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.