Atomistic simulation of the FEBID-driven growth of iron-based nanostructures

TL;DR

This study uses atomistic simulations to investigate how different electron beam currents influence the growth, morphology, and composition of iron-based nanostructures during FEBID, revealing distinct regimes and structural characteristics.

Contribution

It introduces atomistic IDMD simulations to predict nanostructure growth in FEBID, linking electron current to morphology and composition changes at the atomic level.

Findings

Low current (1 nA) produces nanogranular structures with isolated iron clusters.

High current (4 nA) leads to dendrite-like structures with coalesced metal clusters.

Deposit morphology and metal content vary significantly with electron current.

Abstract

The growth of iron-containing nanostructures in the process of focused electron beam-induced deposition (FEBID) of Fe(CO)$_5$ is studied by means of atomistic irradiation-driven molecular dynamics (IDMD) simulations. The geometrical characteristics (lateral size, height and volume), morphology and metal content of the grown nanostructures are analyzed at different irradiation and precursor replenishment conditions corresponding to the electron-limited and precursor-limited regimes (ELR & PLR) of FEBID. A significant variation of the deposit's morphology and elemental composition is observed with increasing the electron current from 1 to 4 nA. At low beam current (1 nA) corresponding to the ELR and a low degree of Fe(CO)$_5$ fragmentation, the nanogranular structures are formed which consist of isolated iron clusters embedded into an organic matrix. In this regime, metal clusters do not coalesce with increasing electron fluence, resulting in relatively low metal content of the nanostructures. A higher beam current of 4 nA corresponding to the PLR facilitates the precursor fragmentation and the coalescence of metal clusters into a dendrite-like structure with the size corresponding to the primary electron beam. The IDMD simulations enable atomistic-level predictions on the nanoscopic characterization of the initial phase of nanostructure growth in the FEBID process. These predictions can be verified in high-resolution transmission electron microscopy experiments.