Properties Of ZnO Nanorod Arrays Research Articles

Influence of metal covering with a Schottky or ohmic contact on the emission properties of ZnO nanorod arrays

Influence of metal covering with a Schottky or ohmic contact on the emission properties of ZnO nanorod arrays

PET/ZnO@MXene-Based Flexible Fabrics with Dual Piezoelectric Functions of Compression and Tension.

The traditional self-supported piezoelectric thin films prepared by filtration methods are limited in practical applications due to their poor tensile properties. The strategy of using flexible polyethylene terephthalate (PET) fabric as the flexible substrate is beneficial to enhancing the flexibility and stretchability of the flexible device, thus extending the applications of pressure sensors. In this work, a novel wearable pressure sensor is prepared, of which uniform and dense ZnO nanoarray-coated PET fabrics are covered by a two-dimensional MXene nanosheet. The ternary structure incorporates the advantages of the three components including the superior piezoelectric properties of ZnO nanorod arrays, the excellent flexibility of the PET substrate, and the outstanding conductivity of MXene, resulting in a novel wearable sensor with excellent pressure-sensitive properties. The PET/ZnO@MXene pressure sensor exhibits excellent sensing performance (S = 53.22 kPa-1), fast response/recovery speeds (150 ms and 100 ms), and superior flexural stability (over 30 cycles at 5% strain). The composite fabric also shows high sensitivity in both motion monitoring and physiological signal detection (e.g., device bending, elbow bending, finger bending, wrist pulse peaks, and sound signal discrimination). These findings provide insight into composite fabric-based pressure-sensitive materials, demonstrating the great significance and promising prospects in the field of flexible pressure sensing.

Solution Processed Zn1-x-ySmxCuyO Nanorod Arrays for Dye Sensitized Solar Cells.

Cu- and Sm-doped ZnO nanorod arrays were grown with 1 wt% of Sm and different weight percents (0.0, 0.5, 1.0 and 1.5 wt%) of Cu by two-step hydrothermal method. The influence of Cu concentration and precursor of Sm on the structural, optical and photovoltaic properties of ZnO nanorod arrays was investigated. An X-ray diffraction study showed that the nanorod arrays grown along the (002) plane, i.e., c-axis, had hexagonal wurtzite crystal structure. The lattice strain is present in all samples and shows an increasing trend with Cu/Sm concentration. Field emission scanning electron microscopy was used to investigate the morphology and the nanorod arrays grown vertically on the FTO substrates. The diameter of nanorod arrays ranged from 68 nm to 137 nm and was found highly dependent on Cu concentration and Sm precursor while the density of nanorod arrays almost remains the same. The grown nanorod arrays served as photoelectrodes for fabricating dye-sensitized solar cells (DSSCs). The overall light to electricity conversion efficiency ranged from 1.74% (sample S1, doped with 1 wt% of Sm and 0.0 wt% of Cu) to more than 4.14% (sample S4, doped with 1 wt% of Sm and 1.5 wt% of Cu), which is 60% higher than former sample S1. The increment in DSSCs efficiency is attributed either because of the doping of Sm3+ ions which increase the absorption region of light spectrum by up/down conversion or the doping of Cu ions which decrease the recombination and backward transfer of photo-generated electrons and increase the electron transport mobility. This work indicates that the coupled use of Cu and Sm in ZnO nanorod array films have the potential to enhance the performance of dye-sensitized solar cells.

The dependence of the optical properties of ZnO nanorod arrays on their growth time

As a multifunctional optoelectronic material, ZnO nanorod array has attracted wide attention. In this work, transparent and highly c-axis oriented ZnO nanorod arrays were grown by a simple chemical solution method using zinc acetate and urea as raw materials. Compared with widely used zinc nitrate and hexamethyltetramine, zinc acetate and urea are safer and cheaper. The relationship between crystallization quality, surface defects, optical properties and growth time of ZnO nanorods was investigated. The results show that with the rise of growth time, the length of ZnO nanorods gradually increases, and the crystalline quality gradually improves. The transmittance in the visible range is gradually enhanced, and the absorption edge near 375 nm becomes steeper. The photoluminescence spectra show that as the growth time increases, the intrinsic emission of the ZnO nanorods, i.e., the ultraviolet emission, is gradually enhanced, and the visible emissions related to the defects are gradually weakened. X-ray photoelectron spectroscopy (XPS) analysis show that the oxygen-related defects on the surface of ZnO nanorods gradually decrease with the increase of growth time, which is consistent with the results of the photoluminescence spectra.

