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The effects of zinc nitrate solution concentrations on the crystal structures, surface morphologies and optical properties of ZnO thin films were examined. X-ray diffraction patterns and scanning electron microscopy images indicated that all the samples exhibited the hexagonal structure and the morphologies of the thin films changed from 1D nanorods to 2D nanosheets with the increasing of solution concentration. The thin film grown in the 0.075 M solution presents the 3D network nanostructure, which was composed of many very thin 2D ZnO nanosheets, and possesses the largest first LO phonon mode, optical band gap, ratio for the intensity of deep level emission to that of UV emission. The results indicated that the optical properties of the ZnO thin films were affected by the solution concentration. Finally, the as-deposited ZnO thin film was used to generate a photocurrent and as a photocatalyst. Observations showed that the thin film grown in the 0.075 M solution exhibits the largest photocurrent density and degradation rate constant per unit area. The formation mechanism of the enhanced photoresponse and photocatalytic performance for the ZnO thin film has been investigated in detail. [ABSTRACT FROM AUTHOR]

NaZnO thin films were successfully synthesized on quartz glass substrates by sol-gel method. The effect of Na content on the microstructure, optical properties and UV photoresponse of the thin films was investigated using X-ray diffraction, optical absorbance, photoluminescence, and conductivity measurements. The results indicate that the NaZnO thin film exhibits the strongest preferential c-axis orientation with a polycrystalline hexagonal wurtzite structure and has the largest optical band gap. An obvious decrease in crystal size has been observed with the increasing of Na content. A weak ultraviolet emission band at about 381 nm and a strong visible emission band have been observed in the photoluminescence spectra. The NaZnO thin film has the shortest growth and decay time (45 and 18 s, respectively) and the largest photoresponse. The results indicate that the photoresponse can be effectively improved by means of moderate Na doping. [ABSTRACT FROM AUTHOR]

NaCuZnO thin films were prepared by sol-gel method on quartz glass. The effect of Na (or Cu) doping on the microstructure, surface morphology, optical properties of the thin films was investigated. The NaCuZnO thin film has the largest average grain size and the best preferential c-axis orientation, which may be attributed to the difference in ionic radius between Zn and Na (or Cu). The NaCuZnO thin film also presents denser morphology with little voids and the smallest optical band gap, which may be attributed to band edge bending and the larger grain size. The largest intensity of A(LO) modes may be due to the major structural defect concentrations. The quenching of UV and visible emissions, which may be attributed to the increase of non-radiative recombination transition, has been observed in the NaCuZnO and NaCuZnO thin films. [ABSTRACT FROM AUTHOR]

Cuprous oxide thin films were successfully synthesized on FTO substrates via the electrochemical method by changing the deposition potential. The effects of deposition potential on the microstructure, morphology, optical band gap and photoresponse of the thin films were investigated. The results revealed that intensity of (111) diffraction peak and preferential orientation along (111) plane increase with increasing the absolute value of deposition potential. The thin film with the more negative deposition potential has an increased average particle size and compact degree. The optical band gap of the sample deposited at −0.5 eV presents the largest value of 1.82 eV. Upon sunlight illumination, the photocurrent of thin film rises quickly at first and then gets slower. The slow photoresponse may be attributed to the capture of carriers by deep level traps in our case. [ABSTRACT FROM AUTHOR]

ZnO thin films were prepared by hydrothermal method in mixed solvent with different reaction temperatures. Microstructure, surface morphology, optical properties and UV photoresponse of the thin films have been investigated by means of X-ray diffractometer, scanning electron microscopy, laser micro-Raman spectrometer, UV-Vis spectrophotometer and interactive source meter instrument. The results indicated that ZnO thin films consist of ZnO nanoparticles with hexagonal wurzite structure. A small quantity of Zn(OH) appear as reaction temperature increase to 125 °C. ZnO thin film grown at 175 °C consists of many densely vertically aligned ZnO nano rods on the substrate and has the best preferential c-axis orientation. Three peaks centered at about 446, 568 and 1150 cm have been attributed to E(high), A( LO) and 2 A( LO) phonon mode. Broadening of the visible emission band may be attributed to abundant surface defects and surface states of the thin films. Variation of the E may be attributed to the synergy of surface morphology and oxygen-vacancy (V) density. The fast and slow UV photo response may be attributed to the adsorption and photo desorption of oxygen molecules on the surface of ZnO thin films and exchange process between oxygen gas and native deep defect level, respectively. [ABSTRACT FROM AUTHOR]

