Aligned ZnO Nanorod Arrays Research Articles

Effect of samarium doping on structural, optical and magnetic properties of vertically aligned ZnO nanorod arrays

Samarium doped vertically aligned one dimensional ZnO nanorod (NR) arrays were grown by vapor phase transport (VPT) method through vapor solid (VS) growth process. Influence of different concentrations (0% to 8%) of Sm (all Sm contents in the paper are in mass fraction) on the ZnO NR arrays were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), Raman spectroscopy and vibrating sample magnetometry (VSM) techniques, respectively. X-ray diffraction studies revealed that the ZnO NR arrays were perfectly oriented along (002) crystallographic orientation with wurtzite crystal structure. Photoluminescence results showed an increase in oxygen vacancies due to increase in Sm doping. M-H curves revealed enhanced ferromagnetic behavior, and the magnetic moment values were 0.45, 0.363, 1.694, 3.613 and 2.197 emu/cm3 for (0–8%) Sm doped ZnO NR arrays respectively. The curve revealed that paramagnetic behavior was observed for undoped ZnO NR arrays and on increasing the Sm dopant to 4%, paramagnetic switched to ferromagnetic behavior.

Indium-doped ZnO nanorods grown on Si (1 1 1) using a hybrid ALD-solvothermal method

Atomic layer deposition (ALD) followed by microwave hydrothermal processing was successfully employed for producing doped and vertically aligned ZnO nanorod arrays with different aspect ratio. Firstly, a textured ZnO layer with preferential orientation normal to the c-axis was formed on substrate (1 1 1) silicon single crystals by means of the ALD technique. This was achieved through the decomposition of diethylzinc at 190 °C and 3.289 × 10−4 atm, which provided an adequate template with nucleation sites, favoring further growth of vertical nanorods. Subsequently, nanorod array growth was produced on the same surfaces through solvothermal synthesis using as promoter a solution of Zn(NO3)2. In addition, growth of indium-doped ZnoO nanorods over the substrates was produced by using In(CH3COO)3 as a doping agent. The method presented allows good quality ZnO and Zn1−xInxO thin films to be obtained. Photoluminiscence spectra show clear evidence of the inclusion of indium in the ZnO matrix. The higher intensity ratio Zn0.96In0.4O/ZnO was increased 40-fold, demonstrating such an effect.

Robust water repellent ZnO nanorod array by Swift Heavy Ion Irradiation: Effect of Electronic Excitation Induced Local Chemical State Modification

Tailoring the surface properties by varying the chemistry and roughness could be of interest for self-cleaning applications. We demonstrate the transformation of hydrophobic ZnO Nano rod (NR) array into superhydrophobic nature by changing the local chemical state and without altering the surface roughness by swift heavy ion (SHI) irradiation. The aligned ZnO NR arrays were irradiated using 150 MeV Ag ions with different fluences from 5E10 to 3E12 ions/cm2. The observed static water contact angles of ZnO NRs samples were 103° ± 3°, 152° ± 4°,161° ± 3°, 164° ± 2°, 167° ± 2°,154 ± 3° and 151° ± 2° for the pristine, ion fluencies of 1E11, 3E11, 5E11, 7E11, 1E12 and 3E12 ions cm−2, respectively. The change in local surface chemistry via formation of surface oxygen related defects due to electronic excitations induced by ion irradiation determine the water dewetting properties. It is found that surface oxygen related defects could be tuned by varying the fluence of the SHIs. Durability tests show that the SHI induced surface oxygen-deficient ZnO NRs have the stable superhydrophobic behavior for more than a year.

Electrochemical Deposition of MgO@ZnO Shell−Core Nanorod Arrays Largely Enhances the Photoelectrochemical Water Splitting Performance

AbstractWell aligned ZnO nanorod array (NRA) core coated with MgO nanolayer shell was fabricated via a facile pulse electrodeposition method. Using this method, a homogeneous MgO nanolayer could be formed on the surface of the wurtzite ZnO nanorod. This novel nanostructure with controllable shell thickness, provided a high photoinduced current density of 2.4 mA cm−2 at 1 V (vs. Ag/AgCl) under 100 mW cm−2 illumination (AM 1.5), which value is almost three times larger than that of pristine ZnO NRA and also much superior to those of analogous ZnO based photoanodes. The as‐prepared photoanodes exhibited excellent behaviors in photoelectrochemical (PEC) water splitting, significantly improved the photoconversion efficiency. This is attributed to the interface effect and surface hydrophilia provided by the MgO ultrathin nanolayer, suppressing the recombination rate of electron‐hole pairs and improving interfacial charge exchange capacity. Thus, this work provides a cost‐effective route to improve the performance of ZnO based photoanodes, in addition it can be used in other solar energy conversion devices, for example, this hydroxyl groups dominant surface can be employed for other visible light response semiconductors (CdS, CdTe etc.) assembly.

