Multilayer ZnO Research Articles

Synthesis of Zn2SnO4 hollow spheres by a template route for high-performance acetone gas sensor

Hollow and porous ZnO, SnO2 and Zn2SnO4 spheres were synthesized by the hydrothermal synthesis using carbonaceous spheres as templates in combination with calcination. The structure, morphology and gas sensing characteristics of the resultant product were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and gas-sensing measurement device, and the results showed that the variety of reaction parameters such as size of the template and different precursor materials have important effects on the formation of the shell structure. Compared with the solid counterparts, the hollow structures of the obtained samples were exploited as gas sensors and exhibited improved sensing performance to a series of gases (especially with regard to acetone). Moreover, sensitivity and response/recovery time of Zn2SnO4 hollow spheres to acetone were both higher than multilayered ZnO and SnO2 core-shell, and comparing the operating temperature (240°C) of zinc oxide and stannic oxide, zinc stannate had lower operating temperature (200°C). The formation mechanism and acetone sensing mechanism of Zn2SnO4 hollow spheres were also discussed in detail.

Characteristics of ZnO Multi-Layer Film Fabricated by Electrodeposition Method

Characteristics of ZnO Multi-Layer Film Fabricated by Electrodeposition Method

Sol-gel synthesis and characterization of undoped and Al-doped ZnO thin films for memristive application

The Sol-gel route is a versatile method to fabricate multi-layer, dense and homogeneous ZnO thin films with a controlled thickness and defects for a memristive application. In this work, sol-gel derived multi-layer undoped and Al-doped ZnO thin films were prepared by a spin-coating technique on SiO2/Ti/Pt and silica glass substrates. The effect of both Al doping and curing conditions on the structural and morphological features of ZnO films was investigated by complementary techniques, including electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction analysis. Electrical measurements were performed on SiO2/Ti/Pt/ZnO/Pt(dishes) and SiO2/Ti/Pt/ZnO(Al)/Pt(dishes) fabricated memristive cells and preliminary current-voltage curves were acquired.

Characteristics of Nano-Laminated Al-Doped ZnO (AZO) Multilayers

This work was supported by the Nano Materials Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2015M3A7B7045490).

Low temperature processed ZnO thin film as electron transport layer for efficient perovskite solar cells

Organic inorganic lead halide Perovskite photovoltaic devices are promising candidates for commercial application because of their high efficiency and low production cost. One integral part of these high efficiency solar cells is electron transport layer that provides the electron contact selectivity and mitigates recombination phenomena for enhanced device performance. However, high temperature sintering process of most widely used Titanium oxide electron transport layer or the sophisticated, time consuming processing with nanostructured electron extraction material is a fundamental barrier to mass production of Perovskite solar cell with roll-to-roll process. In this work, we have reported the application of simple, low temperature processed (<150 °C) sol-gel ZnO thin film as electron transport layer with efficient (PCE: 8.77%), highly reproducible Perovskite solar cell. Consecutive spin coating process has been implemented to find a multi-layer ZnO film that ensures high optical absorption in photoactive Perovskite layer by acting as a highly transmitting, less reflective, transparent layer. The optimized ZnO film also provides coherent surface morphology for the proper crystalline growth of overlying Perovskite layer and suppresses the deep trap states existing at the ZnO/perovskite interface. A systematic impedance spectroscopy study has been presented in this work to comprehend the improved device performance with the optimized multilayer electron transport material. The electronic properties like contact resistance, recombination resistance, flat-band potential and depletion width of the best performing device have been investigated. The interfacial charge transfer characteristics between methyl ammonium lead triiodide perovskite and low temperature solgel ZnO have also been elaborated based on the interface electronic properties.

