Structure Of ZnO Research Articles

Synthesis of zinc oxide semiconductor nanoparticles using natural extract: a systematic evaluation of cationic dye photodegradation influenced by extract concentration, catalyst dose, and pH.

This work obtained zinc oxide nanoparticles (ZnO NPs) using organic components extracted from Waltheria americana at different concentrations. ZnO materials were subsequently applied in the photodegradation of two cationic dyes, Rhodamine B (RB) and methylene blue (MB), at different doses of catalyst and pH. The crystallinity and hexagonal Wurtzite structure of ZnO were established through XRD analysis. The Zn-O bond in the ZnO NPs was confirmed in the FTIR, with the characteristic signals observed in the fingerprint region at ~ 400cm-1. SEM and TEM revealed the formation of quasi-spherical particles with an average size ranging from 2 to 12nm, depending on extract concentrations during synthesis. UV-Vis studies indicated the optical bandgap of ZnO, with values below 3eV, also dependent on extract concentration. PL analysis revealed the recombination of free excitons and defects in ZnO. Photocatalytic studies of ZnO materials demonstrated excellent degradation efficiency of RB and MB dyes, which was influenced by the extract concentration of NPs, while the degradation of MB was enhanced with a 1:1 dye-to-catalyst ratio under acidic conditions. In contrast, due to RB more complex structure, an increased ratio of 1:1 to 1:3 and acidic pH conditions improved its degradation. Green-synthesized ZnO NPs using photocatalysis techniques exhibit significant potential as eco-friendly alternatives for removing contaminants from water.

ZnO Nanowall Network-Based Tactile/Gesture Sensors and Prediction with Machine Learning.

In low-dimensional material systems, augmented physical and chemical properties may be witnessed through a unique morphological evolution. Here, we report the development of an optimized nanowall network of ZnO for the fabrication of a flexible single-electrode triboelectric nanogenerator (STENG)-based tactile and gesture sensors. The chemically grown nanowall network with an adequate pore area endows superior triboelectric output (current ∼0.6 μA and power ∼20 μW/cm2) by offering an optimum surface area and dielectric constant for pressure sensing applications. The rational comparison of the triboelectric properties of nanowall and nanorod structures of ZnO reveals that the higher surface area offered by the hollow walls leads to superior output characteristics. The demonstration of pressure sensitivity of the STENG ∼1 V/N is promising for self-powered tactile sensing applications. The array of STENG sensors, when attached to a user hand, generates distinguishable signals while holding objects of varying curvature and mass. Again, the observation of sensitivity of ∼0.1 V per degree during finger movement activity indicates the gesture sensing ability of the nanowall-based TENG system, facilitating sign language expression through the movement of fingers. Further, the generated electrical signals during tactile and gesture sensing can be classified and recognized through the deployment of machine learning (ML) techniques. In fact, the implementation of Random Forest and K-Nearest Neighbor models has offered an accuracy of 96% while recognizing the output signals generated by the sensor arrays. The demonstration of superior sensing characteristics with the optimized nanowall network may be advantageous in innovating prototype sensors for the differently abled people to distinguish or classify objects on the basis of material, morphology, and mass during their regular activities.

Fabrication and Potential Characterization of Silver‐Doped Zinc Oxide Glucose Biosensor

This work is devoted to studying and manufacturing a highly sensitive nonenzymatic glucose biosensing system of metal oxides via the sol–gel technique. The X‐ray diffraction patterns of all the prepared samples confirm that the samples present hexagonal crystal lattice structures of ZnO and Ag–ZnO nanoparticles. Ultraviolet (UV) analysis of all the samples is carried out to evaluate the absorption of silver in the UV region for electrical and chronoamperometric analysis. The transmittance of all the samples is observed, and the maximum transmittance is 11% for 4% AgZnO. Fourier transform infrared spectroscopy reveal the functional group stretching and vibration of the particles at different wavelength ranges. Scanning electron microsocpy analysis reveals the grain size and morphology of the samples, which decrease with increasing doping agent. Chronoamperometric analysis of all the samples reveals that the value increases with time for the 4% doped sample. The sensing response is also observed and is enhanced with increasing temperature for the 4% doped sample. The sensing response of the samples coated with carbon fiber electrodes is assessed from −0.2 to +0.5 V at a scan rate of 50 mV s−1.

ZnO@In2O3 Core-Shell Heterojunctions Constructed With ZIF-8 and MIL-68 (In) for Improving Photogenerated Carrier Transfer Process.

