Design of Volatile Mixed-Ligand Tantalum(V) Compounds as Precursors to Ta2O5 Films

Synthesis and structural characterization of six monomeric, heteroleptic tantalum­(V) complexes of the general formula Ta­(OiPr)4(ArTFP), where Ar = pyridine (1), 4,5- dimethyloxazole (2), 4,5-dimethylthiazole (3), benzimidazole (4), benzoxazole (5), benzthiazole (6), and TFP = trifluoropropenol, are described. Introduction of a donor-functionalized β-heteroarylalkenolate in the coordination sphere of Ta in the dimeric Ta2(OiPr)10 increases significantly the stability and volatility of these precursors, simplifying the depositions of Ta2O5. The molecular structures of 1–6 exhibited a distorted octahedral coordination around the tantalum center by four isopropoxide groups and one β-heteroarylalkenolate. Thermal decomposition studies (TG/DTA) and analysis of byproducts by NMR spectroscopy confirmed the decomposition mechanism and gas-phase stability of the heteroleptic compounds necessary for Ta2O5 depositions. Chemical vapor deposition studies with 1 and 2 demonstrated their suitability as efficient precursors for the growth of Ta2O5 thin films, whose properties were compared with Ta2O5 thin films obtained from homoleptic alkoxides.