Optical Properties Of ZnO Research Articles

First-principle calculation of the electronic structures and optical properties of the metallic and nonmetallic elements-doped ZnO on the basis of photocatalysis

In the present paper, the electronic structure and the optical properties of metallic and nonmetallic elements-doped ZnO were investigated based on the principle of photocatalysis by first-principle density functional theory. Element doping shortens the band gap of ZnO. Due to the p-type characteristics, Fe, Cu, B and N doping brings impurity states over the Fermi level of ZnO, resulting in the shortening of the band gap, extending the absorption and utilization of solar light and thus enhancing the photocatalytic properties of ZnO. However, no impurity states appear in the band gap of Cd- and S-doped ZnO due to the intrinsic doping of Cd and S. Further investigations indicate that different doping atoms can indeed alter the near-Fermi level density of states (DOS) of ZnO and their electronic structures via substitution of zinc and oxygen atoms. In addition, the optical properties of ZnO are improved after doped with different atoms by comparing with those of pure ZnO. Due to the difference of their outer shell electrons of the doped atoms, the optical absorption properties of the investigated materials are followed as the following order: Fe-/B-doped ZnO > Cu-/N-doped ZnO > Cd-/S-doped ZnO > pure ZnO.

Mg-doped ZnO nanostructures for efficient Organic Light Emitting Diode

ZnO and Mg-doped ZnO nanostructures have been synthesized by a hydrothermal method for its potential application in Organic Light Emitting Diodes (OLED). Studies have been undertaken for structural as well as optical properties of ZnO after Mg doping with various concentrations. Field Emission Scanning Electron Microscopy with Energy-dispersive X-ray analysis reveals the morphology and chemical composition of nanostructures shows the formation of ZnO rod-like structure which, interestingly, converted into the multi-pod structure with Mg doping. X-ray diffraction reveals the hexagonal phase of the wurtzite structure of ZnO. UV–Visible absorption spectroscopy suggests the exciton characteristic, at room temperature, with band gap variation while Photoluminescence spectra reveal emission in two different spectral regions (ultraviolet and blue). Synthesized materials have been blended with Poly [9, 9-dioctylfluorenyl-2, 7-diyl] (PFO) and prototype OLED has been fabricated using these materials as an emissive layer. An electroluminescence spectrum shows prominent blue emission at 433 nm, 460 nm, and 490 nm at 6 V. Current-Voltage (I-V) characteristics indicate that the OLED device with 10% Mg doping in ZnO is most stable compared to others.

Defect Related Green-Red Luminescence of Sb-Doped ZnO Nanorods Grown by Vapor-Phase Oxidation Method.

Vertically aligned undoped and Sb-doped ZnO (ZnSbO) nanorods were grown by the vapor-phase oxidation process on sapphire substrates at 700 °C using Fe as the catalyst. The effect of Sb doping on surface morphology, structural and optical properties of ZnO were studied. The grown undoped and Sb-doped ZnO nanorods have a hexagonal wurtzite structure with preferential c-axis orientation. The as-grown nanorods morphology has shown length of 2-5 μm and a diameter of 100-250 nm. An elongated nanorods and high aspect ratio was observed in Sb-doped ZnO. The undoped ZnO nanorods showed a strong and sharp ultraviolet (UV) emission centered at ~381 nm, whereas Sb-doped ZnO nanorods exhibited two defect related emissions centered at ~530 nm (green) and ~630 nm (red) with a suppressed UV emission. The dominance of the red emission in the nanorods indicates that it exhibits a much higher defect caused by the Sb doping.

Structural, Morphological and Optical Properties of ZnO, ZnO:Ni2+ and ZnO:Co2+ Nanostructures by Hydrothermal Process and Their Photocatalytic Activity

ZnO, ZnO:Ni2+ and ZnO:Co2+ nanoparticles (NPs) were prepared via hydrothermal process. The synthesized samples were characterized by using various techniques such as, FT-IR, powder XRD, SEM-EDX, TEM-SAED, UV–Visible, PL and BET. The as-synthesized ZnO, ZnO:Ni2+ and ZnO:Co2+ NPs exhibit strong physicochemical properties including in structural, surface morphology, chemical composition, surface area, optical and photocatalytic activity were comparatively investigated as function of Ni2+ and Co2+ doping. UV–Visible absorption spectra exhibit blue shifted in absorption edge of ZnO, ZnO:Ni2+ and ZnO:Co2+ NPs compared to bulk counterparts. The photocatalytic activity of the ZnO, ZnO:Ni2+ and ZnO:Co2+ NPs have been evaluated by monitoring the degradation of MeB and RhB dyes under UV light irradiation. In degradation efficiency, 84 and 93% of the MeB and RhB dyes is degraded in the presence of the ZnO:Ni2+ and ZnO:Co2+ photocatalyst under optimum experimental conditions. The rate of de-coloration of MeB and RhB dyes are detected by UV–Visible absorption spectroscopy and organic dye mineralization is confirmed by table of carbon study. In addition, the mechanism of the photocatalytic degradation of MeB and RhB dyes has been briefly discussed.

