Low-Energy Electron-Induced Decomposition and Reactions of Adsorbed Tetrakis(trifluorophosphine)platinum [Pt(PF3)4]

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• 作者：Kees Landheer ; Samantha G. Rosenberg ; Laurent Bernau ; Petra Swiderek ; Ivo Utke ; Cornelis W. Hagen ; D. Howard Fairbrother
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：September 8, 2011
• 年：2011
• 卷：115
• 期：35
• 页码：17452-17463
• 全文大小：1016K
• 年卷期：v.115,no.35(September 8, 2011)
• ISSN：1932-7455

文摘

The effect of 500 eV electrons on nanometer-thick films of the platinum precursor tetrakis(trifluorophosphine)platinum [Pt(PF₃)₄] has been studied in situ under ultra-high-vacuum (UHV) conditions using a combination of X-ray photoelectron spectroscopy (XPS), mass spectrometry (MS), and high-resolution electron energy loss spectroscopy (HREELS). Electron irradiation of adsorbed Pt(PF₃)₄ molecules initially proceeds through a single Pt鈥擯 bond-cleavage event and the ejection of one PF₃ ligand, analogous to the electron-stimulated reactions of Pt(PF₃)₄ in the gas phase. The electron-stimulated deposition cross section of Pt(PF₃)₄, 蟽_Pt(PF3)4, is governed by the rate of this initial Pt鈥擯F₃ cleavage event, which is calculated to be 2.5 脳 10^鈥?5 cm² at an incident electron energy of 500 eV. In contrast to the initial deposition step, subsequent electron-stimulated reactions of the surface-bound Pt(PF₃)₃ intermediate occur exclusively through P鈥擣 bond cleavage and the release of fluorine into the gas phase. In this second phase of the decomposition process, oxygen uptake into the film is observed because of reactions between water vapor and the coordinatively unsaturated phosphorus atoms formed by P鈥擣 bond cleavage. Electron-beam-induced deposition (EBID) of Pt(PF₃)₄ was also performed by electron irradiating a substrate at room temperature and at higher electron fluxes, in the presence of a constant partial pressure of Pt(PF₃)₄. The absence of fluorine in these films underscores the role of electron-stimulated P鈥擣 bond cleavage, whereas the absence of oxygen highlights the important role that deposition conditions (e.g., substrate temperature and background gas composition) play in determining the ultimate composition of typical EBID films.