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Pure and cobalt-doped ZnO nanoparticles (2.5, 5, 7.5, and 10 atom % Co) are synthesized by sol-gel method. The as-synthesized nanoparticles are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM) analysis. The nanoparticles of 0, 2.5, and 5 atom % Co-doped ZnO exhibited hexagonal wurtzite structure and have no other phases. Moreover, the (101) diffraction peaks position of Co-doped ZnO shift toward a smaller value of diffraction angle compared with pure ZnO powders. The results confirm that Co ions were well incorporated into ZnO crystal lattice. Simultaneously, Co doping also inhibited the growth of particles, and the crystallite size decreased from 43.11 nm to 36.63 nm with the increase in doping concentration from 0 to 10 atom %. The values of the optical band gap of all Co-doped ZnO nanoparticles gradually decreased from 3.09 eV to 2.66 eV with increasing Co content. Particular, the dielectric constant of all Co-doped ZnO ceramics gradually increased from 1.62 x [10.sup.3] to 20.52 x [10.sup.3], and the dielectric loss decreased from 2.36 to 1.28 when Co content increased from 0 to 10 atom %. Key words: cobalt doping, ZnO, dielectric properties, ceramics, nanoparticles. Nous avons synthetise des nanoparticules de ZnO pur et dope au cobalt (2,5 at. %, 5 at. %, 7,5 at. % et 10 at. % de Co) par une methode sol-gel. Nous avons caracterise telles quelles les nanoparticules resultantes par diffraction des rayons X (DRX), spectroscopie infrarouge a transformee de Fourier (FTIR) et microscopie electronique a balayage a emission de champ (MEB-EC). Les nanoparticules de ZnO dopees a 0 at. %, 2,5 at. % et 5 at. % de Co ont revele une structure de wurtzite hexagonale sans presenter aucune autre phase. En outre, nous avons observe que la position (101) des pics de diffraction du ZnO dope au Co est deplacee vers une valeur plus faible d'angle de diffraction comparativement aux poudres de ZnO pur. Les resultats confirment que les ions de Co ont bien ete incorpores dans le reseau cristallin du ZnO. Parallelement, le dopage au Co a aussi inhibe la croissance des particules et la taille des cristallites, qui est passee de 43,11 nm a 36,63 nm, en fonction de l'augmentation de la concentration de dopage dans l'intervalle de 0 a 10 at. %. Les valeurs de la bande interdite optique de toutes les nanoparticules de ZnO dope au Co ont graduellement diminue, passant de 3,09 eV a 2,66 eV, en fonction de l'augmentation de la teneur en Co. Notamment, la constante dielectrique de toutes les ceramiques de ZnO dope au Co a graduellement augmente, passant de 1,62 x [10.sup.3] a 20,52 x [10.sup.3], et la perte dielectrique a diminue, passant de 2,36 a 1,28, en fonction de l'augmentation de la teneur en Co dans l'intervalle de 0 a 10 at. %. [Traduit par la Redaction] Mots-cles : dopage au cobalt, ZnO, proprietes dielectriques, ceramiques, nanoparticules., Introduction In the last decades, nanostructured zinc oxides (ZnO) have gained a lot of attention due to their potential applications in different areas of science and technology. (1) ZnO is [...]

The performance of resistance random access memory (RRAM) devices based on spin-coated sol-gel-derived zinc oxide (ZnO) thin films is examined. The devices are fabricated on a flexible plastic substrate and have displayed excellent durability upon repeated bending tests, thus showing their potential for flexible low-cost memory devices.

The extensive state-of-the-art experiments over a wide range of synthesis parameters are used to study the qualitatively different growth kinetics for ZnO nanocrystals, as compared to the kinetics of all other semiconducting nanocrystals. The results show that the formation of an effective passivating layer around the growing nanocrystals inhibits the reaction, instead of facilitating it, hence giving all the different results and observations.

The reaction of [[Zn(II)[[[H.sub.2]O].sub.6]].sup.2+] with a minimal, unstructured, tetracysteine 16-mer peptide, GGG is described to elucidate the thermodynamic contribution of a Zn(II)-[(S.Cys).sub.4] site toward metalloprotein stability relevant to classic structural Zn(II) sites. It is demonstrated that the entropy driven binding of Zn(II) reflects the proton dependent chemical speciation of the Zn(II)-[(S.Cys).sub.4] peptide complex.