The realization of fast carrier transport can effectively enhance photocatalytic performance. A core-shell structure of ZnO and In2O3 is successfully constructed by using MIL-68 (In) and ZIF-8 as a substrate, forming a heterojunction. This MOF-derived core-shell heterojunction inherits the advantages of ZIF-8, with pores facilitating carriers transfer to the surface for reactions and a large specific surface area providing more active sites. This Z-scheme heterojunction of ZnO and In2O3 can effectively separate and improve the utilization of photogenerated carriers. The well-designed interface of the core-shell structure achieves the rapid transfer of photogenerated carriers. The photocatalytic degradation capability of ZnO@ In2O3 is enhanced by the synergistic effect of Z-scheme heterojunction and core-shell structure. This work provides insight into the investigation of constructing core-shell heterojunctions.

First-principle calculation of the electronic structure and optical properties of ZnO and Al:ZnO

First-principle calculation of the electronic structure and optical properties of ZnO and Al:ZnO

Development of a new carbon xerogel/ZnO/BaSnO3 photocatalyst for solar and visible light photodegradation of salicylic acid

A novel carbon xerogel/ZnO/BaSnO3 photocatalyst was developed, characterized, and evaluated for the photodegradation of salicylic acid (SA) under solar and visible radiation. The development of the proposed photocatalyst involved the investigation of multiple synthesis parameters, aiming to optimize the photocatalytic activity of the ternary system. The best photocatalytic efficiency was obtained at 5 % w/w BaSnO3, 0.375 g of added tannin, and calcination temperature of 600 °C, yielding the 0.375CX/ZnO/BaSnO3 5 % 600 °C photocatalyst. After thorough characterization, it was concluded that the ternary materials are composed of a mixture of crystalline ZnO and BaSnO3 structures and carbon xerogel (CX). Additionally, the ternary materials displayed significant capacity to absorb visible radiation, mostly due to CX addition. Morphology-wise, the 0.375CX/ZnO/BaSnO3 5 % 600 °C was composed of nodular and polyhedral nanometric particles, displaying higher surface area when compared to materials without CX. Through chronoamperometry and electrochemical impedance spectroscopy, it was determined that the optimized ternary material achieved the highest photocurrent generation and lowest charge transfer resistance among the materials evaluated, indicating a superior photocatalytic activity. Photocatalytic tests demonstrated the superiority of the ternary system in the degradation of SA under solar and visible light irradiation, achieving 93 % and 52.3 % degradation after 5 h, respectively. The superior mineralization of SA (72.2 %) achieved by the optimized ternary material under solar radiation further demonstrated its increased efficacy. The suppression methodology allowed for the identification of the hydroxyl radical as the major active species in the SA degradation. A Z-type heterojunction was proposed for the ternary system, based on the staggered band alignment between ZnO and BaSnO3 and the role of CX as a solid-state mediator, possibly leading to effective charge separation and enhanced redox activity. Phytotoxicity tests showed favorable Lactuca sativa growth in SA solutions treated with 0.375CX/ZnO/BaSnO3 5 % 600 °C (especially under solar radiation), indicating reduced toxicity.

Nickel-decorated ZnO nanoparticles for effective solar reduction of hexavalent chromium and removal of selected pharmaceuticals

The efficient visible light driven photocatalytic reduction of hexavalent chromium, Cr(VI) was demonstrated using ZnO nanoparticles (NPs) decorated with oxo-clusters of transition metals. The ZnO NPs were synthesized by a facile one-pot solvothermal synthesis followed by a fast microwave-assisted (MW) grafting of transition metals on the surface of NPs. Nickel was found to be the most active transition metal for photocatalytic activity as demonstrated by reduction of Cr(VI) to Cr(III). The optimally grafted samples contained 0.5 wt% Ni and increased photocatalytic activity by almost one-fold. The oxo-clusters did not enter the lattice of ZnO but rather resided on the surface and their efficient bonding to the ZnO surface was proved by Raman, TEM and X-Ray absorption techniques. Influence of MW power was studied and shown that excessive power load leads to formation of elongated structures of ZnO which decreases the photocatalytic activity. It was demonstrated by measuring fluorescent radical products that electrons, efficiently transferred via oxygen, were the main active species in combination with the unchanged oxidation power of holes and •OH in the grafted samples. The applicability of the materials was tested in immobilized plug flow photoreactor system degrading five pharmaceuticals simultaneously where their long-term use was shown.

