Co-doped Zinc Oxide Research Articles

Polymer-Assisted Deposition of Co-Doped Zinc Oxide Thin Films for the Detection of Aromatic Organic Compounds

Co-doped Zinc oxide thin films are deposited onto SiO2/Si substrate by polymer-assisted deposition method. The surface morphology, structures and chemical states of the thin films are examined by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The gas-sensing properties of the thin films upon exposure to aromatic organic compound vapors are also investigated. Co-doping is shown to be very effective in enhancing the response of ZnO thin film to aromatic organic compound.

Implementation of High Carrier Mobility in Al-N Codoped p-Type ZnO Thin Films Fabricated by Direct Current Magnetron Sputtering with ZnO:Al2O3Ceramic Target

In this study, Al-N codoped p-type zinc oxide (ZnO) thin films were deposited on Si and homo-buffer layer templates in a mixture of and gas with ceramic ZnO:(2 wt% ) as a sputtering target using DC- magnetron sputtering. X-ray diffraction spectra of two-theta diffraction showed that all films have a predominant (002) peak of ZnO Wurtzite structure. As the fraction in the mixed and gases increased, field emission secondary electron microscopy revealed that the surface appearance of codoped films on Si varied from smooth to textured structure. The p-type ZnO thin films showed carrier concentration in the range of , resistivity in the range of 131.2-2.864 , and mobility in the range of respectively.

Structural and optical properties of Co-doped ZnO nanocrystallites prepared by a one-step solution route

Zinc oxide (ZnO) nanocrystallites with different Co-doping levels were successfully synthesized by a simple one-step solution route at low temperature (95 °C) in this study. The structure and morphology of the samples thus obtained were characterized by XRD, EDS, XPS and FESEM. Results show that cobalt ions, in the oxidation state of Co 2+, replace Zn 2+ ions in the ZnO lattice without changing its wurtzite structure. The dopant content varies from 0.59% to 5.39%, based on Co-doping levels. The pure ZnO particles exhibit well-defined 3D flower-like morphology with an average size of 550 nm, while the particles obtained after Co-doping are mostly cauliflower-like nanoclusters with an average size of 120 nm. Both the flower-like pure ZnO and the cauliflower-like Co:ZnO nanoclusters are composed of densely arrayed nanorods. The optical properties of the ZnO nanocrystallites following Co-doping were also investigated by UV–Visible absorption and Photoluminescence spectra. Our results indicate that Co-doping can change the energy-band structure and effectively adjust the luminescence properties of ZnO nanocrystallites.

Charge Compensated (Al, N) Co-Doped Zinc Oxide (ZnO) Films for Photoelectrochemical Application

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Characterization of gallium–nitrogen co-doped zinc oxide thin films prepared by RF diode sputtering

We investigated the possibility of achieving p-type zinc oxide (ZnO) by RF diode sputtering and gallium–nitrogen co-doping. ZnO:Ga:N thin films were prepared with a different N2 content in Ar/N2 working gas, ranging from 0 to 100%, and at a varying substrate temperature, from room temperature (RT) to 300 °C. A hole conduction with maximum carrier concentration of 2.6 × 1018 cm−3, mobility of 2 cm2/Vs and resistivity of 1.5 Ω cm resulted from deposition at RT with 100% N2. It arose from N incorporation and formation of NO acceptors. In the secondary ion mass spectrometry (SIMS) depth profiles of the co-doped films were observed NO/NO2 negative ions. Average transmittance (including Corning glass substrate) across the visible spectrum varied (60 ÷ 66%) with increasing nitrogen content (50 ÷ 100% N2). As the substrate temperature increased (RT – 300 °C), highly transparent (T ∼72–83%) and conductive (electron concentrations of 1017–1019 cm−3) n-type ZnO:Ga:N films were attained. Reduction of optical band gap (Eg) (∼3.13–3.08 eV) was observed for co-doped ZnO films. Atomic force microscopy (AFM) images revealed that the films grown at RT have roughness of approximately 5.3 nm while roughness of those grown at 300 °C is approximately 3.9 nm.

