Internal Stresses and Formation of Switchable Nanowires at Thin Silica Film Edge

TL;DR

This paper investigates how internal stresses influence the formation of switchable nanowires in thin silica films, revealing the importance of vertical edges and residual stresses in optimizing nanowire conductivity.

Contribution

It provides a detailed analysis of the intrinsic evolution of silicon nanocrystals and switchable nanowires driven by internal stresses and electro-osmosis, supported by extensive experimental data.

Findings

Vertical edges are essential for SNW formation.

Internal stresses and electro-osmosis drive nanowire evolution.

Formation mechanisms are intrinsic and stress-dependent.

Abstract

At vertical edges, thin films of silicon oxide (SiO_{2-x}) contain semiconductive c-Si layered nanocrystals (Si NC) embedded in and supported by an insulating g-SiO2 matrix. Tour et al. have shown that a trenched thin film geometry enables the NC to form switchable nanowires (SNW) when trained by an applied field. The field required to form SNW decreases rapidly within a few cycles, or by annealing at 600 C in even fewer cycles, and is stable to 700C. Here we describe the intrinsic evolution of Si NC and SNW in terms of the competition between internal stresses and electro-osmosis. The analysis relies heavily on experimental data from a wide range of thin film studies, and it explains why a vertical edge across the planar Si-SiOx interface is necessary to form SNW. The discussion also shows that the formation mechanisms of Si NC and Si/SiO_{2-x} SNW are intrinsic and result from optimization of nanowire conductivity in the presence of residual host misfit stresses.