Wanyu Ding

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.

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.

PREPARATION AND CHARACTERIZATION OF ATO NANOPARTICLES BY COPRECIPITATION WITH MODIFIED DRYING METHOD

Antimony-doped tin oxide (ATO) nanoparticles were prepared by coprecipitation by packing drying and traditional direct drying (for comparison) methods. The as-prepared ATO nanoparticles were characterized by TG, XRD, EDS, TEM, HRTEM, BET, bulk density and electrical resistivity measurements. Results indicated that the ATO nanoparticles obtained by coprecipitation with direct drying method featured hard-agglomerated morphology, high bulk density, low surface area and low electrical resistivity, probably due to the direct liquid evaporation during drying, the fast shrinkage of the precipitate, the poor removal efficiency of liquid molecules and the hard agglomerate formation after calcination. Very differently, the ATO product obtained by the packing and drying method featured free-agglomerated morphology, low bulk density, high surface area and high electrical resistivity ascribed probably to the formed vapor cyclone environment and liquid evaporation-resistance, avoiding fast liquid removal and improving the removal efficiency of liquid molecules. The intrinsic formation mechanism of ATO nanoparticles from different drying methods was illustrated based on the dehydration process of ATO precipitates. Additionally, the packing and drying time played key roles in determining the bulk density, morphology and electrical conductivity of ATO nanoparticles.

The Diffusion of Low-Energy Methyl Group on ITO Film Surface and Its Impact on Optical-Electrical Properties

Indium tin oxide (ITO) film is one of the ideal candidates for transparent conductive cathode in methylammonium lead halide perovskite solar cells. Thus, the diffusion of methyl group in ITO film is inevitable, which could deteriorate the optical-electrical property of ITO film. In this study, ITO films with and without (100) preferred orientation were bombarded by the low-energy methyl group beam. After the bombardment, the optical-electrical property of ITO film without (100) preferred orientation deteriorated. The bombardment of methyl group had little influence on the optical-electrical property of ITO film with (100) preferred orientation. Finally, combining the crystallographic texture and chemical bond structure analysis, the diffusion mechanism of low-energy methyl group on ITO lattice and grain boundary, as well as the relation between the optical-electrical property and the diffusion of the methyl group, were discussed systematically. With the above results, ITO film with (100) preferred orientation could be an ideal candidate for transparent conductive cathode in methylammonium lead halide perovskite solar cells.

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.