =2 to 3 nm . However, an oxide layer thicker than 3 nm would only be grown if the particles were heated in the presence of oxygen.…”

Ab-initio study of the segregation and electronic properties of neutral and charged B and P dopants in Si and Si/SiO2 nanowires

“…8 This results from the stress generated at the Si/SiO 2 interface induced by their lattice mismatch. 9,10 A recent experimental study of SiNWs indicated that B and P impurities segregate towards the Si/SiO 2 interface during thermal oxidation. It was observed that P remains on the Si side while B moves inside the SiO 2 shell.…”

Molecular Dynamics Simulations for Plasma‐Surface Interactions

“…An example is shown in Figure . The transition from complete oxidation of the nanowire to a core/shell structure was found to depend, on the one hand, on the combination of oxidation temperature and nanowire diameter, and on the other hand on the plasma oxidation species …”