Growth Of ZnO Research Articles

Crystalline native defects in ZnO analyzed by photoluminescence applying Maxwell-Boltzmann statistics in the visible region

Zinc oxide (ZnO (s) ) is prepared by Chemical Bath Deposition. This manuscript continues with previous research examining the Photoluminiecence at UV-Vis-region. According to emission bands situated at Vis-region by means of Photoluminescence, green (GE) and yellow emission (YE) bands are discussed, which are associated with native intrinsic crystalline defects. The Photoluminescence dependence with the trap density and the surface recombination velocity in the light of the Maxwell-Boltzmann theoretical model (MBM) results associated with the electronic transitions related to the native intrinsic defects situated at9 Vis-region are investigated. The trap density (cm -1 ) of nanocrystals located at range ~8.9-9.9 An approximate a theoretical-experimental kinetic model is presented, considering that the coordination complex ion is a key parameter in the crystal growth of ZnO (s) nanocrystals. The optimized geometry of [Zn(NH 3 ) 4 ] 2+ molecule was obtained with the DFT method using the functional of H-GGA B3LYP.

Effect of UV Irradiation on the Growth of ZnO:Er Nanorods and Their Intrinsic Defects

Nanorods of erbium-doped zinc oxide (ZnO:Er) were fabricated using a hydrothermal method. One batch was prepared with and another one without constant ultraviolet (UV) irradiation applied during the growth. The nanorods were free-standing (FS) as well as deposited onto a fused silica glass substrate (GS). The goal was to study the atomistic aspects influencing the charge transport of ZnO nanoparticles, especially considering the differences between the FS and GS samples. We focused on the excitons; the intrinsic defects, such as zinc interstitials, zinc vacancies, and related shallow donors; and the conduction electrons. UV irradiation was applied for the first time during the ZnO:Er nanorod growth. This led to almost total exciton and zinc vacancy luminescence reduction, and the number of shallow donors was strongly suppressed in the GS samples. The effect was much less pronounced in the FS rods. Moreover, the exciton emission remained unchanged there. At the same time, the Er3+ content was decreased in the FS particles grown under constant UV irradiation while Er3+ was not detected in the GS particles at all. These phenomena are explained.

Sensor-on-Microtips: Design and Development of Hydrothermally Grown ZnO on Micropipette Tips as a Modified Working Electrode for Detection of Glucose.

Miniaturization of electrochemical components has become less common in the last decade, with the focus predominantly being the design and development of state-of-the-art microelectrodes for achieving small volume analysis of samples. However, such microelectrodes involve cumbersome processing procedures to convert the base material for the required application. A potential paradigm shift in such miniaturization could be achieved by using cheaper alternatives such as plastics to build electrochemical components, such as micropipette tips made of polypropylene, which are commercially available at ease. Hence, this work presents the design of an electrochemical working electrode based upon a micropipette tip, involving minimal processing procedures. Furthermore, such a working electrode was realized by sputtering silver onto a bare micropipette tip using a radio-frequency sputtering technique, to obtain electrical contacts on the tip, followed by hydrothermal growth of ZnO, which acted as the active electrode material. The ZnO nanostructures grown on the micropipette tip were characterized for their morphology and surface properties using a scanning electron microscope (SEM), laser microscope, Raman spectrometer, and X-ray photoelectron spectrometer (XPS). The developed micropipette tip-based electrode was then used as the working electrode in a three-electrode system, wherein its electrochemical stability and properties were analyzed using cyclic voltammetry (CV). Furthermore, the above system was used to detect glucose concentrations of 10-200 µM, to evaluate its sensing properties using amperometry. The developed working electrode exhibited a sensitivity of 69.02 µA/µM cm-2 and limit of detection of 67.5 µM, indicating the potential for using such modified micropipette tips as low-cost miniaturized sensors to detect various bio-analytes in sample solutions.