The Influence of the Growth Time on the Size and Alignment of Zno Nanorods

Vertically aligned ZnO nanorods arrays were synthesized on glass substrates. ZnO seed layers were prepared on the glass substrate by RF Sputtering technique. ZnO nanorods synthesized using low-cost chemical bath deposition method at low temperature (95 ºC). The effect of the different growth time such as (0.5, 1, 2, 3, 4 and 5) h on the morphology, elemental chemical composition and structure of the ZnO nanorods were obtained systemically, and tested by Field emission scanning electron microscopy (FESEM), Energy dispersive analysis (EDX), and XRD measurements. The results found that the ZnO nanorods with hexagonal wurtzite structure grow vertically on the glass substrates. Most of the prepared samples have strong and sharp (002) peak intensities and the diffraction peaks (002) become higher and narrower as growth time increasing, obtaining that the ZnO crystalline quality became better with growth time increasing. The growth rate was decreased with increasing growth time, and the high aspect ratio was found at 4 h as a growth time. The size, length and crystalline size of the ZnO nanorods increase with increasing growth time. Furthermore, the ZnO nanorods vertically grow at (002) direction along the c-axis on the glass substrate, with elementary chemical compositions of zinc and oxygen only for all prepared samples.

Efficiency enhancement of silicon solar cells with vertically aligned ZnO nanorod arrays as an antireflective layer

Vertically aligned ZnO nanorods grown by the hydrothermal method have been explored as an antireflection layer on polished, textured, and antireflection coating (ARC) coated textured silicon (Si) wafers. Average reflectance (from 380 to 1100 nm) of polished and textured Si wafers reduced from 32 to 9% and 14 to 2%, respectively. With nanorods, multiple light interactions and good optical impedance matching with graded refractive index (effective medium) from air to Si favored for light confinement in Si. Optimized nanorods on ARC coated textured Si cell led to an enhancement of photocurrent from 34.30 to 36.38 mA/cm2 and efficiency from 15.11 to 16.43%.

Modulating the morphology of ZnO nanorod arrays on SiOx-mask-patterned GaN template

Highly ordered vertically aligned ZnO nanorod arrays are fabricated via a recyclable SiOx-mask-patterned GaN template by hydrothermal method. The morphology of ZnO nanorods can be modulated, and the mechanism is studied for the first time. The modulation depends on the nucleation state, which can be tuned by varying PH value through adding ammonia. Tight contact is observed between a monolayer graphene and the smooth surface of the arrays due to the uniform height and horizontal c-plane of nanorods. The ZnO nanorod arrays are characterized by XRD and Room-temperature PL.

수열합성법에 의한 정렬된 ZnO 나노로드 구조의 합성

수열합성법에 의한 정렬된 ZnO 나노로드 구조의 합성

Solution-processed Cd free kesterite Cu2ZnSnS4 thin film solar cells with vertically aligned ZnO nanorod arrays

In order to development of non-toxic thin film photovoltaic devices the ZnO/ZnS are quite attractive as window/buffer layer due to its suitable semiconductor properties and abundant availability. We report CZTS based solar cells devices of layer configuration ITO/ZnO (NR's)/ZnS/CZTS/Au. The vertically aligned ZnO nanorod arrays have been grown using hydrothermal technique, whereas the ZnS and CZTS thin films has been deposited by chemical bath deposition and solution processing method respectively. In proposed device architecture ZnO nanorods arrays/ZnS films work as window/buffer layer and CZTS as photo active layer respectively. The nanostructured ZnS/ZnO array provides improved light harvesting behaviour compared to a thin film configuration. The prepared Cd free CZTS/ZnS/ZnO NR device exhibit a solar energy conversion efficiency of 3.63%, which is the highest efficiency yet reported for nanostructured ZnS/ZnO superstrate CZTS solar cells from best of our knowledge.