Properties of Co/Ni codoped ZnO based nanocrystalline DMS

Nanoparticles of Co and Ni codoped zinc oxide, Zn0.9Co0.1−xNixO (x=0.0, 0.03, 0.06 and 0.09), diluted magnetic semiconductors (DMSs) are synthesized by the sol–gel method at annealing temperature of 500°C. X-ray diffraction (XRD) patterns confirm the single phase character of the samples with x=0.0 and 0.03. However, minor NiO secondary phase is detected in the samples with x=0.06 and 0.09. All of them possess the hexagonal wurtzite structure. There is no significant change in the lattice parameters due to variation of doping concentration. The average particle size is found to be 19.31–25.71nm. FTIR and UV–vis spectroscopic results confirm the incorporation of the dopants into the ZnO lattice structure. Magnetization data reveal the presence of room temperature ferromagnetism (RTFM). The XRD patterns rule out the formation of secondary phase of either metallic Co cluster or CoO in the samples. Nevertheless, the secondary phases are a concern in any DMS system as a source of spurious magnetic signals. Therefore, we carried out the XPS studies from which the oxidation states of Co and Ni are found to be Co2+ and Ni2+, respectively. Moreover, XPS O 1s spectra show evidence of the presence of the oxygen vacancy in the ZnO matrix.

Effect of aluminum and indium co-doping on zinc oxide films prepared by dc magnetron sputtering

Aluminum and indium co-doped zinc oxide (AIZO) thin films were prepared by direct current (dc) magnetron sputtering on glass substrate in pure argon atmosphere. Three inches of zinc oxide ceramic with 0.5 wt.% of aluminum and indium doping was used as a target in static mode. The influence of sputtering conditions i.e. substrate–target distance, pressure and power on AIZO films was studied. The electrical resistivity and microstructure of thin films were investigated by the four point probe technique and the scanning electron microscope, respectively. The optical transmittance of AIZO films was measured by UV visible spectrophotometer in the wavelength of 300–1100 nm. Depending on the deposited conditions, highly transparent films up to 80% with low resistivities in the range of 2.6–7.9 × 10 − 4 Ω cm were achieved at room temperature. Possible mechanism in the processing which, ultimately, determines the physical properties of AIZO films will be discussed.

Physical properties of indium and fluorine codoped zinc oxide thin films deposited by chemical spray

Indium and fluorine codoped zinc oxide (ZnO:In + F) thin films were deposited on glass substrates by the chemical spray technique. The effect of the dopant concentration ratio in the starting solution, as well as the substrate temperature on the electrical, morphological, structural, and optical properties of ZnO:In + F thin films was studied. A minimum electrical resistivity, in the order of 3.4 × 10 −3 Ω cm, for as-grown films deposited at 475 °C from a starting solution containing [In]/[Zn] = 3 and [F]/[Zn] = 20 at.%, was obtained. All the films were polycrystalline, and some differences in the intensity of the peaks and preferential growth, depending on the doping ratios, were observed. The deposited ZnO:In + F thin films showed an average optical transmittance in the order of 85%, in the visible region (400–700 nm). The band gap values oscillated around 3.35 and 3.39 eV, and a shift towards higher values with the increase of the dopant concentration was observed. The surface morphology of the films was also strongly affected by the dopant concentration ratio, since a variation in both geometry and grain size was observed.

CuO Codoped ZnO Based Nanostructured Materials for Sensitive Chemical Sensor Applications

Due to numerous potential applications of semiconductor transition metal-doped nanomaterials and the great advantages of hydrothermal synthesis in both cost and environmental impact, a significant effort has been employed for growth of copper oxide codoped zinc oxide (CuO codoped ZnO) nanostructures via a hydrothermal route at room conditions. The structural and optical properties of the CuO codoped ZnO nanorods were characterized using various techniques such as UV-visible, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), etc. The sensing performance has been executed by a simple and reliable I-V technique, where aqueous ammonia is considered as a target analyte. CuO codoped ZnO nanorods of thin film with conducting coating agents on silver electrodes (AgE, surface area of 0.0216 cm(2)) displayed good sensitivity, stability, and reproducibility. The calibration plot is linear over the large dynamic range, where the sensitivity is approximately 1.549 ± 0.10 μA cm(-2 )mM(-1) with a detection limit of 8.9 ± 0.2 μM, based on signal/noise ratio in short response time. Hence, on the bottom of the perceptive communication between structures, morphologies, and properties, it is displayed that the morphologies and the optical characteristics can be extended to a large scale in transition-metal-doped ZnO nanomaterials and efficient chemical sensors applications.

