  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.