The epitaxial growth and properties of Co and Cu codoped ZnO thin films deposited onto sapphire c-plane single crystals by using pulsed-laser deposition are studied. The presence of high oxygen vacancies in the films have allowed possible defect mediated mechanisms for mediating exchange coupling of the dopant ions resulting in room temperature ferromagnetism.

A study prepared Al doped ZnO (AZO) films with varying fluorine content by radio frequency magnetron sputtering at a room temperature to investigate doping effects of fluorine on the structural, the optical, and the electrical properties. The small amount of fluorine addition to AZO films resulted in beneficial effect on the electrical conductivity by improving the direct current Hall mobility, and the minimum specific resistivity is as low as 5.9 x [10.sup.-4] [omega] cm.

The strain-induced defects and their effects on structural and optical properties in ZnO epitaxial layers deposited on SiC substrates are demonstrated. It is learnt that the biaxial strain in ZnO/SiC heterostructure is the main driving force for generation of defects, together with impurities and imbalanced interfaces.

The green emission band of ZnO is investigated by both experimental and theoretical means. Two sets of equally fine structures with the same periodicity are well resolved in the low-temperature broad green emission spectra.

In this study, we integrated zinc oxide nanomaterials, which possess a high surface-to-volume ratio and take part in specific interactions with organic functional groups, into infrared sensing devices to improve both the sensitivity and selectivity of the detection of volatile organic compounds (VOCs). An annealing method was developed to modify ZnO nanoparticles directly onto the surface of an IR internal reflection element. The ZnO nanoparticles produced this way are spherical (diameters, ~20 nm). When this modified sensing element was used to detect VOCs, intense IR signals for compounds bearing polar functional groups were observed. The conditions for preparing the ZnO nanoparticles for IR sensing of VOCs were optimized by varying such factors as the volume of the coating zinc solution, the calcination temperature, and calcination time. After mapping the IR signals obtained with respect to these factors, the optimal IR signal from this modified IR sensing element occurred when using 100 [micro]L of zinc solution and performing the calcination at 400 [degrees]C for at least 30 min. VOCs having different functional groups were used to characterize the behavior of the ZnO-modified sensing element; our results indicate that the selectivity of this device favors polar compounds. Based on detection of several polar VOCs, the results indicate that quantitative analysis is possible when using the ZnO nanoparticle-modified sensor; in some cases, the detection limit was below an injected sample volume of 0.5 nL (~2.2 ppm), with a linear regression coefficient ([R.sup.2]) above 0.99 when up to 0.3 [micro]L of sample (~1400 ppm) was injected to a 100 mL of sample cell.

A study was conducted on the interfaces between the catalyst droplet and the nanostructure grow in well-defined mutual crystallographic relationships using Au guided growth of ZnO. The results revealed that the nanostructure defines the crystallographic orientation of the solidifying Au droplet.

The hetrostructured zinc oxide-aluminosilicate nanohybrids were synthesized through a hydrothermal reaction between the colloidal suspensions of exfoliated montmorillonite nanosheets and sol solution of zinc acetate. The intercalation of zinc oxide nanoparticles expands the basal spacing of the host montmorillonite clay, and the crystallites of nanohybrids were assembled to form a bubble structure.

An ab initio quantum mechanical/molecular mechanical (QA/MM) molecular dynamics (MD) simulations was performed at an elevated temperature to study the temperature effects on the structural and dynamical properties of a Zn(II)-water complex in aqueous solution. Within the simulation time, no first shell was observed in the QM/MM simulation even at 90 degrees centigrade.

The band structures of wurtzite ZnO are calculated by the empirical pseudopotential method (EPM). The eight parameters of the Zn and O atomic preudopotential form factors are obtained.

Abstract: The band-gap energy, [E.sub.g], of ZnO doped with 0.1 to 2.0 mol% of MnO and sintered at different isothermal sintering temperatures is studied by photopyroelectric spectroscopy in the wavelength [...]

A demonstration is presented on molten salt route in tuning of the growth directions of nanowires with specific crystal structures by using Zinc oxide (ZnO) as an example. This study deepens the understanding of the mechanism of molten-salt synthetic process, which indicates that molten salts are very effective to influence the surface energies of the crystals having polar surfaces.

Unusual ZnO micropheres constructed of interconnected sheetlike nanostructures were prepared by the hydrothermal synthesis approach. These microsphere possess high surface areas but are amorphous, by increasing the reaction time, the microspheres gradually dissolved to form short hexagonal microrods with platelike nanostructures stacked together and adsorption of metal nanoparticles onto the surfaces of these microstructures may yield enhanced catalytic of the catalyst nanoparticles.

