Atomistic modeling of thermal effects in focused electron beam-induced deposition of Me2Au(tfac)

The role of thermal effects in the focused electron beam-induced deposition (FEBID) of Me2Au(tfac) is studied by means of irradiation-driven molecular dynamics simulations. The FEBID of Me2Au(tfac), a commonly used precursor molecule for the fabrication of gold-containing 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 Me2Au(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 Me2Au(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 0.32 upon the temperature increase from 300 to 450 K, being within the range of experimentally reported values.