Molecular structures of volatile Ce(IV) tetrafluoroisopropoxide complexes with TMEDA and diglyme. CVD experiments Stephane Daniele a , Liliane G. Hubert-Pfalzgraf a, *, Monique Perrin b a IRC, Universite ´ Claude Bernard-Lyon 1, 2 avenue A. Einstein, 69629 Villeurbanne cedex, France b Laboratoire de Cristallographie, Universite ´ Claude Bernard-Lyon 1, 69622 Villeurbanne cedex, France Received 8 January 2002; accepted 7 March 2002 Abstract The structures of the cerium tetrafluoroisopropoxide adducts with TMEDA (1) and diglyme [Me(OC 2 H 4 ) 2 OMe] (2) were established by single crystal X-ray diffraction (TMEDA /tetramethylethane-1,2-diamine). The cerium atom is hexa- and heptacoordinated for 1 and 2, respectively. The Ce /O(hfip) bond distances are quite short [2.115(5)  /2.152(6) A ˚ ] and are associated to large Ce  /O(hfip) angles ( /1568). Both complexes display a range of short FÁÁÁC contacts, the shortest ones having values of 3.754 and 4.060 A ˚ for 1 and 2, respectively. Decomposition experiments were achieved in a cold-wall reactor. The films deposited on glass substrates were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV  /Vis spectroscopy. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Cerium; Fluoroalkoxides; Structures; Complexes; MOCVD; Films 1. Introduction Cerium oxide is a candidate for various areas of technological applications due to high chemical stability and insulating properties [1], interesting optical proper- ties [2] and lattice parameters close with high Tc superconductors and silicon, and thus its potential value for buffer layers [3]. Various methods have been used for deposition of ceria thin films. Chemical routes, namely sol  /gel processing and metal-organic chemical vapor phase deposition (MOCVD) are quite flexible and cheaper than physical methods [4]. MOCVD processes have a high potential for CeO 2 layers having the quality required for microelectronics and several types of volatile cerium derivatives, mostly b-diketonates have been used for the growth of pure or doped [5] ceria layers. After the use of Ce(thd) 4 (thd /2,2,6,6-tetra- methylheptane-3,5-dionate) [5,6] and of fluorinated Ce(IV) or Ce(III) derivatives such as Ce(fdh) 4 (fdh / 6,6,6-trifluoro-2,2-dimethyl-3,5-hexanedionate) [7], a second generation of precursors was based on adducts such as Ce(fdh) 3 (o -phen) [8]; [Ce 2 (fod) 6 (tetraglyme)] [9a] (fod /heptafluoro-7,7-dimethyl-4,6-octanedionate) and more recently [Ce 2 (etbd) 6 (tetraglyme)], [NH 4 ][Ce(etbd) 4 ] (etbd /1-ethoxy-4,4,4-trifluorobutane-1,3-dionate) [9b] and Ce(hfac) 3 complexes (hfac /hexafluoroacetylaceto- nate) with various glymes [10]. Fluorinated alkoxides are another class of volatile derivatives and have been used for either oxide or fluoride films for gallium [11], barium [12], lanthanides or transition metals such as yttrium [13], zirconium [14] and are available for cerium [15]. We wish to report herein the solid state characteriza- tion of Ce(IV) hexafluoroisopropoxide adducts namely Ce(hfip) 4 (TMEDA) (1) and Ce(hfip) 4 (diglyme) (2), the polydentate Lewis bases being used for stabilization of Ce(hfip) 4 toward hydrolysis. These volatile complexes were used as cerium sources in a cold wall CVD reactor. Films were characterized by X-ray photoelectron spec- troscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction. * Corresponding author. Tel.:  /33-4-7244-5322; fax:  /33-4-7244- 5399 E-mail address: hubert@catalyse.univ_lyon1.fr (L.G. Hubert- Pfalzgraf). Polyhedron 21 (2002) 1985  /1990 www.elsevier.com/locate/poly 0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII:S0277-5387(02)01005-7