Simulation of electron transport in electron beam induced deposition of nanostructures

TL;DR

This paper uses Monte Carlo simulations to analyze electron transport during the growth of tungsten nanostructures on SiO2, providing insights into energy and charge distribution crucial for understanding and optimizing electron-beam-induced deposition processes.

Contribution

It introduces a mesoscopic simulation approach to model electron transport in EBID, highlighting how deposit density affects electron backscattering and transport behavior.

Findings

Thicker nanostructures lead to electron transport mainly within the deposit.

Higher deposit density increases electron backscattering.

Early growth stages involve significant substrate interaction.

Abstract

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.