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The vertical alignment technology by processing sputtered ZnO film for LCD with ozone is proposed in this paper. The prepared ZnO thin films were treated with ozone in the ultraviolet cleaning machine through polarizer. The wettability of the treated ZnO films switched to hydrophobicity, reaching a contact angle of 92°. With the prepared ZnO film as the alignment layer in the transmissive LCD cell, the vertical alignment (VA) can be realized. The results demonstrated that the test cells not only possessed the photo‐electronic characteristics of traditional VA liquid crystal cells but also had a smaller threshold voltage of 1.95V. In addition, the ZnO films are applied into character display successfully since the VA test cell has a high contrast ratio. [ABSTRACT FROM AUTHOR]

Transparent conductive thin films based on Tin (Sn) doped zinc oxide (TZO) were prepared using the chemical spray pyrolysis technique. The crystalline structure, strain, stress, roughness characteristics, electrical and nonlinear optical susceptibility of TZO were studied The films have been investigated using x-ray diffraction, atomic force microscopy (AFM), electrical resistivity, and third harmonic generation (THG) techniques. The greatest value of the susceptibility χ(3) was about 10.91×10-12(esu) obtained from the 2% doped films, which have less roughness and the low electrical resistivity of 5×10-2 Ω cm. Moreover, third order non-linear optical susceptibilities were of the order of 10-12 (esu), higher than that of the undoped ZnO. [ABSTRACT FROM AUTHOR]

The ZnO and NiO stacking films are prepared by sol–gel spin‐coating method to explore the impact of bending on device resistive switching. Compared with others, the device with NiO/ZnO/NiO/indium tin oxide/PET stacking structure exhibits a higher ON/OFF ratio. After bending 1000 times, the switching performance is reduced by two orders of magnitude due to the branch breakage of the conductive filaments. The finite element studies indicate that stress mutation between the ZnO and NiO functional layers leads to microcrack formation and interfacial delamination, increasing the interfacial barrier and depletion width. The cracks propagate along the grain boundary and thus result in more traps, which may act as electron blocking layers to restrict the carrier transport. The scanning electron microscopy observation shows that when the crack density increases to about 0.03 μm−1, the device is broken down. Under threshold bending cycles as simulated by Comsol Multiphysics, the grain boundary is completely torn leading to fatigue fracture. The proposed work provides some information for improving the flexibility of memory devices. [ABSTRACT FROM AUTHOR]

ZnO thin films have been synthesized by chemical vapor deposition technique at substrate temperature 400°C and doped with Cu at (1,3,5 wt.%). The morphologies of pure and doped ZnO films were investigated by SEM and the grain size was become larger by increasing the amount of Cu doped. From X-ray diffraction measurements, the maximum intensity peak was (002) for ZnO:Cu films at diffraction angle 34.4° and crystallized of hexagonal phase. Based on XPS Measurements on the surface of ZnO:Cu films, it has been found that the peak was shift to higher diffraction angle and full width half maximum of the films were become wider with increasing Cu doping. The band gap of ZnO film was 3.3 eV and it was decreased as an increasing of Cu dopant. [ABSTRACT FROM AUTHOR]

Using Zn/ZnO composite target, ZnO films were prepared by RF magnetron sputtering under Ar, Ar + O2 and Ar + H2 atmospheres and substrate temperatures of 150 and 300 °C. The effects of gas (O2 or H2) flow rate and substrate temperature on the thickness, preferred orientation, crystallinity, stress, transparent conductive properties, electrically conductive stability in air, Eg and Raman spectrum of the films were investigated. The results show that the film prepared in Ar atmosphere exhibits poor transparent conductive properties and conductive stability. Substrate temperature of 300 °C is advantageous to prepare ZnO films with (002) preferred orientation, high crystallinity, low compressive stress and good transparent conductive properties under Ar + O2 atmosphere. Under Ar + H2 atmosphere, ZnO films with low compressive stress and better transparent conductive properties can be obtained at substrate temperature of 150 °C. The related mechanisms for the effect of gas flow rate and substrate temperature on structure and properties of ZnO films are discussed. [ABSTRACT FROM AUTHOR]

Silver (Ag) doped ZnO (SZO) nanomaterials were synthesized by hydrothermal method and characterized. ZnO nanostructures were doped with 0.0%, 0.5%, 1%, 1.5mol% Ag. These obtained SZO nanomaterials were analyzed using X-ray diffraction measurement (XRD), Scanning Electron Microscopy (SEM), and Energy Dissipative X-ray (EDX) spectroscopy. The structural analysis confirmed the formation of synthesized SZO samples having a hexagonal ZnO wurtzite phase. The morphology of SZO samples changed partially and the ZnO nanorod length increased somewhat as the Ag doping ratio increased. Despite this increase, it was seen that the average crystal sizes first increased and then decreased. The crystallite sizes calculated from XRD data for 0.0, 0.5, 1.0 and 1.5mol% SZO were obtained as 41, 42, 38 and 37 nm, respectively. Ag doping concentration has increased the absorbance of SZO nanomaterials increased and the transmission decreased was observed. The band gap of the 0.0%, 0.5%, 1.0% and 1.5mol% SZO nanomaterials were measured 3.19, 3.18, 3.16 and 3.19 eV, respectively. Then dye sensitized solar cells (DSSCs) were fabricated using these SZO nanomaterials, cis-Bis(isothiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylato) (4,4'-di-nonyl-2'-bipyridyl) ruthenium (II) dye (Z907), (Ditetrabutylammonium cis-bis(isothiocyanato) bis (2,20-bipyridyl-4,40 dicarboxylato) ruthenium (II) dye (N719) and examined their photovoltaic performances. The calculated efficiencies of DSSCs fabricated using Z907 dye for 0.0%, 0.5%, 1.0% and 1.5mol% SZO were 0.005, 0.51, 0.46 and 0.22%, respectively. Then the calculated efficiencies of DSSCs fabricated using N719 dye for 0.0%, 0.5%, 1.0% and 1.5mol% SZO were 0.06, 0.17, 0.07 and 0.06%, respectively. In both works, DSSCs with ZnO film doped with 0.5mol% SZO showed the best photovoltaic performance. Consequently, these results indicated that the synthesized SZO nanomaterial for DSSCs of the optimum ratio of Ag doping is 0.5mol% clearly. [ABSTRACT FROM AUTHOR]