The detection of 100 ppm of butane in superatmospheric N2 on air with an m-lines setup is reported. The sensing elements were ZnO-nanostructured coatings prepared by pulsed laser deposition and a refractive index in the 1.95 region was observed.

As-supplied polycrystalline ZnO samples are annealed at different temperatures and subsequently characterized by positron annihilation spectroscopy. Annealing up to 300 degree Celsius, an increase of defect lifetime and shape parameter is observed.

A ZnO/SnO2 core-shell heterostructure is used to demonstrate the possibility of establishing a three-dimensional epitaxial interface between two materials with different crystal systems for the first time and show possible tailoring optical properties by building the heteroepitaxial crystal interface. The structural characterizations show that as-prepared ZnO/SnO2 heterostructure exhibits unique luminescence properties in contrast with individual tetrapod ZnO and SnO2 nanostructures, in which the epitaxial interface induces new luminescence properties.

Near-field scanning optical microscopy (NSOM) is used to investigate the 300-nm-wide ZnO nanopatterns fabricated by micromolding in capillary technique using a sol-gel route. The results show that spatially resolved ZnO luminescence features with an optical resolution of

Flowerlike ZnO nanostructures (FZNs) are deposited on Si substrate from aqueous solution by the hexamethylenetetramine (HMT)-assisted thermolysis of zinc-ethylenediamine (en) complex at low temperature. The flower petals constructed by many well-aligned nanorods possess the typical tapering feature with tip sizes of 30-50 nm.

Nanobelts of protonated pentatitanate (H2Ti5O11.H2O) are synthesized hydrothermally for the first time. With a main emphasis on organizational manipulation, the investigation examines general issues of morphological complexity, synthetic interconvertibility, and material combinability related to fabrication of inorganic nanocomposites.

Unusual ZnO superstructures with ring-like nanosheets standing the backbone of spindles were synthesized from Zn5(OH)(sub 8)Cl2[.]H2O nanosheets by a mild solution route. The fast supersaturation for the formation of the ZnO phase can be achieved by using the precursor, which already has rich hydroxyl groups.

In this article, by studying structural and magnetic properties of transition metal substituted polycrystalline ZnO samples, it is found that no bulk ferromagnetism exists for single-phase materials, contrary to the existing theories.

Nanostructural zinc oxide fibers are fabricated by a simple vapor transport method of heating the mixture of zinc oxide, gallium oxide, and carbon powders in air. The field emission of the vertically aligned zinc oxide fiber array shows a low field emission threshold, high current density, rapid surge, and high field enhancement factor.

Tubular ZnO was fabricated in a microwave plasma system by using a nanowire-nanocable-nanotube scheme. A three-step route for the fabrication of ZnO is proposed.

The structural relationship with single crystalline GaN and the quality of epitaxial Zinc Oxide(ZnO) is studied. It is shown that the in-plane misorientation increases significantly with the dye loading or negative potential.

Conductive hydrophobic zinc oxide thin films are prepared by a simple method of electrochemical deposition. The superhydrophobic surface with a water contact obtained by (fluoroalkyl)silane modification has potential use in microfluidic devices in the future.

A new structure, mesoporous structured polyhedral drum and spherical cages and shells formed by textured self-assembly of ZnO nanocrystals made by a novel self-assembly process during epitaxial surface oxidation is presented. The structures of cages and shells are studied and a growth mechanism is proposed to be a process following solidification of Zn liquid droplets, surface oxidation, and sublimation.d

The conduction mechanism in aluminum-doped zinc oxide is studied. Structural investigation shows that crystallographic orientation as well as grain boundary scattering can be neglected.

The charge transport in nanoparticulate ZnO layers held at different potentials is studied by analyzing the anodic transient photocurrents. The results reveal that the effective diffusion constant for the electron transport through ZnO film held at positive potentials is calculated to be 1.7 x 10(super -4) cm(super 2)/s which is in good agreement with diffusion constants.

The pulsed-laser deposition (PLD) technique is currently used in research laboratories to obtain thin films from a broad range of materials even with a complex composition. The differences in the crystalline properties of ZnO films grown by laser ablation, using either nanosecond or femtosecond pulsed-laser deposition (PLD) is presented.

