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ZnO nanotubes with the wurtzite structure have been successfully synthesized via simple hydrothermal solution route using zinc nitrate, urea and KOH for the first time. The structural, compositions and morphology architectures of the as synthesized ZnO nanotubes was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and high resolution transmission scanning electron microscopy (HRTEM). TEM showed that ZnO nanotubes exhibited a wall thickness of less than 2 nm, with an average diameter of 17 nm and the length is 2 μm. In addition, the antibacterial activity of ZnO nanotubes was carried out in vitro against two kinds of bacteria: gram - negative bacteria (G -ve) i.e. Escherichia coli (E. coli) and gram - positive bacteria (G +ve) i.e. Staphylococcus aureus. Therefore, this work demonstrates that simply synthesized ZnO nanotubes have excellent potencies, being ideal antibacterial agents for many biomedical applications., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Aluminum doped ZnO (AZO) thin films were successfully deposited via spin coating technique onto glass substrates. Structural properties of the films were analyzed by X-ray diffraction, atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy. X-ray diffraction results reveal that all the films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction (002) plane. The crystallite size of ZnO and AZO films was determined from Scherrer's formula and Williamson-Hall analysis. The lattice parameters of the AZO films were found to decrease with increasing Al content. Energy dispersive spectroscopy (EDX) results indicate that Zn, Al and O elements are present in the AZO thin films. The electrical conductivity, mobility carriers and carrier concentration of the films are increased with increasing Al doping concentration. The optical band gap (Eg) of the films is increased with increasing Al concentration. The AZO thin films indicate a high transparency in the visible region with an average value of 86%. These transparent AZO films may be open a new avenue for optoelectronic and photonic devices applications in near future., (Copyright © 2014 Elsevier B.V. All rights reserved.)

CdZnO thin films with different ratio of CdO and ZnO (3:1, 1:1, and 1:3) were grown on glass substrate using sol-gel spin coating method. The morphology of the CdZnO films depends on the amount of ZnO and CdO in the films. The optical band gap of the CdZnO films depends on the compositions of CdO and ZnO. Films having higher amount of CdO shows the presence of grains along with the fiber nature of ZnO, whereas the film with lower percentage of CdO shows fiber nature of the film very similar to pure ZnO film. The optical bandgap of CdZnO (3:1), CdZnO (1:1), and CdZnO (1:3) films was calculated to be 2.80, 2.49, and 2.52 eV, respectively. Other optical properties such as refractive index, extinction coefficient, and dielectric constants were calculated using the optical data. The volume and surface energy loss functions were also calculated and observed to increase with increase in the photon energy., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Zinc oxide thin film was grown on glass substrate using sol-gel spin coating method. The optical constants and dispersion energy parameters of the zinc oxide thin film were determined using optical characterization method. The optical band gap of the n-type ZnO semiconductor was found to be 3.24 eV. The refractive index dispersion of the ZnO obeys the single oscillator model. The dispersion energy and oscillator energy values of the ZnO film were found to be 13.74 eV and 6.61 eV, respectively. The real and imaginary parts of the dielectric constant of the ZnO film were determined. The photoluminescence spectra of the ZnO film indicate a peak around 401 nm (3.10 eV) due to the electron transition from the energy level of interstitial Zn to valance band and the another peak is observed around 530 nm (2.34 eV) which is attributed to the oxygen vacancies in ZnO., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Effect of In, Al and Sn dopants on the optical and structural properties of ZnO thin films have been investigated by X-ray diffraction technique and optical characterization method. X-ray diffraction patterns confirm that the films have polycrystalline nature. The thin films have (002) as the preferred orientation. This (002) preferred orientation is due to the minimal surface energy which the hexagonal structure, c-plane to the ZnO crystallites, corresponds to the densest packed plane. The grain size values of the films are found to be 29.0, 35.2 and 39.5 nm for In, Al and Sn doped ZnO thin films, respectively. The optical band gaps of the films were calculated. The absorption edge shifts to the lower wavelengths with In, Al and Sn dopants. The inclusion of dopant into films expands also width of localized states as E(UIn)>E(UAl)>E(USn). The refractive index dispersion curves obey the single oscillator model. The dispersion parameters and optical constants of the films were determined. These parameters changed with In, Al and Sn dopants.

