Y.A. Zhang

Synthesis and photoelectric properties of ZnO nanostructure with different morphologies via hydrothermal method

Abstract Numerous zinc oxide (ZnO) nanomaterials, with unique physical and chemical properties, have recently been synthesised by various methods. In this study, a hydrothermal method was developed to synthesise ZnO nanomaterials with different morphologies on indium doped tin oxide (ITO), and the growth mechanism was discussed. The structure and morphologies of the synthesised samples were characterised by X-ray diffraction and SEM. The photoluminescence (PL) and field emission characteristics of ZnO nanomaterials with different morphologies were measured. X-ray diffraction and SEM images indicate that ZnO with morphologies of nanocones, nanorods and nanotubes is grown along c axis to the ITO substrates. The room temperature PL spectra reveal a strong and sharp ultraviolet emission band at 386 nm and a weak blue emission band at 470 nm. The field emission measurements show that the turn-on field of ZnO nanocones, nanorods and nanotubes at emission current density of 10 μA cm−2 is approximately 2·62, 4·31 and 3·92 V μm−1. Moreover, the emission image of ZnO nanocones is more homogeneous than that of ZnO nanorods and nanotubes at the electric field of 4·5 V μm−1. The experimental results indicate that ZnO nanomaterials with different morphologies have good photoelectric properties. As cold cathode materials, ZnO has a great number of potential applications for the field emission display in the future.

Improving field emission properties of CuO nanowires by coating with ZnO nanoparticles

Abstract A facile solution route of self-assembled zinc oxide (ZnO) nanoparticles (NPs) on the surface of cupric oxide (CuO) nanowires (NWs) was presented, and field emission arrays with ZnO NPs–CuO NWs hybrid emitters were fabricated. The NW based conjugation by coating ZnO NPs on CuO NWs was confirmed by transmission electron microscopy (TEM) image. The turn on electric fields of the ZnO NPs–CuO NWs hybrid emitters decreased to 2·37 V μm−1 compared with 4·95 V μm−1 of pure CuO NWs, and the field enhancement factor was significantly enhanced from ∼869 (pure CuO NWs) to ∼1678 (ZnO NPs–CuO NWs). The ZnO–CuO NWs hybrid emitters also have higher emitting uniformity, which indicated the efficient field emission properties for the hybrid emitters.

Fabrication and properties of planar gate field emission arrays with patterned ZnO nanowires

Abstract Field emission arrays (FEAs) based on a planar gate triode with patterned ZnO nanowires have been successfully fabricated by conventional photolithography, screen printing and thermal evaporation. ZnO nanowires were synthesised on the cathode and the gap between cathode and gate electrodes (C–G gap). The SEM images show that the diameters of ZnO nanowires are scattered in a range of 80–200 nm and the length up to 5 μm. Field emission investigations indicate that the turn-on voltage of 875 V at emission current density of 1 μA cm−2 in the triode mode is lower than that of 1575 V in the diode mode. In triode mode, the anode current and gate current come to 330 and 320 μA at the gate voltage and anode voltage of 300 and 1000 V respectively and at the anode–cathode spacing of 500 μm, which indicates that the triode mode based on planar gate FEAs with patterned ZnO nanowires has efficient field emission characteristics.

Preparation and characterization of ZnSe quantum dots by the cation-inverting-injection method in aqueous solution

Abstract ZnSe quantum dots (QDs) were synthesised by the cation-inverting-injection method in aqueous solution, using thioglycolic acid (TGA) as a stabiliser, zinc acetate dihydrate (Zn(OAc)2·2H2O) and sodium hydrogen selenide (NaHSe) as precursors solution. The morphology structure and optical properties of ZnSe QDs were characterised by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X ray spectrometer (EDS), photoluminescence (PL) and UV–visible absorption spectra. The experimental results indicate that the as-synthesised ZnSe QDs with the average size of 4.1 ± 0.2 nm were zinc blende cubic crystal structure and approximate spherical shape. PL spectra were mainly the contribution of excitonic emission. The excitonic emission peak could be tuned by changing the refluxing time, the molor ratios of Zn2+/HSe− (nZn2+/nHSe− ratios), the concentration of Zn2+/HSe− (CZn2+/CHSe− ratios) and pH value. Under the optimal conditions, the strong PL peak located about 397 nm and ZnSe QDs with the fitted average lifetime of 25.1 ns reveals the strong deep-blue fluorescence.

Morphology and field emission properties of tetrapod shaped Sn doped ZnO nanostructures under different growth times

Abstract The morphology, microstructure and field emission (FE) properties of tetrapod shaped Sn doped ZnO (T-SZO) nanostructures grown for different times were investigated. It is found that the morphology, particularly the aspect ratio of the T-SZO, can be controlled by adjusting the growth time and that the aspect ratio affects its FE properties. The aspect ratio increases first with the growth time, and after 90 s, a new series of T-SZO with smaller size and lower aspect ratio appear, leading to the deterioration of the FE properties. The sample grown for 90 s exhibits the highest aspect ratio of 16:5 and the lowest turn on field of 1·82 V μm− 1.