Fabrication Of Zinc Oxide Research Articles

A wide-band UV photodiode based on n-ZnO/p-Si heterojunctions

We report on the fabrication of zinc oxide (ZnO) nanorods on p-type silicon (p-Si) photodiodes. The nanorods are prepared by low-temperature hydrothermal processing. The fabricated photodiodes exhibit an excellent rectifying ratio of 370 at 10V. The responsivity to ultraviolet (UV) photons is stable at 0.29A/W up to 300nm, with a peak value of 0.38A/W at 360nm. Furthermore, the prepared photodiodes demonstrate visible blind behavior, indicating that ZnO nanorods grown on p-Si substrates can be used as UV photodiodes with visible blind responses.

Fabrication of zinc oxide nanowires/polymer composites by two‐photon polymerization

ABSTRACTWe present an approach to fabricate ZnO nanowires/polymer composite into three‐dimensional microstructures, based on two‐photon polymerization direct laser writing, a fabrication method that allows submicrometric spatial resolution. The structural integrity of the structures was inferred by scanning electron microscopy, while the presence and distribution of ZnO nanowires was investigated by energy dispersive X‐ray, Raman spectroscopy, and X‐ray diffraction. The optical properties of the produced composite microstructures were verified by imaging the characteristic ZnO emission using a fluorescence microscope. Hence, such approach can be used to develop composite microstructures containing ZnO nanowires aiming at technological applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 333–337

Zinc Oxide Nanowire Lateral Field Emission Devices and its Application as Display Pixel Structures

The rational design and fabrication of zinc oxide (ZnO) nanowire (NW) lateral field electron emission device and the possible application as a display pixel structure are reported. In the device, the cathode and anode are ranked side-by-side on the same panel. The NW-clusters were controlled to locally grow on the edges of the electrodes with different tilted status, i.e., in angle range of 75°-110°, 0°-110°, and 0°-57°, respectively. The devices with NWs at different tilt-angle showed distinct field electron emission properties. The device with 0°-57° tilted NWs possess the best performance, i.e., an emission current of 9.3 μA (current density: 6.22 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) was obtained at a low cathode-anode (50 μm in separation) bias of 477 V. Stable cathodoluminescence was observed from the indium titanic oxide anode, suggests a possibility for display application. Mechanisms responsible for the enhanced field electron emission and the related device physics are proposed. Significantly, the low temperature (~ 80°C) solution-phase growth of ZnO NWs enables the fabrication of the devices on flexible polyimide substrate, which has also been demonstrated here. This paper opens up possibilities on developing NW-based lateral field electron emission device for vacuum micro/nanoelectronics applications.

Photoconductivity and surface chemical analysis of ZnO thin films deposited by solution-processing techniques for nano and microstructure fabrication

The fabrication of zinc oxide (ZnO) from inexpensive solution-processing techniques, namely, electrochemical deposition and electrospinning were explored on various conducting and mesoporous semiconducting surfaces. Optimised conditions were derived for template- and self-assisted nano/micro structures and composites. ZnO thin films were annealed at a fixed temperature under ambient conditions and characterised using physical and optical techniques. The photocurrent response in the UV region shows a fast rise and double decay behaviour with a fast component followed by a slow oscillatory decay. Photocurrent results were correlated with surface chemical analysis from X-ray photoelectron spectroscopy. Various characterisation details reveal the importance of fabrication parameter optimisation for useful low-cost optoelectronic applications.

Controlled synthesis of ZnO spheres using structure directing agents

Controlled liquid phase deposition has been developed for fabricating zinc oxide (ZnO) nano/microspheres using a mixture of precursor solution of zinc acetate dihydrate, ammonium hydroxide, and structure directing agents (SDAs) such as ethanol and urea. We found that ZnO spheres can be formed when the SDAs are optimized with the proper pH values. At pH values less than 12, an anisotropic growth of ZnO flowers and rod structures was produced with/without SDAs. On the contrary, at a pH value of 12 the directional growth of ZnO was absolutely controlled and an isotropic growth of ZnO spheres was developed with the presence of SDAs. We also found that the volume ratio of ethanol and urea in the solution was a key factor to modulate the uniform size distribution and diameter of the ZnO spheres from nanometer to micrometer range.

