A facile approach is developed to easily fabricate field emission (FE) cathodes based on TiO2 nanotubes with different geometrical structures at low temperature. Planar TiO2 nanotubes (P-TNTs) are first synthesized using the electrochemical anodization process with applied voltages of 20-50 V for 1 h at room temperature followed by thermal oxidation at 280 degrees C for 2 h under atmosphere ambient. P-TNTs can be transformed into aggregated TiO2 nanotubes (A-TNTs) after H2O2 post-treatment for 1 hat room temperature. FESEM, XRD, and Raman spectroscopy were used to analyze the surface morphology, crystallinity, and chemical binding, respectively. The A-TNTs fabricated with the applied voltages of 30-50 V cathodes possess higher levels of FE properties (lower turn-on electric field and higher current density) than the other cathodes due to their greater number of emission sites and decrement of the screening effect. The A-TNT with an applied voltage of 40V cathode exhibits the lowest turn-on electric field (4.87 V/mu m, 1 mu A/cm(2)) and the highest enhancement factor beta (1486). These superior properties indicate that the A-TNTs are promising field cathodes for future FE applications. (C) 2014 Elsevier B.V. All rights reserved.