Dual Eu3+ and Er3+ doping in ZnO nanoporous 2D frameworks for tuning photocatalytic activity, linear and non-linear optical response

Recent days, the greater attention of research materials are focusing on the porous nano frame structure due to their distinctive properties and high photocatalytic activity. The porous defective materials revealed a significant role in numerous research fields like sensors, catalysts, energy production, magnetic memory storage, bio medical etc. In our work, pure ZnO and 4f shell shielded rare earth metals doped ZnO metal oxide nanomaterials attributed in the photocatalytic dye degradation, non-linear optical and magnetic properties. We were synthesized pure ZnO and ZnO0.1–2xEuxErxHMT0.1–2x (2x = 0.025,0.05,0.075, 0.010 wt%) nanoparticles using a straightforward hydrothermal route. The hexagonal wurtzite structure of ZnO and Eu:Er-doped ZnO (Eu:Er@ZnO) exhibited by PXRD, and the optical bandgap (Eg) range from 3.14 eV to 3.18 eV was determined by Tauc relation (αhγ)2 = 0. The porous nanoplate morphology of as-synthesized materials revealed by HR-SEM and HR-TEM techniques. All synthesized materials exposed weak ferromagnetic property nature by VSM studies. Among all the synthesized materials, the 0.0025 wt% Eu:Er@ZnO nanoparticles exhibited porous nanoplate structures capable of catalyzing the breakdown of reactive black 5 (RB5) dye, achieving a photocatalytic activity of 93.2 % after 65 min of UV light exposure. The dopant concentration significantly influenced this photocatalytic activity, with lower concentrations showing enhanced performance, particularly in acidic conditions. Moreover, all synthesized porous nano-plate materials followed pseudo-first-order kinetics. Additionally, the Z-scan technique was employed to assess the nonlinear optical properties of the synthesized materials using Q-switched nanosecond Nd laser pulses at 532 nm wavelength. The open-aperture Z-scan revealed reverse saturable absorption (RSA) in all samples. The Eu:Er@ZnO porous nano-plates exhibited promising nonlinear absorption characteristics, with a higher nonlinear absorption coefficient ranging from 5.21 to 7.84 × 10−11 m/W and a lower optical limiting threshold between 0.87 and 0.95 × 1012 W/m2.

Investigation of Spintronic Properties of Transition Metal Doped ZnO Thin Films Produced by Sol-Gel Spin Coating

Transition metal-doped diluted semiconductor materials have attracted significant interest in spintronic applications. In order to investigate the structural, optical, electrochemical, and magnetic properties of these diluted magnetic semiconductors, transition metal-doped ZnO thin films were successfully produced at room temperature using a low-cost sol-gel spin coating technique with the same molar ratios. XRD analyses revealed that all samples adopted the crystal structure of ZnO. Optical measurements indicated high transparency in the visible region for all samples, while electrical measurements confirmed that all samples were n-type semiconductors. Finally, magnetic measurements showed that pure ZnO and Al-doped ZnO exhibited diamagnetic behavior, while Ni and Co doped ZnO displayed magnetic behavior. These results show that Co and Ni-doped ZnO films can be used as diluted magnetic semiconductor materials in spintronic applications.

Biogenic fabrication of NiO-ZnO-CaO ternary nanocomposite using Azadirachta Indica (Neem) leaves extract with proficient photocatalytic degradation of rhodamine B dye

In the current study, a ternary nanocomposite (NiO–ZnO–CaO) was successfully synthesized through the co-precipitation method using Azadirachta Indica (neem) leaves extract as green approach. The characterization of prepared nanocomposite was conducted using FT-IR, XRD, SEM and EDS to determine the metal oxides absorption bands, structural properties, elemental composition, and surface morphology of the nanocomposite. FT-IR analysis revealed characteristic vibrational peaks at 621, 684, and 721 cm−1, corresponding to Ni-O, Zn-O, and Ca-O bond vibrations, respectively. XRD patterns showed distinct diffraction peaks, indicative of the hexagonal structure of ZnO and the cubic structures of NiO and CaO. EDS analysis confirmed the presence of calcium, nickel, zinc, and oxygen with weight percentages of 9.2%, 14.4%, 15.1%, and 20.9%, respectively. SEM images displayed an irregular cube like morphology with noticeable clustering within the nanocomposite. The ternary nanocomposite was employed as photocatalyst and exhibited degradation efficiency (97%) against rhodamine B dye under 180 min of irradiation time. The kinetic studies of dye on the photocatalyst surface were accurately explained by a first-order kinetics model, with all R2 > 95, signifying a strong correlation between time and dye concentration. The potocatalytic degradation mechanism of ternary nanocomposite was proposed based on band positions of of NiO, ZnO and CaO forming double type II heterojunction. Furthermore, species trapping experiments employing different scavengers were carried out, revealing the active participation of OH● and O2●─ radicals in the degradation mechanism.

