VOLATILITY BY DESIGN - SYNTHESIS AND CHARACTERIZATION OF POLYETHER ADDUCTS OF S(1,1,1,5,5,5-HEXAFLUORO-2,4-PENTANEDIONATO)BARIUM AND THEIR IMPLEMENTATION AS METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION PRECURSORS

The synthesis and characterization of a series of polyethers and volat ile, low-melting polyether complexes of bis(1,1,1,5,5,5-hexafluoro-2,4 -pentanedio)barium having the general formula Ba(hfa)(2) . RO(CH2CH2O) (n)R' where R = R' = CH3, n = 3; R = CH3, R' = C2H5, n = 3; R = R' = H , n = 5, 6; R = R' = CH3, n = 4; R = CH3, R' = C2H5, n = 5; R = CH3, R ' = n-C4H9, n = 5, 6; R = CH3, R = C5H11O, n = 3; R = CH3, R' = n-C6H1 3, n = 4, 5; R = C2H5, R' = n-C4H9, n = 5; R = n-C4H9, RI = n-C4H9, n = 4, 6; R = n-C4H9, R' = n-C6H13, n = 5 are reported. The complexes ar e conveniently synthesized by reaction of n-propylammonium(+)-hfa(-) i n DMF with an aqueous solution of Ba(NO3)(2) and the polyether or, alt ernatively, by reaction of the polyether with Ba(hfa)(2) in toluene. T hese new complexes were characterized by elemental analysis, FT-IR, H- 1, C-13, and F-19 NMR, MS, X-ray diffraction (Ba(hfa)(2) . CH3O(CH2CH2 O)(3)CH3 . H2O, Ba(hfa)(2) . CH3O(CH2CH2O)(5)C2H5), and thermogravimet ric analysis. The melting points of the complexes are strongly depende nt on the architecture of the polyether chain and dimensions of the te rminal polyether substituent, with the lowest melting points correspon ding to the longest polyethers having the largest terminal groups. The volatility of the Ba(hfa)(2) . polyether compounds is dependent on mo lecular weight and molecular structure; however, there is little direc t correlation between melting point depression and enhanced volatility . The applicability of these complexes in metal-organic chemical vapor deposition is demonstrated by the successful growth of phase-pure BaT iO3 thin films using Ba(hfa)(2) . CH3O(CH2CH2O)(5)C2H5 as the Ba sourc e. Phase composition and epitaxy in these films is analyzed by energy- dispersive X-ray spectroscopy and X-ray diffraction Theta-2 Theta, ome ga, and phi scans.