Atomistic modeling of thermal effects in focused electron beam induced deposition of Me$_2$Au(tfac)

TL;DR

This study uses molecular dynamics simulations to investigate how temperature affects the structure, composition, and growth of gold deposits created by focused electron beam induced deposition of Me$_2$Au(tfac), revealing temperature-dependent changes in gold content.

Contribution

The paper introduces a simulation approach that incorporates fragmentation mechanisms to predict temperature effects on FEBID of Me$_2$Au(tfac), aligning with experimental findings.

Findings

Gold content increases with temperature from 0.18 to 0.25 in Au:C ratio.

Deposits consist of small gold clusters in a carbon-rich matrix.

Simulations match experimental trends in deposit composition.

Abstract

The role of thermal effects in the focused electron beam induced deposition (FEBID) process of Me$_2$Au(tfac) is studied by means of irradiation-driven molecular dynamics simulations. The FEBID of Me$_2$Au(tfac), a commonly used precursor molecule for the fabrication of gold nanostructures, is simulated at different temperatures in the range of $300-450$ K. The deposit's structure, morphology, growth rate, and elemental composition at different temperatures are analyzed. The fragmentation cross section for Me$_2$Au(tfac) is evaluated on the basis of the cross sections for structurally similar molecules. Different fragmentation channels involving the dissociative ionization (DI) and dissociative electron attachment (DEA) mechanisms are considered. The conducted simulations of FEBID confirm experimental observations that deposits consist of small gold clusters embedded into a carbon-rich organic matrix. The simulation results indicate that accounting for both DEA- and DI-induced fragmentation of all the covalent bonds in Me$_2$Au(tfac) and increasing the amount of energy transferred to the system upon fragmentation increase the concentration of gold in the deposit. The simulations predict an increase in Au:C ratio in the deposit from 0.18 to 0.25 upon the temperature increase from 300 K to 450 K, being within the range of experimentally reported values.