Effects of a surfactant on the morphology and photocatalytic properties of polycrystalline Fe-doped ZnO powders

In this study, we compared the structural, morphological, and optical properties of a series of Zn1-xFexO (x = 0.00, 0.01, and 0.03) powders synthesized via a hydrothermal route with and without cetyltrimethylammonium bromide as a cationic surfactant. Our results highlighted the critical effects of the surfactant and the iron concentration on the structure, morphology, and optical properties of ZnO. X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy analyses indicated the presence of a single phase comprising ZnO with a hexagonal wurtzite structure in all samples and a single oxidation state (+3) for the iron (Fe3+) that replaced Zn2+ in the ZnO structure. Morphological investigations by scanning electron microscopy showed that the surfactant and Fe3+ dopant greatly affected the shape of the ZnO grains, which varied between sheets and rod-like flowers. We found that the morphological and photocatalytic properties of the two series of samples comprising iron-doped ZnO with and without the surfactant were in opposition. We propose a possible growth mechanism for the ZnO polycrystalline grains in the presence of the Fe dopant and/or surfactant. The photocatalytic properties increased for the samples prepared with surfactant as the iron content increased, which was confirmed by ultraviolet-visible reflection measurements. The photocatalytic activities of the samples prepared without surfactant decreased in both the ultraviolet and visible spectral regions as the iron content increased in the samples.

Structural, morphological, optical and biological properties of pure ZnO and agar/zinc oxide nanocomposites

In this work, ZnO nanoparticles were prepared by in situ chemical precipitation method in the presence of Agar biopolymer. The influence of Agar concentrations on the structural, morphological and optical properties of ZnO have been investigated. The XRD pattern of Pure ZnO and Agar/ZnO nanocomposites indicates the hexagonal wurtzite phase of ZnO. The crystallite size of pure ZnO and Agar/ZnO nanocomposites was found to be in the range of 35.5 to 19.73 nm. Pure ZnO and Agar/ZnO nanocomposites showed nanospheroid and nanopaddy shaped morphology from FESEM studies. The interplanar distance observed from the HRTEM image confirms the plane of the prepared material. The elemental composition of the samples were characterized by EDX. The optical properties of Pure ZnO and Agar/ZnO nanocomposites were characterized by UV, FTIR and PL. The band gap of Agar/ZnO nanocomposites were varied with the Agar concentration. Oxygen vacancy induced photoluminescence of ZnO are observed and its intensity is found to be increased linearly with the Agar concentration. The antibacterial activity of ZnO and Agar/ZnO nanocomposites was evaluated by disc diffusion method against Gram-positive (B.subtilis) and Gram-negative (P. aeruginosa) bacteria. The cytotoxicity of Agar/ZnO nanocomposites was studied against Normal (L929) and Breast cancer cell line (MB231). The result of this investigation reveals that the Agar/ZnO nanocomposites deliver a dose dependent toxicity in normal and cancer cell line.

Electronic and Optical Properties of Atomic Layer-Deposited ZnO and TiO2

Metal oxides are attractive for thin film optoelectronic applications. Due to their wide energy bandgaps, ZnO and TiO2 are being investigated by many researchers. Here, we have studied the electrical and optical properties of ZnO and TiO2 as a function of deposition and post-annealing conditions. Atomic layer deposition (ALD) is a novel thin film deposition technique where the growth conditions can be controlled down to atomic precision. ALD-grown ZnO films are shown to exhibit tunable optical absorption properties in the visible and infrared region. Furthermore, the growth temperature and post-annealing conditions of ZnO and TiO2 affect the electrical properties which are investigated using ALD-grown metal oxide as the electron transport channel on thin film field-effect devices.

Photocatalytic Activity of High Energy Ball Mill Derived (ZnO)1−x(C)x Nanocomposite

Nanocomposite of (ZnO)1−x(C)x in two different ratio were prepared by high energy Fritsch Pulveristte—P5 planetary ball mill using tungsten carbide vials and balls. Structural analysis such as phase and lattice strain were studied using Seifert X-ray powder diffractometer using Cu-kα1 radiation (λ = 1.5406 A) in a wide range of Bragg angles 2θ (20° to 80°) with a scanning rate of 0.2°/min. In order to study the effect of the presence of carbon on the optical properties of ZnO, diffused reflectance spectroscopic analysis (DRS) was performed using the Varian Cary 5000 spectrophotometer. Further, photocatalytic activity of (ZnO)1−x(C)x nanocomposite were studied under visible light illumination. The observed experimental results will be discussed in detail.

