Co-doped Zinc Oxide Research Articles

Varistor Properties and Aging Behavior of V/Mn/Co/ La/Dy Co-doped Zinc Oxide Ceramics Modified with Various Additives

The effects of additives (Nb, Bi and Cr) on the microstructure, varistor properties, and aging behavior of V/Mn/Co/ La/Dy co-doped zinc oxide ceramics were systematically investigated. An analysis of the microstructure showed that all of the ceramics that were modified with various additives were composed of zinc oxide grain as the main phase, and secondary phases such as Zn3(VO4)2, ZnV2O4, and DyVO4. The Bi2O3-modified samples exhibited the lowest density, the Nb2O5-modified sample exhibited the largest average grain size, and the Cr 2O3-modified samples exhibited the highest breakdown field. All additives improved the non-ohmic coefficient ( α) by either a small or a large margin, and in particular an Nb2O5 additive noticeably increased the non-ohmic coefficient to be as large as 36. The Bi2O3-modified samples exhibited the highest stability with variation rates for the breakdown field and for the non-ohmic coefficient ( α) of -1.2% and -26.3%, respectively, after application of a DC accelerated aging stress of 0.85 EB/85℃/24 h.

Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10−4 Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films.

Aging characteristics of ZnO–V2O5-based varistors for surge protection reliability

The effect of sintering temperature on clamping characteristics and pulse aging behavior of V2O5/MnO2/Nb2O5 co-doped zinc oxide varistors was systematically investigated at 875–950°C. Experimental results related to varistor effect showed that the breakdown field decreased dramatically from 6830 to 968V/cm with the increase in the sintering temperature and the non-ohmic coefficient exhibited a maximum (49.5) at 900°C in the sintering temperature. Varistors sintered at 900°C exhibited the best clamp characteristics for the pulse current of 1–100A, with the clamp voltage ratio of K=1.86–2.77. Varistors sintered at 875°C exhibited the strongest stability; variation rates for the breakdown field, for the non-ohmic coefficient, and for the leakage current density were −14.2%, −63.6%, and 59.0%, respectively, after application of a multi-pulse current of 100A.

First-principles study of p-type nitrogen/aluminum co-doped zinc oxide

First-principles calculations have been performed to investigate the electronic structures and the defects formation energies of the pure and nitrogen/aluminum (N-A1) co-doped zinc oxide. The calculated results of the pure ZnO using LDA+U method show band gap and lattice parameters are in reasonable agreement with previous data. Incorporation of N into ZnO host induces distortions of the lattice. According to the results, the Fermi-level of Al doped ZnO shift upward into conduction band and show n-type conductivity, while codoped structures show p-type conductivity. The defects formation energies of Al doped structure on Zn-rich and O-rich conditions are low. When codoped with N, the complexes exhibit high defects formation energy on O-rich condition, indicating it is difficult to realize p-type ZnO in this case. On Zn-rich condition, the codoped structures display lower defects formation energies and show p-type conductivity. From hole carriers analysis, it is shown that the carriers in N-Al doped ZnO possess a better transfer character. All these results indicate that codoped ZnO structures are beneficial for the realization of p-type ZnO.

Structural, Optical, and Magnetic Properties of Cobalt-Doped Dip Coated ZnO Films

Co-doped zinc oxide thin films (ZnCoO) have been deposited on glass substrates by sol-gel dip coating deposition method. X-ray diffractometer patterns for these thin films prove crystalline behavior with wurtzite structure. The films have lattice parameters similar to that of ZnO. When Zn is replaced by Co, more impurity levels are produced within the bandgap, and more defects are developed. However, Co-doping does not alter the wurzite structure. The bandgap of the films tends to decrease with increasing withdrawal speed. These transparent thin films possess bandgap in the ultra-violet (3.86-3.45 eV) and high transparency throughout the visible spectral region. Ellipsometry also show the same trend for bandgaps (3.83-3.45). Morphological analysis by scanning electron microscope shows surface with porous structure. Magnetic property studied shows the ferromagnetic behavior. Chemical composition of these Co-doped ZnO thin films was investigated through Fourier transform infrared analysis.