Laser-induced in-situ electrohydrodynamic jet printing of micro/nanoscale hierarchical structure

With the rapid advancement of micro/nanoscale devices, there is a growing demand for hierarchical micro/nano porous-structure, particularly in fields of high-performance sensors, electrochemical energy storage, and photocatalysis. The fabrication methods for hierarchical micro/nano-porous structures have been limited by complex processes and high costs, making further development and application difficult. In this paper, a novel strategy of laser-induced in-situ electrohydrodynamic jet (E-Jet) printing of hierarchical micro/nano-porous structures was proposed. Based on the mechanism of high-energy laser beam induction on the jet, it successfully fabricated hierarchical porous ZnO structures from nanoscale to dozens of microns. The jet size focusing and solidification behavior were analyzed by combining experimental and simulative exploration. The resultant effects of the thermal field, flow field, and laser field on the spatial temperature distribution and the jetting morphology were examined. Furthermore, the laser-induced influence on the morphology of the printed micro/nano-porous ZnO structures was explored. Meanwhile, the performance of micro/nano-porous ZnO photoelectric sensors printed by E-Jet under different laser powers was investigated. The laser-induced in-situ E-Jet printing method provided an innovative pattern for the high-resolution additive manufacturing of hierarchical porous structures, demonstrating its potential for applications in advanced material and high-performance devices.

Impact of Silver Incorporation and Flash-Lamp-Annealing on the Photocatalytic Response of Sputtered ZnO Films.

Thin films of silver-doped zinc oxide (SZO) were deposited at room temperature using a DC reactive magnetron co-sputtering technique using two independent Zn and Ag targets. The crystallographic structure, chemical composition and surface morphology of SZO films with different silver concentrations were correlated with the photocatalytic (PC) properties. The crystallization of the SZO films was made using millisecond range flash-lamp-annealing (FLA) treatments. FLA induces significant structural ordering of the wurtzite structure and an in-depth redistribution of silver, resulting in the formation of silver agglomerates. The wurtzite ZnO structure is observed for silver contents below 10 at.% where Ag is partially incorporated into the oxide matrix, inducing a decrease in the optical band-gap. Regardless of the silver content, all the as-grown SZO films do not exhibit any significant PC activity. The best PC response is achieved for samples with a relatively low Ag content (2-5 at.%) after FLA treatment. The enhanced PC activity of SZO upon FLA can be attributed to structural ordering and the effective band-gap narrowing through the combination of silver doping and the plasmonic effect caused by the formation of Ag clusters.

Polyvinylpyrrolidone mediated electrospun ZnO-ZnFe2O4 composite nanofibers for removing malachite green from water

This study explores the application of ZnO-ZnFe2O4 composite nanofibers for the adsorption of Malachite Green (MG) dye from water. The composite nanofibers were fabricated using simple polyvinylpyrrolidone (PVP) mediated electrospinning method by changing zinc and iron precursor weight ratio named as Zn–Fe (1-1), Zn–Fe (2–1) and Zn–Fe (1–2). The diameter of 1D nanofibers was found to be 40–60 nm. The formation of hexagonal wurtzite structure of ZnO and cubic spinel structure of ZnFe2O4 was confirmed by XRD and HRTEM analysis. The effects of various parameters such as pH, contact time and initial concentration on the adsorption process were investigated. The Zn–Fe (1-1) nanofibers showed higher adsorption efficiency than other two. The adsorption results demonstrated excellent adsorption performance, with a maximum adsorption capacity of 146.77 mg/g at pH = 7 for Zn–Fe (1-1). Furthermore, the adsorption kinetics and isotherms were analyzed to understand the adsorption mechanism and equilibrium behaviour. It was found that the nanofibers material can be recycled and reused up to five cycles.