Features of the mechanism of gas sensitivity of the zinc oxide nanorods arrays to carbon monoxide

In the paper electrophysical properties of ZnO nanorod arrays are investigated and features of the mechanism of gas sensitivity of the sensors to carbon monoxide (II) and humidity are examined. The ZnO nanorod arrays were grown on p-type silicon substrates. Metal contacts formed over the array of nanorods. Sensory structures were heated to a temperature of 100-200 ° C and subjected to carbon monoxide (II) at a concentration of 100-1000 ppm in nitrogen atmosphere and humidity at 50-75% in air. The results of the research showed that the properties of sensor structures based on ZnO nanorod arrays grown on silicon p-type substrates with respect to carbon monoxide (II) and humidity differ from the properties of chemoresistive sensors based on zinc oxide films.

Analysis of structural and UV photodetecting properties of ZnO nanorod arrays grown on rotating substrate

ZnO nanorods (NRs) were successfully synthesized on seed layered substrate by a novel rotational hydrothermal method. The effect of substrate rotational speed on the growth of ZnO NRs were systematically characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). With an increase of the rotational speed, the mean diameter of the ZnO NRs decreased from ~ 43 nm in ZnO NRs grown on a steady substrate to ~27 nm in a sample with 60 rpm while the number density was increased about one order. The optical studies indicated that band gap of ZnO NRs was shifted towards higher values with increasing speed up to 60 rpm and then decreases gradually. The electrical resistance variation of samples was described according to structural properties of NRs and their coalescence, where the increasing of NRs lateral junction through substrate rotation, improves the electrons transition in samples. Finally, photosensing properties of ZnO based ultraviolet (UV) detectors were investigated. It was observed that the photdetector based on ZnO NRs grown at 120 rpm shows an optimum performance with sensitivity 570 and responsivity 1.9 A/W.

Fabrication and Field Emission Properties of ZnO Nanorod Arrays with Different Orientation Degrees

Fabrication and Field Emission Properties of ZnO Nanorod Arrays with Different Orientation Degrees

Optimized properties of ZnO nanorod arrays grown on graphene oxide seed layer by combined chemical and electrochemical approach

Novel hybrid architectures based on ZnO nanostructures supported on reduced graphene oxide films are reported by a facile two-step aqueous electrochemical approach. Graphene oxide (GO) obtained by oxidizing graphite with either H2SO4:H3PO4 mix or H2SO4 was subjected to electrochemical reduction (ErGO) by constant potential and sweeping potential methods and further employed as seeding layer for electrodeposition of ZnO nanorods. The results showed the GO reduction rate was markedly influenced by oxygen content while Infrared spectroscopy indicated the sweeping potential was effective in removing the carbonyl and alkoxy groups but also as more defect-inducing reduction approach than constant potential, according to the Raman measurements. The subsequent electroreduction of ErGO during the electrodeposition of ZnO resulted in interfacial interaction between the seed layer and ZnO nanorods. H2SO4:H3PO4 mix induced a less disrupted graphitic plane in GO which proved beneficial for the growth of higher density ZnO nanorods with improved crystalline quality. By controlling the chemical introduction/electroreduction conditions for oxygen groups in GO materials, the interfacial interaction with ZnO nanorods and their properties could be tailored in order to obtain high performance nanoplatforms.

Effect of Electrodeposition Time on Microstructure, Wettability and Optical Properties of ZnO Nanorod Arrays

In this article, we fabricated ZnO nanorod arrays on ITO substrates by cathodic electrodeposition method under different electrodeposition times. The XRD results illustrate that all of the peaks can be attributed to the hexagonal wurtzite structure. Besides, the crystallinity and the preferred c-axis orientation increase with longer electrodeposition time. With the increasing electrodeposition time, the diameter of nanorods, the surface roughness and thickness of ZnO nanorod arrays also increased. All samples exhibit hydrophobic behavior and the water contact angle (CA) increases to 120° with the electrodeposition time increases to 120 min. After 10 min of ultraviolet (UV) irradiation, the wettability of the ZnO surfaces turn from hydrophobic to hydrophilicity, and the change of the CA reduction rate are 73.5, 63.5, 48.3 and 24.2%, corresponding to the sample electrodeposited 10, 30, 60 and 120 min, respectively. The intensity of UV emission peak ratio increases from 2.26 to 63.84% while the visible emission peak ratio decreases in PL spectra, which reveals defects decrease when electrodeposition time increases from 10 to 120 min. Raman spectrum shows three peaks which are located at 439, 566 and 1097 cm−1, corresponding to the E2, E1L and E3 mode of ZnO.