ZnO thin films were prepared by chemical vapour transport method in inductively coupled plasma (ICP). The films were synthesized at different substrate positions and various oxygen/argon ratios. X-ray diffraction (XRD) revealed that all the synthesized films at different positions are mixture of hexagonal ZnO and hexagonal Zn phases. The relative peak integrated intensity (RPII) of the ZnO phase is 83.6, 25.3 and 45.3%, for positions 1, 2 and 3, respectively. Morphology of ZnO films was found to be sensitive to substrate position. Flat flakes, bended nanowires (NWs) and nanoparticles morphologies are observed for positions 1, 2 and 3, respectively. The sample synthesized at 1 is stoichiometric, whereas the samples prepared in positions 2 and 3 are sub-stoichiometric. The films prepared at positions 1 and 3 have relatively high transmittance and low reflectance values, whereas the film prepared at position 2 has low transmittance and high reflectance. The ZnO film prepared at position 2 is hydrophobic with water contact angle of 112.2°, which can be used as self-cleaning coating. For ZnO films prepared with various O2 ratios, the RPII was 83.2, 88.0, 96.4 and 100% for films prepared with 10, 20, 30 and 40%, respectively. With increasing O2 ratio, the nanograins became bigger and the stoichiometry improved. The transmittance and optical bandgap increased, whereas the reflectance and refractive index decreased with increase in O2 ratio. The ZnO film synthesized with 30% O2 ratio has the highest figure of merit (FOM) value; thus, this film may be considered as the best ZnO film for transparent conducting coating applications. [ABSTRACT FROM AUTHOR]

In this work, hydrothermal oxidation of electrodeposited zinc coatings is used to produce zinc oxide (ZnO) films. In the first step, zinc (Zn) coating is electrodeposited on indium tin oxide (ITO) coated glass substrate. The Zn films are then immersed in deionized water at 9 5 ∘ C. The exposure time of Zn coating in deionized water is varied from 1 h to 24 h in sequence. At the 24 h exposure time, X-ray diffraction (XRD) patterns reveal that zinc film has been completely converted to ZnO. Scanning electron microscope (SEM) results show morphological changes from flakes (for pure Zn) or 2D plates to rod (ZnO) like morphology which further changes to cotton-flower like shapes with an increase in oxidation time. Diffuse reflectance spectral measurements show the band gap tuning with oxidation time (it decreases from 3.28 eV to 3.19 eV). Photoluminescence (PL) spectra have depicted phonon replicas with energy separation of ∼ 1 2 4 meV for the ZnO films obtained after 6 and 12 h exposure time in deionized water at 9 5 ∘ C temperature. [ABSTRACT FROM AUTHOR]

Optical properties of as‐grown high nitrogen‐doped ZnO:Al,N films (with a variation of nitrogen concentration from 2.3 to 4.3 atomic %) are studied by Raman, photoluminescence, and Fourier‐transform infrared spectroscopy (FTIR). The intensity of mode A1LO, peaked at 580 cm−1, increases with increasing nitrogen concentration. The silent mode B1low at 275 cm−1 is clearly observed testifying increased disorder‐activated scattering in ZnO. Photoluminescence spectra reveal near‐band edge emission as well as several defect‐related bands, the intensity of which increases with nitrogen content. The blue band (2.61 eV) can be related to the transition from shallow donor level to deep nitrogen acceptor level. Also, incorporation of nitrogen in ZnO lattice causes appearance of both Zni and Oi defects responsible for violet (3.08 eV) and yellow (2.16 eV) emission band, respectively. At the same time near‐band edge emission of ZnO:Al,N films is not suppressed by simultaneously introduced Al and N impurities. Al compensates distortions in ZnO crystal lattice caused by nitrogen doping and, thus, stabilizes near‐band edge emission. [ABSTRACT FROM AUTHOR]

This paper reports the effect of Fe incorporation on structural and electro-optical properties of ZnO thin films prepared by spin coating techniques. The Fe/Zn nominal volume ratio was 7 % in the solution. X-ray diffraction patterns of the films showed that doped incorporation leads to substantial changes in the structural characteristics of ZnO films. All the films have polycrystalline structure, with a preferential growth along the ZnO (002) plane. The crystallite size was calculated using a well-known Scherrer’s formula and found to be in the range of 22-17 nm. The highest average optical transmittance value in the visible region was belonging to the Fe doped ZnO film. The results of the Raman scattering confirmed the observations of XRD and UV-Vis analysis techniques by the appearance of these occupancies at Zn+2 sites. These results are explained theoretically and are compared with those reported by other workers. The results of Hall measurement of ZnO and ZnO:Fe thin films reveal a high electron concentration around 1016 cm–3 and low mobility 2.6 cm2/Vs. All as-grown samples show ambiguous carrier conductivity type (p-type and ntype) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li-doped ZnO and in As-doped ZnO films by other groups before. However, by characterizing our samples whit XPS, we have demonstrated that the ambiguous carrier type n in intended our ZnO films is not intrinsic behavior of the samples. It is due to the persistent photoconductivity effect in ZnO. [ABSTRACT FROM AUTHOR]