Contribution of surface carboxyl of cellulose in the formation mechanism and interfacial catalysis activity of ZnO/cellulose nanocomposites

The morphology, structure, and dispersion of photocatalysts play important roles in tailoring the surface active sites, photocatalytic productivity, and light utilization efficiency. Cellulose has been widely used in supporting and dispersing ZnO catalysts. However, surface groups of cellulose were ignored as a factor governing ZnO morphology. This work aims to explore the effects of cellulose surface groups on the formation and properties of ZnO catalysts. The reactivity, electronegativity, ion adsorption, and dispersion of the cellulose are improved after the introduction of carboxyl groups, which is beneficial to observe the induction of cellulose surface charge on the growth of ZnO. The results indicate that the diameter, sheet number, and thickness of flower-like ZnO in porous ZnO/cellulose nanocomposites are increased with the enhancement of cellulose surface electronegativity. The ZnO/cellulose nanocomposites with surface carboxyl content of 1.63 mmol*g−1 and zeta potential of –52.6 mV (ZnO/TOCNF3) have the highest photocatalytic activities and recycling for MO degradation due to the exposure of the interfacial active sites and strong electrostatic adsorption between carboxyl and ZnO. These findings provide a green method to regulate the formation and properties of catalysts by adjusting the surface electronegativity of cellulose nanofibers.

Novel Flexible Friction Layer Constructed from ZnO In Situ Grown on ZnSnO3 Nanocubes Toward Significantly Enhancing Output Performances of a Triboelectric Nanogenerator

Material innovation plays an important role in improving the output performance of a triboelectric nanogenerator (TENG). In this work, a flexible ZnO@ZnSnO3/ZnSnO3/polydimethylsiloxane (PDMS) composite film is designed and prepared as the negative friction layer of TENG by a facile hydrothermal method based on in situ growth of the semiconductor ZnO on ferroelectric nanocubic ZnSnO3, which is lead-free and has a high dielectric constant, and cooperative uniform dispersion of nanoparticles. The effects of surface charge density, effective contact area, and interfacial polarization of the negative friction layer on the output performance of TENG are discussed experimentally and theoretically. Compared with the TENG involving pure PDMS, the overall performance of TENG based on the composite film is greatly enhanced, including an open-circuit voltage of 218 V, a short-circuit current of 14.2 μA, a transferred charge of 60 nC, and a power density of 24.625 μW/cm2. The achieved output voltage, current, and transferred charge are 6.8, 9.7, and 10 times higher than those of TENG comprising of pure PDMS, respectively. The TENG designed also successfully lights up 212 light-emitting diodes and charges the electronic devices without any charging equipment. Besides, it can be used as a favorable motion monitoring device. This work provides a facile and effective approach to enhance the overall performance of TENG by utilizing an elaborately designed flexible negative friction layer. The resulting TENG will have a respectable application prospect in self-powered sensing detection and flexible wearable devices.

Influence of Zinc Acetate Concentration on ZnO Growth on Anodized Nb2O5 Nanoporous Films and Photocatalytic Dye Degradation

Influence of Zinc Acetate Concentration on ZnO Growth on Anodized Nb2O5 Nanoporous Films and Photocatalytic Dye Degradation

High-photosensitive ultraviolet photodetector based on an n-ZnO microwire/p-InGaN heterojunction