Effect of Na Doping on the Nanostructures and Electrical Properties of ZnO Nanorod Arrays

The p-type ZnO nanorod arrays were prepared by doping Na with hydrothermal method. The structural, electrical, and optical properties were explored by XRD, Hall-effect, PL, and Raman spectra. The carrier concentrations and the mobility of Na-doped ZnO nanorod arrays are arranged from1.4×1016 cm−3to1.7×1017 cm−3and 0.45 cm2 v−1 s−1to 106 cm2 v−1 s−1, respectively.

Photoactive area modification in bulk heterojunction organic solar cells using optimization of electrochemically synthesized ZnO nanorods

In this work, ZnO nanorod arrays grown by an electrochemical deposition method are investigated. The crucial parameters of length, diameter, and density of the nanorods are optimized over the synthesize process and nanorods growth time. Crystalline structure, morphologies, and optical properties of ZnO nanorod arrays are studied by different techniques such as x-ray diffraction, scanning electron microscope, atomic force microscope, and UV–visible transmission spectra. The ZnO nanorod arrays are employed in an inverted bulk heterojunction organic solar cell of Poly (3-hexylthiophene):[6-6] Phenyl-(6) butyric acid methyl ester to introduce more surface contact between the electron transporter layer and the active layer. Our results show that the deposition time is a very important factor to achieve the aligned and uniform ZnO nanorods with suitable surface density which is required for effective infiltration of active area into the ZnO nanorod spacing and make a maximum interfacial surface contact for electron collection, as overgrowing causes nanorods to be too dense and thick and results in high resistance and lower visible light transmittance. By optimizing the thickness of the active layer on top of ZnO nanorods, an improved efficiency of 3.17% with a high FF beyond 60% was achieved.

Hydrothermal Synthesis and Properties of ZnO Nanorod Arrays

ZnO nanorods arrays were synthesized by hydrothermal method from an aqueous solution of Zn(CH3COO)2 and C6H12N4 with additives of NH4NO3 and Al(NO3)3. The results show that the use of NH4NO3 in the solution leads to a decrease in nonradiative recombination centers in the ZnO nanorods by lowering their defect density. The reduction of the nonradiative recombination in ZnO nanorods results in a descent in the Stokes shift of the nanorods by 49%. In addition, the optical band gap of the ZnO nanorods could be adjusted in a range of 3.36-3.57 eV by controlling the additives concentration in the solution. The increase of the carrier concentration as a result of the Al doping leads to a blue shift of the optical band gap of the ZnO nanorods to 3.56-3.57 eV, which can be ascribed to the Burstein-Moss effect.

Characterization of Boron-Doped ZnO Nanorods Fabricated Using Diborane Plasma

ZnO nanowire or nanorod arrays have caused great interest owing to their unique properties and versatile applications in short-wavelength lasers, electroluminescent devices, photocatalytic systems, and solar cells, etc. The electrical and optical properties of ZnO nanorod arrays can be altered and controlled through doping. In this paper, B2H6 plasma treatment was employed to improve the electrical properties of ZnO nanorod arrays prepared by hydrothermal synthesis. A clear decrease in the resistivity of ZnO nanorod arrays with B2H6 plasma treatment was observed. Moreover, the measurement results of XPS and Hall measurement show that the B2H6 plasma treatment can be used to achieve n-type doping via B atoms substitution for Zn atoms.

Effect of buffer layer on growth and properties of ZnO nanorod arrays

ZnO nanorods arrays on ZnO buffered Si substrates have been obtained by conventional chemical vapor deposition. The influence of ZnO buffer layer on the growth and properties of the ZnO nanorods have been studied. The morphology and the alignment ordering of ZnO nanorods arrays were greatly affected by the thickness of ZnO buffers. Photoluminescence and field emission properties can be enhanced by modulating the thicknesses of the ZnO buffer layers. ZnO nanorods with the best crystallinity and the highest ordering were obtained with 50-nm-thick ZnO buffer layer, which exhibits the strongest UV emission.

