Morphology control of rutile TiO2 hierarchical architectures and their excellent field emission properties

Titanium dioxide nanoarchitectures with well-defined morphologies have been successfully synthesized by a hydrothermal process at temperature 180 °C for 4 h using titanium butoxide, oleic acid and hydrochloric acid as precursor materials. Different hierarchical morphologies such as cauliflower, 3D microsphere, densely-packed nanorod array, step edge faceted nanorod, branched structures of the rutile TiO2 nanostructures could be easily controlled by varying the volume fraction of the added hydrochloric acid. The structural, photoluminescence and field emission properties of the as-prepared nanoarchitectures were investigated. Among the different morphologies, dense nanorod arrays and multilevel branched architectures showed good field emission properties. Morphology, surface-related defects and oxygen vacancies were found to be the major responsible factors for the observed variations of field emission properties. Compared to any previously reported TiO2 based field emitter, lower turn-on field at 2.76 V μm−1 and higher field-enhancement factors 7.44 × 103 were observed for the hierarchically dense TiO2 nanorods array. Therefore, these nanoarchitectures can be used in vacuum microelectronic applications.