Researchers have focused on the achievement of high-performance self-biasing ultraviolet photodetectors because of their significance in scientific research and realistic applications. Herein, we proposed and constructed a high-photosensing ultraviolet photodetector, which is made of a single ZnO microwire doped by Ga (ZnO:Ga MW) and p-type InGaN layer. The carefully designed n -ZnO:Ga MW/p-InGaN heterostructure device can sensitively monitor a broadband wavelengths of light in the range of 300–500 nm. The photodetector can also operate in self-biased and reversely biased modes. Especially for the photoelectrical measurements operated in a self-driving manner, the device exhibits excellent photodetection performances, containing a maximum responsivity of 217 mA/W, a photodetectivity of 4.57 × 10 12 Jones, a fast response speed (the rising/decaying times ∼175 μs/30 m) and a high I on /I off ratio of about 6.5 × 10 4 upon 360 nm light illumination. The broadband and ultraviolet spectrum-selective photoresponse of the single ZnO:Ga wire heterojunction detector was principally derived from the resulting combination of ultraviolet-sensitive ZnO:Ga microstructures and ultraviolet–visible-sensitive capability of InGaN materials. Furthermore, the as-proposed n -ZnO:Ga/p-InGaN heterojunction could be functioned as an electrical power source with output voltage of about 1.18 V. This study may enable a potential significance in achieving high-performance self-driving ultraviolet photodetector, and other cost-effective and multifunctional optoelectronic devices. • Catalyst-free growth of ZnO:Ga microwires was achieved using a facile CVD method. • The proposed n -ZnO:Ga MW/p-InGaN heterojunction can sensitively monitor a broadband wavelengths of ultraviolet–visible light. • The photodetector can operated in a self-driving manner, exhibiting excellent and competitive photodetection performances. • The n -ZnO:Ga MW/p-InGaN heterojunction can be employed as a miniature photo-induced power unit with a stable output voltage of about 1.18 V.

Numerical Modelling on the Effect of Temperature on MOCVD Growth of ZnO Using Diethylzinc and Tertiarybutanol

The dynamic growth of MOCVD-grown ZnO thin films under temperature effect was systematically investigated by a numerical approach using computational fluid dynamics (CFD) technique. A three-dimensional (3D) reactor-scale model was developed to determine the growth rate and uniformity of ZnO thin film in the temperature range of 593 K to 713 K. The mixed-convection flow and heat transfer inside the reactor chamber were assessed. The results showed that as the temperature increased, ZnO thickness increased initially before decreasing. At 673 K, the highest deposition rate with acceptable uniformity was achieved. The admixture of transverse and longitudinal rolls was observed for the flow conditions. Temperature variations were found to directly affect the axial and lateral uniformity of deposition, but had a minor impact on the size and position of transverse rolls. Experimental verification studies were conducted, and high-quality ZnO films were successfully fabricated by using diethylzinc (DEZn) and tertiarybutanol (t-BuOH) as precursors; it was found that the comprehensive thickness and structural properties of ZnO deposited at temperature of 673 K are preferred. Experimental results and numerical simulations exhibited good agreement.

Enhanced superhydrophobicity of electrospun carbon nanofiber membranes by hydrothermal growth of ZnO nanorods for oil–water separation

Development of electrospun nanofiber membranes with the selective wettability characteristics for effectively separating oil–water mixtures is an extremely advisable strategy. In this study, a superhydrophobic electrospinning carbon nanofiber (F/ZnO/CNF) membrane was successfully prepared by electrospinning and in-situ growth of ZnO, and subsequent fluorination reaction with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (POTS). Benefiting from the influence of needle-like nanostructure and low surface energy, the as-prepared F/ZnO/CNF membrane shows excellent superhydrophobicity. When the growth duration of ZnO is 3 h, the obtained F/ZnO/CNF-3 membrane possesses outstanding water contact angle (WCA, 159.7°) and splendid oil–water separation efficiency (>99 %). Meanwhile, due to its the superior environmental stability the obtained F/ZnO/CNF-3 membrane exhibits excellent low and high temperature resistance, and enhanced resistance to various organic solvents in the face of a series of harsh environments.

Inhibition of the atomic layer deposition of ZnO and SnO2 using a vapor-based polymer thin film

Area-selective atomic layer deposition (AS-ALD) of thin films is considered as a promising approach to reduce the manufacturing costs of integrated devices and continue their miniaturization. In this work, the ALD growth of ZnO is studied using a polymeric inhibiting layer deposited by initiated chemical vapor deposition (iCVD). It is shown that poly(neopentyl methacrylate) [P(npMA)] is a very good inhibiting layer for ALD growth of zinc oxide from diethylzinc and water. For example, 12 nm of P(npMA) permit us to inhibit up to 100 nm of ZnO. The need for a minimum polymer thickness due to possible diffusion of the precursor in the polymer layer is also highlighted. Finally, our work shows that the same iCVD polymer can also inhibit the ALD growth of SnO2. This work paves the way for the realization of AS-ALD of transparent conducting oxide using a full vacuum-based approach.