Ultraviolet response of ZnO nanorod/Sb-doped ZnO thin film homojunction structure prepared by all-chemically wet process

In this work, ZnO nanorod/Sb-doped ZnO thin film structure was fabricated and its relevant properties were investigated. The device was prepared by Sb-doped ZnO sol-gel spin coating technique onto ITO substrate annealed in nitrogen atmosphere followed by the hydrothermal process to obtain ZnO nanorod. The crystal structure demonstrates (002) plane dominant hexagonal wurtzite ZnO without phase impurity. The deterioration in the crystal structure of Sb-doped ZnO due to the Sb is incorporated in the ZnO lattice. The element component in each layer is confirmed by depth profile measurement. The low transmittance in the visible region is due to high reflection at the surface of the ZnO nanorod. The electrical measurement confirms that ZnO nanorod/Sb-doped ZnO thin film has p-n homojunction properties under dark conditions and 18 times higher photovoltage than the Sb-doped/undoped ZnO double layer device under UV LED irradiation due to enhanced photon harvesting of ZnO nanorod structure.

Synthesis, characterization, and evaluation of antibacterial and antifungal activities of CuO-ZnO-Co3O4 nanocomposites

The co-precipitation method was used to prepare CuO, ZnO, Co3O4 nanoparticles and CuO-ZnO-Co3O4 nanocomposite. The structural, morphological, and optical properties of the prepared samples were studied using X-ray diffraction (XRD), total reflection X-ray fluorescence (TXRF), transmission electron microscopy (TEM), selected area electron diffraction (SAED), diffuse reflectance spectroscopy (DRS), and zeta potential. XRD analysis revealed that the crystal structures of CuO, ZnO, and Co3O4 nanoparticles are monoclinic, hexagonal, and cubic, with average crystallite sizes of 30.8 nm, 31.8 nm, and 32.8 nm, respectively. For CuO-ZnO-Co3O4 nanocomposites, the corresponding sizes were 24.9 nm, 13.6 nm, and 16.1 nm. The optical bandgaps of CuO, ZnO, Co3O4 nanoparticles, and CuO-ZnO-Co3O4 nanocomposites were 1.5 eV, 3.14 eV, 1.2 eV, and 1.3 eV, respectively. In this study, the antibacterial activity of CuO-ZnO-Co3O4 nanocomposite against Gram-negative bacteria (E. coli, Klebsiella, pseudomonas, and Salmonella) and Gram-positive bacteria (Staphylococcus aureus) was investigated and compared with the antibiotic Azithromycin. In addition, the effect of the nanocomposite on fungi was studied and compared with the antifungal Mystatin.

Effect of sputter power on red-shifted optoelectronic properties in magnetron sputtered Ag/ZnO thin films

This study explores Ag/ZnO thin films on glass (Corning 0211) substrates, which were deposited using dc/rf magnetron reactive sputtering at varying Ag-sputter powers. The impact of Ag-sputter power on physical properties, such as structural, surface, compositional, optical, and electrical properties, is systematically explored. Grazing angle x-ray diffraction affirms a single-phase hexagonal wurtzite ZnO structure in all films, predominantly oriented along (002) normal to the substrate. Thin films deposited at 90 W Ag-sputter power exhibit superior structural and morphological properties, including greatest crystallite and grain size, minimum stress, and roughness. Electrical studies indicate that the material exhibits a semiconducting nature, with its electrical resistivity decreasing to a minimum of 0.8 Ω cm at 95 W. At this level of Ag sputter power, the films demonstrate low resistivity, high mobility (0.49 cm2/V s), a charge carrier concentration of 9.6 × 1019 cm−3, and an optical transmittance of 79%, along with an optical band gap energy (Eg) of 3.06 eV. This underscores the influence of Ag sputter power in tailoring Ag/ZnO thin films for optoelectronic applications.

Investigating the dielectric and ferromagnetic behaviour of Ni and Co dual doped ZnO for diluted magnetic semiconductor

Herein, Ni/Co co-doped ZnO nanoparticles (NPs) were successfully prepared via chemical co-precipitation process. The structural, purity and crystallite size of as-prepared particles were confirmed by using x-ray diffraction (XRD). The results revealed the hexagonal wurtzite structure of ZnO without any impurity phase of as-prepared samples. The crystallite size decreased from 34.9 to 9.6 nm, whereas lattice strain reduced to 0.00086. The change in crystallite size, lattice parameters, strains and dislocation density further indicates the successful incorporation of dopants in ZnO host lattice. The dielectric properties, ac conductivity, and magnetic behaviour were steadily examined. The dielectric constant has been found to be 1070 with 5wt% at low frequency and become constant at higher frequency. It was revealed that dopant additions lead to attain high dielectric constant and low loss possibly attributed to interface polarization, and dipole polarization due to oxygen vacancy defects. M-H measurement observed that ferromagnetism at room temperature pure and doped ZnO samples. The ferromagnetic behaviour of pure ZnO NPs with Ms = 0.17 emu g−1, Mr = 0.11 emu g−1 and Hc = 67 which was increased to Ms = 0.85 emu g−1 and Mr = 0.65 emu/g for 5wt% Co. This improvement with increasing Co concentration indicates that oxygen defects may stabilize the ferromagnetic order. These interesting features encouraging to use this material for ultrahigh dielectric materials and spintronics.

