Desorption of fragments upon electron impact on adsorbates: implications for electron beam induced deposition

A molecular level understanding of surface chemistry involved in the focused electron beam induced deposition (FEBID) with metalorganic molecules is crucial for enhancing the metal content in the fabricated nanostructures. Here, we investigate the FEBID process of trimethyl(methylcyclopentadienyl)platinum(IV) [MeCpPtMe₃] using focused electron beam induced mass spectrometry (FEBiMS), a recently developed in situ analytical technique. A comparison with experimental gas-phase electron impact fragmentation spectra, alongside density-functional theory calculations and molecular dynamics simulations is presented. The results indicate that charged fragments generated via dissociative ionization exhibit strong adsorption to the substrate and lack sufficient kinetic energy to desorb. This suggests that the most observed charged species during FEBID originate from gas-phase fragmentation above the surface. Furthermore, this study proposes processes like charge neutralization and dissociative recombination, not previously considered in FEBID, could be significant contributors to increasing the metal content in the resulting nanostructures.