Guo Tailiang

Synthesis and efficient field emission characteristics of patterned ZnO nanowires

Patterned ZnO nanowires were successfully synthesized on ITO electrodes deposited on the glass sub- strate by using a simple thermal evaporation approach. The morphology, crystallinity and optical properties of ZnO nanowires were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray and pho- toluminescence spectroscopy. Their field emission characteristics were also investigated. SEM images showed that the ZnO nanowires, with a diameter of 100-200 nm and length up to 5m, were highly uniform and well distributed on the linear ITO electrodes. The field emission measurement indicated that patterned ZnO nanowire arrays have a turn-on field of 1.6 V/ m at current density of 1 A/cm 2 and a threshold field of 4.92 V/m at current density of 1 mA/cm 2 at an emitter-anode gap of 700 m. The current density rapidly reached 2.26 mA/cm 2 at an applied field of 5.38 V/ m. The fluctuation of emission current was lower than 5% for 4.5 h. The low turn-on field, high current density and good stability of patterned ZnO nanowire arrays indicate that it is a promising candidate for field emission application.

Application of ZnO nanopillars and nanoflowers to field-emission luminescent tubes

Zinc oxide (ZnO) nanopillars on a ZnO seed layer and ZnO nanoflowers were synthesized by electrochemical deposition on linear wires. The morphologies and crystal orientation of the ZnO nanostructures were investigated by a scanning electron microscopy and an X-ray diffraction pattern, respectively. Detailed study on the field-emission properties of ZnO nanostructures indicates that nanopillars with a high aspect ratio show good performance with a low turn-on field of 0.16 V/μm and a high field enhancement factor of 2.86 × 104. A luminescent tube with ZnO nanopillars on a linear wire cathode and a transparent anode could reach a luminance of about 1.5 × 104 cd/m2 under an applied voltage of 4 kV.

Improvement of the field emission properties of carbon nanotubes by CNT/Fe3O4 composite electrophoretic deposition

A simple CNT/Fe3O4 composite electrophoretic deposition method to improve the field emission cathode properties of carbon nanotubes (CNTs) is proposed. It is found that CNT/Fe3O4 composite electrophoretic deposition leads to better field emission performance than that of single CNT electrophoretic deposition. The result is investigated using SEM, J-E and FE. After the process, the turn-on electric field decreases from 0.882 to 0.500 V/μm at an emission current density of 0.1 mA/cm2, and the latter increases from 0.003 to 1.137 mA/cm2 at an electric field of 0.64 V/μm. CNT/Fe3O4 composite electrophoretic deposition is an easy and effective cathode preparation for field emission display applications.

Influence of morphologies on the field emission performance of oriented ZnO nano-arrays

Different morphologies of comb-like ZnO and oriented ZnO nano-arrays such as ZnO nanoneedles and ZnO nanorods were synthesized by using flexible thermal evaporation method via simply adjusting the temperature and oxygen content. The ZnO nanorods arrays have the lowest turn-on field, highest current density and the largest emission efficiency owning to its good contact with the substrate and relatively weaker field screening effects. The experiments show that the morphologies and orientation of one-dimensional (1D) ZnO nanomaterials have considerable effects on the turn-on field and the emission current density, and the nanoarray also contributes to electrons emission. The results could be valuable for the application of ZnO nanorod arrays as cathode materials in field emission based devices.

Improved field emission properties of carbon nanotube cathodes by nickel electroplating and corrosion

Carbon nanotube (CNT) cathodes prepared by electrophoretic deposition were treated by a combination of nickel electroplating and cathode corrosion technologies. The characteristics of the samples were measured by scanning electron microscopy, energy dispersive X-ray spectroscopy, J−E and F—N plots. After the treatment, the CNT cathodes showed improved field emission properties such as turn-on field, threshold electric field, current density, stability and luminescence uniformity. Concretely, the turn-on field decreased from 0.95 to 0.45 V/μm at an emission current density of 1 mA/cm2, and the threshold electric field decreased from 0.99 to 0.46 V/μm at a current density of 3 mA/cm2. The maximum current density was up to 7 mA/cm2 at a field of 0.48 V/μm. In addition, the current density of the CNT cathodes fluctuated at around 0.7 mA/cm2 for 20 h, with an initial current density 0.75 mA/cm2. The improvement in field emission properties was found to be due to the exposure of more CNT tips, the wider gaps among the CNTs and the infiltration of nickel particles.

Field electron emission from structure-controlled one-dimensional CuO arrays synthesized by wet chemical process

One-dimensional CuO nanostructure arrays have been synthesized on Cu foil by a low-temperature wet chemical process. Different CuO nanostructures including nanorods with facet heads, nanorods with needle-like tips and nanotubes are shaped simply by varying the concentration of oxidant. Field emission measurements show that CuO nanorods with needle-like tips are of superior performance than other shapes, having a turn-on field of 3.5V/μm and a field enhancement fact or of 2107. The good field emission performance is assigned to the sharp tips contributing to the high field enhancement effect and to the moderate density reducing the field screening effect.

Fabrication and field emission characteristics of a novel planar-gate electron source with patterned carbon nanotubes for backlight units

This paper describes the fabrication of backlight units (BLUs) for a liquid crystal display (LCD) based on a novel planar-gate electron source with patterned carbon nanotubes (CNTs) formed by electrophoretic deposition. The electric field distributions and electron trajectories of this triode structure are simulated according to Ansys software. The device structure is optimized by supporting numerical simulation. The field emission results show that the emission current depends strongly on the cathode-gate gap and the gate voltage. Direct observation of the luminous images on a phosphor screen reveals that the electron beams undergo a noticeable expansion along the lateral direction with increasing gate voltage, which is in good agreement with the simulation results. The luminous efficiency and luminance of the fabricated device reaches 49.1 lm/W and 5500 cd/m2, respectively. All results indicate that the novel planar-gate electron source with patterned CNTs may lead to practical applications for an electron source based on a flat lamp for BLUs in LCD.

Synthesis and Field Emission properties of SnO 2 nanowires

In this work, SnO2 nanowires were synthesized by thermal evaporation. The morphology investigation and field emission measurement revealed the excellent field emission property and low turn on electric field.

ELECTRON EMISSION OUT OF POLY(VINYLIDENE FLUORIDE) THIN FILMS

ABSTRACT Pulse electric field induced electron emission from the ferroelectric polymer has been investigated. Electron emission of unpoled and poled poly(vinylidene fluoride) thin films prepared by spin coating was measured under increasing driving field with fixed pulse-exited frequency. The results showed that the emission current from poled polymer thin film is attributed to its polarization, including the polarization reversal in the crystalline phase or amorphous phase, and the emission of excess charges in the Maxwell–Wagner interface. And besides, it is found that the charges frozen and injected in the Maxwell–Wagner interface under an appropriate driving pulse field played an important role of electron emission for unpoled thin film sample.