Excited States of Pt(PF₃)₄ and Their Role in Focused Electron Beam Nanofabrication

Abstract

Electron induced chemistry of metal-containing precursor molecules is central in focused electron beam induced deposition (FEBID). While some elementary processes leading to precursor decomposition were quantitatively characterized, data for neutral dissociation is missing. We provide this data for the model precursor Pt­(PF3)4 by using the available cross sections for electronic excitation and characterizing fragmentation of the excited states theoretically by TDDFT. The potential energy curves for a number of states visible in the experimental electron energy loss spectra are dissociative, either directly or via conical intersections, indicating that the quantum yield for dissociation is close to 100%. Taking into account typical electron energy distribution at the FEBID spot reveals that the importance of neutral dissociation exceeds that of dissociative electron attachment, which has been so far considered to be the dominant decomposition process. We thus established neutral dissociation as an important, albeit often neglected, channel for FEBID using Pt­(PF3)4. The calculations revealed a number of other phenomena that can play a role in electron induced chemistry of this compound, e.g., a considerable increase of bond dissociation energy with sequential removal of multiple ligands.

Electron attachment to hexafluoropropylene oxide (HFPO)

“…This process can lead to very different reaction channels than DEA or the positive ionization. 34,35 Several findings outlined above suggest that the DEA mechanism is a vertical electron attachment followed by a prompt dissociation, rather than an internal vibrational redistribution of the excess energy and statistical dissociation. These findings are the absence of the collisional stabilization in the swarm experiment and the fact that the relative abundances of the fragments are not at all correlated with the asymptotic energetics.…”

in/out Isomerism of cyclophanes: a theoretical account of 2,6,15-trithia-[34,10][7]metacyclophane and [34,10][7]metacyclophane as well as their halogen substituted analogues

“…27 Bearing this in mind, we explored how substitution of the hydrogen atom protruding towards the aromatic ring with a halogen (fluorine, chlorine and bromine) reflects on isomer relative stability. An elegant way of isolating individual contributions in bond formation is by Extended Transition State Energy Decomposition Analysis (EDA) [28][29][30] alongside Natural Orbitals for Chemical Valence (NOCV) 31,32 sheme. Also, in order to examine the nature and contribution of CH/π and CX/π interactions in cyclophane isomers stability extensive SAPT calculations were performed on model systems.…”

Calculation of the Jahn-Teller parameters with DFT

“…Several processes occur during this process, and the importance of so-called neutral dissociation was first highlighted in Pt(PF 3 ) 4 . 117 Neutral dissociation is the dissociation of electronically excited states initiated by incoming electrons. At first sight, this small symmetric molecule is not related to the JT effect.…”

“…Therefore, the JT effect in the excited states triggers dissociation. 117 These four excited states are directly dissociative, while other excited states are dissociative via many conical intersections. 117 Five-coordinated Ni(II) trigonal-bipyramidal complexes (D 3h ) in a high spin are in 3 Eʹ ground state, hence prone to the JT distortion to the C 2v structure.…”

“…117 These four excited states are directly dissociative, while other excited states are dissociative via many conical intersections. 117 Five-coordinated Ni(II) trigonal-bipyramidal complexes (D 3h ) in a high spin are in 3 Eʹ ground state, hence prone to the JT distortion to the C 2v structure. It has been shown that controlling the geometry of a transition metal complex is the way to chemically control their magnetic properties, particularly that spin-orbit coupling (SOC) could be used to tune the magnetic anisotropy.…”