Soft chemistry routes to transparent metal oxide thin films. The case of sol–gel synthesis and structural characterization of Ta2O5 thin films from tantalum chloromethoxide

Abstract

Ta2O5 thin films were prepared by spin-coating methanol solutions of Ta chloromethoxide. It was prepared by reacting TaCl5 with methanol, followed by water addition (H2O: Ta molar ratio was 16). Thin films were deposited by spin-coating onto SiO2/Si substrates, followed by drying at 90°C and heat-treatment up to 700°C. The films were characterized by X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. Crystallization was obtained only after heating at 700°C, in the Ta2O5 orthorhombic phase. The resulting films had a thickness of 100nm. Their structure was constituted by porous crystals with size up to 50nm, while the pores had a size of about 10nm. The results demonstrated that TaCl5 is very convenient precursor for the wet chemical synthesis of Ta2O5 thin films.