Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> thin films prepared by sulfurizing different multilayer metal precursors

Cu₂ZnSnS₄ (CZTS) thin films were successfully fabricated on glass substrates by sulfurizing Cu-Sn-Zn multilayer precursors, which were deposited by ion beam sputtering and RF magnetron sputtering, respectively. The structural, electrical and optical properties of the prepared films under various processing conditions were investigated in detail. Results showed that the as-deposited CZTS thin films with the precursors by both ion beam sputtering and RF magnetron sputtering have a composition near stoichiometric. The crystallization of the samples, however, has a strong dependence on the atomic percent of constituents of the prepared CZTS films. A single phase stannite-type structure CZTS with a large absorption coefficient of 10₄/cm in the visible range could be obtained after sulfurization at 520°C for 2 h. The samples relative to the RF magnetron sputtering showed a low resistivity of 0.073 Ωcm and band gap energy of about 1.53 eV. The samples relative to the ion beam sputtering exhibited a resistivity of 0.36 Ωcm and the band gap energy is about 1.51 eV. Supported by the National Natural Science Foundation of China (Grant No. 10574106), the Planned Science and Technology Project of Guangdong Province (Grant No.2003C05005) and the Natural Science Fund of Zhanjiang Normal University (Grant No.200801)     

Optical and magnetic properties of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> nano-composite films

Fe₂O₃/SiO₂ nano-composite films were prepared by sol-gel technique combining heat treatment in the range of 100–900 °C. The particle size was observed by FE-SEM. Optical properties of the films were investigated by UV-visible spectra. Structural and magnetic characteristics were investigated through FT-IR and VSM. The transparency of the Fe₂O₃/SiO₂ nano-composite films decreased with the content of the Fe₂O₃. Water and organic solvent in the films were evaporated with heat treatment, so the transparency of the films was enhanced under high temperature. It is also found that the saturation magnetization (M _s) of the films increases with the temperature. As the content of the Fe₂O₃ increases, when the content of the Fe₂O₃ is around 30wt%, the M _s of the films has a maximum value.     

Preparation and characteristics of Cu/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/MgF<Subscript>2</Subscript>/Au tunnel junction

The fabrication process of Cu/Al₂O₃/MgF₂/Au double-barrier metal/insulator/metal junction (DMIMJ) was introduced, and more stable light emission from this junction was successfully observed. The light emission physical mechanism of the junction was discussed. Results show that light emission spectrum of this structure locates at wavelength of 250–700 nm with two peaks at around 460 nm and 640 nm, which moves towards shorter wavelength region in comparison with that of the Al/Al₂O₃/Au junction. The light emission efficiency of this junction ranges from 0.7×10⁻⁵–2.0×10⁻⁵, which is 1 to 2 orders higher than that of the single-barrier Al/Al₂O₃/Au junction. The improved properties of this structure should be due to the electrons resonant tunneling effect in the double-barrier.     

Biomolecule-assisted solvothermal synthesis and enhanced visible light photocatalytic performance of Bi<Subscript>2</Subscript>S<Subscript>3</Subscript>/BiOCl composites

Novel Bi₂S₃/BiOCl photocatalysts were successfully synthesized via a facile biomolecule-assisted solvothermal method and biomolecule L-cysteine was used as the sulfur source. The structures, morphology, and optical properties of the synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (DRS). The presence of Bi₂S₃ in the Bi₂S₃/BiOCl composites could not only improve the optical properties but also enhance the photocatalytic activities for the degradation of Rhodamine B (RhB) under visible-light irradiation (λ > 420 nm) as compared with single Bi₂S₃ and BiOCl. Especially, the sample displayed the best performance of the photodegradation when the feed molar ratio of BiCl3 and L-cysteine was 2.4:1, which was about 10 times greater than that of pure BiOCl. The enhanced photocatalytic activities could be ascribed to the effective separation of photoinduced electrons and holes and the photosensitization of dye. Moreover, the possible photodegradation mechanism was also proposed, and the results revealed that the active holes (h⁺) and superoxide radicals (?O₂ ^?) were the main reactive species during photocatalytic degradation.     

