Thin Film Deposition and Photodissociation Mechanisms for Lanthanide Oxide Production from Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)Ln(III) in Laser-Assisted MOCVD

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• 作者：Qingguo Meng ; Robert J. Witte ; Yajuan Gong ; Elizabeth L. Day ; Jiangchao Chen ; P. Stanley May ; Mary T. Berry
• 刊名：Chemistry of Materials
• 出版年：2010
• 出版时间：November 23, 2010
• 年：2010
• 卷：22
• 期：22
• 页码：6056-6064
• 全文大小：928K
• 年卷期：v.22,no.22(November 23, 2010)
• ISSN：1520-5002

文摘

Photoionization mass spectrometry reveals details of the multistep unimolecular mechanism, whereby the 2,2,6,6-tetramethyl-3,5-heptanedionato (thd⁻) anionic ligand decomposes, while still bound in the metal complex, to yield a gas-phase metal oxide product in metal−organic chemical vapor deposition (MOCVD) of lanthanide oxides from Ln(thd)₃ precursors. The decomposition occurs with stepwise elimination of small closed-shell hydrocarbon fragments and carbon monoxide up to a penultimate Ln(OC₂H) ethyneoxide, from which both LnO (dominant) and LnC₂ (minor) products are derived. Formation of the metal oxide and carbide occurs in competition with a previously described mechanism(1-3) wherein sequential dissociation of ligand radicals produces the reduced metal Ln⁰. Evidence for gas-phase formation of a Ln₂(thd)₆ dimer as a result of expansion-cooling in the precursor source assembly is also given. Laser-assisted MOCVD of Eu(thd)₃ on silica, with subsequent exposure to atmosphere, produces amorphous Eu₂O₃ with small areas of crystallinity attributed to reaction of the oxide with atmospheric carbon dioxide and water.