CuO/CuO composite thin films were synthesized by a facile hydrothermal method on Cu foils. Surface morphology, chemical composition, microstructure and wettability were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, X-ray diffractometer and water contact angle apparatus. The results indicate that the Sample 2 is composed of many regular CuO octahedrons, tiny nanovillus and a small amount of spheric particles. The other samples were composed mainly of flower-like microparticles and regular CuO octahedrons. The content of copper (II) increases firstly and then decreases and the maximal value of content of copper (II) has been observed in the Sample 2. The Sample 2 displayed superhydrophobic property owing to its hierarchical porous micro/nanostructured surface. [ABSTRACT FROM AUTHOR]

Cuprous oxide (CuO) thin films were prepared by using electrodeposition technique at different applied potentials (−0.1, −0.3, −0.5, −0.7, and −0.9 V) and were annealed in vacuum at a temperature of 100°C for 1 h. Microstructure and optical properties of these films have been investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), UV-visible (vis) spectrophotometer, and fluorescence spectrophotometer. The morphology of these films varies obviously at different applied potentials. Analyses from these characterizations have confirmed that these films are composed of regular, well-faceted, polyhedral crystallites. UV-vis absorption spectra measurements have shown apparent shift in optical band gap from 1.69 to 2.03 eV as the applied potential becomes more cathodic. The emission of FL spectra at 603 nm may be assigned as the near band-edge emission. [ABSTRACT FROM AUTHOR]

Highly ordered TiO nanotube array (TN) films were prepared by anodization of titanium foil in a mixed electrolyte solution of glycerin and NHF and then annealed at 200°C, 400°C, 600°C, and 800°C, respectively. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle (WCA), and photoluminescence (PL). It was found that low temperature (below 600°C) has no significant influence on surface morphology, but the diameter of the nanotube increases from 40 to 50 nm with increasing temperature. At 800°C, the nanotube arrays are completely destroyed and only dense rutile film is observed. Samples unannealed and annealed at 200°C are amorphous. At 400°C, anatase phase appears. At 600°C, rutile phase appears. At 800°C, anatase phase changes into rutile phase completely. The wettability of the TN films shows that the WCAs for all samples freshly annealed at different temperatures are about 0°. After the annealed samples have been stored in air for 1 month, the WCAs increase to 130°, 133°, 135°, 141°, and 77°, respectively. Upon ultraviolet (UV) irradiation, they exhibit a significant transition from hydrophobicity to hydrophilicity. Especially, samples unannealed and annealed at 400°C show high photoinduced hydrophilicity. [ABSTRACT FROM AUTHOR]

MgZnO thin films were prepared on silicon substrates by a sol-gel dip-coating technique. Microstructure, surface topography and optical properties of the thin films were characterized by X-ray diffraction, atom force microscopy, Fourier transform infrared spectrophotometer and fluorescence spectrometer. The results show that the thin film annealed at 700 °C has the largest average grain size and exhibits the best c-axis preferred orientation. As annealing temperature increases to 800 °C, the grain along c-axis has been suppressed. Roughness factor and average particle size increase with the increase of annealing temperature. The IR absorption peak appearing at about 416 cm is assigned to hexagonal wurtzite ZnO. The thin film annealed at 700 °C has the maximum oxygen vacancy, which can be inferred from the green emission intensity. Photocatalytic results show that the thin film annealed at 700 °C exhibits remarkable photocatalytic activity, which may be attributed to the larger grain size, roughness factor and concentration of oxygen vacancy. Enhanced photocatalytic activity of MgZnO thin films after a cycle may be attributed to the increase of surface oxygen vacancy and photocorrosion of amorphous MgO on the surface of thin film under UV irradiation. [ABSTRACT FROM AUTHOR]

Highlights: [•] CAO films with different Al volume fraction of 1–5% were prepared. [•] The microstructure, optical and hydrophily properties were studied. [•] CAO films changes from hydrophobicity to hydrophily after annealing. [•] The mechanism of the evolution of WCA is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Ag-TiO2 nanostructured thin films with silver volume fraction of 0–40% were prepared by RF magnetron sputtering. The microstructure, surface topography, and optical properties of the films were characterized by X-ray diffractometer, transmission electron microscope, and ultraviolet–visible spectrophotometer. Photocatalytic activity of the films was evaluated by light-induced degradation of methyl orange (C14H14N3NaO3S) solution using a high pressure mercury lamp as lamp-house. The relation of photocatalytic activity and silver content was studied in detail. It is found that silver content influences microstructure of TiO2 thin films, and silver in the films is metallic Ag (Ag0). Photocatalytic activity of the films increases with increasing silver content up to 5vol.% Ag and then decreases to values significantly still bigger than that of pure TiO2 thin films. Silver nanoparticles significantly enhance the photocatalytic activity of TiO2 films. The better separation between electrons and holes on silver modified TiO2 thin films surface allowed more efficiency for the oxidation and reduction reactions. The enhanced photocatalytic activity was mainly attributed to the decrease of energy gap of the films and the increase of oxygen anion radicals O2 − and reactive center of surface Ti3+ on silver modified TiO2 thin films surface. [Copyright &y& Elsevier]

