Xu-Qiang Zhang

Enhancement of the Field Emission from the TiO2 Nanotube Arrays by Reducing in a NaBH4 Solution

A mass of oxygen vacancies are successfully introduced into TiO2 nanotube arrays using low-cost NaBH4 as a reductant in a liquid-phase environment. By controlling and adjusting the reduction time over the range of 0-24 h, the doping concentration of the oxygen vacancy is controllable and eventually reaches saturation. Meanwhile, the thermal stability of oxygen vacancies is also investigated, indicating that part of the oxygen vacancies remain stable up to 250 °C. In addition, this liquid-phase reduction strategy significantly lowers the requirements of instruments and cost. More interesting, reduced TiO2 nanotube arrays show drastically enhanced field emission performances including substantially decreased turn-on field from 25.01 to 2.65 V/μm, a high current density of 3.5 mA/cm(2) at 7.2 V/μm, and an excellent field emission stability and repeatability. These results are attributed to the oxygen vacancies obtained by reducing in NaBH4 solution, resulting in a reduced effective work function and an increased conductivity.

Low-temperature liquid phase reduced TiO2 nanotube arrays: synergy of morphology manipulation and oxygen vacancy doping for enhancement of field emission.

The partially reduced TiO(2) nanotube arrays (TNAs) are prepared via an uncomplicated and low-cost liquid phase reduction strategy using NaBH(4) as the reducing agent. By controlling and adjusting the reduction temperatures from 30 to 90 °C, the reduction treatment can not only change their surface morphology but also introduce oxygen vacancies into them, resulting in an optimized morphology, elevated Fermi-level, reduced effective work function and improved conductivity of the TNAs. Meanwhile, the thermal and long-term stability of oxygen vacancy are also investigated, indicating that the oxygen vacancies retain long-term stability from room temperature up to 150 °C. More interesting, partially reduced TNAs show drastically enhanced field emission (FE) performances including substantially decreased turn-on field from 18.86 to 1.53 V μm(-1), a high current density of 4.00 mA cm(-2) at 4.52 V μm(-1), and an excellent FE stability and repeatability. These very promising results are attributed to the combination of the optimized morphology and introduced oxygen vacancies, which can increase FE sites, reduce effective work function and increase conductivity.

Enhanced field emission from hydrogenated SnO2 nanoparticles embedded in TiO2 film on fluorinated tin oxide substrate

Hydrogenated SnO2 nanoparticles (H:SNPs) were prepared on fluorinated tin oxide covered glass using reduction and hydrogenation technologies with TiO2 sol. By adjusting the hydrogenated temperature over the range of 400–550 °C, the H:SNPs were uniformly embedded in the TiO2 film, exhibiting the ability to precisely control their density and size using this method. Simultaneously, their band structures were modified, resulting in a reduced work function and an increased electrical conductivity. Hence, the optimized H:SNPs prepared at 500 °C showed excellent field emission (FE) performances, with both a low turn-on field of 3.81 V/μm and remarkable FE stability over a 480-min period.