It is the purpose of this work to research the formation process of zinc oxide by the method of HF magnetron sputtering on silicon substrates of orientation (100) with the previously applied system of macropores. Samples of porous silicon were obtained by electrochemical etching. n-type Si (100) wafers were used. Precipitation of thin ZnO films was carried out in an RF discharge in an argon atmosphere with oxygen by sputtering a zinc target. The target had a diameter of 80 mm and a thickness of 6 mm. The deposition time was 1200 s. The pressure in the growth chamber was maintained at a level of 10–3 Pa. The substrate temperature was fixed at 300 °C. X-ray examination of ZnO has shown that the films have a polycrystalline nature with a wurtzite-type structure and hexagonal phase. ZnO crystallites in the coatings are highly oriented along the c-axis and perpendicular to the substrate surface. The lattice constant along the crystallographic c-axis of ZnO film was 5.2260 Å. The average crystallite size calculated by the Selyakov-Scherrer formula was 12 nm. According to SEM, grain size was ~ 50-100 nm. These discrepancies are explained by the presence of microstrains in the atomic matrix of the sample, as well as instrumental factors. The microelement analysis revealed practically perfect stoichiometry of ZnO grown on porous-Si/Si. [ABSTRACT FROM AUTHOR]

The effect of Fe and Mn impurities on the magnetic parameters of ZnO wide-gap semiconductor films produced by high-frequency sputtering with wide variations in the defect concentration is studied. The introduction of Mn and Fe magnetic impurities brings about the existence of a magnetically ordered state in the semiconductor matrix, with different positions of the axis of easy magnetization. In the case of doping with Mn, this axis lies perpendicularly to the film plane, and in the case of doping with Fe, this axis lies in the film plane. [ABSTRACT FROM AUTHOR]

Multidrug resistant bacteria are well-recognized as one of the greatest threats to human health worldwide. Antibacterial activity of nanoparticles has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. The antimicrobial effects of Ag, ZnO mixed solutions were examined in this work. Silver nitrate and zinc acetate were precursors for preparing two solutions (referred to as Sol1 and Sol2). These solutions contained well-known active antibacterial ions: Zn+2 and Ag+. The mixed solutions were made using Sol1 and Sol2 at three volume ratios (0.2, 0.4 and 0.8 %). The antibacterial activities of the mixed solutions were studied against Klebsiella pneumoniae; Acinetobacter baumannii; Escherichia coli; Pseudomonas aeruginosa and Staphylococcus aureus using the agar well diffusion method. All mixtures had an inhibitory effect against all pathogenic bacteria but with different inhibition zones. These zones were compared with those formed by Sol2 only to investigate the effect of Ag particles. The coexistence of nano and micro Ag particles was one of the important factors used to explain the results of inhibition zones. Utilizing the spin coating method, mixed solutions were deposited on glass substrates to produce three silver doped zinc oxide (Ag: ZnO) films. An experimental study of antiadhesive effects of Ag:ZnO films against pathogenic bacteria Pseudomonas aeruginosa has been performed. These effects increased by increasing the silver amount as a dopant material inside ZnO matrix. [ABSTRACT FROM AUTHOR]

Theory predicts Cu‐doped ZnO (ZnO:Cu) has p‐conductivity; however, this has only been demonstrated in a small number of experimental and mechanistic studies. In this paper, ZnO:Cu films were grown in situ with varying Cu content, prepared using radiofrequency atomic source–assisted molecular‐beam vapor deposition. The results indicate that ZnO:Cu films with dopant of Cu2+ only had n‐type behavior. As the Cu content increased, Cu+ was the major dopant and the ZnO:Cu films had p‐type behavior. However, excess Cu dopant resulted in the formation of second phases of Cu2O and Cu–Zn. The formation of a Cu–Zn phase increased the content of Zn vacancy, thus increasing hole concentration. Stronger alloy scattering decreased carrier mobility. Therefore, Cu+ dopant and Zn vacancy give ZnO:Cu films p‐conductivity properties. [ABSTRACT FROM AUTHOR]