A nanocrystalline ZnO/PVP (polyvinylpyrrolidone) composite film was directly prepared on Zn foil via hydrothermal etching method. The microstructure, morphology, photocatalysis and photoluminescence of the composite film were investigated. X-ray diffraction, scanning electron microscopy and transmission electron microscopy indicated that all the nanocrystalline ZnO nanoparticles were embedded in the PVP matrix randomly with a single crystalline hexagonal wurtzite structure. The photoluminescence spectrum of the ZnO/PVP composite film showed enhanced ultraviolet emission and no green emission, which was due to the improved crystal quality of ZnO nanocrystallines. Moreover, the obtained ZnO/PVP film exhibited good photocatalytic activity for decomposing methyl orange. [ABSTRACT FROM AUTHOR]

ZnO thin films were deposited using an electrodeposition method and porous morphologies could be achieved by annealing treatment. A variety of Ag nanoparticles were loaded on the surface of the ZnO thin films. Surface morphology, chemical composition, crystal phase and optical properties were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV–vis spectrophotometer and micro-Raman spectroscopy. Evidence of Ag nanoparticles on the Ag-4/ZnO thin film was be verified by the SEM and XPS measurements. The XRD results indicated that the Ag nanoparticles had little effect on crystallinity of the thin films. The photoresponse and photocatalytic results indicated that the photocurrent and photocatalytic performance could be enhanced by moderate Ag nanoparticles modification on the surface of the ZnO thin film. The best photoresponse and photocatalytic activity in Ag-4/ZnO thin film results from the moderate Ag nanoparticles on the surface of ZnO thin film, which could enhanced separation and suppressed recombination of photogenerated electron-hole pairs. [ABSTRACT FROM AUTHOR]

Al-doped zinc oxide (AZO) thin films were deposited on ultra-thin flexible glass substrate using a direct current magnetron sputter. Microstructure, electrical and optical properties of the AZO films were investigated as a function of film thickness. The XRD pattern shows that all deposited AZO films have a highly preferred c-axis orientation along (0002) direction. When the film thickness is over 100 nm, all the AZO films have similar grain size about 30 nm and good uniformity. The sheet resistance of the AZO films decreased with the increase of film thickness, whereas the 230.1 nm thick AZO film has the minimum resistivity of 1.65 × 10 − 3 Ω cm. The average transmittance of all AZO films in the visible range was about 80%, while the optical band gap of the films was in the range of 3.483–3.526 eV. The sheet resistance of AZO films deposited on flexible glass using strained growth is different with that of AZO films using normal growth method. Moreover, the sheet resistances of AZO film with different pre-strain are very different, which may be due to their different microstructures of AZO films. [ABSTRACT FROM AUTHOR]

SVs-In 2 S 3 /TiO 2 system activates PMS under visible light to degrade levofloxacin hydrochloride. [Display omitted] • For the first time, thin-film heterojunction photocatalysts grown on FTO are applied to the activation of PMS. • The SVs-In 2 S 3 /TiO 2 + PMS system exhibits excellent degradation performance for LVFH. • Thin-film photocatalysts are more recoverable and relevant than powder photocatalysts in real environment. • The formation of internal electric field and the molecular structure of LVFH were analyzed using DFT calculations. Photocatalytic activation of peroxymonosulfate is considered an effective method for degrading organic pollutants. However, the difficulty in recovering powder photocatalysts restricts their practical applications. In this study, we hydrothermally generated sulfur-vacancy-modified In 2 S 3 /TiO 2 thin films on fluorine-doped tin oxide substrates. We further investigated the formation mechanism of heterojunctions and the degradation pathways of levofloxacin hydrochloride by activated PMS using density functional theory calculations. Results from a series of experiments showed that the levofloxacin hydrochloride degradation performance by thin-film catalyst-activated peroxymonosulfate is comparable to that of powder photocatalysts, while the ease of recycling makes the thin film more suitable for applications in a real environment. Furthermore, the construction of heterojunctions and introduction of sulfur vacancies compensated for the poor separation efficiency of photogenerated electron-hole pairs in single photocatalysts. Overall, this study provides novel insights into the degradation of organic pollutants using thin-film photocatalysts in advanced oxidation processes. [ABSTRACT FROM AUTHOR]