Al/ZnO/p-Si diodes have been fabricated using different doping concentrations of a boric acid (H3BO3)-doped zinc oxide (ZnO) interlayer. The boric acid-doped ZnO films were obtained by the sol–gel method and coated by the spin-coating technique. The optoelectronic and electronic properties of the prepared diodes were studied under different illumination and frequency conditions. Current measurements of the diodes under both dark and illumination indicate that they exhibit a photovoltaic behavior. The diode with 5 wt.% H3BO3-doped ZnO interlayer showed the best diode properties with a rectification ratio of 4.23 × 104 at ± 5 V. Also, the photocurrent, photoconductance, and photocapacitance transients of the diodes prove that they exhibit both photodiode and photocapacitor behavior. In addition, the capacitance and conductance measurements of the diodes were carried out over a wide frequency range. The results denote that the generated diodes can be utilized as photo-diode/capacitors in optoelectronic technologies. [ABSTRACT FROM AUTHOR]

In this research, we present the production of series of bottom-gate/bottom-contact hybrid thin-film transistors by utilizing a blend of poly(3-hexylthiophene) (P3HT) and zinc oxide (ZnO) as active layers. ZnO nanoparticles are used as electron acceptors in hybrid organic–inorganic-based thin-film transistors as well as electron extraction materials. The nanoparticles of ZnO were produced by the sol–gel protocol. The P3HT:ZnO nanocomposite layers were deposited on silicon dioxide using the spin-coating method. The experimental study indicated that the hysteresis phenomenon of the components can be controlled by varying the amount of ZnO nanoparticles in P3HT:ZnO hybrid blend active layers. As a result, a major improvement of electron transport was observed with the increase of ZnO nanoparticles amount in the active layer, indicates that trapping was reduced in the P3HT:ZnO/SiO2 insulator interface. Furthermore, with increasing the ZnO nanoparticles concentration in the active layer, a critical improvement in the reduction of the trap density at the active layer/SiO2 interface was noticed even without using a dielectric surface treatment. Therefore, these results indicate that the incorporation of ZnO nanoparticles into the P3HT polymer has a crucial role in reducing the trap density in the active layer at the active layer/SiO2 insulator interface, thereby allowing the enhancement the transistor efficiency in terms of carrier mobility, on/off current ratio, threshold voltage, sub-threshold voltage, interface trapped, and density trapped carriers. The fabricated organic thin-film transistors, with significant hysteresis depended on ZnO nanoparticles in the active layer, prove a high possibility to use them for low-cost non-volatile memory thin-film transistors and sensing array applications. The best electrical performance was obtained with the OFET-PZ100 device. Finally, the output characteristics for this thin-film transistor was reproduced by using an analytic model, and good consistency between the different results has been illustrated. [ABSTRACT FROM AUTHOR]

In our research described here nanocomposites containing a newly synthesized methacrylate polymer, poly 2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate (PFPAMA) and ZnO nanoparticles in various mass ratios (1, 3 and 5 w %) were synthesized using the hydrothermal method. The synthesized nanocomposites were characterized by Fourier-transform infrared spectroscopy (FTIR), Hydrogen-1 nuclear magnetic resonance (1H-NMR) and X-ray diffraction (XRD) techniques. Both real and imaginary components of the complex dielectric permittivity of pure PFPAMA and the three different PFPAMA/ZnO nanocomposites were measured as a function of frequency. The dielectric study revealed that the ZnO nanoparticles improved the dielectric properties of pure PFPAMA. The variation of electrical conductivity, with frequency showed that the σ value increased linearly with increasing ZnO content. The frequency dependence of the conductivity suggested that the conduction occurs via a barrier hopping process. The obtained results suggest that the ZnO-doped, poly-2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate nanocomposites can be used as a dielectric material in dielectric device applications. [ABSTRACT FROM AUTHOR]