Abstract We studied the effect of europium (Eu) doping on the near band edge emission of ZnO thin films, fabricated by sputtering and high temperatures annealing. The doping concentration of Eu in the ZnO films was varied from 0.01 to 0.62 at.%. Photoluminescence (PL) spectra showed that the films ultra-violet (UV) emission was enhanced very much by high temperature treatment and was stronger for the Eu doped ZnO than that for the un-doped ZnO films after 1100 °C annealing. X-ray diffraction showed the films had hexagonal wurtzite structure, the width of the ZnO (002) plane diffraction peak was sensitive to the anneal temperature and also to the Eu doping concentration, and Zn silicates had formed after the 1100 °C annealing. Scanning electron microscopy showed that the surface morphology of the films became more uneven with increasing Eu concentration. The PL decay spectra inferred that the lifetime of the UV PL was correlated with the size of ZnO nanocrystals in the films. The results support that the intensity of the UV PL is primarily influenced by the crystalline perfection of the films which is also influenced by the Eu doping concentration. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • For the ZnO films/Ag NPs (II) structure, oscillating electrons can be excited to higher energy level by LSP and transfer to the CB of ZnO, causing an enhanced PL intensity of NBE emission. • For the Ag NPs (I)/ZnO films structure, electron transition to Fermi level of metal occurs at the MS interface due to the bending energy band that excites electrons to be close to the Fermi level of the metal, leading to a reduced PL intensity of NBE emission. • The enhancement or reduction of luminescence intensity depends on the transport probability of electrons to the LSP level or to the Fermi level of the metal. • The defect emission subsequently remained almost the same with weak LSP resonance coupling and energy mismatch in the structure. Abstract By employing localized surface plasmon resonance (LSPR), the near band edge (NBE) emission intensity of ZnO films were greatly varied, while defect emission remained almost the same. This photoluminescence (PL) intensity enhancement or reduction is tunable by changing the position of Ag nanoparticles (NPs) relative to the ZnO films. The remarkable variation of the NBE emission was investigated deeply. These experimental results reveal that the Ag NPs play a key role in tuning the PL performance of the semiconductor material, where LSPR occurs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Studies on ZnO, Zn 1-x La x O [x = 0.02, 0.05, 0.10, and 0.15] thin films were prepared by spray technique. • Influence of La-doping on the structural, microstructural, Seebeck coefficient, optical, UV photodetectors, and photocatalytic properties of ZnO thin films. • The development of the parameters: lattice parameters, average crystalline sizes, Seebeck coefficient, and band gap energy with doping are discussed. • The 5%La-ZnO layers remain the best for UV photodetection with a good sensitivity of 5.07. • The 5%La_ZnO films had a 95% degradation rate. In this study, ZnO, Zn1-xLaxO [2, 5, 10, 15 at.%] thin films were grown on glass substrates using the spray-pyrolysis technique, to investigate the effect of doping on the structural, morphological, thermoelectric and optical properties of the layers, Also the samples were tested as UV photodetectors and photocatalyst for MB degradation. Firstly, diffraction patterns showed a hexagonal structure, with preferential grain orientation along the (0 0 2) direction, for pure ZnO and 2%La_ZnO layers, and at 5 at.% the preferential orientation changes, and crystallite sizes range from 10 nm to 19 nm. However, SEM images reveal that the ZnO and 2%La_ZnO layers are nanorods distributed over their surfaces, and the other 5%LZO, 10%LZO and 15%LZO layers characterized by nanocrystals were hexagonal prisms. The UV–visible analysis of the prepared layers shows high transparency (80–90%) in the visible range, with a constant optical gap of 3.26 eV. Thermoelectric measurements show that the ZnO and LZO layers are non-degenerate, with a maximum charge concentration of 9.18 × 1017 cm−3 for the 15% LZO films. The thin films show an ability for UV detection, while the 5%La_ZnO layers remain the best for UV photodetection with a good sensitivity (5.07) compared with the other layers. In terms of methyl blue degradation, the 5%La_ZnO thin films had a better degradation of 95%. [ABSTRACT FROM AUTHOR]

Microstructures and native defects are very important for the optical, electrical and magnetic properties of ZnO-based materials. In this study, microstructures of the Cu-doped ZnO (ZnO:Cu) films were changed by applying high magnetic field (HMF) during different growth processes of the as-deposited Zn-Cu films and the subsequent thermal oxidation treatment. The effects of the microstructure evolutions on the defects formation and photoluminescence performance are examined. The results show that the interaction between magnetization and thermal motion promotes (002) preferred orientation of the as-deposited Zn-Cu films. Meanwhile, the variation of the atomic deposition sites due to the HMF leads to the significant differences of surface morphology of the as-deposited films. The application of the HMF during the oxidation affects the adsorption sites of O 2− and leads the surface spherical particles change to rod-like particles. Moreover, the HMF shows more significant effects during the deposition of the Zn-Cu films in enhancing on the amount of the oxygen vacancy, which improves green emission of the ZnO:Cu films. [ABSTRACT FROM AUTHOR]

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The thin films of zinc oxide (ZnO) were grown on sapphire (0 0 1) substrates using pulsed laser deposition (PLD) in O 2 gas ambient and at different growth (substrate) temperatures (200, 300, 400, 500 and 600 °C). The effect of growth temperature on the crystallographic and morphological and photoluminescence properties of the films were investigated using X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectrometer. All the films reveal a wurtzite ZnO structure. The XRD results are well supported by the surface morphological and photoluminescence studies. The film characteristics were interrelated to their ultraviolet (UV) photo-sensing properties. The UV photodetection properties of the films were investigated at room temperature in metal–semiconductor–metal (MSM) planar configurations and are observed to be strongly driven by the growth temperature dependent crystallographic properties. The dark-current and the photocurrent of the ZnO film-based UV photodetectors are relational to the crystallite/grain size and the quality of ZnO thin films. For the photodetector based on ZnO film with a greater crystallite size, a lower dark current, and a higher photocurrent were achieved under 5 V bias voltage. The time-dependent photoresponse investigations illustrate a highly stable and fast switching UV photoresponse for the photodetector with ZnO film grown at 400°C growth temperature, which exhibits the maximum responsivity of ∼21.65 mA/W upon 2 mW/cm 2 UV light exposure (365 nm), at a bias voltage of 5 V. [ABSTRACT FROM AUTHOR]

Due to the mismatch between ZnO film and -Si lattice, there are a large number of interface states which seriously affect the photoelectric properties of ZnO/-Si heterojunction optoelectronic devices. In this research, ZnO thin films were deposited on -Si by magnetron sputtering and ZnO/-Si heterojunction was prepared. CuSCN film buffer layer was inserted into the interface of ZnO/-Si heterojunction to reduce the interface state and improve the electric properties of heterojunction. The results show that the insertion of CuSCN films can effectively improve the interface state of ZnO/-Si heterojunction, increase the forward current, reduce the reverse current and improve the heterojunction rectification ratio. [ABSTRACT FROM AUTHOR]

