ADVANCED MATERIALS FOR OPTICS AND ELECTRONICS Adv[ Mater[ Opt[ Electron[ 09\ 112Ð121 "1999# Received 15 May 1999 Copyright Þ 1999 John Wiley + Sons\ Ltd[ Accepted 10 June 1999 Substituent Effects on the Volatility of Metal b-diketonates Bradley D. Fahlman 1 and Andrew R. Barron 1,2 * 1 Department of Chemistry and Center for Nanoscale Science and Technology, Rice University, Houston, Texas 77005, USA 2 Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas 77005, USA Volatile trends are established for a series of M( b-diketonate) n complexes, where M = Cu (n = 2); Al, Sc, Cr, Fe, Co, Ga (n = 3); Zr (n = 4) and b-diketonate = acetylacetonate (acac), trifluoroacetylacetonate (tfac), hexafluoroacetylacetonate (hfac) and 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd). Sublimation enthalpies (DH sub ) were calculated from thermogravimetric analysis (TGA) data, which show that the dependence of DH sub on the number and type of intermolecular interactions appears to be more substantial than molecular mass effects. Irrespective of the metal, the DH sub values for the M(tmhd) 3 derivative have a DH sub value of between 93 and 99% of that of the M(acac) 3 derivative. In contrast, the M(tfac) 3 and M(hfac) 3 derivatives have DH sub values of ca. 82% and 54% of the values for the cor- responding M(acac) 3 . Similar trends are observed for M(b-diketonate) 2 and M( b-diketonate) 4 derivatives. The relationship between the DH sub and (T sub ) of the substituted b-diketonate derivatives as compared with the values for parent M(acac) n may be used to predict either quantity for a range of M( b-diketonate) n complexes where the values for M(acac) n are known. Using the TGA sublimation data, vapour pressures have been calculated for each of the M( b-diketonate) n complexes. Copyright 2000 John Wiley & Sons, Ltd. KEYWORDS b-diketonate; CVD precursor; enthalpy of sublimation; thermogravimetric analysis; vapour pres- sure INTRODUCTION Metal b!diketonate chelate compounds are invalu! able precursors for the chemical vapour deposition "CVD# of metal and non!metal thin _lms[ 0\1 In general\ these compounds are favoured since they are relatively volatile\ non!toxic and in the case of the parent acetylacetonate complexes "I#\ inex! pensive[ 2 Furthermore\ replacing the substituent methyl groups of the parent derivative with other moieties has been demonstrated to in~uence the  Correspondence to] A[ R[ Barron\ Department of Chemistry\ Rice University\ 5099 Main Street\ Houston\ TX 66994\ USA[ e!mail] arbÝrice[edu Contract grant sponsor] National Science Foundation[ Contract grant sponsor] O.ce of Naval Research[ volatility of these complexes[ A common method used to enhance precursor volatility and cor! responding e.cacy for CVD applications is to incorporate partially "II# or fully "III# ~uorinated ligands[ 3 The observed enhancement in volatility may be rationalized either by an increased amount of inter! molecular repulsion due to the additional lone pairs