Expedient route to volatile zirconium metal-organic chemical vapor deposition precursors using amide synthons and implem
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MATERIALS RESEARCH Expedient route to volatile zirconium metal-organic chemical vapor deposition precursors using amide synthons and implementation in yttria-stabilized zirconia film growth John A. Belot, Richard J. McNeely, Anchuan Wang, Charles J. Reedy, and Tobin J. Marksa) Department of Chemistry, the Materials Research Center, and the Science and Technology Center for High Temperature Superconductivity, Northwestern University, Evanston, Illinois 60208-3113
Glenn P. A. Yap and Arnold L. Rheingold Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (Received 14 January 1998; accepted 29 June 1998)
This communication reports rapid, efficient syntheses of the zirconium-organic metal-organic chemical vapor deposition (MOCVD) precursors Zr(acac)4 and Zr(dpm)4 (acac acetylacetonate; dpm dipivaloylmethanate) as well as a new, highly volatile, air- and moisture-stable Zr precursor based on a tetradentate Schiff-base ligand, Zr(tfacen)2 (tfacen bis-trifluoroacetylacetone-ethylenediiminate). The improved one-step synthetic routes employ tetrakis(dimethylamido)zirconium as a common intermediate and represent a major advance over previous methods employing ZrCl4 or diketonate metathesis. Furthermore, Zr(tfacen)2 is shown to be an effective metal-organic precursor for the MOCVD-mediated growth of (100) oriented yttria-stabilized zirconia thin films.
Thin-film zirconium oxides are a technologically important class of materials with a wide range of applications.1–8 A subset of these oxide ceramics is the solid solution yttria-stabilized zirconia (YSZ), of interest due to the low dielectric constant, chemical inertness, low thermal expansion coefficient (i.e., good adhesion properties), and appreciable hardness.9–14 Indeed, these attributes render it an excellent substrate/buffer layer in high temperature cuprate superconductor (HTS) thin-film growth,15–23 and recent work has focused on application as an intermediate layer in HTS coated conductor growth on metallic substrates.17,20,22–24 In our continuing work25 on the metal-organic chemical vapor deposition (MOCVD) of lattice-matched dielectric insulators for HTS applications, we are developing MOCVD routes to YSZ thin films. A prerequisite for this study was the identification of suitable, volatile zirconium precursors and development of the accompanying synthetic chemistry. Successful metal-organic chemical vapor deposition of thin-film metal-oxide ceramics relies on the availability of suitable molecular precursors that exhibit high volatility and, ideally, stability to air, moisture, and repeated thermal cycling.13,26–29 Common classes of metal-organic precursors that fulfill many of these requirements are homoleptic b-diketonate and alkoxide complexes, which have enjoyed considerable success. However, when the metal center has a small ionic charge-to-radius ratio (normally leading to a)
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http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 1, Jan 1999
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