Synthesis and evaluation of κ(2)-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 : [WO(OCH3)3(acac) (); WO(OCH2CH3)3(acac) (); WO(OCH(CH3)2)3(acac) (); WO(OCH3)3(tbac) (); WO(OCH2CH3)3(tbac) (); WO(OCH(CH3)2)3(tbac) (); WO(OCH2CH3)3(dpm) (); WO(OCH(CH3)2)3(dpm) (); WO(OCH2C(CH3)3)3(acac) (); WO(OCH2C(CH3)3)3(tbac) (); WO(OCH2C(CH3)3)3(dpm) (); WO(OCH2C(CH3)3)3(tbpa) (); WO(OC(CH3)3)3(tbac) ()]. 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 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 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.