Influence of the ZnO:Al dispersion on the performance of ZnO:Al/Ag/ZnO:Al transparent electrodes

Highly transparent and conductive Al-doped ZnO/Ag/Al-doped ZnO (AZO/Ag/AZO) multilayers were prepared by industrial inline DC magnetron sputtering on glass substrates at room temperature. With optimized film thicknesses of 37nm/10nm/37nm, an optimized low sheet resistance of only 6Ω/sq. and high transmittances of T550=87.4% at 550nm and T400–800=79.9% in the spectral range between 400nm and 800nm were reached. Furthermore, an increase of the AZO/Ag/AZO-performance was achieved when a small amount of oxygen was added to the process gas during the AZO deposition which was found to be because of a beneficial adjustment of the AZO dispersion. In this way, owing to both a decreased extinction coefficient as well as a higher refractive index of the AZO film, the maximum transmittance of the AZO/Ag/AZO three-layer structure is further increased (T550=89.0%) and the bandwidth of the transmittance range is broadened (T400–800=83.3%). With the adaption of the AZO dispersion a very high Figure-of-Merit (Haacke) Φ400–800=26.2mΩ−1 and Φ550=52.9mΩ−1 was achieved by industrial inline DC magnetron sputtering process.

Morphology and properties of ZnO films obtained by repeated spin coating on porous silicon substrates

Layers of porous silicon (PS), multilayered ZnO films, and heterostructures based on them are obtained. The surface morphology, chemical and phase composition of the PS layers and ZnO films, and the transverse cleavage of ZnO–PS nanocomposite, are investigated via energy-dispersive X-ray spectral analysis (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The current–voltage characteristics of Al/Ag/p-Si(100)/PS/ZnO/Ag/Al and Al/Ag/p-Si(100)/PS/ZnO/SiC/Ag/Al heterostructures are studied.

Sol-gel derived oriented multilayer ZnO thin films with memristive response

Sol-gel derived multi-layer ZnO films were prepared by spin coating technique on soda-lime glass, silica, silicon and platinum substrates from an alcoholic solution of zinc acetate dihydrate and monoethanolamine at different synthetic conditions. The curing and annealing conditions for the ZnO films were adjusted based on the study performed on the ZnO xerogel powders. Structural and morphological features as well as the thermal behavior of the samples were investigated by complementary techniques including electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analyses, and X-ray diffraction analysis. According to the electrical measurements performed on ZnO thin films sandwiched between Pt/Ti/SiO2 substrate and Ag dishes as a top electrode, the selected fabrication conditions were suitable for fulfilling the requirements of active resistive layers for the development of memristive devices.

Sputter deposition of Sn-doped ZnO/Ag/Sn-doped ZnO transparent contact layer for GaN LED applications

Sn-doped ZnO/Ag/Sn-doped ZnO (ZAZ) multilayers prepared using sputtering process was employed in GaN-based blue light-emitting diodes(LEDs) as transparent contact layers (TCLs). The ZAZ layer had better optical and electrical properties without any thermal annealing. The ZAZ TCLs improved the current spreading on p-GaN layer and increased the light output power in the large area devices. The efficiency droop was also quite small in the case of adopting a ZAZ TCL in GaN-based LEDs. These results are promising for the development of a ZAZ TCL using sputtering process for GaN LED applications.

Energetic and electronic properties in a multilayered ZnO graphene-like nanostructure

Nanostructures based on ZnO have been widely studied due to their electronic and piezoelectric properties. Experimental studies have shown that thin films based on ZnO can be used as chemical and optoelectronic sensors. The great goal of this work is to study of the role of the number of graphene-like layers in the physical properties of the ZnO. Therefore, the geometrical and electronic properties of graphene-like structures will be compared with the wurtzite one. In this work, the pn-type semiconducting behavior of the graphene-like structures and its relationship with the number of layers will be also analyzed.

