SCHEDULED MAINTENANCE
Synthesis and evaluation of κ2-β-diketonate and β-ketoesterate tungsten(vi) oxo-alkoxide complexes as precursors for chemical vapor deposition of WOx thin films†
Abstract
Reactions of [WO(OR)4]x (x = 1, 2) complexes with bidentate ligands (LH = acacH, tbacH, dpmH, tbpaH) afforded complexes 1–13: [WO(OCH3)3(acac) (1); WO(OCH2CH3)3(acac) (2); WO(OCH(CH3)2)3(acac) (3); WO(OCH3)3(tbac) (4); WO(OCH2CH3)3(tbac) (5); WO(OCH(CH3)2)3(tbac) (6); WO(OCH2CH3)3(dpm) (7); WO(OCH(CH3)2)3(dpm) (8); WO(OCH2C(CH3)3)3(acac) (9); WO(OCH2C(CH3)3)3(tbac) (10); WO(OCH2C(CH3)3)3(dpm) (11); WO(OCH2C(CH3)3)3(tbpa) (12); WO(OC(CH3)3)3(tbac) (13)]. The synthesis is facilitated by the lability of the bridging ligands of the [WO(OR)4]2 complexes in solution, which provides a pathway for exchange of L with an alkoxide ligand. Thermogravimetric analysis and the conditions for sublimation or distillation of 1–13 demonstrate that they have sufficient vapor pressure and thermal stability for volatilization in a conventional Chemical Vapor Deposition (CVD) reactor. High solubility in hydrocarbon and ether solvents establishes that the complexes are also potential candidates for Aerosol-Assisted Chemical Vapor Deposition (AACVD). AACVD from 10 on ITO or bare glass resulted in growth of continuous, dense and amorphous thin films of substoichiometric WOx between 250–350 °C and nanorods of W18O49 above 350 °C.
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