ALD growth of ZnO on GaN: Schottky barrier height engineering using ZnO interlayer

Electrical properties of Pt/GaN Schottky diodes have been explored using ZnO interlayers (ILs) grown by thermal atomic layer deposition, which were systematically tuned by varying the growth temperature and thickness of ZnO ILs. For the 20-nm-thick ZnO ILs grown at different temperatures, the growth temperature of 100 °C showed the best rectifying characteristics. The thermionic field emission (TFE) model could explain the forward current characteristics for the growth temperatures of 80, 100 and 150 °C while the tunneling current became dominant for the growth temperature of 200 °C. For the ZnO ILs grown at 100 °C with different thicknesses, the barrier height decreased first and then increased with increasing the ZnO thickness. The samples revealing high interface state density showed the strong tunneling current. It is inferred from the result that both growth temperature and thickness of ZnO IL can be modulated to achieve good Schottky or ohmic contacts for GaN based devices.

Applicability of the Ohmic Model for voltammetric growth of ZnO on galvanized steel sheets containing Sb or Pb

The aim of this study was to verify the applicability of the Ohmic Model with variable ionic resistivity to the voltammetric zinc oxide growth on galvanized steel sheets, without chromate passivating film. Two kind of galvanized steel sheets were studied: one produced from a bath of molten zinc containing antimony and the other containing lead. The galvanized steel sheets produced from a bath containing Sb presented better performance against corrosion in comparison on with those produced from a bath containing Pb. The electrochemical experiments were performed in a buffer solution of pH 8.7 with of 0.3 mol L-1 H3BO3 plus 0.15 mol L-1 Na2B4O7. It was found that the passivating zinc oxide grown on the galvanized steel sheet containing Sb showed higher ionic resistivity than that of the galvanized sheet containing Pb. This can explain the corrosion results.

Facile synthesis of ZnO films with anisotropic preferred orientations: An effective strategy for controllable surface and optical property

Although one-dimensional ZnO nanodevices have already been widely used in practical applications, there still exists limitation of inevitable growth along polar orientation for wurtzite ZnO. Herein, ZnO films grown along diverse preferred orientations including the non-polar, semi-polar and polar directions could be acquired by a facile and reproducible low-temperature aqueous solution deposition method. The non-epitaxial growth pattern was realized by introducing moderate amount of sodium citrate and ammonia into the non-polar solution without any surfactant or passivated agent. Preferential growth mechanism and surface properties of as-prepared anisotropic ZnO films were investigated. Transmission spectra of ZnO films with anisotropic preferred orientations exhibited an isotropic transmittance. Visible emission spectra indicated multifarious defect types and quantities related to diverse preferred orientations of anisotropic ZnO films. This work could not merely enrich the crystallographic growth of ZnO films along anisotropic orientations, but also benefit for designing ZnO film-based nanodevices with desirable performances from the perspective of regulating anisotropic growth of ZnO.

Bioinspired Interfacial Spontaneous Growth of ZnO Nanocatalysts onto Recycled Textiles as a Sustainable Approach for Water Purification.

