  We present a numerical investigation of energy and charge distributions
during electron-beam-induced growth of W nanostructures on SiO2 substrates
using Monte Carlo simulation of electron transport. This study gives a
quantitative insight into the deposition of energy and charge in the substrate
and in already existing metallic nanostructures in the presence of the electron
beam. We analyze electron trajectories, inelastic mean free paths, and
distribution of backscattered electrons in different deposit compositions and
depths. We find that, while in the early stages of the nanostructure growth a
significant fraction of electron trajectories still interact with the
substrate, as the nanostructure becomes thicker the transport takes place
almost exclusively in the nanostructure. In particular, a larger deposit
density leads to enhanced electron backscattering. This work shows how
mesoscopic radiation-transport techniques can contribute to a model which
addresses the multi-scale nature of the electron-beam-induced deposition (EBID)
process. Furthermore, similar simulations can aid in understanding the role
played by backscattered electrons and emitted secondary electrons in the change
of structural properties of nanostructured materials during post-growth
electron-beam treatments.