Structure analysis on Ni and V co-doped zinc oxide prepared by solid state reactions

Powder samples of ZnO co-doped with Ni and V have been grown by standard solid state reaction technique with varying concentrations 2, 4 and 6 %. The grown samples were found to be dilute magnetic in nature along with semiconducting property. The structure of the grown material was solved using powder X-ray diffraction refinements and the electronic structure of the material was determined by maximum entropy method. Magnetic properties of the samples were studied using vibrating sample magnetometry and the samples exhibited ferromagnetic characteristics at room temperature. Inductively coupled-atomic emission spectroscopy was employed to identify the elemental composition of the grown samples. Direct band gap of the material was calculated using UV–vis studies.

Structure and characterization of Sn, Al co-doped zinc oxide thin films prepared by sol–gel dip-coating process

Transparent conductive zinc oxide co-doped with tin and aluminum (TAZO) thin films were prepared via sol–gel dip-coating process. Non-toxic ethanol was used in this study instead of 2-methoxyethanol used in conventional work. Dip-coating was repeated several times to obtain relatively thick films consisting of six layers. The films were then annealed at 500°C for 1h in air or in vacuum and not subsequently as employed in other studies. The X-ray diffraction patterns indicated that all the samples revealed a single phase of hexagonal ZnO polycrystalline structure with a main peak of (002). The optical band gap and resistivity of the TAZO films were in the ranges of 3.28 to 3.32eV and 0.52 to 575.25Ωcm, respectively. The 1.0at.% Sn, 1.0at.% Al co-doped ZnO thin film annealed in vacuum was found to have a better photoelectrochemical performance with photocurrent density of about 0.28mA/cm2 at a bias of 0.5V vs. SCE under a 300W Xe lamp illumination with the intensity of 100mW/cm2. Compared to the same dopant concentration but annealed in air (~0.05mA/cm2 bias 0.5V vs. SCE), the photocurrent density of the film annealed in vacuum was 5 times higher than the film annealed in air. Through electrochemical measurements, we found that the dopant concentration of Sn plays an important role in TAZO that affected photocurrent density, stability of water splitting and anti-corrosion.

Nonohmic properties of V/Mn/Nb/Gd co-doped zinc oxide semiconducting varistors with low-temperature sintering process

The microstructure and nonohmic properties of the ZnO–V2O5–MnO2–Nb2O5–Gd2O3 (ZVMNG) semiconducting varistors were systematically investigated at low sintering temperature. With increasing sintering temperature, the average grain size increased from 4.1 to 11.7μm, the sintered densities decreased from 5.54 to 5.42g/cm3, and the breakdown field decreased noticeably from 7138 to 920V/cm. The sample sintered at 900°C exhibited excellent nonohmic properties, which are 66.1 in the nonohmic coefficient and 77μA/cm2 in the leakage current density.

The Structure and Photoelectrochemistry of Al, Ti Co-Doped Zinc Oxide Thin Films Prepared by Sol–Gel Dip-Coating Process

The Structure and Photoelectrochemistry of Al, Ti Co-Doped Zinc Oxide Thin Films Prepared by Sol–Gel Dip-Coating Process

Influence of lithium substitution on the orange emission in manganese doped ZnO thin films

Lithium (Li) and Manganese (Mn) co-doped zinc oxide (ZnO) thin films have been deposited on glass substrates by sol–gel spin-coating technique. The influence of the defect states on the orange emission has been studied by altering the defect chemistry through appropriate Li substitution. The results of the defect related fluorescence in the blue and green regions have been combined to elucidate comprehensively the defect-mediated energy transfer mechanism of orange emission in Li and Mn co-doped ZnO thin films.