Solution blowing of ZnO nanoflake-encapsulated carbon nanofibers as electrodes for supercapacitors

A facile spinning-based strategy is developed to fabricate zinc oxide nanoflake-encapsulated carbon nanofibers (ZnO/CNFs) as electrodes for supercapacitors. The zinc oxide/carbon nanofiber mats were solution blown with zinc acetate (Zn(Ac)2) and polyacrylonitrile (PAN) as the metal and carbon precursor to get Zn(Ac)2 core-enriched precursor nanofibers. After annealing under nitrogen, the precursor nanofibers were converted to ZnO/CNFs with ZnO nanoflakes encapsulated in the core of carbon nanofibers. In the constructed architecture, carbon nanofibers can avoid the direct exposure of ZnO to the electrolyte and preserve the structural and interfacial stabilization of ZnO nanoflakes. Meanwhile, the flexible entangled carbon nanofibers can accommodate temperate porosities thus providing the pore channel for electrolyte ions and maintain the structural and electrical integrity of the ZnO/CNF electrode during the charge–discharge processes. By loading different contents of ZnO, the microstructures of CNFs were changed, and the textural parameters significantly affected their electrochemical properties as electrodes. As a result, the ZnO/CNF electrodes exhibit high specific capacitance (216.3, 212.7, 208.8 and 172.5 F g−1 at 1, 5, 10, and 50 A g−1, respectively) and extremely excellent cycling performance at high current density (only 5.41% capacitance loss after 2000 cycles at a high rate of 10 A g−1), with promising energy densities of 29.76 kW h kg−1, over a power density range of 2.5–30 kW kg−1. The ZnO/CNFs simultaneously exhibit excellent capacity retention. These encouraging results indicate great potential applications of ZnO/CNFs in developing energy storage devices with high energy and power densities.

Fabrication and characterization of ZnO thin film using sol–gel method

In this work, the sol–gel method used to fabricate zinc oxide (ZnO) thin film on silicon (Si) substrate. To this purpose, zinc acetate dihydrate and monoethanolamine were used as solvent and stabilizer materials respectively. Structural and optical properties of ZnO films were studied. X-ray diffraction (XRD) analysis of the films showed polycrystalline nature of the prepared films. Depend on XRD peak of ZnO film with orientation (100), therefore, Scherrer's formula was used to calculate crystallite size of prepared films. Scanning electron microscopy (SEM) used to describe the surface morphology and Photoluminescence (PL) measurements revealed the energy bandgap of the films was in UV emission at 380nm. Finally, thickness of the films was measured with Filmetric (F-20). The result showed that we successful to fabricate ZnO films in simple and low cost method with high quality.

LED光激活氧化锌纳米棒的乙醇气敏特性

We fabricated zinc oxide(ZnO) nanorods using the hydrothermal method and investigated their ethanol gas sensing characteristics under the excitation of light emitting diodes(LEDs) with various wavelengths.The results indicate that the ethanol gas-sensing characteristics of ZnO nanorods strongly depend on the excitation wavelength and intensity of the LEDs.The light-activated gas-sensing mechanism is also discussed.

Fabrication of ZnO-Based Flexible Thin-Film Transistors by a Low-Temperature Process

In this paper we have studied a low-temperature process of fabricating zinc oxide (ZnO) thin-film transistors (TFTs) on polyethylene terephthlate (PET) substrate. PET film has a lower glass transition temperature (Tg = 120°C) than costly Polyethersulphone (PES) film (Tg = 230°C). Therefore we applied a low-temperature cross-linked poly-vinylphenol (c-PVP) process to annealing at 110°C instead of the conventional c-PVP process (annealing at 165°C). The resulting TFTs based on oxide fabricated by the low-temperature process were similar in electrical characteristics to conventional TFTs. In addition, the ZnO TFTs fabricated by the low-temperature process exhibited a field-effect mobility of 0.075 cm2/Vs, a threshold voltage of 15 V and an on/off ratio of 1.7 × 105 respectively.

ZnO Field-Effect Transistor Fabricated by RF Magnetron Suputtering and Lithographic/Wet Etching Processes

The fabrication of zinc oxide （ZnO）based thin-film field-effect transistors (TFTs) on p-Si substrates by rf magnetron sputtering, photolithography and wet etching processes was presented. Bottom-gate-type thin film transistors using ZnO as an active channel layer were constructed, and their properties were characterized by atomic force microscope, X-ray diffraction and I-V measurements. The fabricated ZnO transistors exhibited enhancement mode characteristics with the on-to-off current ratio of ∼105 and the threshold voltage of 10V. It is believed that the ZnO TFTs fabricatd by the simple and low-cost technique could be applicable to electronic devices.

