Photodissociation and Photoionization Mechanisms in Lanthanide-based Fluorinated β-Diketonate Metal−Organic Chemical-Vapor Deposition Precursors

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• 作者：Qingguo Meng ; Robert J. Witte ; P. Stanley May ; Mary T. Berry
• 刊名：Chemistry of Materials
• 出版年：2009
• 出版时间：December 22, 2009
• 年：2009
• 卷：21
• 期：24
• 页码：5801-5808
• 全文大小：834K
• 年卷期：v.21,no.24(December 22, 2009)
• ISSN：1520-5002

文摘

A detailed photodissociation mechanism for the fluorinated lanthanide (Ln) β-diketonate metal−organic chemical-vapor deposition (MOCVD) precursors Ln(fod)₃, Ln(hfac)₃, and Ln(hfac)₃diglyme was elucidated using photoionization time-of-flight mass spectrometry. The collisionless environment of the molecular beam source revealed a series of unimolecular steps, starting with dissociation of an intact β-diketonate ligand. Dissociation steps for the second and third ligands are associated with the attachment of a fluoride to the metal ion, leading to one of three ultimate products: Ln, LnF, or LnF₂. Except in the case of Pr, no LnO is observed. The pattern of ligand fragmentation strongly supports a mechanism for the fluoride-attachment step which is similar to one previously proposed for the thermally activated decomposition of Ce(hfac)₃glyme.lick="showRef(this, 'ref1'); return false;" href="JavaScript:void(0);" class="ref">(1) The detailed mechanistic understanding of the step-by-step fluorination will provide a basis for new ligand design, which maintains the advantageous mass-transport properties of the fluorinated precursors while controlling LnF_x formation.