Synthesis, characterization, crystal structure and mass transport properties of lanthanum beta-diketonate glyme complexes, volatile precursors for metal-organic chemical vapor deposition applications

The monoglyme {CH3OCH2CH2OCH3}, diglyme {CH3O(CH2CH2O)(2)CH3}, and triglyme {CH3O(CH2CH2O)(3)CH3} adducts of the lanthanum trishexafluoroacetylacetonato {La(hfa)(3). monoglyme . H2O, La(hfa)(3). diglyme and La(hfa)(3). triglyme} have been synthesized in a single-step reaction. They have been characterized by elemental analyses, mass spectrometry, IR spectroscopy, H-1 and C-13 NMR spectroscopy. Single-crystal X-ray diffraction studies provide evidence of a mononuclear 9-coordinated complex with a monocapped square antiprismatic structure for the La(hfa)(3). diglyme (monoclinic system, space group = P2(1)/c; a = 10.075(2) Angstrom, b = 15.599(4) Angstrom, c = 21.038(9) Angstrom, beta = 103.48(5)degrees, Z = 4). The La(hfa)(3). monoglyme . H2O consists of asymmetric units containing two similar molecules (monoclinic system, space group = P2(1)/c; a = 21.812(7) Angstrom, b = 13.232(3) Angstrom, c = 22.100(6) Angstrom, beta = 111.28(4)degrees, Z = 4), while a more complex structure having asymmetric tetramolecular units has been found in the case of the La(hfa)(3). triglyme (monoclinic system, space group = P2(1)/n; a = 24.701(5) Angstrom, b = 11.762(4) Angstrom, c = 49.204(7) Angstrom, beta = 104.32(3)degrees, Z = 4). The "thermal robustness" and mass transport properties of these adducts' have been investigated by thermogravimetric analysis and chemical vapor deposition experiments. Thermal analysis data revealed the high volatility and very good thermal stability with a residue of less than 4% left. The La(hfa)(3). diglyme and La(hfa)(3). triglyme have been successfully applied to the low-pressure chemical vapor deposition (CVD) of LaAlO3 and to the atmospheric-pressure CVD of lanthanum fluoride (LaF3) films. The good quality of the deposited layers indicates that both the adducts are very attractive precursors for MOCVD applications.