The Sputter Time Duration Effect on the Structural and Optical Properties of Zinc Oxide by RF Magnetron Sputtering

Nanocrystalline ZnO thin films have been fabricated by an RF magnetron sputtering method for the different time duration. The effect of process parameters on the structural, morphological and Optical properties of ZnO were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Photoluminescence and UV-Vis. Spectrometer. All of the films were polycrystalline, and the preferred crystal plane orientation was (101) corresponding to 2𝜃 = 36.57∘, the crystallite sizes were increased from 12 nm to 18 nm as in XRD calculations and increase from 24nm to 33 nm as in SEM image. Optical constants, such as refractive index n, were determined from the transmittance spectrum in the ultraviolet -visible. The refractive index varies in the range of 1.664 to 8.706 with an increase in deposition time. Optical energy gap estimated from the transmittance (3.304 eV) and the PL (3.44 eV) shows good agreement and increased as the time duration was increased.

Synthesis, structural and optical properties of ZnO spindle/reduced graphene oxide composites with enhanced photocatalytic activity under visible light irradiation

In the present work, spindle-shaped ZnO and reduced graphene oxide sheets were successfully synthesized by a hydrothermal method and then ZnO/r-GO composite was prepared by a direct solution mixing method. Various characterization results confirmed the interior and surface decoration of spindle-shaped ZnO on the reduced graphene oxide sheets. The phase formation, crystalline structure, morphology, surface states and optical properties were characterized using Powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and UV–Vis spectroscopy. The X-ray diffraction analysis showed the formation of the hexagonal wurtzite crystalline structure of ZnO with high crystalline quality. The band gap of the ZnO/r-GO composite was found to be low (3.03eV) compared to the band gap of spindle shaped ZnO (3.13 eV), as calculated from optical studies. The spindle-like morphology of the single crystalline ZnO was clearly shown in the electron microscopic images. The chemical bonding and surface states of the samples were studied using XPS measurement. Moreover, a possible growth mechanism for the ZnO spindle was proposed. The catalytic activity of the as-synthesized samples was evaluated for the photodegradation of methylene blue under visible light irradiation. Among the synthesized samples, the ZnO/r-GO composite showed higher degradation efficiency of 93% and successfully reused for four consecutive run without any activity loss.

Surface plasmon resonance aided analysis of quantum wells for photonic device applications

The present report aims at analyzing the quantum well (QW) structures using the highly sensitive surface plasmon resonance (SPR) technique in Otto configuration. The optical properties of ZnO and Ni doped ZnO (NiZnO) based QW structures grown using Pulsed laser deposition technique are investigated. An optimal value of QW width (8nm) is deduced from the SPR study for maximum charge carrier confinement which is in coherence with the photoluminescence (PL) studies conducted on the same QW structures. The metal-dielectric interfaces were modelled primarily for the design of QW structures to be analysed experimentally. The mechanism behind the coupling of QWs with SP excitation has been proposed theoretically and experimentally to substantiate the results of PL and SPR studies. The variation in the SPR curves observed as a function of the QW width can be attributed to the interaction of evanescent SP field originating at the Au/QW interface and electroabsorptive behaviour of QWs towards the SP field.

The Effect of Thickness and Annealing on Structural and Optical Properties of ZnO: Al Thin Films

ZnO: Al transparent conductive thin films was prepared by home-made chemical vapor deposition system at (500oC). Zinc acetate dehydrate precursor was used to obtain ZnO films and aluminum nitrate nonahydrate as a dopant source to prepare different thickness (0.539µm, 0.369µm, 0.227µm, 0.057µm) of ZnO: Al thin films. In this study the structural and optical properties of thin films were investigated. X-ray measurements revealed that films structure was polycrystalline of hexagonal quartzite type with preferential orientation along (002) direction. The surface morphology of the films was determined by atomic force microscope (AFM) and the measurements indicate an increase in the smoothness of the upper surfaces after annealing (2.93 nm-1.6nm), and the grain sizes of the sample was in the Nano metric scale. The effect of thickness and annealing time on optical properties of the films were investigated. From the measurements, it was found that the transmittance decrease with increasing thickness. On the other hand, the transmittance and the optical gap increase with increasing the annealing time for low thicknesses, while for the higher thicknesses, a little changes were observed

Effect of Ag Doping on the Electronic Structure and Optical Properties of ZnO(0001) Surface

Using first-principle calculations, the geometrical structure, the electronic and optical properties of Ag-doped ZnO(0001) surface have been investigated. We found that Ag-doped ZnO(0001) surface is more easily formed on the first layer. On the other hand, the doped surface has gradually become an equipotential body, showing obvious metallic characteristics. We found that a new peak appeared in the low energy region after Ag doping, which was mainly due to the electron transition between the two orbital levels of Ag-4d and O-2p.