Zinc oxide, as a commonly used photocatalytic degradation of organic pollutants, typically shows limitations in wastewater treatment, such as aggregation and recycling problems caused by nanoscale dimensions and inappropriate substrates. Anchoring ZnO on substrates is a strategy to obtain stable catalytic performance. Particularly, natural fibers with hollow structures are an attractive alternative for ecological and economical ZnO loading templates, but depositing ZnO onto hollowed fiber surfaces presents a challenge. Here, a straightforward in situ growth method for producing nanostructured zinc oxide on cotton fibers from recycled garments is reported. The modified polydopamine on the fiber surface captures the catalyst required for in situ growth of ZnO and serves as a platform for spontaneous catalytic crystal growth on the fiber surface. The ZnO nanocrystals are uniformly dispersed on the outer and inner walls of cotton fibers, demonstrating excellent durability in wastewater treatments. Moreover, the photocatalytic performance of functional fibers is optimized by doping Ag nanoparticles to improve degradation efficiency. This can extend the prospect of further applications of developed ZnO/fibers in optoelectronics, spintronics, and provide inspiration for recycling and upgrading of used garments.

Decay emission study of ZnO nanostructures obtained by low-pressure vapor transport technique

Currently, the search for inexpensive, non-toxic, and environmentally friendly materials for optoelectronic applications has led to an increased interest in one-dimensional ZnO materials. Attributes such as their high surface area, crystalline phase purity, and high photoexcited response make them attractive for light emission, biosensing, and energy harvesting applications. However, there is still a need for studies that correlate the optical and structural properties of these materials, so they can be integrated as functional building blocks in practical devices. In this work, we report the growth of 1D ZnO nanostructured films using a low-pressure vapor transport technique. Gold-plated substrates allowed us to achieve different types of homogeneous films composed of nanowires/nanorods. Through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-Ray diffraction (XRD) the high-crystalline structure and morphological properties of the materials were determined. The presented methodology also offers control over the growth direction of the nanostructures, as both random and highly aligned matrixes were obtained. Finally, the optical properties of the system were studied by photoluminescence spectroscopy (PL). Along with the excitonic emission, a significant role of defect-related luminescence was found, allowing us to interpret the emission mechanism for the different morphologies of ZnO nanostructures. Time-resolved PL experiments determined decays between 1.9-0.3 ns where an enhancement in the carrier's lifetime was observed as the size of the nanostructure increased. The present study could help us to design efficient ZnO nanostructures with control over their morphology and controllable optoelectronic properties for modern device fabrication.

Revealing the corrosion product films of ion-implanted biodegradable Zn–Cu alloys

In this work, a type of biodegradable Zn–Cu alloy was modified by Cu ion implantation method to achieve graduated degradation rates. A nanometer-thick oxide layer with micron-thick 000121̅1̅0 textured layer structure was obtained on the surface. Focused ion beam and transmission electron microscopy were conducted to investigate the corrosion products. These early corrosion products mainly consisted of ZnO, CuO, and Ca/P phases, and the growth of ZnO showed a preferred orientation of {0001} planes. The amorphous Ca/P layer dominated the later corrosion product films, and products with good crystallinity, such as ZnO, CuO, and Zn3(PO4)2, were also found.

Molecular dynamics study of the growth of ZnOx films

Crystalline zinc oxide thin films are important due to a combination of optical transparency, electrical conductivity, and piezoelectric and pyroelectric properties. These functional properties are improved with increasing perfection of the crystalline structure. In this paper, classical molecular dynamics with a reactive force field was used to simulate the atom-by-atom growth of ZnOx films on a crystalline template. Contrary to previous modeling studies, the effect of a wide range of process parameters (elemental ratio x, kinetic energy of arriving atoms, and fraction of fast atoms in the particle flux) on the film crystallinity was investigated. All the parameters were found to have a significant impact. Counterintuitively, the highest crystal quality was obtained for slightly overstoichiometric films with x > 1. The results provide a quantitative insight into the role of individual deposition parameters, and the identification of their optimum values facilitates a further improvement of the film properties.