Preparation and characterization of CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript>:Sb films deposited on glass substrates by R.F. sputtering

CeO2-TiO2 films and CeO2-TiO/SnO2：Sb （6 mol%） double films were deposited on glass substrates by radio-frequency magnetron sputtering （R.F. Sputtering）, using SnO2：Sb（6 mol%） target, and CeO2- TiO2 targets with different molar ratio of CeO2 to TiO2 （CeO2：TiO2-0：1.0; 0.1：0.9; 0.2：0.8; 0.3：0.7; 0.4：0.6; 0.5：0.5; 0.6：0.4; 0.7：0.3; 0.8：0.2; 0.9：0.1; 1.0：0）. The films are characterized by UV-visible transmission and infrared reflection spectra, scanning electron microscopy （SEM）, Raman spectroscopy, X-ray photoelectron spectroscopy （XPS） and X-ray diffraction （XRD）, respectively. The obtained results show that the amorphous phases composed of CeO2-TiO2 play an important role in absorbing UV, there are Ce^3-, Ce^4- and Ti^4- on the surface of the films; the glass substrates coated with CeO2-TiO2 （Ce/Ti=0.5：0.5; 0.6：0.4）/SnO2：Sb（6 mol%） double films show high absorbing UV（〉99）, high visible light transmission （75%） and good infrared reflection （〉70%）. The sheet resistance of the films is 30-50 Ω/□. The glass substrates coated with the double functional films can be used as window glass of buildings, automobile and so on.     

Nanocomposite films of V<Subscript>2</Subscript>O<Subscript>5</Subscript>−MoO<Subscript>3</Subscript> xerogel with poly ethylene oxide intercalation

Poly ethylene oxide (PEO)_x−V₂O₅−V₂O₅−MoO₃ (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD, TG-DTA, FTIR, etc. The results show that V₂O₅−MoO₃ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement indicates that the intercalation of PEO improves insertion/extration properties of Li⁺ ions in the interlayer. ZHENG Jin-xia: Born in 1976 Funded by the National Natural Science Foundation of China (No. 50172036) and Natural Science Foundation of Hubei Province(No. 2001ABB083)     

Microstrueturc and Mcehanieal Propcrtics of Heat-treated GeSb2Te4 Thin Films

The effect of annealing on microstructure, adhesive and frictional properties of GeSb2Te4 films were experimentally studied. The GeSb2Te4 films were prepared by radio frequency （RF） magnetron sputtering, and annealed at 200℃ and 340℃ under vacuum circumstance, respectively. The adhesion and friction experiments were mainly conducted with a lateral force microscope （LFM） for the GeSb2Te4 thin films before and after annealing. Their morphology and phase structure were analyzed by using atomic force microscopy （AFM） and X-ray Diffraction （XRD） techniques, and the nanoindention was employed to evaluate their hardness values. Moreover, an electric force microscope （EFM） was used to measure the surface potential. It is found that the deposited GeSb2Te4 thin film undergoes an amorphous-to-fcc and fcc-to-hex structure transition; the adhesion has a weaker dependence on the surface roughness, but a certain correlation with the surface potential of GeSb2Te4 thin films. And the friction behavior of GeSb2Te4 thin films follows their adhesion behavior under a lower applied load. However, such a relation is replaced by the mechanical behavior when the load is relatively higher. Moreover, the GeSb2Te4 thin film annealed at 340℃ presents a lubricative property.     