Position controlled and seed/catalyst free growth of ZnO nanorod arrays on reduced graphene oxide nanosheets

A new type of seed/catalyst-free and selective-growth process is developed for in situ grown vertically-aligned ZnO nanorods on the reduced graphene oxide (rGO) nanosheets. The dense and single-crystalline ZnO nanorods have been successfully grow on rGO nanosheets with the position- and size-controlled. The effect of rGO layer on the ZnO nanorods and the growth mechanism were investigated. The position of ZnO nanorod arrays correlates well with the size and position of rGO nanosheets, which is determined by dangling bonds such as oxygen-containing groups on rGO surface. Meanwhile, ZnO nanorods could grow laterally to form a continuous arrays with a large coverage on rGO substrates, which is mainly due to the step edges in rGO boundaries. The diameter and density of ZnO nanorods were readily determined by the growth temperature, and the length was easily controlled by the growth time. The absorption and PL spectrums suggest that ZnO nanorods/rGO have a strong UV absorption ranging from 330 to 375 nm and no obvious UV PL emission at room temperature, which indicates that the ZnO nanorods/rGO nanohybrids could be an excellent candidate for application in UV photodetectors. This work represents the success in seed/catalyst-free fabrication of aligned ZnO nanorod arrays directly on rGO nanosheets and the process can be readily scaled up for industrial applications of optoelectronic devices.

Lanthanum ions-induced synthesis of ZnO nanostructures from zinc foil: Morphology change and photocatalytic activity

High-density aligned ZnO nanorod array film was synthesised by hydrothermal oxidation of zinc foil in a mixture including n-butylamine and lanthanum nitrate aqueous solution. The shape of ZnO nanostructure was strongly associated with the amount of lanthanum ions, which provided a valuable way to control the rate of nucleation and growth of ZnO. HRTEM, XRD and XPS analysis confirmed that the La3+ had been doped into ZnO lattice, which led to the red shift of the absorption edges and the decrease of PL intensity. The photocatalytic studies showed that the ZnO nanorod array film exhibited superior photocatalysis for the degradation of both methyl orange and methylene blue solutions due to its exposed crystal plane, density and the defects on the surface.

Plasmon-enhanced Electrically Light-emitting from ZnO Nanorod Arrays/p-GaN Heterostructure Devices.

Effective and bright light-emitting-diodes (LEDs) have attracted broad interests in fundamental research and industrial application, especially on short wavelength LEDs. In this paper, a well aligned ZnO nanorod arrays grown on the p-GaN substrate to form a heterostructured light-emitting diode and Al nanoparticles (NPs) were decorated to improve the electroluminescence performance. More than 30-folds enhancement of the electroluminescence intensity was obtained compared with the device without Al NPs decoration. The investigation on the stable and transient photoluminescence spectraof the ZnO nanorod arrays before and after Al NPs decoration demonstrated that the metal surface plasmon resonance coupling with excitons of ZnO leads to the enhancement of the internal quantum efficiency (IQE). Our results provide aneffective approach to design novel optoelectronic devices such as light-emitting diodes and plasmonic nanolasers.

Role of ZnO thin film in the vertically aligned growth of ZnO nanorods by chemical bath deposition

The effect of ZnO thin film on the growth of ZnO nanorods was investigated. ZnO thin films were sputter-deposited on Si substrate with varying the thickness. ZnO nanorods were grown on the thin film using a chemical bath deposition (CBD) method at 90°C. The ZnO thin films showed granular structure and vertical roughness on the surface, which facilitated the vertical growth of ZnO nanorods. The average grain size and the surface roughness of ZnO film increased with an increase in film thickness, and this led to the increase in both the average diameter and the average length of vertically grown ZnO nanorods. In particular, it was found that the average diameter of ZnO nanorods was very close to the average grain size of ZnO thin film, confirming the role of ZnO film as a seed layer for the vertical growth of ZnO nanorods. The CBD growth on ZnO seed layers may provide a facile route to engineering vertically aligned ZnO nanorod arrays.

Effect of preparing method of ZnO powders on electrical arc erosion behavior of Ag/ZnO electrical contact material

Abstract

Efficient H2 Production Using Ag2S-Coupled ZnO@ZnS Core–Shell Nanorods Decorated Metal Wire Mesh as an Immobilized Hierarchical Photocatalyst

Ag2S-coupled ZnO@ZnS core–shell nanorods heterostructures were grown on stainless steel wire mesh substrates along the c-axis by sulfidation of aligned ZnO nanorod arrays as immobilized hierarchical photocatalysts (Ag2S-coupled ZnO@ZnS/metal wire mesh) for photocatalytic H2 production. The effects of the sulfidation time and AgNO3 precursor concentration on the morphology, crystalline properties, optical property, photocurrent response, and photocatalytic H2 production activity of the photocatalysts under UV or visible light irradiation, together with the stability of photocatalytic activity for recycled photocatalysts were investigated. In comparison with ZnO/metal wire mesh under the same conditions, the ZnO@ZnS/metal wire mesh photocatalysts showed excellent photocatalytic H2 production activity that can be attributed to the formation of Ag2S-coupled ZnO–ZnS heterojunctions on conductive metal wire mesh substrate that favors the absorption of light, separation of photogenerated electron–hole pairs, and...