Intrinsic magnetic properties of ZnO nanoislands: Insight from first-principles study

First-principles calculations have been employed to investigate magnetic and electronic properties of monolayer and multi-layer ZnO nanoislands which are hexagonal BN (h-BN) prototype structures with zigzag edges and a triangular form. Two types of the zigzag edges, that is, O-terminated and Zn-terminated ones are considered. It has been found that monolayer ZnO nanoislands with the O-terminated edges exhibit magnetic properties, regardless of the nanoislands size. However, the nanoislands with Zn-terminated edges are semiconductors, and the magnetic properties are observed just for some specific sizes. Charge transfer according to Bader charge analysis is introduced to elucidate the magnetic properties of the monolayer ZnO nanoislands. Besides, multi-layer ZnO nanoislands exhibit magnetic features when their layers are odd, while those of even layers are nonmagnetic.

The Effect of the Annealing on the Properties of ZnO/Cu/ZnO Multilayer Structures

Study of ZnO / Cu / ZnO multilayer film stack using Cu film as a sandwich layer, in order to improve the overall performance of the transparent conductive film, structural, electrical and optical properties. ZnO / Cu / ZnO multilayer films prepared at room temperature by a DC and RF magnetron sputtering technique. The results showed that ZnO / Cu / ZnO multilayer film has good crystalline properties. With an increasing Cu layer thickness, a visible light transmittance of the multilayer film is reduced, while the electrical performance improved significantly. In the Cu layer thickness of 20nm, ZnO / Cu / ZnO multilayer film optoelectronic integrated for optimal performance

High Performance Amorphous Multilayered ZnO-SnO&amp;amp;lt;sub&amp;amp;gt;2&amp;amp;lt;/sub&amp;amp;gt; Heterostructure Thin-Film Transistors: Fabrication and Characteristics

Multilayered ZnO- heterostructure thin films consisting of ZnO and layers are produced by alternating the pulsed laser ablation of ZnO and targets, and their structural and field-effect electronic transport properties are investigated as a function of the thickness of the ZnO and layers. The performance parameters of amorphous multilayered ZnO- heterostructure thin-film transistors (TFTs) are highly dependent on the thickness of the ZnO and layers. A highest electron mobility of , a low subthreshold swing of a 0.22 V/dec, a threshold voltage of 1 V, and a high drain current on-to-off ratio of are obtained for the amorphous multilayered ZnO(1.5nm)-(1.5 nm) heterostructure TFTs, which is adequate for the operation of next-generation microelectronic devices. These results are presumed to be due to the unique electronic structure of amorphous multilayered ZnO- heterostructure film consisting of ZnO, , and ZnO- interface layers.

Highly Transparent and Low-Resistance Indium-Free ZnO/Ag/ZnO Multilayer Electrodes for Organic Photovoltaic Devices

We investigated the effect of ZnO layer thickness on the optical and electrical properties of ZnO/Ag/ZnO multilayer films deposited on glass substrates. The transmission window became wider and shifted toward the lower energy side with increasing ZnO thickness. The ZnO/Ag/ZnO (40 nm/18.8 nm/40 nm) multilayer sample showed transmittance of ~96% at 550nm. As the ZnO thickness was increased from 8 nm to 80 nm, the carrier concentration gradually decreased from 1.74 × 1022 cm−3 to 4.33 × 1021 cm−3, while the charge mobility varied from 23.8 cm2/V-s to 24.8 cm2/V-s. With increasing ZnO thickness, the samples exhibited similar sheet resistances of 3.6 Ω/sq to 3.9 Ω/sq, but the resistivity increased by a factor of 4.58. The samples showed smooth surfaces with root-mean-square roughness in the range of 0.47 nm to 0.94 nm. Haacke’s figure of merit (FOM) was calculated for all the samples; the ZnO (40 nm)/Ag (18.8 nm)/ZnO (40 nm) multilayer produced the highest FOM of 148.9 × 10−3 Ω−1.