Laser-induced spark ignition of H<Subscript>2</Subscript>/O<Subscript>2</Subscript>/Ar mixtures

Laser-induced spark ignition of hydrogen-oxygen-argon mixtures was experimentally investigated using a Q-swiched Nd:YAG laser to break down the gas at 532 nm. The laser-based high-speed schlieren system was employed to record flame front evolution for the gas mixtures with different initial pressure or laser output energy or argon dilution. The results show that the breakdown of the gas leads to the generation of ellipsoidal plasma. The rarefaction waves create the toroidal rings at the leading and trailing edges of the plasma, which provides a reasonable explanation for inward wrinkle of the plasma and the resultant flame. The toroidal rings at leading edge decays more rapidly and a gas lobe is generated that moves towards the laser. The hot gas in the plasma induces the generation of the spark kernel. Affected by the very weak shock wave or compression waves reflected off the wall, the initial laminar flame decelerates. The arc flame front interactions with the wall, reversed shock wave or compression waves, rarefaction waves, etc. induce the transition from laminar flame to turbulent one. These induce the transition from laminar flame to turbulent flame. For stoichiometric hydrogen-oxygen mixtures diluted by 76.92% argon at an initial pressure of 53.33 kPa, the minimum output energy of the laser is 15 mJ for successful laser-induced spark ignition. With increasing initial pressure or the output energy of the laser, or decreasing argon dilution, the speed of the flame front increases.     

Preparation and characterization of nanocomposite MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript>

Nanocomposites MgFe₂O₄/SiO₂ were successfully synthesized by the sol-gel method in the presence of N, N-dimethylformamide (DMF). The formation of pure MgFe₂O₄ was confirmed by powder X-ray diffraction (XRD) and electron diffraction. The structural evolution of MgFe₂O₄ nanocrystals was followed by powder X-ray diffraction and IR absorption spectroscopy. The formation of spinel structure of MgFe₂O₄ started at 800 °C, and completed at 900 °C. The transmission electron microscopy (TEM) measurements suggest that the particle sizes increase with the increasing annealing temperature, and the mean particle sizes of the spherical samples annealed at 800 °C, 900 °C and 1 050 °C are ca. 3 nm, 8 nm and 11 nm, respectively. Magnetization measurements at room temperature and 78 K indicate superparamagnetic nature of these MgFe₂O₄ nanocrystals. Funded by the National Natural Science Foundation of China(No. 30771676), the Natural Science Foundation of Jiangsu Province (No. BK20081842), and the Foundation of Nanjing Bureau of Personal for the Returned Overseas Chinese Excellent Scholars     

Phase structure and electrical properties of La<Subscript>2</Subscript>O<Subscript>3</Subscript>-doped BiInO<Subscript>3</Subscript>-PbTiO<Subscript>3</Subscript> ceramics with high curie temperature

The phase structure and electrical properties of pure and La2O3-doped Bi-InO3-PbTiO3 （BI-PT） ceramics were studied respectively. In （1 -x）BI-xPT （x=0.72-0.80） ceramics, the stability of tetragonal phase increased with increasing x, and pure perovskite structure was obtained for x=-0.80 ceramics. The phase transition temperature range was between 575 ℃ and 600 ℃ for x=0.72-0.80 ceramics, higher than that of PT （-490 ℃）. The c/a ratio almost linearly decreased with increasing La2O3 content in x-0.80 ceramics. It is believed that Pb^2＋ vacancies were formed by La^3＋ substituting Pb^2＋ in La2O3-doped BI-PT ceramics. Tc shifted to lower temperature by 30 ℃/mol% La2O3. The maximum dielectric constant 8557 around 559 ℃ was exhibited in 0.5mol%-doped BI-0.80PT ceramics. La2O3-doped ceramics could be poled resulting from decreasing of c/a ratio and improving of dielectric loss and resistivity. The maximum piezoelectric coefficient d33 was 12 pC/N for 2mol%-doped BI-0.80PT ceramics.     