Atomic layer deposition of Zr-sandwiched ZnO thin films for transparent thermoelectrics

Atomic layer deposited (ALD) transparent thermoelectric materials enable the introduction of energy harvesting and sensing devices onto surfaces of various shapes and sizes in imperceptible manner. Amongst these materials, ZnO has shown promising results in terms of both thermoelectric and optical characteristics. The thermoelectric performance of ZnO can be further optimized by introducing extrinsic doping, to the realization of which ALD provides excellent control. Here, we explore the effects of sandwiching of ZrO2 layers with ZnO on glass substrates. The room-temperature thermoelectric power factor is maximised at 116μW m−1 K−2 with samples containing a 2% nominal percentage of ZrO2. The addition of ZrO2 layers is further shown to reduce the thermal conductivity, resulting in a 20.2% decrease from the undoped ZnO at 2% doping. Our results contribute to increasing the understanding of the effects of Zr inclusion in structural properties and growth of ALD ZnO, as well as the thermal and thermoelectric properties of Zr-doped ZnO films in general.

(Invited) ALD-Based Infiltration and Growth of Inorganic Materials in Polymers

Sequential infiltration synthesis (SIS) has emerged in the past decade as a powerful technique for growth of inorganic materials within polymers through atomic layer deposition (ALD) chemistry. In SIS, ALD precursors diffuse into the polymer and interact with it, leading to inorganic materials growth within the polymer’s free volume. If desired, the polymer can later be removed, yielding polymer-templated inorganic structures. Combining SIS with self-assembled block copolymer (BCP) patterns results in selective growth of inorganic materials within the polar domains of the BCP, making it an attractive method for directed templating of inorganic nanostructures. Thus, SIS opens a pathway for exploiting ALD precision and rich materials library in new 3D morphologies, defined by the polymer.To build SIS design rules and expand SIS’ possibilities, we probed SIS growth and evolution at the atomic scale and explored the role of reversible polymer-precursor interactions in SIS growth through a plethora of methods: in-situ growth analysis (microgravimetry and FTIR), ex-situ high-resolution electron microscopy and extended X-ray absorption fine structure (EXAFS), and density functional theory (DFT) calculations. This knowledge was then applied in fabrication by design of metal oxide fibers, porous particles, and membranes.We fabricated Al2O3 and ZnO nanofibers, nanobelts, and core-shell fibers using designed growth profiles within electrospun polymer fibers. By controlling the organometallic precursors’ diffusion time, simultaneous but spatially controlled growth of Al2O3 and ZnO within the fibers was achieved, leading to the formation of metal oxide core-shell fibers. Self-assembled BCP particles were used to template porous metal oxide particles by selective growth of Al2O3 in the major block of the self-assembled structure. The uniform BCP assembly led to uniporous pores in the metal oxide particles. Finally, we utilized SIS and ALD within and onto BCP membranes for exceptional pore size control and pores’ surface engineering, yielding highly selective filtration membranes.

High output power density owing to enhanced charge transfer in ZnO-based triboelectric nanogenerator

We have fabricated triboelectric nanogenerarators (TENGs) using ZnO and polydimethylsiloxane (PDMS) in which ZnO growth temperature was varied in the range from 450 °Ct 750 °C. The output voltage/current of TENGs increases with increase of ZnO growth temperature up to 600 °C and then decreases with further increase of growth temperature up to 750 °C. TENG fabricated with ZnO grown at 600 °C exhibits maximum electrical output with peak to peak voltage of ∼210 V, current ∼95 μA and power density ∼8.8 mW/cm2 upon application of a periodic force of ∼30 N @ 6 Hz, which is higher than the power densities reported till date in the case of ZnO-based TENGs. This enhanced output power density can be mainly attributed to the large effective work function difference obtained between ZnO and PDMS. Electrical, photoluminescence and ultra-violet photoelectron spectroscopy measurements clearly suggest the dominant role of electron transport in the charge transfer between ZnO and PDMS. Practical applications of TENGs have been demonstrated by powering 38 LEDs and a stopwatch display. This study not only deepens the understanding of contact electrification between ZnO and PDMS, but opens up the immense potential of ZnO-based TENGs for possible vibration energy harvesting applications.