Weiping Chai

Influences of working pressure on properties for TiO2 films deposited by DC pulse magnetron sputtering.

TiO2 films were deposited at room temperature by DC pulse magnetron sputtering system. The crystalline structures, morphological features and photocatalytic activity of TiO2 films were systematically investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and ultraviolet spectrophotometer, respectively. The results indicated that working pressure was the key deposition parameter influencing the TiO2 film phase composition at room temperature, which directly affected its photocatalytic activity. With increasing working pressure, the target self-bias decreases monotonously. Therefore, low temperature TiO2 phase (anatase) could be deposited with high working pressure. The anatase TiO2 films deposited with 1.4 Pa working pressure displayed the highest photocatalytic activity by the decomposition of Methyl Orange solution, which the degradation rate reached the maximum (35%) after irradiation by ultraviolet light for 1 h.

An XPS study on the chemical bond structure at the interface between SiOxNy and N doped polyethylene terephthalate

The super-thin silicon oxynitride (SiOxNy) films were deposited onto the N doped polyethylene terephthalate (PET) surface. Varying the N doping parameters, the different chemical bond structures were obtained at the interface between the SiOxNy film and the PET surface. X-ray photoelectron spectra results showed that at the initial stage of SiOxNy film growth, the C=N bonds could be broken and C-N-Si crosslink bonds could be formed at the interface of SiOxNy∕PET, which C=N bonds could be formed onto the PET surface during the N doping process. At these positions, the SiOxNy film could be crosslinked well onto the PET surface. Meanwhile, the doped N could crosslink the [SiO4] and [SiN4] tetrahedrons, which could easily form the dense layer structure at the initial stage of SiOxNy film growth, instead of the ring and∕or chain structures of [SiO4] tetrahedrons crosslinked by O. Finally, from the point of applying SiOxNy∕PET complex as the substrate, the present work reveals a simple way to crosslink them, as well as the crosslink model and physicochemical mechanism happened at the interface of complex.

Effect of Sb doping on the microstructure and optoelectrical properties of Sb-doped SnO2 films prepared by spin coating

Sb-doped SnO2 (ATO) films were successfully prepared by the spin-coating method starting from colloidal suspensions of ATO nanocrystalline particles. The structural, surface morphological, electrical and optical properties of the films were studied as a function of Sb-doping concentration ranging from 0 to 20% (Sb/(Sb + Sn)). The results indicated that all films were ATO polycrystalline with the typical tetragonal crystal structure of bulk SnO2. The monotonic decrease of the x-ray diffraction (XRD) peak intensity and the increase of XRD peak width with Sb-doping concentration indicated a finer crystal size distribution and a decrease in crystallization. The films had a porous and netlike microstructure with a more homogeneous and closely packed distribution of nanoclusters when the Sb-doping concentration was increased. The electrical resistivity decreased sharply from 1765 to 0.66 Ω cm when the Sb-doping concentration was increased from 0 to 15% and then decreased slightly to 0.52 Ω cm when the Sb-doping concentration was increased from 15 to 20%. The film transmittance decreased from 82 to 61% in the visible region. The calculated optical band gap energy first decreased from 4.01 to 3.61 eV and then slightly increased to 3.61 eV, reaching a minimum value at 15% Sb-doping concentration. The pore/grain contact scattering mechanism of an electron and a photon is presented to explain the novel optoelectrical properties of the films.

Effect of Doped Boron on the Properties of ZnO Thin Films Prepared by Sol-gel Spin Coating

Transparent conductive boron-doped ZnO thin films were prepared by sol-gel spin coating method. The effect of doped boron concentration on the properties of the films was systematically discussed. The films were characterized by X-ray diffraction, atomic force microscopy, spectrophotometry, and Hall effect measurement system. All the doped and undoped ZnO films were of a single hexagonal structure, and showed a preferred orientation of (002). The particle size and surface roughness of the films decreased with increased doped boron concentration. All the films exhibited an average transmittance of approximate 90% in visible-light region and an energy gap of about 3.3 eV. The maximum carrier concentration, the highest carrier mobility and the lowest resistivity were observed at a doped boron concentration of 0.5%(molar fraction). Based on these results, we suggested that the saturation concentration of doped boron in ZnO film is 0.5%(molar fraction).

SYNCHRONOUS IMPROVEMENT OF DISPERSIBILITY AND ELECTRICAL PROPERTY OF ANTIMONY DOPED TIN OXIDE NANOPARTICLES PROCESSED BY POLYVINYL ALCOHOL

Antimony doped tin oxide (ATO) nanoparticles were prepared by wet chemical coprecipitation method with different contents of polyvinyl alcohol (PVA) dispersant. The prepared ATO nanoparticles have been characterized by means of XRD, SEM, HRTEM, SAED, EDS, bulk density and electrical resistivity measurement. Results indicated that the approach functionalized by PVA dispersant enables a synchronous improvement of two important properties namely the dispersibility and electrical conductivity due to the mechanism of avoiding the formation of agglomeration of nanoparticles, which could be regarded as primary factors for the enhanced electron transfer of powders: The surface area over which are crucial for the interfacial arrangement and electron charge scattering/transfer processes. The bulk density and electrical resistivity decreased to a minimum of 0.90 g/cm3 and 1.44 Ω⋅cm at PVA dispersant content of 5%, and increased rapidly at higher PVA contents. The prepared ATO nanoparticles can serve as a kind of effective conductive filler in insulating species such as plastics, textile and rubber.