Effects of LaNiO<Subscript>3</Subscript> interlayer on the microstructures and electrical properties of Ba<Subscript>0.9</Subscript>Sr<Subscript>0.1</Subscript>Ti<Subscript>0.99</Subscript>Mn<Subscript>0.01</Subscript>O<Subscript>3</Subscript> multilayer

The aim of this work was to investigate the effects of low-resistivity interlayer on the physical properties of periodic Ba_0.9Sr_0.1Ti_0.99Mn_0.01O₃ (BSTM) multilayers prepared by a chemical solution deposition method. A LaNiO₃ (LNO) layer was inserted into the periodic BSTM multilayer artificially to form a sandwiched configuration of BSTM/LNO/BSTM. The capacitances at low frequencies (<100 kHz) of the sandwiched multilayer are significantly enhanced compared to that of the pure BSTM multilayer. The space charge accumulated at the LNO layer was proposed to explain the enhancement based on Maxwell-Wagner (M-W) model. However, LNO interlayer leads to an increase in the leakage current. A non-Ohmic conduction region is observed for BSTM/LNO/BSTM multilayer when the electric field exceeds 100 kV/cm. The results offer a new approach to achieve dielectric films with high dielectric constant.     

UV-vis and photoluminescent spectra of TiO<Subscript>2</Subscript> films

TiO₂ fims have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0. 10 Pa.to 0.65 Pa. The transmittance (UV-vis) and photoluminescence (PL) spectra of the films were recorded. The results of the UV-vis spectra show that the deposition rate of the films decreased at oxygen partial pressure P(O₂)≥0.15 Pa, the band gap increased from 3.48 eV to 3.68eV for direct transition and from 3.27 eV to 3.34 eV for indirect transition with increasing the oxygen partial pressure. The PL spectra show convincingly that the transition for films was indirect, and there were some oxygen defect energy levels at the band gap of the films. With increasing the O₂ partial pressure, the defect energy levels decreased. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63 eV and 2.41 eV, corresponding to 0.72 eV and 0.94 eV below the conduction band for a band gap of 3.35 eV, respectively. For the films sputtered at 0.10 Pa and 0.15 Pa, there was an energy band formed between 3.12 eV and 2.06 eV, corresponding to 0.23 eV and 1.29 eV below the conduction band. ZHAO Qing-nan : Born in 1963 Funded by Natural Science Foundation of Hubei Province, China.     

Improved Breakdown Strength in (Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>)<Subscript>0.85</Subscript>Bi<Subscript>0.1</Subscript>TiO<Subscript>3</Subscript> Ceramics with Addition of CaZrO<Subscript>3</Subscript> for Energy Storage Application

(Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics doped with x wt%CaZrO₃ (x= 0-10) were synthesized by solid-state reaction method. The effects of CaZrO₃ amount on the dielectric properties and structure of (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO₃. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO₃, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 kV/mm at x=7.5. In virtue of low dielectric loss (tan δ<0.001 5), moderate dielectric constant (ε_r >1 500) and high breakdown strength (E_b >17.5 kV/mm), the CaZrO₃ doped (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramic is a potential candidate material for high power electric applications.     

Preparation and optical properties of Er<Superscript>3+</Superscript>: Na<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> transparent glass-ceramics

Na₂O-Al₂O₃-SiO₂ glass-ceramics doped with Er³⁺ ions were synthesized by the conventional melt quenching technique at a low melting temperature. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis-NIR scanning spectrophotometry, and fluorescence spectrometry. The results show that the main crystalline phase of glass-ceramics is nepheline.The best heat-treatment process is at 520 °C for 2 h. Because the up-conversion luminescence and near infrared luminescence properties of glass doped with Eu³⁺ are studied in detail.     