Abstract: The zinc oxide semiconductor thin film transistor was fabricated on a SiO2/Si substrate by sol gel method. The ZnO film is consisted of nanofibers with the changing diameter along the fibers. Electrical characteristics of the zinc oxide transistor under dark and white light illuminations were analyzed. The mobility value of the ZnO TFT was found to be 1.86×10−2 cm2/Vs. The ZnO thin film transistor works in an n-channel operational mode because the drain current increases with the positive gate voltages. A significant increase in the drain current of ZnO TFT is observed with a maximum photosensitivity of 100 under visible light illumination. It is concluded that the ZnO thin film transistor can be used in visible photo-detecting device applications. [Copyright &y& Elsevier]

Abstract: The heterojunction diodes based on cobalt doped zinc oxide (ZnO) were prepared by sol–gel deposition method. The compositional fraction of cobalt dopant was varied to control the electrical parameters of the diode. Atomic force microscopy was used to determine the structural properties of ZnO:Co films. The ZnO:Co films have a microfiber structure and the structure of microfibers was changed with the cobalt dopant. The ideality factor values of 5% and 15% Co doped ZnO:Co/p-Si diodes were determined to be 3.49 and 7.51, respectively. The barrier height of the ZnO:Co/p-Si diodes were found to vary from 0.75eV to 0.78eV. It is concluded that the electrical and interface state density properties of ZnO:Co/p-Si diodes can be controlled by compositional fraction of cobalt dopant. [Copyright &y& Elsevier]

Abstract: Undoped and Sn-doped ZnO nanopowder samples were prepared by the sol–gel method. The crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy. X-ray diffraction results indicate that the samples exhibit a hexagonal crystal structure. Electrical properties of the samples were measured by two probe method. The activation energies of the ZnO samples for low and high temperatures regions were determined. The optical band gaps of the samples were determined by optical absorption method. It was found that the samples have a direct transition optical band gap and the optical band gap values of the ZnO samples were changed with Sn doping. Quartz crystalline microbalance (QCM) technique was employed to investigate sensor features of the ZnO samples. The humidity sensor properties of undoped and Sn-doped ZnO samples based on quartz crystalline microbalance sensors were investigated. The obtained results indicate that the undoped and Sn-doped ZnO nanopowder samples can be used for humidity sensor applications. [Copyright &y& Elsevier]

Abstract: In this study, a Schottky diode based on wide band gap semiconductor ZnO was fabricated on p-type Si substrate using sol–gel spin coating method. Al/ZnO/p-Si diode indicates a rectification behavior. At lower voltages, the forward current of the diode was found to obey the intrinsic thermally generated charge carriers and at relatively higher voltages, the current mechanism of the diode is controlled by a space charge limited conduction mechanism. Under reverse bias conditions, the current–voltage characteristics of the diode exhibit the lower current as compared under forward bias, indicating the existence of a current limitation mechanism induced by two field lowering mechanisms which are Poole–Frenkel and Schottky mechanisms. The parameters, series resistance R S, the ideality factor n and the barrier height φ B0 of the diode were determined by performing different plots obtained from the experimental forward bias current–voltage. The capacitance measurements show that the values of capacitance were almost independent of the forward bias under various frequencies. The higher values of the capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the ZnO. [Copyright &y& Elsevier]

