The thermal decomposition behavior of Sr(DPM) 2 (DPM: 2,2,6,6-tetramethyl-3,5-heptadionate, C 11 H 19 O 2 ) was studied using thermogravimetry, mass, UV, and in situ infrared spectroscopy. In particular, dissociation of the chemical bonds in the complex ligand has been studied by monitoring the change in the intensity of the IR peaks while the sample is heated. The decomposition behavior of Sr(DPM) 2 is sensitive to the ambient gases and the Sr complex is severely degraded after storage for a year. The chemical bonds in the complex begin to be dissociated at low temperatures and are sequentially decomposed at elevated temperatures. The Sr-O and the C-C(CH 3 ) 3 bonds dissociate most easily, then the C-H bond, while the C-O and the C-C bonds are stable up to high temperatures. Decomposition of the Sr complex is enhanced when it is exposed to O 2 because removal of the tert-butyl group from the ligand skeleton facilitates the Sr-O bond dissociation. Compared with the Ti-O bond in Ti(O-iPr) 2 (DPM) 2 , the Sr-O bond is easily dissociated due to its ionic bond character as confirmed by UV spectroscopy. Removal of the tert-butyl group and dissociation of the Sr-O bond trigger oligomerization of the Sr compound so that a large amount of carbonate residue is obtained at high temperatures.

Ferroelectric thin films of barium strontium titanate (BST) and lead zirconate titanate (PZT) have the potential for application to electronic devices, such as dynamic random access memory (DRAM) and nonvolatile random access memory. One of the versatile techniques for preparation of the ferroelectric films is metallorganic chemical vapor deposition (MOCVD) which offers the advantages of good step coverage and high deposition rates, as well as control over the film composition and thickness. [1][2][3] The basic requirements of the MO compounds for the CVD process are thermal stability, sufficient and stable evaporation, and good delivery behaviors under the process conditions. For the deposition of the mixed oxide films, it is also important to use the MO compounds of similar properties.Until now, titanium tetraisopropoxide (TTIP), Ti(O-iC 3 H 7 ) 4 , has been one of the most frequently used precursors of titanate in the deposition of BST or PZT. 1-5 However, films of low quality are likely to be obtained since the reactive TTIP is easily changed into titanate that nucleates in the gas phase. As TTIP is liquid at room temperature with a vapor pressure higher than other MO sources, it is difficult to control the composition and the thickness of the ferroelectric thin films. Furthermore, TTIP is easily hydrolyzed by exposure to air.Recently, diisopropoxide dipivaloylmethanato titanium [Ti(O-iPr) 2 (DPM) 2 ; DPM ϭ bis(2,2,6,6-tetramethyl-3,5-heptadionate), C 11 H 19 O 2 ] has been used as an alternative to TTIP for the titanate in the MOCVD process. 6,7 The chemical structure of Ti(O-iPr) 2 (DPM) 2 is shown in Fig. 1. Ti(O-iPr) 2 (DPM) 2 is solid at room temperature and has physical properties similar to the other MO compounds for BST and PZT films such as Pb(DPM) 2 and Sr(DPM) 2 .However, little has been reported about the thermal decomposition behavior of the new Ti source which is necessary to optimize the MOCVD conditions for the best film properties. In this work, we have studied the thermal properties of Ti(O-iPr) 2 (DPM) 2 by thermogravimetric (TG) and mass spectroscopic (MS) analyses and by monitoring the IR spectra of the complex at elevated temperatures. We have compared the TG behavior of Ti(O-iPr) 2 (DPM) 2 with that of Sr(DPM) 2 which is a common precursor of Sr in fabrication of SrTiO 3 and (Ba, Sr)TiO 3 films. Similar studies have been made previously to compare other Ti precursors with Sr(DPM) 2 . 8,9Experimental Ti(O-iPr) 2 (DPM) 2 and Sr(DPM) 2 were purchased from Strem chemicals and used without further purification. Thermogravimetric properties of the samples were analyzed either in N 2 or in the air with Perkin Elmer TGA7. The samples were also analyzed after storage in a desiccator for a year.The Fourier transform infrared (FTIR) spectrum of the sample was monitored at elevated temperatures in an in situ IR cell which can be evacuated down to 10 Ϫ5 Torr and heated up to 550ЊC. 10 The sample was mixed with KBr power, pressed into a self-supporting disk, and then placed at the center of the IR ce...

A widely accepted definition of epidemiology is ‘the study of the distribution and determinants of health‐related states or events in specified populations, and the application of this study to control of health problems’. Reproductive epidemiology focuses on the events in various stages of the human reproductive process, including sperm production, menstrual cycling, ovulation, sexual interaction, conception, fetal growth, and growth and development of the infant.

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