Substrate effect on morphology and photoluminescence from ZnO monopods and bipods

A simple wet chemical bath deposition has been successfully deployed to fabricate zinc oxide (ZnO) nanostructures. For substrate free growth, the nanostructure is spindle like monopods. But when the nanostructures grow on the glass and quartz substrates, they are bipods (two monopods joined together base to base). Variation in the size of the spindles of the monopods and bipods and the particle size was observed due to the strain exists in the thin film due to lattice mismatch at the interface of the thin film and the substrates. The X-ray diffraction (XRD) and selected area diffraction results confirmed the hexagonal unit cell structures of the monopods and bipods. Also the growth rates of various planes are different and the growth is anisotropic. The substrate free grown monopods show visible photoluminescence (PL) at 421 nm. But the emission gets shifted by 3 and 6 nm for ZnO thin film deposited on quartz and glass substrates respectively due to interfacial strain. In case of ZnO on quartz substrate a strong ultra-violet (UV) peak was observed at 386 nm due to band edge transition. These emissions are also accompanied by few weaker emission peaks due to various defect related transition.

Zinc Oxide Nanorods Grown by Arc Discharge

The arc discharge method was employed to fabricate zinc oxide (ZnO) nanorods with wurtzite structure. The microstructure analysis by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that the ZnO nanorods grew along the [0001] direction. On average, the diameter and length of the nanorods were about 40 nm (some are as thin as 5 nm) and several hundred nanometers, respectively. The photoluminescence (PL) of the nanorods showed an ultraviolet band, a violet band, and a green band. The PL mechanism was discussed with the growth process and Raman spectroscopy.

Oxide Nanowire Arrays and Two-Dimensional Photonic Crystals for Control of Light(Review)

This article reviews our research into artificial microstructures made of inorganic oxides and their optical functions. The described microstructures, which are potential ingredients of the emerging optical devices, include oxide nanowires and photonic crystals. Chemical solution methods were used to fabricate zinc oxide nanowire ultraviolet laser arrays and two-dimensional oxide photonic crystals with photonic band gaps at visible wavelengths. The dimensions of these microstructures were determined by considering the calculated results of the guided modes in nanowires and the band structures in photonic crystals. Current issues in fabrication and the applications of these oxide microstructures as optical devices are discussed.

Wet Oxidation: A Promising Way for Fabrication of Zinc Oxide Nanostructures

A two-step deposition-oxidation method was successfully developed to fabricate zinc oxide thin films and nanostructures. Morphological observations clearly showed that a controllable growth of dense/porous oxide films, nanowhiskers, nanowires, and nanobelts could be obtained by controlling the deposition and oxidation conditions. Photoluminescence properties of the ZnO films were also studied. A strong and predominant ultra-violet near-band-edge emission could be observed on most of the samples, while a green or red color emission accompanying with a largely suppressed ultra-violet emission could be realized on the samples with different processing conditions. The results therefore indicated that ZnO films and structures with desirable microstructural and optical properties could be obtained with this deposition-oxidation technique under controllable conditions.

Fabrication of zinc oxide nanostructures using solvent-assisted capillary lithography

We present a simple solvent-assisted capillary molding method to fabricate zinc oxide(ZnO) nanostructures using an ultraviolet (UV) curable polyurethane acrylate (PUA)mold. A thin film of the ZnO sol–gel precursor solution in methyl alcohol was prepared byspin coating on a solid substrate and subsequently a nanopatterned PUA mold wasbrought into conformal contact with the substrate under slight physical pressure(∼3.5 bar). Afterannealing at 230 °C for 4 h, well-defined ZnO nanostructures formed with feature size down to∼50 nm, aided by capillary rise and solvent evaporation. It was found that the height ofcapillary rise depended highly on the applied pressure. A simple experimental setup wasdevised to examine the effects of pressure, revealing that the optimum pressure ranged from3.5 bar to 5 bar. Also, ZnO nanorods could be selectively grown on patterned regions usingthe seed layer as a pseudocatalyst when the width of the seed layer was larger than∼200 nm.