In this work, 3% Fe doped zinc oxide (ZnO) doped by Nitrogen thin films were grown by reactive radio frequency magnetron sputtering on p -Si substrates. The structural and optical properties of the 3% Fe doped ZnO doped by Nitrogen thin films were investigated by the scanning electron microscope and spectrophotometry. The diodes with the configuration of Al/ p -Si/3% Fe-ZnO:N/Al have been fabricated and it has been observed that the diodes exhibit a good rectification. The optical band gap was found to be 3.98 ± 0.02 eV for 3% Fe doped ZnO:N thin film deposited at the N 2 flow rate of 15 sccm. The electrical parameters of the diode were determined using Cheung's and Norde's method. The capacitance–voltage and conductance–voltage characteristics of Al/ p -Si/3% Fe-ZnO:N/Al structure have been investigated in the frequency range 10 kHz–1 MHz. The increase in capacitance at lower frequency is attributed to the density of interface states. It is evaluated that the prepared diodes can be used as nanoscale electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The device parameters of Al/p-Si/Zn1-xAlxO-NiO/Al Schottky diode for x = 0.005 were investigated over the 50 K–400 K temperature range using direct current–voltage (I–V) and impedance spectroscopy. The films were prepared using the sol–gel method followed by spin-coating on p-Si substrate. The ideality factor, barrier height, resistance and capacitance of the diode were found to depend on temperature. The calculated barrier height has a mean. Capacitance–voltage (C–V) measurements show that the capacitance decreases with increasing frequency, suggesting a continuous distribution of interface states over the surveyed 100 kHz to 1 MHz frequency range. The interface state densities, N ss , of the diode were calculated and found to peak as functions of bias and temperature in two temperature regions of 50 K–300 K and 300 K–400 K. A peak value of approximately 10 12 /eV cm 2 was observed around 0.7 V bias for 350 K and at 3 × 10 12 /eVcm 2 around 2.2 V bias for 300 K. The relaxation time was found to average 4.7 μs over all the temperatures, but showing its lowest value of 1.58 μs at 300 K. It is seen that the interface states of the diode is controlled by the temperature. This suggests that Al/p-Si/Zn1-xAlxO-NiO/Al diode can be used as a thermal sensors for low temperature applications. [ABSTRACT FROM AUTHOR]

The undoped ZnO and the Cr-doped ZnO nanomaterials were prepared by the sol–gel spin coating technique. The effects of chromium on the structural, morphological and optical properties of the zinc oxide films were investigated. The ZnO samples were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and UV–vis–NIR spectrophotometer. XRD patterns of Cr doped ZnO samples were identified with a hexagonal wurtzite structure of ZnO. Atomic force microscopy results indicate that the Cr doped ZnO films have the nanostructure. The influence of the Cr doping on the film growth is resulted in a change of grain size. The optical band gap of the films was calculated by optical absorption method. The optical band gap of the ZnO films was significantly changed by Cr dopant. The obtained results indicate that the structural and optical properties of ZnO films can be controlled with Cr doping. [ABSTRACT FROM AUTHOR]

For the purpose of this study, the nanorods of zinc oxide were synthesized by rapid microwave-assisted hydrothermal route. The microstructure and surface morphology of the sensitized nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). XRD results indicate that synthesized ZnO nanorods have wurtzite phase. The calculated value of the particle size using Debye Scherrer formula and Williamson Hall plot was found to be 20–28 nm and 35.3 nm, respectively. Low uniformity distribution of rod-like morphology (60–80 nm in diameter and average length about 250 nm) are seen in TEM micrographs. The optical parameters of the prepared ZnO nanorods have been calculated using Kubeleka–Munk approach for the UV–vis diffuse reflectance spectrum. It is found that the direct transition optical band gap of the studied sample is 3.17 eV. The direct current electrical conductivity ( σ ) was increased from 6.7 × 10 - 8 to 3 × 10 - 7 Ω - 1 cm - 1 with increasing the temperature ( T ) in the range (300–425 K). The obtained variation of σ with T refers that the conductivity mechanism is controlled by thermally activated process. [ABSTRACT FROM AUTHOR]