The nanocrystalline structure of TiO2 film deposited by DC magnetron sputtering at room temperature

At room temperature, titanium dioxide (TiO2) films were deposited by the direct current pulse magnetron sputtering technique. Varying O2/Ar flow ratio, TiO2 films with different nanocrystalline structures were obtained. The high resolution transmission electron microscopy results show that with O2/Ar = 6/14, the nanocrystalline in rutile phase appears in as-deposited film. Then X-ray diffraction patterns of annealed films revealed that with O2/Ar = 6/14, the higher weight fractions of rutile TiO2 appear in films. The optical emission spectroscopy results show that with O2/Ar < 6/14, O element was mainly existed as O-/O+ ions, instead of excited state of O atoms.

Study on the optical property and surface morphology of N doped TiO2 film deposited with different N2 flow rates by DCPMS

N doped TiO2 films were deposited by direct current pulse magnetron sputtering system at room temperature. By using UV-Vis spectrophotometer and atomic force microscope, we studied the influence of N2 flow rate on the optical property and surface morphology of films. The results indicate that the optical property and surface morphology of N doped TiO2 film was dominated by the N2 flow rate. The mean absorbency in visible range of pure TiO2 films is near to 0%, which means that the pure TiO2 could hardly display the photocatalytic property in visible range. When N2 flow rate is 2 sccm, the mean absorbency in visible range of N doped TiO2 film could reach at 24%. In this case, the film could be used as photocatalyst induced by visible light. While with increasing N2 flow rate, the mean absorbency in visible range of N doped TiO2 film decreased abruptly. Especially when N2 flow rate exceeded 8 sccm, the mean absorbency in visible range of N doped TiO2 film decreased to about 0%, which is like pure TiO2 fimls.

Double-textured ZnO:Al films obtained by a one-step etching method for enhanced light trapping

Double-textured ZnO:Al (AZO) transparent conducting films with good optoelectronic characteristics and enhanced light trapping ability were prepared by a method including deposition, etching and re-deposition, and only one-step etching process was adopted during the whole process. The effects of the one-step etching method on the structural and optoelectronic properties, surface morphology and light trapping ability of double-textured AZO films were studied systematically. Double-textured films were covered with uniformly and distinctly crater-like textured structure after the re-deposition. And double-textured AZO films exhibited higher haze values compared with the single-textured films. Effective enhancement of light trapping was obtained from the double-textured AZO films by the one-step etching method.

The investigation of band gap and N chemical bond structure of N–TiO2 film prepared by N ion beam implantation

Titanium dioxide (TiO2) film was deposited by the direct current pulse magnetron sputtering technique. Then the surface of TiO2 film was implanted by the N ion beam at room temperature. Through this way, N-doped TiO2 (N–TiO2) film was obtained and the band gap of N–TiO2 film was decreased to 2.97 eV. XPS result revealed that N ion was doped into TiO2 film as Ti–N and Ti–NO bonds. N ion was substitutionally/interstitially doped into TiO2 crystal lattice and Ti–N bond was formed. N ion was doped into amorphous TiO2 and Ti–ON bond was formed. The polycrystal TiO2 film could result in that more N ion was substitutionally/interstitially doped into TiO2 crystal lattice, which could effectively narrow the band gap of N–TiO2 film. This work provides a potential N doping method which could be applied commercially.

Composition and crystal structure of N doped TiO2 film deposited at different O2 flow rate by direct current sputtering.

N doped Ti02 films were deposited by direct current pulse magnetron sputtering system at room temperature. The influence of 02 flow rate on the crystal structure of deposited films was studied by Stylus profilometer, X-ray photoelectron spectroscopy, and X-ray diffractometer. The results indicate that the 02 flow rate strongly controls the growth behavior and crystal structure of N doped Ti02 film. It is found that N element mainly exists as substitutional doped state and the chemical stiochiometry is near to TiO1.68±0.06N0.11±0.01 for all film samples. N doped Ti02 film deposited with 2 sccm (standard-state cubic centimeter per minute) 02 flow rate is amorphous structure with high growth rate, which contains both anatase phase and rutile phase crystal nucleuses. In this case, the film displays the mix-phase of anatase and rutile after annealing treatment. While N doped Ti02 film deposited with 12 cm(3)/min 02 flow rate displays anatase phase before and after annealing treatment. And it should be noticed that no TiN phase appears for all samples before and after annealing treatment.