Visible light assisted photocatalytic performance of Ni and Th co-doped ZnO nanoparticles for the degradation of methylene blue dye

Nickel (Ni) and thorium (Th) co-doped zinc oxide (ZnO) nanoparticles were prepared by the co-precipitation method. The synthesized nanoparticles were characterized using UV–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. The photocatalytic activity of the prepared catalysts was evaluated by the degradation of methylene blue (MB) dye under visible light irradiation. XRD and SEM results revealed that Ni–Th–ZnO has a hexagonal and rods like morphology with an average crystallite size of 30nm. Ni–Th–ZnO possesses excellent photocatalytic activity for the degradation of MB when compared to that of Ni–ZnO, Th–ZnO, ZnO and TiO2. The photocatalytic activity of Ni–Th–ZnO is obviously affected by the reaction parameters. The maximum MB degradation (93% with 70% COD removal) was achieved with Ni–Th–ZnO concentration of 0.375g/L, initial MB concentration of 1.5μM, pH 10 and irradiation time of 180min. A possible photocatalytic mechanism has also been proposed. Moreover, the photocatalyst could be reused for four times without remarkable loss of its activity.

Indium‐Nitrogen Codoped Zinc Oxide Thin Film Deposited by Ultrasonic Spray Pyrolysis on n‐(111) Si Substrate: The Effect of Film Thickness

Indium‐nitrogen codoped zinc oxide (INZO) thin films were fabricated by spray pyrolysis deposition technique on n‐(111) Si substrate with different film thicknesses at 450°C using a precursor containing zinc acetate, ammonium acetate, and indium nitrate with 1 : 3 : 0.05 at.% concentration. The morphology and structure studies were carried out by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The grain size of the films increased when increasing the film thickness. From XRD spectra, polycrystalline ZnO structure can be observed and the preferred orientation behavior varied from (002) to (101) as the film thickness increased. The concentration and mobility were investigated by Hall effect measurement. the p‐type films with a hole mobility around 3 cm2V−1s−1 and hole concentration around 3 × 1019 cm−3 can be achieved with film thickness less than 385 nm. The n‐type conduction with concentration 1 × 1020 cm−3 is observed for film with thickness 1089 nm. The defect states were characterized by photoluminescence. With temperature‐dependent conductivity analysis, acceptor state with activation energy 0.139 eV dominate the p type conduction for thin INZO film. And the Zn‐related shallow donors with activation energy 0.029 eV dominate the n‐type conduction for the thick INZO film.

In-Line Sputtered Gallium and Aluminum Codoped Zinc Oxide Films for Organic Solar Cells

Gallium and aluminum codoped zinc oxide (GAZO) films were deposited at different temperatures by in-line sputtering. Aluminum is thermally unstable compared to other elements in GAZO films. The grains of GAZO films increase with deposition temperature. Coalescence between grains was observed for GAZO films deposited at 250°C. The deposition temperature exhibits positive influence on crystallinity, and electrical and optical properties of GAZO films. The carrier concentration and mobility of GAZO films increase, while the electrical resistivity of GAZO films decreases with deposition temperature. The average optical transmittance of GAZO films rises with deposition temperature. In-line sputtering demonstrates a potential method with simplicity, mass production, and large-area deposition to produce GAZO films with good electrical and optical quality. The electrical resistivity of 4.3×10−4 Ω cm and the average optical transmittance in the visible range from 400 to 800 nm of 92% can be obtained for GAZO films deposited at 250°C. The hybrid organic solar cells (OSC) were fabricated on GAZO-coated glass substrates. Blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were the photoactive materials in OSC. The power conversion efficiency of OSC is 0.65% for the OSC with the 250°C deposited GAZO electrode.

Transparent conductive aluminium and fluorine co-doped zinc oxide films via aerosol assisted chemical vapour deposition

Aerosol assisted chemical vapour deposition (AACVD) was employed to synthesise highly transparent and conductive ZnO, fluorine or aluminium doped and aluminium–fluorine co-doped ZnO thin films on glass substrates at 450 °C.