Simple and a facile chemical solution strategy was utilized for the synthesis of ZnO nanoparticles (NPs) and then Ag 2 S quantum dots (QDs) were deposited on the surface of ZnO NPs by a successive ionic layer adsorption and reaction deposition method. The formation of Ag 2 S QDs on ZnO films significantly improved the performance of quantum dot sensitized solar cells (QDSCs). The higher photoconversion efficiency, 2.41% was achieved for the ZnO–Ag 2 S 6-cycles photoanode which corresponds to an increase of 35% when compared with bare ZnO electrode. The improved photoconversion efficiency of the ZnO–Ag 2 S QDSCs is attributed to the Ag 2 S sensitization which broadened the absorption into visible light region and exhibits higher short-circuit current density (J sc ) values. [ABSTRACT FROM AUTHOR]

We show that graphene device could be controllably doped by the bottom substrate by inserting atomic layer deposition grown ZnO between graphene and SiO 2 substrate. To clarify the effect of bottom ZnO, length of the graphene transistor channel was varied from 20 to 200 μm, while that of ZnO was fixed to 10 μm. Graphene devices supported on ZnO film show marked difference from those supported on SiO 2 substrates; bottom ZnO layer behave as an electron donor. UV illumination experiment on hybrid graphene-ZnO device reveals that the effect of doping from ZnO becomes negligible when the graphene channel length made about four times larger than that of ZnO stripe. [ABSTRACT FROM AUTHOR]

We have optimized the photovoltaic properties of active ZnO/p-GaAs heterojunction solar cells by pulsed laser deposition method by varying the oxygen pressure from 0 to 50 mTorr during the fabrication process. We observed the crystallinity and grain size of ZnO enhanced with increasing oxygen pressure from 0 to 30 mTorr. In addition, with this increase of oxygen flux, the intensity of E 1 (LO) modes obtained by Raman measurements declines significantly and almost disappears under an oxygen pressure of 50 mTorr. The change of intensity is assumed to be the change of oxygen vacancy and zinc interstitial concentrations in ZnO films with oxygen pressures. Current-voltage measurements and extractions show that ZnO grown at 30 mTorr displays the best performance with the I SC of 24.3 mA/cm2, the efficiency of 8.746 %, and FF 0 of 68.73 %. The high performance of the heterojunction solar cell grown at the oxygen partial pressure of 30 mTorr might be due to the reduction of oxygen vacancies by increasing oxygen during the deposition. The results reveal the importance of the oxygen processing gas in promoting devices performance. • ZnO films are deposited by PLD on p-GaAs substrates. • Current-voltage measurements and extractions show that ZnO grown at 30 mTorr displays the best performance with the I SC of 24.3 mA/cm2, the efficiency of 8.746 %, and FF 0 of 68.73 %. [ABSTRACT FROM AUTHOR]

Cobalt-iron-codoped ZnO films were synthesized with different precursor sol pHs by a sol–gel method. All the samples possess hexagonal wurtzite structure, with no evidence of secondary phases. The average crystallite size of the samples was in the range of 10–40 nm, accompanying significant differences with the increase of the H + ion level. The Co/Fe ions are indeed substituted at the Zn 2+ site into the ZnO lattice, as shown by XRD and XPS. Strong ultraviolet emission, blue double emission and weak green emission peaks are observed in the photoluminescence spectra of all samples at room temperature. Further studies reveal that the bandgap energy of the ZnO films increases from 3.15 eV (pH = 5) to 3.24 eV (pH = 9). Enhanced room-temperature ferromagnetism is observed for the (Co, Fe)-codoped ZnO films at sol pHs lower than 8. Our work clearly establishes that the origin of room-temperature ferromagnetism in the (Co,Fe)-codoped ZnO films is linked to O vacancies, tunable by the sol pH. [ABSTRACT FROM AUTHOR]

The quality and optical homogeneity of thin films are necessary for optoelectronic devices and semiconductor technology. The influence of Pb doping, Zn 1− x Pb x O (0≤ x ≤0.05), and Mg co-doping, Zn 0.95− y Pb 0.05 Mg y O (0≤ y ≤0.05), on the microstructural properties, optical parameters and wettability of ZnO films were investigated. X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) results show that the films have polycrystalline and hexagonal structure with a preferred (002) orientation combined with wrinkle network structure for the Pb doped films. The crystalline quality is slightly enhanced with the Pb doping and then deteriorated after Mg co-doping. The influences of the crystallinity and chemical composition on the film wettability are studied. All films show transparency between 85–93%. The reflectance and optical band gap of ZnO films decrease for Pb doping and then increase with Mg co-doping. Well-known Swanepoel׳s method is employed to determine the refractive index ( n ) and film thickness ( d ). The influences of Pb and Mg co-doping on the Urbach energy and optical dispersion parameters are also discussed. [ABSTRACT FROM AUTHOR]

Cu-doped ZnO thin films with a single phase (002) oriented were prepared on glass substrate by magnetron co-sputtering. The influences of Cu doping on the microstructure, surface morphology and photoluminescent characteristics of the films were systematically investigated. XRD and SEM results show that the moderate Cu doping could promote the preferential growth of (002) crystal plane and help Cu atoms orderly merge into lattice of ZnO, but the excessive Cu doping inhibits it. The blue emissions peaks were mainly originated from the transition from the conduction band bottom to Zinc vacancy and the transition from antisite Zinc to zinc vacancy. We can control the intensity of blue emissions peaks by changing the Cu doping content. [ABSTRACT FROM AUTHOR]

This paper demonstrates zinc oxide (ZnO) film formation by using supercritical fluid chemical deposition and the application of the ZnO films in improving the adhesion of Cu/glass stacks. Bis(2-methoxy-6-methyl-3,5-heptanedionate)zinc(II) was used as a precursor, and the deposition was carried out at different oxygen contents and temperatures. When oxygen content was high and/or deposition temperature was high, white polycrystalline ZnO films were deposited; otherwise, the films were brown and had a higher carbon content. XPS analyses revealed that the white ZnO films had less carbon contamination. A significant improvement in the adhesion of the Cu/glass stacks was observed when the fabricated ZnO film was inserted between Cu and glass. [ABSTRACT FROM AUTHOR]

