Synthesis and evaluation of κ 2 -β-diketonate and β-ketoesterate tungsten( vi ) oxo-alkoxide complexes as precursors for chemical vapor deposition of WO x thin films

Reactions of [WO(OR) 4 ] x ( x = 1, 2) complexes with bidentate ligands (LH = acacH, tbacH, dpmH, tbpaH) afforded complexes 1–13 : [WO(OCH 3 ) 3 (acac) ( 1 ); WO(OCH 2 CH 3 ) 3 (acac) ( 2 ); WO(OCH(CH 3 ) 2 ) 3 (acac) ( 3 ); WO(OCH 3 ) 3 (tbac) ( 4 ); WO(OCH 2 CH 3 ) 3 (tbac) ( 5 ); WO(OCH(CH 3 ) 2 ) 3 (tbac) ( 6 ); WO(OCH 2 CH 3 ) 3 (dpm) ( 7 ); WO(OCH(CH 3 ) 2 ) 3 (dpm) ( 8 ); WO(OCH 2 C(CH 3 ) 3 ) 3 (acac) ( 9 ); WO(OCH 2 C(CH 3 ) 3 ) 3 (tbac) ( 10 ); WO(OCH 2 C(CH 3 ) 3 ) 3 (dpm) ( 11 ); WO(OCH 2 C(CH 3 ) 3 ) 3 (tbpa) ( 12 ); WO(OC(CH 3 ) 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 WO x between 250–350 °C and nanorods of W 18 O 49 above 350 °C.