Analysis of structural, dielectric, magnetic and impedance spectroscopy of ZnO/CuFe2O4 nanocomposites

The nanocomposites of ZnO/CuFe 2 O 4; abbreviated as (ZnO) x /(COF) 1-x (x; 10 ∼ 50 wt%) were prepared by powder mixing method. The x-ray diffraction pattern revealed the formation of nanocomposites (NCs) with inverse spinel structure of COF and hexagonal wurtzite structure of ZnO. The scanning electron microscope analysis depicts the nano-plates like morphology, non-homogenous mixing and agglomeration of particles. The dielectric properties and impedance spectroscopy of NCPs were measured by LCR meter in the frequency range of 1 kHz to 2 MHz. There is decrease in the real and imaginary parts of dielectric constant (ε′ and ε″) were observed with frequency, which is explained by Maxwell–Wagner’s polarization mechanism. The real and imaginary parts of impedance (Z′ and Z″) also show decreasing trend with frequency owing to increase in hopping of charge carriers that result in enhancement of a.c. conductivity (σ a.c ). The impedance spectroscopy shows a semicircular arc at higher frequency which is attributed to the conduction from grains. Finally, the vibrating sample magnetometer result showed the change in the magnetic nature of NCPs; as saturation magnetization (M s ) and coercivity (H c ) decreases substantially with incorporation of non-magnetic ZnO weight fractions.

Optimization of the thermoelectric performance of aluminum-doped zinc oxide-graphene heterojunctions under high temperature and high pressure

High-pressure effects can be used to effectively optimize the thermoelectric performance of wide-bandgap oxides. We build upon this finding to show that the synergistic effects of doping with aluminum and graphene composite give excellent thermoelectric performance under high pressure. By employing the parabolic band model, the Pisarenko curves are derived at different pressures, coupled with the band structure of Al-doped ZnO. An analysis indicates that pressure-induced narrowing of the bandgap in Al-doped ZnO reduces the electron excitation energy, thereby optimizing the electrical properties of the samples. The Debye Callaway model is also used to fit the lattice thermal conductivity of the samples, thus enabling an in-depth analysis of the phonon scattering mechanisms. Our analysis suggests that graphene composites significantly enhance point defect scattering and Umklapp scattering, thus increasing the phonon relaxation time and effectively reducing the lattice thermal conductivity of the samples. The improvement in the figure of merit (zT) of ZnO is attributed to the simultaneous enhancement of its electrical properties under high pressure and the synergistic optimization of reducing the lattice thermal conductivity through doping and composites. In this work, we consider a fixed doping ratio of Al and a constant proportion of graphene composite, and analyze the microstructure and thermoelectric properties of 0.1C–ZnAl0.04O (C–ZnAlO) samples synthesized under pressures ranging from 1 to 5 GPa, with the aim of elucidating the influence of pressure and graphene composite on the electro-acoustic transport properties of ZnO. We find that the zT value for a sample synthesized at 5 GPa is increased to 0.27 at 973 K.

Emission mechanisms in low-threshold UV random laser based on ZnO microrod array

Despite rather extensive study of the random lasing effect in ZnO structures, the issue of the optical gain mechanisms in microstructured ZnO random lasers remains poorly understood. In this work, the radiative properties of an array of vertically aligned ZnO microrods, synthesized by a modified thermal evaporation method, were studied. The microrods exhibited lengths up to 60 μm and diameters ranging from 1 to 5 μm. Random lasing from a microrod array was observed in the near-UV range (with a laser emission peak wavelength of ∼391 nm) with a threshold down to 40 kW/cm2 under optical excitation. An analysis of the nature of optical gain in the grown structure was conducted at various temperatures. It was found that at room temperature, two-phonon-assisted exciton recombination is the main process leading to light amplification.