Synthesis and characterization of well-aligned anatase TiO2 nanocrystals on fused silica via metal-organic vapor deposition

Well-aligned anatase (A)-TiO2 nanocrystals (NCs) were grown by cold-wall metalorganic chemical vapor deposition (MOCVD) on fused silica using titanium-tetraisopropoxide (Ti(OC3H7)(4)) as the source reagent. Field emission scanning electron microscopy (FESEM) micrographs showed the growth of vertically aligned NCs. X-ray diffractometry (XRD) pattern revealed the aligned A-TiO2 with a preferential orientation of (220). Raman spectrum confirmed the deposition of pure anatase phase TiO2 on fused silica. Luminescence of self-trapped excitons and oxygen vacancies were observed in anatase NCs. The indirect band gap of A-TiO2 was determined to be 3.14 +/- 0.01 eV by analyzing the surface photovoltage spectrum. Energy-dispersive X-ray spectroscopy (EDS) and X ray photoelectron spectroscopy (XPS) analyses showed oxygen vs. titanium ratio of 2.0 +/- 0.1 for the as-deposited TiO2 NCs. Further structural characterization of the well-aligned A-TiO2 NCs was studied using transmission electron microscopy (TEM) technique. The formation of building units bonded along {112} facets with preferred (220) orientation of the well-aligned A-TiO2 NCs on fused silica were presented and the probable growth mechanisms were discussed.