ZnO-based silicate glasses are studied in the present paper. Irradiation resistance of glass samples is tested under the [sup.60]Co [gamma]-ray radiation at the doses of 71 and 262 Gy. Ultraviolet and visible transmission spectra of glass samples are compared before and after irradiation treatment. Test results show that radiation damage of ZnO-based glasses increases with dose while the glass with the [Al.sub.2][O.sub.3] donor dopants exhibits improved radiation resistance. The latter can be correlated to bandgap broadening effect due to [Al.sub.2][O.sub.3] doping in the ZnO-based glass and to the role of [Al.sup.3+] as the network intermediate to enter partially the tetrahedral structure of silicate glass. Index Terms--Doping, radiation damage, silicate glass, ZnO.

The finite difference methodology is employed to explain the impact of carrier concentration on the piezoelectric potential exhibited by a bent ZnO nanorod. The observed potential is shown to be completely screened by the redistributed carriers at a carrier concentration of 1 x [10.sup.18] [cm.sup.-3].

Several density-functional calculations are conducted to explain the electronic structure and properties exhibited by the ZnO/GaN-core/shell nanowires. The various effects of quantum confinement on the band gaps of the system are also analyzed.

A hybrid mode in ZnO solidly mounted resonator (SMR) devices is described. The performance of the device is simulated by using COMSOL platform, the eigenfrequencies of the structure is examined and a hybrid mode is found that is trapped both vertically and laterally in the ZnO film.

A nanocomposite electrical generator composed of an array of zinc oxide nanowires is described, where the electric potential distribution along zinc oxide nanowires is modeled by using continuum mechanics and MaxwellEs equations for the case of axial loading. The studies have shown that the proposed system and loading configuration has generated up to 160% more electric potential than the values described for the nanowire in the bended configuration, which has resulted in a more sustainable energy source.

A large scale heterostructure array of ZnO nanowires/silicon nanoporous pillar array (Si-NPA) is prepared by a self-catalytic thermal evaporation and vapor-phase transport method and an ultrahigh field emission current density is obtained with a low turn-on field. The studies have shown that ZnO/Si-NPA is an ideal candidate cathode of potential applications in flat panel displays and high brightness electron sources.

The growth, as well as the structural and magnetic properties exhibited by the epitaxial [Fe.sub.3][O.sub.4/ZnO and ZnO/[Fe.sub.3][O.sub.4] bilayers grown on c-[Al.sub.2][O.sub.3] substrate are discussed. The [Fe.sub.3][O.sub.4/ZnO bilayer is shown to be much more stable, as compared to the other bilayers.

A combination of x-ray diffraction and several other technologies is employed to explain the structure, as well as the properties exhibited by the Co/ZnO films. The conductivity and magnetoresistance of the films are shown to be highly dependent on the temperature.

The electronic and magnetic properties of pure and Mn-doped armchair and zigzag ZnO nanotubes are analyzed by using density functional theory with the generalized gradient approximation. The studies have shown that large magnetic moments have appeared in Mn-doped ZnO nanotubes, which are due to the hybridization between the O 2p and Mn 3d states.

Thin-film light-emitting diodes (LEDs) containing solution-processed ZnO nanocrystals (NCs) are prepared as printed electronics and the electroluminescent (EL) properties of thin-film LEDs are examined along with the structural and photoluminescence (PL) properties of the ZnO NCs. EL spectral measurements have disclosed the presence of weak UV emission, which has increased as the crystal sizes D has decreased.

Epitaxial ZnO films are grown on single crystal spinel substrates in water and Hall measurements have showed that the n-type carrier concentration and conductivity of the ZnO films have decreased as postgrowth annealing temperature has increased or pH of the growth solution decreases. The studies have shown that the unintentionally-incorporated hydrogen in solution grown ZnO has acted as a shallow donor and has increased the n-type carrier density.

The wettability of electrodeposited zinc oxide (ZnO) thin films is controlled by individually engineering surface topology and surface chemical structure. The silanized films are successfully tailored to obtain hydrophilic, hydrophobic as well as ultrahydrophobic behavior.

The coexistence of unipolar resistive switching (BRS) in an Ag/ZnO/Pt structure prepared by sputtering deposition at room temperature is described. The switching mode is changed with adjusting the high compliance current but the transition is irreversible and the results have shown that switching mechanisms based on filament theory has explained both resistive switching.

Zn-ZnO superhydrophobic thin films are prepared by thermal oxidation of sputtered Zn and the superhydrophobicity is the coatings is ascribed to multiscale roughness in the nanometric range only. The wettability of the Zn-ZnO coatings has changed from hydrophobic to superhydrophobic due to the outward self-diffusion of Zn to the surface and the UV irradiation has transformed the Zn-ZnO surface from superhydrophobic to hydrophilic.