In the current work, electrodeposition method has been used to prepare Cu 2 O thin films on ITO substrates. The bath temperature was controlled from 40 to 80 °C and additive concentration varied from 2 to 10 mM. The structure, surface morphology and optical properties of the as-prepared films were investigated by X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), Raman spectrophotometer and UV–visible (vis) spectrophotometer. The morphology of the Cu 2 O films varies obviously at different bath temperature and additive concentration. Intensity of Raman peaks increase with the increase of KCl concentration. UV–vis absorption spectra measurements have shown the average absorbance for the film deposited at 80 °C is higher than those deposited at 40 and 60 °C. Meanwhile, average absorbance of the Cu 2 O thin film deposited at 10 mM KCl is larger than those deposited at 2 and 5 mM KCl, which should be associated with the morphology. [ABSTRACT FROM AUTHOR]

ZnO/Cu 2 O composite thin films were deposited on Cu foil using a simple solution method with a variety of ZnO seed layers inserted between the Cu 2 O and ZnO layers. Effects of the ZnO seed layers on the microstructure, optical properties and photoresponse of the thin films were investigated. The intensity of the ZnO (002) diffraction peak increases with increasing thickness of the seed layer. Dissolution of ZnO nanoparticles also occurs during growth of the ZnO thin films. The optical band gap of the Cu 2 O layer decreases gradually from 1.86 to 1.66 eV as the thickness of the ZnO seed layer increases. Change of the optical band gap could be attributed to Cu 2+ impurities in the Cu 2 O and (or) ZnO layers. A visible emission from sample with a seed layer of four times can be attributed to phonon-assisted exciton recombination in Cu 2 O. An ultraviolet emission centered at 380 nm and a broad visible emission band is observed in the two samples with a seed layer of six and eight times. The best photoresponse performance has been observed in the sample with a seed layer of eight times. This is likely a result of the stronger visible absorption and better band alignment in samples, which facilitates electron transfer from the conduction band of Cu 2 O to the conduction band of ZnO. [ABSTRACT FROM AUTHOR]

Heat-assisted PbS/TiO 2 thin films with different reaction temperatures were prepared. Microstructure, morphology, optical and photoelectron-chemical properties of the as-synthesized thin films were investigated systematically. For the PbS/TiO 2 thin films with reaction temperature changing from 10 to 95 °C, PbS particles obtained by successive ionic layer adsorption and reaction are galena phase, the mean size of PbS particles decreases firstly and then increases, the coverage of PbS particles on surface increases. At the same time, red shift in the adsorption edges from 416 to 594 nm has been detected, and the optical band gap E g decreases from 3.58 to 2.88 eV. What's more, the intensity of photoluminescence increases firstly and then decreases. The photochemistry measurement suggests that the sample prepared at 60 °C possesses the highest photocurrent in the first test cycle. However, the value of photocurrent decreases immediately with increasing the test cycle. The effect of the reaction temperature on the microstructure, morphology, optical and photoelectron-chemical properties of PbS/TiO 2 thin films have been discussed in detail. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 thin films with different reaction time were prepared by hydrothermal method. [•] The microstructure, photoluminescence, Raman and optical properties were investigated. [•] The surface morphology shows obvious change with increasing reaction time. [•] The optical properties, photoluminescence and Raman properties are influenced by reaction time. [•] The ratio of Ti:O is 1:2.206 and close to the atom ratio of TiO2. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cu concentrations enhance preferential c-axis orientation Cu x Zn1− x O thin films. [•] The optical band gap and PL spectra of Cu x Zn1− x O thin films were studied. [•] Effect of Cu concentrations on optical band gap has been reported. [•] We report the photoluminescence mechanism of Cu x Zn1− x O thin films. [ABSTRACT FROM AUTHOR]

Abstract: The ZnS:Ag nano-composite films with different Ag volume fractions (5, 10, 15 and 2vol.%) were deposited on glass substrates by sputtering. The microstructures, optical and electrical properties of the as-deposited films were studied. XRD measurement shows that all films are polycrystalline with a microstructure of body-centered cubic phase belonged to ZnS. The samples in which Ag volume concentrations lower than 20vol.% show a preferential orientation along the (220) direction. When Ag concentration reaches 20vol.%, the intensity of the (220) peak belonged to ZnS decreases dramatically while the Ag (111) peak emerged. Based on our analysis, it can be noted that Ag can help the ZnS grains grow when Ag concentration is lower than 20vol.%. However, the ZnS crystal growth is suppressed when Ag concentration is 20vol.%. The refractive index of the samples decreases with the increase of Ag concentration while the extinction coefficient of the samples increases. The resistivity of the film reaches the minimum when Ag concentration is 20vol.%, showing the electrical conductivity improvement of the composite film by doped Ag nano-particles. [Copyright &y& Elsevier]