Corrigendum to “Investigation of aluminum–gallium co-doped zinc oxide targets for sputtering thin film and photovoltaic application” [J. Alloys Comp. 575 (2013) 174–182

Corrigendum to “Investigation of aluminum–gallium co-doped zinc oxide targets for sputtering thin film and photovoltaic application” [J. Alloys Comp. 575 (2013) 174–182

Enhanced Upconversion Luminescence of Erbium–Nitrogen-Doped Zinc Oxide Nano-Wires by Implantation of Ytterbium Ions

ABSTRACT Erbium–nitrogen codoped zinc oxide nanowires of ytterbium-doped are prepared by thermal evaporation and ion implantation methods. Ytterbium ions are doped into nanowires at a fluence of (0, 1, 3, 5, and 9) × 1015 cm−2. Microstructural and optical properties of specimen are investigated by X-ray diffractometer, absorption spectra, Raman, and upconversion photoluminescence examinations. Upconversion photoluminescence emissions at 550 nm and 660 nm are obtained under 980-nm light excitation. Both intensities of green and red peaks are enhanced by the introduction of ytterbium ions. When ytterbium ion fluence is 5 × 1015 cm−2, light emission intensity reaches maximum value. The energy transfer and cross-relaxation processes are responsible for the change of emission intensity.

Doped zinc oxide window layers for dye sensitized solar cells

The present paper reports the fabrication of dye sensitized solar cell (DSSC), where boron doped ZnO (BZO) and aluminum-boron co-doped ZnO (AZB) thin films were used as front window electrodes. The highly crystalline zinc oxide (ZnO) nanoparticles (NPs) synthesized by the sol-gel route were used as host material for the dye. The efficiencies of the DSSCs formed using the BZO and AZB as window layers were obtained to be 1.56 and 1.84%, respectively. The enhanced efficiency in the case of an AZB window layer based DSSC is attributed to the increase in conductivity induced by co-doping of Al and B and an increase in the number of conducting pathways between the window layer and NPs provided by the nanorods. This facilitates a new approach in the window layer (doped ZnO) for DSSC application.

Structural and Optical Properties of Alumina Templated Undoped and Co-Doped Zinc Oxide Nanoparticles

Structural and Optical Properties of Alumina Templated Undoped and Co-Doped Zinc Oxide Nanoparticles

The Effect of Thickness on the Properties of TGZO Thin Films for Optoelectronic Devices

Titanium and gallium co-doped zinc oxide (TGZO) thin films with highly (002)-preferred orientation were grown on glass substrates by magnetron sputtering. The effect of thickness on structure and optical properties of the deposited films were investigated by X-ray diffractometer and spectrophotometer. The results show that the polycrystalline TGZO films consist of the hexagonal crystal structures with c-axis as the preferred growth orientation normal to the substrate, and that the thickness significantly affects the crystal structure and optical properties of the thin films. It is observed that the average transmitance in the wavelength range of the visible spectrum decreases with the increase of thickness. The TGZO thin film with about 900 nm thickness exhibits the maximum grain size, the lowest dislocation density and the minimum micro strain.

Preparation and Optical Properties of Gallium-Titanium Codoped Zinc Oxide Transparent Conductive Films for Solar Cells

Transparent conducting gallium-titanium codoped zinc oxide thin films were grown onto glass substrates with magnetron sputtering technique in ambient argon gas, and the influence of argon pressure on optical properties of the films were investigated. The refractive indexes of the films were calculated. It is found that the refractive index tends to increase with increasing the photon energy. Meanwhile, the dispersion behavior of the refractive index was analyzed in terms of the single-oscillator model and the oscillator parameters were obtained. Furthermore, the optical energy gaps were evaluated by single-oscillator model and Tauc’s relation, respectively. The values of optical energy gap estimated from single-oscillator model are in agreement with those determined from Tauc’s relation.