We have prepared ZnO films with ∼700 nm sized grains on silicon substrates by a simple hydrothermal process. Then, metal-insulator-semiconductor (MIS) structured devices based on such ZnO films have been fabricated in order to achieve low-threshold electrically pumped random lasing (RL). It is found that the MIS structured device using the as-grown hydrothermal ZnO film exhibits a lower RL threshold current than most of our previously reported devices using the sputtered or hydrothermal ZnO films of much smaller grains, indicating the feasibility of using ZnO films of large grains to improve the RL performance. However, the RL threshold current of the MIS structured device using the hydrothermal ZnO film subjected to 700 °C anneal is unexpectedly ∼10 times that of the device using the as-grown hydrothermal ZnO film. This is due to that the 700 °C anneal results in deep pores and more defects in the hydrothermal ZnO film, which in turn leads to not only the larger optical loss but also the smaller optical gain. Such an unexpected result suggests that the poor thermal-endurance of the present hydrothermal ZnO films significantly limits their applications into random lasers. [ABSTRACT FROM AUTHOR]

ZnO films on glass tubes were prepared by chemical bath deposition method. The glass tubes were surface-activated by KMnO 4(aq) and then submerged in an alkaline aqueous solution, containing Zn(CH 3 COO) 2 , NH 4 OH and HO(CH 2) 2 NH 2 at 75 °C to undergo film formation. The microstructures of the dried and calcined ZnO films prepared using different conditions were examined. The films formed on KMnO 4 -activated glass tubes are composed of steeple-typed wurtzite ZnO columns. Photocatalytic activities of the ZnO films were evaluated by photocatalytically degrading the methylene blue (MB) in water under UV-light irradiation. The apparent reaction order for MB photocatalytic degradation by the ZnO films was 1st-order and the reaction rate constants (k), based on the area of substrates coated by the film, were estimated. The ZnO films prepared using a volume ratio of ammonia/ethanolamine = 2/12 and calcined at 500 °C gave a photocatalytic performance with an average k = 0.549 ± 0.021 L/(m2·min). • ZnO films formed on glass tubes are prepared by a chemical bath deposition method. • Varying ratio of ammonia to ethanolamine in solution alters dimension of ZnO films. • Calcination at 500 °C enhances the photocatalytic reactivity of ZnO films. • Kinetics for ZnO films to photocatalytically degrade organic dyes are studied. [ABSTRACT FROM AUTHOR]

Cu-doped ZnO thin films deposited on glass substrates by a sol–gel method with sol pH ranging from 6 to 10 were investigated. Characterization of the morphology and microstructures by scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed that the grain size decreases slightly with an increase of the pH value of the precursor sol. ZnO vary in their orientation along the preferred (0 0 2) plane, while the best c -axis orientation occurs in the thin film fabricated from the precursor sol with pH = 8.5. X-ray photoelectron spectroscope (XPS) and XRD results indicate that Cu ions are indeed substituted at the Zn 2+ site into the ZnO lattice. Strong ultraviolet emission, blue double emission and weak green emission peaks are observed in the photoluminescence spectra of all samples at room temperature. Further studies show that adjusting the pH of the precursor sol can well tune the bandgap from 3.19 to 2.42 eV. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZnO films have been grown on (0001) sapphire substrates by variable electric field-assisted ALD technique. [•] XRD and XPS spectra demonstrate that not only the crystal orientation, but also the oxygen vacancy defect could be modulated by changing the electric field directions of the chamber during precursor pulses. [•] The results of HRTEM show the obtained ZnO thin films have a high crystal quality. [•] It is supposed that substrate electric polarity would expect to modulate the structures and properties of ZnO films. [ABSTRACT FROM AUTHOR]

Highlights: [•] PL from GO–ZnO and rGO–ZnO compositions was reported. [•] Blue emission peak from these compositions is quenched. [•] Yellow–orange emission peaks from these compositions are increased. [•] PL mechanism in these compositions is proposed. [Copyright &y& Elsevier]

Films have been prepared at substrate temperatures of 125 to 200 °C by chemical vapor deposition. As a substrate temperature decreases, the grain sizes of the films are decreased. From transmission electron microscopic observation, the film grown at 125 °C is found to be constructed from ZnO quantum dots with 5 nm in diameter. Photoluminescence spectra in ultraviolet region at 40 K or less are assigned to both free electron-acceptor and donor-acceptor pair emissions, whereas photoluminescence spectra at temperatures higher than 50 K are due to the free electron-acceptor emission. The peak energy of the free electron-acceptor emission for the film deposited at 125 °C is 0.143 eV larger than that for the film deposited at 200 °C. The blue shift of the emission peak is ascribed to the quantum confinement effect. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The nanostructures of iron-doped zinc oxide (FZO) produced by a simple and low cost dip-coating route onto a glass substrate were studied. The structural, morphological, electrical and optical properties of FZO films were investigated. Nanochains were revealed by SEM analysis at high magnification. A (002)-oriented wurzite structure with a lattice parameter of a 3.24 Å and c 5.19 Å was confirmed by X-rays diffraction. High transmittance was exhibited in the visible spectrum, T (550 nm) > 83 %. Finally, electrical measurements revealed a resistivity and mobility of 10 kΩ cm, and 5 cm² / Vs respectively. [ABSTRACT FROM AUTHOR]