Synthesis and characterization of (PEO)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>−(V<Subscript>0.85</Subscript>Mo<Subscript>0.15</Subscript>)<Subscript>2</Subscript>O<Subscript>5</Subscript> nanocomposite films

(PEO) _x −(V_0.85Mo_0.15)₂O₅(x=0,0.5,1.0) nanocomposite films were prepared by a modified sol-gel method. The structure of the films was analyzed by XRD, and the DC electrical conductivity. Cyclic voltammogram and optical spectral transmittance were investigated. The results show that the (V_0.85Mo_0.15)₂O₅ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1.7897 nm at x=1.0. The introduction of MoO₃ improved the DC electrical conductivities of the films due to the generation of V₄₊ to maintain the electrical neutrality of the oxides. PEO intercalated in the interlayer of (V_0.85Mo_0.15)₂O₅ oxides has interaction with the oxides, enhancing the amount of Li⁺ ions inserted into the interlayer of the oxides. Moreover, the intercalation of PEO into the interlayer of (V_0.85Mo_0.15)₂O₅ oxides improved the cathodic electrochromic property in near ultraviolet region and anodic electrochromic property in visible range. JIANG Cong-sheng: Born in 1963 Supported by the Science Foundation of Hubei Province (Grant No. 2001ABB083)     

Fabrication of high performance 3D SiO<Subscript>2</Subscript>/Si<Subscript>3</Subscript>N<Subscript>4</Subscript> composite via perhydropolysilazane infiltration and pyrolysis

The continuous fiber reinforced ceramic matrix composites have received consider-able attention for structural applications because of their excellent thermal stability, light weight, and damage tolerance imparted by the reinforcing fibers. Silica fibers, with ex-cellent ablative resistance, thermal shock damage resistance, dielectric properties, chemical stability and flexibility, are suitable for fabricating high temperature antenna window materials to meet the requirements of communication, …     

Microstructure and AMR Properties of Permalloy Films Sputtered on （Ni0.81Fe0. 19 ）0.66Cr0.34 Buffer

(Ni_0.81 Fe_0.19)_0.66 Cr_0.34 has a high resistivity and a crystal structure close to that of Ni_0.81 Fe_0.19. The electrical and X-ray diffraction measurements prove that a thin NiFeCr seed layer induces a well (111)-orented Ni_0.81 Fe_0.19 film. Post-annealing treatment improves the magnetic properties of (Ni_0.81Fe_0.19)_0.66 Cr_0.34(45Å)/Ni_0.81Fe_0.19 (150Å)/Ta(55Å) thin film prepared under a deposition field, whereas the inter-diffusion of NiFe/Ta deteriorates the magnetoresistance properties of the film.     

Effect of temperature on polishing and flatting time of float-formed Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> glass

Li₂O-Al₂O₃-SiO₂ glass prepared from traditional melting and cooling process was investigated. The surface characteristic of LAS glass was studied by simulating tin bath with different temperature and time, and the effect of surface tension/viscosity ratio on flatting time was analyzed. The results demonstrated that LAS glass can polish effectively when polishing at 1 300 for 8 °C min, and the optimum flatting and polishing temperature was 1 250–1 300 °C.     

Influences of heat treatments on crystallization in SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgO-K<Subscript>2</Subscript>O-F glass-ceramics

Five kinds of heating treatment processing were chosen according to the experiment result of differential scanning calorimeter to prepare SiO2-Al2O3-MgO-K2O-F glass ceramics samples.The effects of heat treatment processing on the crystallization of these samples were explored by X-ray diffraction and scanning electron microscopy techniques.The results indicate that phase separations can occur in the bulk regions of the glass sample when holding at 670 ℃ for 3 h.The phase separation can accelerate the precip...     

Influence of thickness on the properties of solution-derived LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> thin films

LiMn₂O₄ thin films of different thickness were derived from solution deposition and heat treated by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the films were examined by galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy. LiMn₂O₄ thin films of different thickness derived from solution deposition and rapid thermal annealing are homogeneous and crack free with the grain size between 20 nm and 50 nm. The specific capacity of these films is between 42 and 47 μAh·cm²·μm⁻¹. The capacity decreases with the increase of discharge current density. The capacity loss per cycle increases from 0.012% to 0.16% after being cycled 50 times as the film thickness increases from 0.18 μm to 1.04 μm. The lithium diffusion coefficients of these films are in the same order of 10⁻¹¹ cm²·s⁻¹.