Field emission properties of ZnO nanorod arrays by few seed layers assisted growth

ZnO nanorod arrays were grown on Si substrate by a simple two-step process with sol–gel and hydrothermal methods. To investigate the effect of seed layers on the growth of ZnO nanorods, different numbers of the seed layers have been spin-coated on the substrates. The morphologies of ZnO nanorods including diameter, density, length, and orientation have been studied. The crystallization and band structure have also been discussed. The correlation between the nanorod arrays grown on different seed layers and field emission (FE) properties has also been analyzed. The ZnO nanorod array grown on 4 seed layers possesses the best field emission properties, including a lowest turn-on electric field of 13.3V/μm and largest field emission current. It can be attributed to the higher field enhancement factor, the vertical orientation, larger density, and better conductivity of the nanorod arrays.

Effect of hydroxide anion generating agents on growth and properties of ZnO nanorod arrays

In chemical growth of 1-D ZnO nanorods the selection of hydroxide anion generating agent plays a crucial role in determining the growth rate and morphological features. Due to misconception regarding the role of hexamethylenetetramine (HMTA) in the growth of ZnO nanorods, it is heavily used as hydroxide anion generating agent for ZnO nanorod growth. Though it needs repetitive renovation of growth solution and longer time deposition for the growth of high aspect ratio ZnO nanorods. Here we have carried out a comparative study on the effect of hydroxide anion generating agents (HMTA and ammonia) on growth, morphological, structural, chemical, optical, and photo-electrochemical properties of ZnO nanorods, in view to assist in the selection of the these agents in ZnO nanorod growth.

Controlling the hydrothermal growth and the properties of ZnO nanorod arrays by pre-treating the seed layer

Annealing or plasma pre-treating the ZnO seed layer influences the nucleation and hydrothermal growth of ZnO nanorods and their photoluminescence.

Growth temperature dependent properties of ZnO nanorod arrays on glass substrate prepared by wet chemical method

In this work, ZnO nanorod arrays were grown on glass substrate by the wet chemical method, and the effect of synthesis temperature on the properties was investigated. The grown nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman and Photoluminescence (PL) measurements. XRD pattern showed that nanorod prepared at 80°C and 90°C has high crystallinity with wurtzite structure and orientated along the c-axis. However, nanorods were not formed at 60°C and 70°C due to less energy supply for the growth of the ZnO. FE-SEM results showed that the morphology and the size of ZnO can be effectively controlled. In particular, as the temperature increased, diameter of the nanorod was increased while length decreased. Raman scattering spectra of ZnO nanorod arrays revealed the characteristic E2high mode that is related to the vibration of oxygen atoms in the wurtzite ZnO. Room-temperature PL spectra of the ZnO nanorods revealed a near-band-edge (NBE) emission peak. The NBE (UV light emission) band at ~383nm might be attributed to the recombination of free exciton. The narrow full-width at half-maximum (FWHM) of the UV emission indicated that ZnO nanorods had high crystallinity.

Effect of growth temperature on the structure and optical properties of ZnO nanorod arrays grown on ITO substrate

ZnO nanorod arrays have been successfully prepared on ITO substrate by a chemical‐bath deposition method at different growth temperatures. The influence of the growth temperature on the morphology and microstructure of the ZnO nanorods was investigated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The results showed that the diameter of the ZnO nanorods decreased and the size of the nanocrystals increased with increasing growth temperature. Optical absorption measurements showed the absorption band edge has shifted to a lower‐energy region due to the quantum size effect. Green emission and UV emission bands were observed and they are found to be temperature dependent, which indicates that the deep‐level emission and band‐edge emission of ZnO nanorods is closely related to the rod diameter, and the related mechanism is discussed.

Growth and optical properties of ZnO nanorod arrays on Al-doped ZnO transparent conductive film

ZnO nanorod arrays (NRAs) on transparent conductive oxide (TCO) films have been grown by a solution-free, catalyst-free, vapor-phase synthesis method at 600°C. TCO films, Al-doped ZnO films, were deposited on quartz substrates by magnetron sputtering. In order to study the effect of the growth duration on the morphological and optical properties of NRAs, the growth duration was changed from 3 to 12 min. The results show that the electrical performance of the TCO films does not degrade after the growth of NRAs and the nanorods are highly crystalline. As the growth duration increases from 3 to 8 min, the diffuse transmittance of the samples decreases, while the total transmittance and UV emission enhance. Two possible nanorod self-attraction models were proposed to interpret the phenomena in the sample with 9-min growth duration. The sample with 8-min growth duration has the highest total transmittance of 87.0%, proper density about 75 μm−2, diameter about 26 nm, and length about 500 nm, indicating that it can be used in hybrid solar cells.