Abstract: Cu/ITO thin films were deposited on glass and silicon substrates by DC and RF magnetron sputtering at room temperature. X-ray diffraction results showed that the films were amorphous. Both of SEM images and 3D Profilometer images indicated that the surface morphology of the ITO films had been affected by the Cu layer. The optical and electric properties of the Cu/ITO films changed significantly with the variation of Cu layer thickness. Cu-5.4nm/ITO film exhibited the highest optical transmittance of 62.9% at 550nm and the lowest sheet resistance of 96Ω/□, whereas Cu-16.1nm/ITO film showed the highest average reflectance of 24.0% and the lowest resistance of 27.4Ω/□. Based on our analysis, it was evaluated that Cu layer had an important effect on the electrical and optical properties of ITO thin films. [Copyright &y& Elsevier]

Abstract: ITO and Ag-ITO composite films were deposited on glass substrates by DC magnetron sputtering. Scanning electron microscope images indicated that Ag existed in the form of nanoparticles. X-ray photoelectron spectroscopic analysis illustrated that both Ag doping and heat treatment had obvious influence on the composition and element chemical state of the films. Ag doping dramatically decreased the transmittance of the film. But after being annealed, Ag-ITO films exhibited the high average transmittance of 80–90% in visible wavelength range. By using the spectroscopic ellipsometry optimization, the optical constants were extracted from the transmittance spectra. The results suggested the potential use of Ag-ITO films for antireflection coating system. [Copyright &y& Elsevier]

Abstract: The structural and optical properties of pure and Na-doped ZnO thin films have been investigated by X-ray diffraction (XRD), atom force microscopy and UV–Vis spectrophotometer. The crystal structure of all the thin films is the hexagonal wurtzite. The average grain size and surface roughness increases with the increase of the Na/Zn ratio. The optical band gap of the thin films decreases from 3.26 to 3.12eV by increasing the Na/Zn ratio from 0.0 to 0.10. Transmittance spectra were used to determine the optical constants of the thin films, and the effect of Na/Zn ratio on the optical constants was investigated. With the increase of Na/Zn ratio, the refractive index decreases and the extinction coefficient increases in the 380–700nm spectral range. [Copyright &y& Elsevier]

Abstract: Undoped and Na-doped ZnO thin films were deposited on Si(111) substrate by the sol–gel method. Microstructure, surface topography and optical property of the thin films have been investigated. X-ray diffraction analysis showed that all the thin films had a polycrystalline hexagonal wurtzite structure. The 8at% Na-doped ZnO thin films exhibited high c-axis preferred orientation. Surface topography revealed that average grain size of ZnO thin films annealed at 873K increased initially, and then decreased with increasing Na concentration, and average grain size of 8at% Na-doped ZnO thin films increased with increasing annealing temperature. PL spectra showed that all the thin films produced violet and yellow–green emissions in the visible region. In addition, the effects of Na concentration and annealing temperature on microstructure, surface topography and PL spectra are discussed. [Copyright &y& Elsevier]

• 20 W-Sputtering-derived Yb 2 O 3 gate dielectrics were deposited on Si substrates. • Optimized 300 °C-annealed Dy 2 O 3 sample exhibits excellent electrical performance. • Annealing temperature dependent leakage conduction mechanism has been discussed systematically. The effect of sputtering power and annealing temperature on the microstructure, optical and electrical properties of sputtering-derived Yb 2 O 3 high-k gate dielectrics on Si substrate have been investigated systematically. Based on measurements by ultraviolet-visible spectroscope (UV-Vis) and spectroscopic ellipsometry (SE), the increase in band gap and reduction in refractive index have been detected. Structural analyses by x-ray diffraction (XRD) reveal that the Yb 2 O 3 thin films exhibit a cubic phase at higher annealing temperature. X-ray photoelectron spectroscopy (XPS) analyses demonstrate the decreased Yb silicate and low-k SiO 2 interfacial layer for the samples annealed at 300 °C. Electrical measurements have indicated that Yb 2 O 3 /Si gate stacks annealed at 300 °C shows excellent dielectric performance with leakage current density of 3.66 × 10−8 A/cm2 at applied voltage of 1 V. As a supplement, the leakage current conduction mechanisms of MOS capacitor for different annealing temperature have been discussed systematically. [ABSTRACT FROM AUTHOR]