Influence of post-deposition annealing on the structural, optical and electrical properties of Li and Mg co-doped ZnO thin films deposited by sol–gel technique

Lithium (Li) and magnesium (Mg) co-doped zinc oxide (ZnO) thin films were deposited by sol–gel method using spin coating technique. The films were deposited on glass substrates and annealed at different temperatures. The effects of annealing temperature on the structural, optical and electrical properties of the deposited films were investigated using X-ray diffraction (XRD), Ultraviolet–Visible absorption spectra (UV–VIS), photoluminescence spectra (PL), X-ray photo electron spectroscopy (XPS) and Hall measurements. XRD patterns indicated that the deposited films had a polycrystalline hexagonal wurtzite structure with preferred (0 0 0 2) orientation. All films were found to exhibit a good transparency in the visible range. Analysis of the absorption edge revealed that the optical band gap energies of the films annealed at different temperatures varies between 3.49 eV and 3.69 eV. Room temperature PL spectra of the deposited films annealed at various temperatures consist of a near band edge emission and visible emission due to the electronic defects, which are related to deep level emissions, such as oxide antisite (O Zn), interstitial zinc (Zn i), interstitial oxygen (O i) and zinc vacancy (V Zn) which are generated during annealing process. The influence of annealing temperature on the chemical state of the dopants in the film was analysed by XPS spectra. Ion beam analysis (Rutherford back scattering) experiments were performed to evaluate the content of Li and Mg in the films. Hall measurements confirmed the p-type nature of the deposited films.

Thin Film Thermocouples Based on Aluminum and Nitrogen Co-Doped Zinc Oxide

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Effect of Sputtering Power on the Properties of Transparent Conducting Ti-Al Co-Doped Zine Oxide Films Prepared by DC Magnetron Sputtering

Transparent conducting Ti-Al co-doped zinc oxide films (TAZO) with high transparency and relatively low resistivity have been successfully prepared by direct current magnetron sputtering. The effect of sputtering power on the structural, optical, and electrical properties of Ti-Al co-doped films were investigated. The XRD patterns show that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. The electrical resistivity decreases when the sputtering power increases from 40W to 120W. When the sputtering power is 120w and the target-substrate distance is 60mm, it is obtained that the lowest resistivity is 3.23×10-4Ω·cm.The lowest stress is 0.864Gpa in all the deposited films. All the films present a high transmittance of above 91% in the visible range.

溅射压强对钛镓共掺杂氧化锌透明导电薄膜性能的影响

Transparent conducting Ti,Ga co-doped zinc oxide films(TGZO) with high transparency and relatively low resistivity have been successfully prepared by DC magnetron sputtering at room temperature.Micro-structural,optical and electrical properties of TGZO films were investigated.XRD photos indicate that the sputtering pressure plays an important role on the microstructure and electrical resistivity of TGZO films.The electrical resistivity decreases when the sputtering pressure increases from 1.0 Pa to 11 Pa.When the sputtering pressure is 11 Pa,it is obtained that the lowest resistivity is 1.48×10-4 Ω·cm.The electrical resistivity increases when the sputtering pressure increases from 11 Pa to 16 Pa.All the films present a high transmittance of above 90% in the visible range.

铝钛共掺杂氧化锌透明导电薄膜的制备与性能研究

Transparent conducting Al-Ti co-doped zinc oxide films have been successfully prepared by DC magnetron sputtering.Microstructural,optical and electrical properties of TAZO films are investigated.The experimental results show that all the deposited films are polycrystalline with a hexagonal structure and a preferred orientation perpendicular to the substrates along the c-axis.When the sputtering pressures is 7.5 Pa,the lowest resistivity is 3.34×10-4 Ω·cm.All the films present a high transmittance of above 89% in the visible range.The sputtering pressures plays an important role on the microstructure and electrical resistivity of TAZO films.

Facile synthesis of highly oriented p-type aluminum co-doped zinc oxide film with aqua ammonia

Zinc oxide (ZnO) is a wide band-gap material with excellent optoelectronic properties. However, the application of ZnO to optoelectronic devices using ZnO has been hindered by the difficulty in obtaining a stable p-type doping. The paper demonstrates that, with a proper selection of the nitrogen precursor, a solution processable, highly c-axis oriented, stable, and p-type aluminium co-doped ZnO (NZO) formation can be obtained. In this study, the NZO films were characterized by using EDS, Raman spectroscopy, photoluminescence, and electrical measurements, respectively. The films were then synthesized through a sol–gel process that was below 600 °C. For the comparative study, NZO films without the Al co-doping were also prepared by sputter. It is observed and shown that, with the formation of nitrous oxide, the basic deposition condition will be more beneficial towards the formation of p-type ZnO.