Nanoimprint assisted transfer of different density vertically aligned ZnO nanorod arrays

Nanoimprint assisted transfer method was used to make vertically aligned ZnO nanorod electronic devices. The method relies on the hot nanoimprint process performed in the transfer process, which enables ZnO nanorod arrays to easily penetrate into the PMMA transfer layers.

BiOBr nanoplate-wrapped ZnO nanorod arrays for high performance photoelectrocatalytic application

BiOBr nanoplate (NP) decorated vertically aligned ZnO nanorod arrays (NRAs) have been successfully synthesized by a facile and cost-effective solvothermal process.

Low Drag Porous Ship with Superhydrophobic and Superoleophilic Surface for Oil Spills Cleanup.

To efficiently remove and recycle oil spills, we construct aligned ZnO nanorod arrays on the surface of the porous stainless steel wire mesh to fabricate a porous unmanned ship (PUS) with properties of superhydrophobicity, superoleophilicity, and low drag by imitating the structure of nonwetting leg of water strider. The superhydrophobicity of the PUS is stable, which can support 16.5 cm water column with pore size of 100 μm. Water droplet can rebound without adhesion. In the process of oil/water separation, when the PUS contacts with oil, the oil is quickly pulled toward and penetrates into the PUS automatically. The superhydrophobicity and low water adhesion force of the PUS surface endow the PUS with high oil recovery capacity (above 94%) and drag-reducing property (31% at flowing velocity of 0.38m/s). In addition, the PUS has good corrosion resistance and reusability. We further investigate the wetting behavior of water and oil, oil recovery capacity, drag-reducing property, and corrosion resistance of the PUS after oil absorbed. The PUS surface changes significantly from superhydrophobic to hydrophobic after absorbing oil. However, the oil absorbed PUS possesses better drag-reducing property and corrosion resistance due to the changes of the motion state of the water droplets.

Large-scale growth of density-tunable aligned ZnO nanorods arrays on GaN QDs

An effective approach for growing large-scale, uniformly aligned ZnO nanorods arrays is demonstrated. The synthesis uses a GaN quantum dot (QD) template produced by a self-assembled Stranski–Krastanow mode in metal organic chemical vapor deposition, which serves as a nucleation site for ZnO owing to the QD’s high surface free energy. The resultant ZnO nanorods with uniform shape and length align vertically on the template, while their density is easily tunable by adjusting the density of GaN QDs, which can be adjusted by simply varying growth interruption. By controlling the density of ZnO nanorod arrays, their optical performance can also be improved. This approach opens the possibility of combining one-dimensional (1D) with 0D nanostructures for applications in sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.

Fabrication and Optimization of Vertically Aligned ZnO Nanorod Array-Based UV Photodetectors via Selective Hydrothermal Synthesis.

Vertically aligned ZnO nanorod array (NRA)-based ultraviolet (UV) photodetectors (PDs) were successfully fabricated and optimized via a facile hydrothermal process. Using a shadow mask technique, the thin ZnO seed layer was deposited between the patterned Au/Ti electrodes to bridge the electrodes. Thus, both the Au electrodes could be connected by the ZnO seed layer. As the sample was immersed into growth solution and heated at 90 °C, the ZnO NRAs were crystallized and vertically grown on the ZnO seed layer, thus creating a metal-semiconductor-metal PD structure. To investigate the size effect of ZnO NRAs on photocurrent, the PDs were readily prepared with different concentrations of growth solution. For the ZnO NRAs grown at 25 mM of concentration, the PD with 10 μm of channel width (i.e., gap distance between two electrodes) exhibited a high photocurrent of 1.91 × 10−4 A at an applied bias of 10 V under 365 nm of UV light illumination. The PD was optimized by adjusting the channel width. For 15 μm of channel width, a relatively high photocurrent on-off ratio of 37.4 and good current transient characteristics were observed at the same applied bias. These results are expected to be useful for cost-effective and practical UV PD applications.