Abstract: Highly c-axis oriented AlN thin film was manufactured on Si (111) substrate using ZnO buffer layer by the direct current (DC) magnetron sputtering method. The X-ray diffraction results showed that the AlN/ZnO thin films had a perfect c-axis preferred orientation, and the full width at half maximum (FWHM) of the rocking curves of the (002) AlN peak decreased remarkably. Atomic force microscopy displayed that the AlN films with ZnO buffer layer had a dense, uniform and crack-free uniform microstructure compared to the microstructure of the AlN films grown on Si substrate. The average grain size and RMS surface roughness of the ZnO layers were, respectively, 90nm and 3.4nm. The scanning electron microscopy images showed that the AlN/ZnO thin films presented an obvious and quite uniform columnar structure, which are well aligned to the surface normal direction. The current–voltage curves results indicated that the ZnO buffer layer highly improved the insulating properties of the AlN films. [Copyright &y& Elsevier]

Abstract: High quality semiconductor layer of n-type ZnO thin film was fabricated on F-doped SnO2 glass substrates by pulsed laser deposition. The Schottky junction diodes with configuration of Ag/ZnO/FTO have been fabricated to study the devices electrical properties by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The results show that the devices have good rectifying behaviors with an ideality factor of 1.64 and a Schottky barrier height of 0.85eV based on the I–V characteristics. Also, Cheung’s functions and Norde’s method were used to evaluate the I–V characteristics and to obtain the series resistance of the Schottky contact. From the C–V characteristics, the capacitance was determined to increase with decrease of frequencies. C–V measurements have resulted in higher barrier heights than those obtained from I–V measurements. The discrepancy between Schottky barrier heights obtained from I–V and C–V measurements was also interpreted. [Copyright &y& Elsevier]

Abstract: The effect of thin ZnO coatings grown on Zn films on further oxidation and thermal stability of Zn films deposited on Mo(110) substrate was in situ investigated under ultrahigh vacuum by photoelectron spectrometries and low-energy electron diffraction. The results indicated that ZnO layers formed by oxidizing Zn films had at least a thickness of 3–5 monolayers. Further oxidation of Zn films was confined by as-formed ZnO coatings due to a surface passivation. It was of advantage to explain the difficulty in growing low oxygen-deficient ZnO films. The surface ZnO coatings strongly enhanced the thermal stability of Zn films, which was useful for understanding the underlying application of Zn/ZnO materials, such as Zn/ZnO nanocables with Zn core and ZnO shell. [Copyright &y& Elsevier]

A series of ZnO films have been prepared on Si (100) substrate at various oxygen pressures and at various substrate temperatures by using a laser molecular beam epitaxy system. Their structure was investigated by the Raman spectroscopy and X-ray diffraction. Raman spectra showed that only E2 (low) and E2 (high) modes were present in all ZnO films. The E2 (low) mode peak changed from disperse to sharp at first and then became more dispersed as either the oxygen pressure or the substrate temperature increased. Its intensity reached a maximum either under the oxygen pressure of 1 Pa or at 773 K. The analyses showed that the sharper and stronger the E2 (low) mode peak, the better the crystal quality, which was confirmed by the X-ray diffraction. Moreover, every E2 (high) mode peak shifted to lower Raman frequencies compared with ZnO single crystal, implying that a tensile stress occurred in all films, which was also proved by the X-ray diffraction. All results indicated that Raman scattering is one of the most useful methods to investigate the structure of ZnO films. In addition, the intensity of Si Raman scattering was enhanced in our results, which might be due to surface-enhanced Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the effect of doping on the composition, surface morphology and optical, structural and electrical properties of Al doped ZnO thin films by pulsed laser deposition. SEM analysis shows that the crystalline nature of the deposited films decreases with an increase of Al doping concentration from 1% to 6%. In the AFM analysis, the surface roughness of the deposited films increases by increasing the doping concentration of Al. Al doping strongly influences the optical properties of the ZnO thin films. Optical transmittance spectra show a very good transmittance in the visible region (450–700 nm). The calculated optical band gap was found to be in the range from 3.405 to 3.464 eV. Structural analysis confirms that the increases of Al concentration decrease the crystallinity of the ZnO films and the particle size decreases from 45.7±0.09 to 28.0±0.02 nm. In the Raman analysis, the active mode of Al(=1%) doped ZnO films were observed at 434.81 cm−1. The shifts of the active mode show the presence of tensile stress in the deposited films. The electrical properties of the deposited films showed that the values of the Hall mobility was in the range between 2.51 and 10.64 cm2/V s and the carrier concentration between 15.7 and 0.78×1017 and the resistivity values between 1.59 and 10.97 Ωcm, depending on the doping concentration. [Copyright &y& Elsevier]

Abstract: ZnO films were deposited on (100) Si substrate by radio frequency magnetron sputtering. These films were irradiated at room temperature with 308MeV Xe-ions to a fluence of 1.0×1012, 1.0×1013 or 1.0×1014 Xe/cm2. Then the samples were investigated using RBS, XRD, FESEM and PL analyses. The obtained experimental results showed that the deposited ZnO films were highly c-axis orientated and of high purity, 308MeV Xe-ion irradiations could not change the c-axis oriented. The topography and PL properties of the ZnO films varied with increasing the Xe-ion irradiation fluence. For 1.0×1013 or 1.0×1014 Xe/cm2 irradiated samples, surface cracks were observed. Furthermore, it was found that the 1.0×1014 Xe/cm2 irradiated sample exhibiting the strongest PL ability. The modification of structure and PL properties induced by 308MeV Xe-ion irradiations were briefly discussed. [Copyright &y& Elsevier]

