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The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study. | LitMetric

AI Article Synopsis

  • Transition metal complexes with β-diketonate and diamine ligands are important for creating metal oxide nanomaterials through chemical vapor deposition (CVD), though the details of metal-ligand bond dissociation on growth surfaces remain unclear.
  • Using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, the study analyzes the precursor Zn(hfa)TMEDA, revealing that its rolling diffusion at elevated temperatures causes a change in molecular geometry from octahedral to square pyramidal.
  • The energy barrier for this conformational change is relatively low, and hydrogen bonding with the surface greatly facilitates the dissociation of the Zn-O bond, providing insights that could help optimize the initial stages of Zn

Article Abstract

Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond dissociation mechanism on the growth surface is not yet clarified in detail. We address this question by density functional theory (DFT) and ab initio molecular dynamics (AIMD) in combination with the Blue Moon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = ,,,-tetramethylethylenediamine), an amenable precursor for the CVD of ZnO nanosystems, show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of magnitude of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyl groups plays a key role in aiding the dissociation of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8037710PMC
http://dx.doi.org/10.3390/molecules26071988DOI Listing

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