Synthesis and characterization of heteroleptic titanium MOCVD precursors for TiO2 thin films

Heteroleptic titanium alkoxides with three different ligands, i.e., [Ti((OPr)-Pr-i)(X)(Y)] (X = tridentate, Y = bidentate ligands), were synthesized to find efficient metal organic chemical vapor deposition (MOCVD) precursors for TiO2 thin films. Acetylacetone (acacH) or 2,2,6,6-tetramethyl-3,5-heptanedione (thdH) was employed as a bidentate ligand, while N-methyldiethanolamine (MDEA) was employed as a tridentate ligand. It was expected that the oxygen and moisture susceptibility of titanium alkoxides, as well as their tendency to form oligomers, would be greatly reduced by placing multidentate and bulky ligands around the center Ti atom. The synthesized heteroleptic titanium alkoxides were characterized both physicochemically and crystallographically, and their thermal behaviors were also investigated. [Ti((OPr)-Pr-i)(MDEA)(thd)] was found to be monomeric and stable against moisture; it also showed good volatility in the temperature window between volatilization and decomposition. This material was used as a single-source precursor during MOCVD to generate TiO2 thin films on silicon wafers. The high thermal stability of [Ti((OPr)-Pr-i)(MDEA)(thd)] enabled the fabrication of TiO2 films over a wide temperature range, with steady growth rates between 500 and 800 degrees C

Synthesis and characterization of lead (IV) precursors and their conversion to PZT materials through a CVD process

New Pb(IV) precursors for lead zirconate titanate (PZT) thin films were synthesized, and their solid-state structures were elucidated by single-crystal X-ray crystallography. First, tetraphenyl lead (Ph4Pb) was synthesized from the reaction of PbCl2 with the Grignard reagent, PhMgBr, by a published method. Two of the phenyl ligands in Ph4Pb were replaced by bromines, and then were substituted with bis(trimethylsilyl)amides (btsa) to yield Ph2Pb(btsa)2 (1), or with 2,2,6,6-tetramethyl-3,5-heptadiketonate (thd) ligands to yield Ph2Pb(thd)2 (2). Single crystals of these two new Pb(IV) precursors were obtained by recrystallization in hexane, and their chemical compositions were characterized by FT-IR and 1H NMR. In TG analyses, both compounds exhibited sharp decomposition curves, with major mass losses in the region of 200???250 ??C. PZT films were fabricated from one of the newly prepared Pb(IV) precursors by an MOCVD process involving Ti(OiPr)4 and Zr(OPr)4, and the development of the perovskite phase with temperature was monitored by an XRD method