Abstract: An undoped ZnO thin film with high resistivity was prepared by rf magnetron sputtering on the quartz substrates using a ZnO (99.999% pure) as target and high pure Ar as sputtering gas. Upon annealing in a temperature range from 513 to 923K under 10−3 Pa, the conductive properties of the film change from high resistivity, to n-type, then to p-type and finally to n-type with increasing annealing temperature and the p-type ZnO film was fabricated near 863K reproducibly. Temperature-dependent photoluminescence (PL) of the p-type ZnO shows a dominant PL band at 3.072eV at low temperature, which is related to Zn vacancy (VZn) acceptor. The intensity of the 3.072eV band decreases with increasing temperature, implying increment of amount of the hole induced by VZn. X-ray photoelectron spectroscopy (XPS) and room temperature PL measurements indicate that the undoped ZnO is Zn-rich and has oxygen vacancy (Vo) and interstitial Zn (Zni) donor defects. The amount of Vo and Zni donors changes with the annealing temperature. The intrinsic p-type conduction of the undoped ZnO film is ascribed to that the VZn acceptor concentration can compensate Vo and Zni donor concentration. [Copyright &y& Elsevier]

Abstract: Cu-doped ZnO films with hexagonal wurtzite structure were deposited on silicon (111) substrates by radio frequency (RF) sputtering technique. An ultraviolet (UV) peak at ∼380nm and a blue band centered at ∼430nm were observed in the room temperature photoluminescent (PL) spectra. The UV emission peak was from the exciton transition. The blue emission band was assigned to the Zn interstitial (Zni) and Zn vacancy (VZn) level transition. A strong blue peak (∼435nm) was observed in the PL spectra when the α Cu (the area ratio of Cu-chips to the Zn target) was 1.5% at 100W, and ZnO films had c-axis preferred orientation and smaller lattice mismatch. The influence of α Cu and the sputtering power on the blue band was investigated. [Copyright &y& Elsevier]

Abstract: Homoepitaxial ZnO films have been grown via liquid-phase epitaxy (LPE) on (0001) oriented ZnO substrates. X-ray rocking curve revealed the high quality of the ZnO films with a FWHM of 40 arc sec. Films of thickness about 20 μm were grown in the temperature range 700–720 °C. The growth rate of ZnO films was estimated to be 0.3 μm h−1. Atomic force microscope analysis showed that the surface roughness of ZnO films was very low, which further confirmed the high crystallinity of ZnO films. [Copyright &y& Elsevier]

Abstract: Nanocrystalline ZnO thin films on p-type Si(100) substrates have been prepared by a sol-gel method. X-ray diffraction results showed polycrystalline wurtzite with a preferential (002) orientation. Morphology studies revealed that the films consisted of uniform grains in size of ∼33nm. A strong ultraviolet emission with no distinct visible emissions was observed in room temperature photoluminescence spectrum. The ultraviolet emission results from the recombination of free exciton with stronger longitudinal optical (LO) phonon replica. Stronger LO phonon replica may be ascribed to the strong interaction between the exciton and LO phonon in nanostructure. Nanostructure of films is also responsible for the blueshift of free exciton emission compared with single-crystal ZnO. The absence of E 1 (LO) mode in Raman spectrum further confirmed low defect density in as-grown nanocrystalline ZnO films. The electrical junction properties characterized by current–voltage measurement showed a rectifying behavior. [Copyright &y& Elsevier]

In this study, the ZnO films were deposited to different thicknesses by r.f. magnetron sputtering. X-Ray diffraction and pole-figure analysis were used to study the crystallinity and crystal orientation. The results showed that ZnO films deposited to a thickness below 500 nm were polycrystalline with a c-axis preferential orientation. However, ZnO films, 500 or 600 nm in thickness, exhibited good self-texture. The optical properties of ZnO films did not depend significantly on the crystallographic orientation or degree of texturing. They were mainly affected by the grain size and carrier concentration. [Copyright &y& Elsevier]

Ultrasonic rinsing procedure was introduced to successive ionic layer adsorption and reaction (SILAR) method. ZnO nanocluster porous films were successfully deposited on glass substrate using zinc–ammonia complexed precursor. The crystallinity, microstructure, optical properties and photoluminescence were measured and analyzed for both as-deposited and annealed films. Effects of experimental parameters and heat treatment on the structural and optical properties were discussed. Results show that as-deposited ZnO film exhibits excellent crystallinity with the preferential orientation of (0 0 2) plane. A porous feature with interconnected particles of 200–400 nm in ZnO films was observed, with each ZnO particle formed by the aggregation of many crystallites in size of 30–50 nm. The low transmittance due to scattering losses over the porous ZnO layer down to 16% was detected. The annealing at 400 °C can promote the preferential orientation along (1 0 0) plane, the interfusion of adjacent particles and the reduction of scattering loss. Intense and sharp ultraviolet emission peaks at 392 nm dominates the PL spectra for both as-deposited and annealed samples, indicating the good optical quality of ZnO layer. [Copyright &y& Elsevier]

In this paper we report on the structural features and optical properties of wurtzite ZnO films epitaxially grown on sapphire, fluorite and mica substrates by means of pulsed laser deposition (PLD). Post-deposition annealing results in a clear improvement of the film quality, reflected by the small width of the exciton-related lines in both the absorption and the photoluminescence spectra. Photoluminescence spectra revealed a multi-line structure which is identified in term of free excitons and excitons complexes with neutral donors and deep centers. The relative intensity of the PL lines mainly depends on the nature of the substrate used. Concerning optoelectronic applications it is especially relevant to investigate the high structural and optical quality of ZnO deposited on low cost mica substrates, in which we observed the narrowest exciton peaks and the lowest surface roughness using atomic force microscopy. [Copyright &y& Elsevier]