Transparent Conducting TGZO Thin Films Deposited by DC Magnetron Sputtering at Room Temperature

Transparent conducting Ti-Ga co-doped zinc oxide (TGZO) thin films with high transmittance, low resistivity were firstly prepared on glass substrate by direct current (DC) magnetron sputtering at room temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the TGZO films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The lowest resistivity obtained in our experiment is 3.95×10-4Ω⋅cm. The average transmittance of the films is over 92% in the range of 400~760 nm.

Influence of the Sputtering Pressure on the Properties of TAZO Films Prepared by DC Magnetron Sputtering

Transparent conducting Ti-Al co-doped zinc oxide films (TGZO) with high transparency and relatively low resistivity have been successfully prepared on water-cooled glass substrate by DC magnetron sputtering at room temperature. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The Ar sputtering pressure was varied from 1.5 to 13 Pa. The electrical resistivity decreases when the sputtering pressure increases from 1.5 to 7.5 Pa. The electrical resistivity increases when the sputtering pressure increases from 7.5 to 13 Pa. When the sputtering pressure is 7.5 Pa, it is obtained that the lowest resistivity is 2.18×10-4Ω⋅cm. In the visible region, all the deposited films show a high average transmittance of above 92 %.

Combustion synthesis of Co-doped zinc oxide nanoparticles using mixture of citric acid–glycine fuels

In this study, cobalt-doped ZnO nanoparticles were synthesized by combustion method. Mixtures of citric acid and glycine were used as fuel. As-prepared powders were characterized by XRD, XPS, SEM-EDX, TEM and spectrophotometer. XRD patterns indicated that combustion reaction by different fuel mixture resulted in the formation of pure ZnO phase. However, citric acid combustion alone led to amorphous powder. Scherrer's equation demonstrated that the crystallite size increases with citric acid/glycine (C/G) ratio (38–61 nm). SEM and TEM images illustrated that the morphology of the powder depends on the C/G ratios and changes from rod-like to spongy hexagonal particles. Reflectance spectra showed that by higher C/G ratios, deeper green colors are obtained.

Studies on the structural and optical properties of zinc oxide nanobushes and Co-doped ZnO self-aggregated nanorods synthesized by simple thermal decomposition route

Abstract Pure and Co-doped zinc oxide nanomaterials were prepared by a simple low temperature synthesis and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), diffused reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) techniques. The results showed the formation of nanobushes that consists of several nanowires for pure ZnO and the nanorods formed by self-aggregation for Co-doped ZnO. The presence of Co 2+ ions replacing some of the Zn 2+ in the ZnO lattice was confirmed by EPR and DRS studies. The mechanism for the formation of self-aggregated and self-aligned ZnO rods after the incorporation of cobalt in the lattice by the building block units is discussed in this study. Morphological studies were carried out using SEM and HR-TEM, which supports the validity of the proposed mechanism for the formation of ZnO nanobushes and Co-doped ZnO nanorods. The synthesized nanomaterials were found to have good optoelectronic properties.

The characteristics of chemical and heat stability properties of chromium–vanadium–aluminum co-doped zinc oxide films for dye-sensitized solar cells

Transparent conducting oxide thin films are used as front contact material for dye-sensitized solar cells. This study investigated the effects of chromium (Cr) and vanadium (V) contents on the chemical and heat stability properties of aluminum-doped zinc oxide (AZO) thin films using pulsed direct current magnetic sputtering on Corning 1737F glass substrates. The experimental results show that Cr and V doping is useful for improving the chemical and thermal stability of AZO films. The energy gap for AZO thin films is between 3.65 and 3.69 eV. The resistivity of the AZO:Cr:V thin film was 4.23 × 10 – 4 Ω cm at a Cr/V ratio of 0.30/0.23 wt.%, deposition power of 150 W, working distance of 5.5 cm, substrate temperature of 473 K, working pressure of 0.4 Pa, and frequency of 10 kHz. This value is lesser than (and therefore superior to) the resistivity of SnO 2:F (FTO) films (6.5 × 10 – 4 Ω cm), but greater than that of SnO 2:In (ITO) thin films (1.2 × 10 – 4 Ω cm). The resistivity increased by about 0.27% after electrolyte etching, which is similar to the 0.16% increase observed for the ITO thin film. After a thermal cycle test at 673 K, the resistivity of the AZO:Cr:V film increased to 5.42 × 10 – 4 Ω cm, which is better than the resistivity of the ITO and FTO films after the same thermal cycle.