The electrical characteristics of sol–gel synthesized n-ZnO/p-GaAs heterojunction were reported. The values of barrier height and ideality factor for n-ZnO/p-GaAs heterojunction diode were determined to be 0.61 eV and 1.83, respectively. The I–V characteristics of the heterojunction diode exhibit a non-ideal behavior. The ideality factor which is greater than unity was attributed to the series resistance, interface states and interfacial layer. The modified Norde׳s function combined with conventional forward I–V method was used to obtain the parameters including the series resistance and barrier height (BH). The capacitance–voltage ( C–V) measurements were performed in the range of 100 kHz to 1 MHz. The interface distribution profile ( D it ) as a function of bias voltage was extracted from the C–V and G adj –V characteristics. The interface state density of n-ZnO/p-GaAs diode is of the order of 10 13 eV −1 cm −2 . Also, the I–V characteristics of n-ZnO/p-GaAs heterojunction diode were investigated in the temperature range of 293–393 K. [ABSTRACT FROM AUTHOR]

Abstract: The copper-doped ZnO thin films were grown on glass substrates using the sol–gel method and the spin coating technique. Cu dopants with ratios less than 10% (in molar ratio) were chosen because they are anticipated to have excellent optical and electrical properties and could be used in many research, environmental, industrial, and technological applications. XRD results indicate that a ZnO single phase with a hexagonal wurtzite structure is formed. The crystallinity of ZnO thin films is gradually deteriorated with increasing the Cu ratio. AFM images of the films indicate that the Cu-doped ZnO films seem to be consisted of nanofibers. The surface roughness of the films is increased with increasing Cu content. The optical band gap is red shifted from 3.3eV to 3.255eV with the increase of Cu content from x =0% to x =9.8%. The refractive index, extinction coefficient, and optical conductivity show a decrease with increasing Cu content. The correlation between the structural modifications and the resultant optical properties are reported. The results of the present system are compared with those of similar materials. [Copyright &y& Elsevier]

Highlights: [•] Zn1−xCr x O thin films were prepared via sol–gel spin coating technique. [•] XRD and AFM were performed to study the crystal structure, morphology and particle size. [•] UV–vis spectroscopy was used to determine the different optical constants. [•] The influence of Cr dopants on the structural and optical properties of ZnO thin films were studied. [ABSTRACT FROM AUTHOR]

Abstract: A comparative study on In and Al doped ZnO thin films grown onto glass and FTO substrates by spray pyrolysis technique has been done. The obtained results show that the structural shape, crystalline, grain size parameter, transmittance, absorption coefficient and optical band gap and photoconductivity of the ZnO films were changed by the nature of the substrate used. [Copyright &y& Elsevier]

In this study, the electrical attributes and exposed solar light impacts on the electrical properties were examined for the Al/p-Si structure having InGaZnO interlayer with different rates of Ga component. The films demonstrated the high transparency in the visible zone within percentages of 84–92%. The prepared films' optical bandgap values were utilized by the aid of optical data, and it is indicated that the bandgap values increased with Ga dopant increases. The electrical characteristics of the produced device and the effect of illumination intensity on these characteristics were investigated by the usage of current-voltage and transient measurements at different intensities of exposed light and the produced devices exhibited photoconducting behavior. In addition, electrical parameters with high importance level such as barrier height and ideality factor were calculated by the help of current-voltage measurements and their values were established at predictable level. The capacitance-voltage and conductance-voltage measurements of the produced device were made, and it was determined that they are depended on voltage and frequency, and also interface conditions and series resistance parameters having very large effects on electrical characteristics were calculated by the help of these measurements. It was determined that the energy band gap of the InGaZnO having different contents of Ga ingredient coincides with the energy levels of the semiconductor and the electrolyte. The analyzed results confirm that the fabricated Al/InGaZnO (with different rates of Ga)/ p- Si/Al devices have high sensitivity to illumination applied and could be used in advancing optoelectronic applications, especially as a photodiode. 1. Al/InGaZnO (with different rates of Ga)/ p- Si/Al devices were fabricated. 2. Electrical and photoelectrical characterizations of devices were reported 3. The devices were sensitive to illumination and depended on the applied voltage and frequency 4. The electronic and optoelectronic properties of the photodiodes changed with the different Ga contents used in the interlayer. [ABSTRACT FROM AUTHOR]