Narrow Results

Nanocrystalline ZnO films were prepared by thermally oxidizing the Zn films deposited on mirror-polished quartz substrates by thermal evaporation of Zn granule. The structure of the films was studied by X-ray diffraction (XRD). The results showed that highly preferred (002) orientation of the ZnO films has been achieved. The oxidation temperature has an important effect on preferred orientation of ZnO films.

Zinc oxide (ZnO) thin films grown on Si(111) substrates by pulsed laser deposition at O₂ ambient pressure of 1.3 Pa at different deposition temperatures have been studied. ZnO thin films underwent annealing treatment after deposition. The structural and optoelectronic properties of deposited and annealed thin films have been characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), infrared absorption (IR) spectra, four-probe measurements and photoluminescence (PL) spectra. The XRD observation shows that the best crystalline quality of ZnO thin films with hexagonal structure are those grown at a temperature of 400°C and annealed at a temperature of 600°C, respectively. AFM results show that the surface roughness of the ZnO films can be decreased with increasing annealing temperature up to 600°C and then increased by further increasing the annealing temperature. The intense absorption peak sited at 417.54 cm^-1 has been observed by IR spectra for ZnO film grown at 400°C and annealed at 600°C, and the property of absorption is improved by post-annealing. ZnO film grown at 400°C with a resistivity of 12.3 Ω·cm shows the best n-type semiconductor property. The PL spectra show the dominant increase in UV emission by annealing. It is concluded that the best post-annealing temperature is about 600°C.

Zinc oxide (ZnO) thin films were grown on sapphire substrates at different deposition temperatures by pulsed laser deposition (PLD). The structure, composition and optical properties of deposited thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectra. The results show that the ZnO thin films deposited at 500°C have the best crystalline quality with hexagonal structure, surface morphology and stoichiometric composition. The PL spectrum reveals that the sample possesses the strongest ultraviolet (UV) emission at 370 nm and the weakest blue emission at 459 nm under this condition. Raman spectra and weak blue emission of PL spectra show that very few oxygen vacancies exist in the ZnO thin films.

Zn_1-xCr_xO(x = 0, 0.03, 0.09) films were prepared by the radio frequency (RF) magnetron sputtering technique on Si(111) and quartz glass substrates. The effects of Cr-doping on the structural and optical properties of ZnO films have been discussed. The structural properties were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) while optical properties using UV-Visible spectrophotometer (UV-VIS). XRD measurement revealed that the films were single phase and wurtzite structure with c-axis orientation. With the increase of Cr concentration, the intensity of the (002) peak and the grain size of the Zn_1-xCr_xO(x = 0, 0.03, 0.09) films decreased, and the Full Width at Half Maximum (FWHM) of (002) peak, the crystal lattice parameter c of Zn_1-xCr_xO(x = 0, 0.03, 0.09) films and the width of optical band gap increased, respectively. In the transmittance spectra of the Zn_1-x Cr_xO(x = 0, 0.03, 0.09) films, the movement of the absorption edge of the ultraviolet region is the Burstein–Moss shift with the increase of Cr concentration.

Due to the mismatch between ZnO film and $p$-Si lattice, there are a large number of interface states which seriously affect the photoelectric properties of ZnO/$p$-Si heterojunction optoelectronic devices. In this research, ZnO thin films were deposited on $p$-Si by magnetron sputtering and ZnO/$p$-Si heterojunction was prepared. CuSCN film buffer layer was inserted into the interface of ZnO/$p$-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/$p$-Si heterojunction, increase the forward current, reduce the reverse current and improve the heterojunction rectification ratio.

The effects of substrate-placing manner, deposition temperature and solution concentration on the preparation of ZnO films by chemical bath deposition were investigated in this work. The structures and the morphologies of as-deposited ZnO films were characterized by X-ray diffraction and scanning electron microscope, respectively. The results show that compared with vertically insertion, floating the substrates on the solutions could greatly improve the c-axis orientation of the films. The growth of ZnO films with orientation would also be favored at lower precursor concentrations and temperatures. When the concentration of Zn(CH₃COO)₂·2H₂O is 0.033 M/L and the deposited temperature is 60°C, ZnO films which are well crystallized and highly c-axis orientated were obtained.

Li-W co-doped ZnO (LWZO) thin films were deposited on quartz glass substrates by RF magnetron sputtering technology. The properties of LWZO films deposited with varied substrate temperatures were investigated. When the substrate temperature was lower than 120°C — according to X-ray diffraction (XRD) patterns, films keep hexagonal wurtzite structure with the (002) plane as preferred orientation — the optical transmittance was higher than 85%. When the substrate temperature was higher than 120°C, the results of XPS and XRD show that W⁶⁺ will work as donors, and the (101) peak appeared; the optical transmittance decreased slightly but still higher than 82%. Scanning electron microscope (SEM) and its two-dimensional Fourier transform images showed that films had smooth surface and columnar particles structure when the substrate temperature was lower than 120°C. The film surface became rougher and flaky-shaped particles structure could be observed when the substrate temperature was higher than 120°C. In addition, the lowest electrical resistivity of sample was 3.6 × 10^-3 Ω ⋅ cm which was obtained at substrate temperature 240°C.

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 $95^{\circ }$C. The exposure time of Zn coating in deionized water is varied from 1h to 24h in sequence. At the 24h 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 3.28eV to 3.19eV). Photoluminescence (PL) spectra have depicted phonon replicas with energy separation of $\sim 124$meV for the ZnO films obtained after 6 and 12h exposure time in deionized water at $95^{\circ }$C temperature.

Undoped and fluorine (F)-doped nanostructured zinc oxide (ZnO) thin films were deposited over glass substrates by spray pyrolysis technique using zinc acetate dihydrate with and without ammonium fluoride as dopant in precursor solution respectively. The deposition conditions and the concentration of the dopant were optimized to obtain nanostructured ZnO thin films. The film obtained from 0.05 M of zinc acetate aqueous solution and 20% F sprayed at the rate of 3 ml/min on preheated substrate kept at 503 K yielded spherical shape well-connected grains, which has large surface to volume ratio. The structural and morphological studies of the films were investigated by using X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. The diffraction peak positions in XRD confirmed the formation of highly crystalline ZnO film with hexagonal wurtzite phase. Further sensing behavior of the films towards various concentrations of volatile organic compounds (VOCs) such as ethanol and trimethyl amine (TMA) has been investigated at an optimized operating temperature of 373 K and reported.

ZnO films with well-aligned hierarchical structures have been successfully synthesized at moderate temperatures using a simple catalyst-free hydrothermal process. The synthesized ZnO films are found to be single-phase, with a hexagonal wurtzite-type structure. Scanning electron microscopy images show that the well-aligned hierarchical structures are assembled with interlaced parallel sheets grown on the (400) silica surface. The water contact angle measurement indicates that the water on the films has a contact angle of about 156.3°. This clearly demonstrates that the ZnO films synthesized by this simple method have superhydrophobic properties and may be important for applications in self-cleaning surfaces, biology, and so on.

Since transparent conducting oxides can be as a buttom layer of complex film electrodes, electrodeposition technique may produce ZnO films depending on variety conditions and modified surface layers of substrates in electrochemical procedures. Here we invested the structure and morphologies of top ZnO layers by using modified surfaces of the substrate in the multilayer film-“ZnO-electrodeposition /ZnO(002)-sputtering /ITO/ glass”.