ZnO varistor ceramics prepared by the reduction–reoxidation method

Multilayer ceramic components with base metal inner electrodes should be sintered in a reducing or protective atmosphere to avoid oxidation of the base metal, and then re-oxidized in air or oxygen to control their electrical properties. It is called reduction–reoxidation method. In this article, ZnO varistors were firstly prepared by the reduction–reoxidation method. Electrical performances of ZnO varistors sintered in air and nitrogen (N2 99.8%) were compared with those prepared by the reduction–reoxidation method. ZnO varistor ceramics sintered in N2 at 1000°C and then re-oxidized in air at 750°C for 2h exhibited excellent electrical properties such as a high nonlinear coefficient of 47.9 and a low leakage current of 0.06μA/cm2, which is promising for producing multilayer ZnO varistors with base metal electrodes.

Polymer-assisted co-axial multi-layered circular ZnO nanodisks

Multi-layered ZnO circular nanodisks were efficiently fabricated using sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) polymer by a controlled hydrothermal method. As-prepared ZnO nanostructures were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The effect of SDS and PVP polymer on the formation of ZnO multi-layer nanostructures was described in detail. Based on experimental results, a possible mechanism of circular disk formation was proposed. The gas-sensing properties of multi-layered nanodisks were reported for formaldehyde under different concentrations from 5 to 1200ppm at 300°C. A higher response toward formaldehyde was observed, rendering the multi-layered nanostructures a promising gas-sensing material for the on-site detection of formaldehyde.

Terahertz Transmission Properties of a Disorderly Piled Hexagonal ZnO Multi-Layer: FDTD Simulations and Stereolithography Fabrication

Terahertz Transmission Properties of a Disorderly Piled Hexagonal ZnO Multi-Layer: FDTD Simulations and Stereolithography Fabrication

Highly flexible ZnO/Ag/ZnO conducting electrode for organic photonic devices

We investigated the electrical, optical and bending characteristics of ZnO (40nm)/Ag (18.8nm)/ZnO (40nm) multilayer film deposited on polyethylene terephthalate (PET) substrate and compared them with those of indium-tin-oxide (ITO) (100nm thick). The ITO single and ZnO/Ag/ZnO multilayer films gave maximum transmittance of 92.9% and ~95% at ~530nm, respectively. For the ITO single and ZnO/Ag/ZnO multilayer films, the carrier concentration was measured to be 1.19×1020 and 6.68×1021cm−3, respectively and the mobility was 32.06 and 21.06cm2/Vs, respectively. The sheet resistance was 175.99 and 4.98Ω/sq for the ITO single and ZnO/Ag/ZnO multilayer films, respectively. Haacke׳s figure of merit (FOM) of the ITO single and ZnO/Ag/ZnO multilayer films was calculated to be 2.36×10−3 and 104.5×10−3Ω−1. The ZnO/Ag/ZnO multilayer films showed dramatically improved mechanical stability when subjected to bending test.

3J2-2 Polarity inverted Al-polar ScAlN/O-polar ZnO multilayers for high conversion efficiency transducer in the GHz range

3J2-2 Polarity inverted Al-polar ScAlN/O-polar ZnO multilayers for high conversion efficiency transducer in the GHz range

Synthesis of Multi-layered Spherical ZnO Micro/Nano-crystals by Hydrothermal Method from Deep Eutectic Solvent and Their Photo Catalytic Performance†

Multi-layered spherical ZnO micro/nano-crystals were synthesized by means of hydrothermal and antisolvent method from the urea-choline chloride deep eutectic solvent(UCC-DES). The effects of reaction time,amount and concentrations of antisolvents on the morphology of ZnO micro/nano-crystals were investigated,and the formation of ZnO micro/nano-crystals was discussed. Furthermore,the photocatalytic activities of the as-prepared ZnO crystals for the degradation of methyl orange were investigated. The results indicate that multi-layered spherical ZnO micro/nano-crystals exhibit a superior photocatalytic activity. The synthetic method of ZnO is facile,safe and environmentally friendly,it is in line with the requirements of green chemistry and should have widespread application in the future.