Effect of Ag Doping on the Electronic Structure and Optical Properties of ZnO(0001) Surface

Using first-principle calculations, the geometrical structure, the electronic and optical properties of Ag-doped ZnO(0001) surface have been investigated. We found that Ag-doped ZnO(0001) surface is more easily formed on the first layer. On the other hand, the doped surface has gradually become an equipotential body, showing obvious metallic characteristics. We found that a new peak appeared in the low energy region after Ag doping, which was mainly due to the electron transition between the two orbital levels of Ag-4d and O-2p.

Structural and Optical Properties of ZnO and Co Doped ZnO Thin Films Prepared by Sol-Gel

Structural and Optical Properties of ZnO and Co Doped ZnO Thin Films Prepared by Sol-Gel

Solution, Solid-State Two Step Synthesis and Optical Properties of ZnO and SnO2 Nanoparticles and Their Nanocomposites with SiO2

Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2·Chitosan and SnCl2·Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 °C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2·Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2·Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2·Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices.

Structural, Morphological, and Optical Properties of Zinc Oxide Nanorods for LPG sensor

In this research, zinc oxide nanorods were prepared by chemical bath deposition method (CBD) through using raw materials on the glass substrate. The crystalline structure, surface morphology, elemental composition and optical properties of ZnO were studied by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectrometers (energy-dispersive X-ray spectroscopy EDXS), and UV-vis spectrophotometer, respectively. The sensing properties of the ZnO nanorod arrays were determined for different flows and temperatures. The results indicate that the ZnO nanorods have good sensitivity and stability when compared with other traditional ZnO films.

Electrodeposited ZnO morphology transformations under the influence of SeO2 additive: Rods, disks, nanosheets network

In this study various morphologies of ZnO including rods, disks, and nanosheets network were synthesised by electrodeposition method. The influence of the SeO2 additive concentration on morphological, structural, and optical properties of ZnO was studied by using scanning electron microscopy, X-ray diffractometry (XRD), energy-dispersive X-ray analysis (EDX), optical (UV–Vis) and photoluminescence (PL) spectroscopy methods. The formation of the disk-like ZnO structure with a diameter of ca. 300–500nm and thickness ca. 80–100nm was observed when 0.03mmol/L of SeO2 was added to the solution. Further increase of dopant concentration up to 0.2mmol/L in the solution yielded a highly-porous network structure composed of thin nanosheets with a wall thickness of ca. 20nm. According to the XRD results, all structures were composed of ZnO, rod-like crystals were strongly c-axis oriented, whereas disks and nanosheets network structures were a-axis oriented. EDX analysis revealed that Se was present in the disks and nanosheets structures. PL study of the rod sample showed UV emission at ~370nm, whereas the disks and nanosheets network showed intense deep-level emission band centred at ~540nm. The disks and nanosheets exhibited total transmittance of ∼80–90% in the region of 380–780nm, whereas transmittance of the rods was increasing from 5% to 50% in this region. According to haze factor calculations, samples possessed scattering ability of 20% for disks, 45% for sheets and ca. 50% for rods. The probable mechanism for the formation of ZnO structures was discussed in detail.

Effects of Eu doping and O vacancy on the magnetic and optical properties of ZnO

We calculated the electronic structure and optical properties of Eu mono-doped ZnO systems with or without O vacancy. We also determined the relative energy of ferromagnetic and antiferromagnetic orders of Eu-double-doped ZnO systems. The double-doped systems possess high Curie temperature and achieve room temperature ferromagnetism. The magnetism in the Eu mono-doped system without O vacancy is caused by the -Eu3+-O2--Eu3+- bound magnetopolaron (BMP) model. The magnetism of Eu mono-doped ZnO systems with O vacancy is more stable than that without O vacancy, and such magnetism is attributed to the -Eu3+-VO++-Eu3+- BMP model. The absorption spectrum for mono-doped systems is red shifted, and this finding confirms that Eu-mono-doped ZnO is a candidate photocatalyst for various applications. Therefore, Eu-double-doped ZnO can be practically used as an unambiguous diluted magnetic semiconductor.

First-principles study of electronic and optical properties of solid-solution ZnO1−xSx

We investigated the electronic and optical properties of ZnO under the circumstances of isovalent anionic doping by sulfur. A pseudopotential implementation of density functional theory is applied within the local density approximation to examine the modification of band structure in wurtzite ZnO by sulfur substitution. Although Fermi level position does not change, a strong localization of Zn-[Formula: see text] orbital is found by S-doping. Optical properties and constants are found to strongly depend on the sulfur content at low photon energies.