Using HF rather than NH4F as doping source for spray-deposited SnO2:F thin films

Fluorine doped tin oxide SnO₂:F thin films were prepared by the spray pyrolysis (SP) technique on glass substrates by using SnCl₂·2H₂O as a precursor and NH4F and HF as doping compounds. A comparison between the properties of the films obtained by using the two doping compounds was performed by using I–V characteristics in the dark at room temperature, AC measurements, and transmittance. It is found that the films prepared by using HF have smaller resistivity, lower impedance and they are less capacitive than films prepared by using NH₄F. In addition, these films have higher transmittance, higher optical bandgap energy and narrower Urbach tail width. These results are interesting for the use of SnO₂:F as forecontact in CdS/CdTe solar cells.     

Enhanced photoelectric property of Mo-C codoped TiO<Subscript>2</Subscript> films deposited by RF magnetron cosputtering

Mo-C codoped TiO₂ films were prepared by RF magnetron cosputtering. Ultraviolet-visible spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray Analysis and X-Ray Diffraction were used to study the influences of codoping on energy gap, surface morphology, valence states of elements, ions content and crystal structure, respectively. The concentration of photogenerated carriers was measured by studying photocurrent density, while catalytic property was evaluated by observing degradation rate of methylene blue under visible light. A Mo-doped TiO₂ film, whose content of Mo had been optimized in advance, was prepared and later used for subsequent comparisons with codoped samples. The result indicates that Mo-C codoping could curtail the energy gap and shift the absorption edge toward visible range. Under the illumination of visible light, codoped TiO₂ films give rise to stronger photocurrent due to smaller band gaps. It is also found that Mo, C codoping results in a porous surface, whose area declines gradually with increasing carbon content. Carbon and Molybdenum doses were delicately optimized. Under the illumination of visible light, sample doped with 9.78at% carbon and 0.36at% Mo presents the strongest photocurrent which is about 8 times larger than undoped TiO₂ films, and about 6 times larger than samples doped with Mo only.     

Effect of additives on the morphologies of cuprous oxides by electrodeposition

Cuprous oxides with different morphologies were formed on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition of cupric acetate. The effects of CTAB and Cl^? on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of the concentrations of CTAB and Cl. The flowerlike and cubic morphologies of Cu₂O crystals were obtained when using higher concentration of CTAB and KCl, respectively. Photoelectrochemical properties of the Cu₂O thin films prepared in the system were also studied.     

Physical properties of Al-doped ZnO and Ga-doped ZnO thin films prepared by direct current sputtering at room temperature

Al-doped zinc oxide(AZO) and Ga-doped zinc oxide(GZO) thin films with the same doping concentration(3.6 at%) were deposited on glass substrates at room temperature by direct current(DC) magnetron sputtering.Consequently,we comparatively studied the doped thin films on the basis of their structural,morphological,electrical,and optical properties for optoelectronic applications.Both thin films exhibited excellent optical properties with more than 85%transmission in the visible range.The GZO thin film had better crystallinity and smoother surface morphology than the AZO thin film.The conductivity of the GZO thin film was improved compared to that of the AZO thin film:the resistivity decreased from 1.01×10~(-3) to 3.5×10~(-4) Ω cm,which was mostly due to the increase of the carrier concentration from 6.5×10~(20) to 1.46×10~(21)cm~(-3).These results revealed that the GZO thin film had higher quality than the AZO thin film with the same doping concentration for optoelectronic applications.     

Growth and characterization of indium doped zinc oxide films sputtered from powder targets

Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10~(-4) Ω·cm and the highest carrier concentration of 1.86×10~(21) cm~(-3) can be obtained from Zn O thin films with an indium content of 5at% in the target.     

Comprehensive optimization of electrical and optical properties for ATO films prepared by pulsed laser deposition

Antimony doped tin oxide(ATO) thin films have been prepared by pulsed laser deposition(PLD) method.The intrinsic effect of Sb dopant,including the Sb content,transition degree between Sb~(3+) and Sb~(5+) and crystallinity on the electrical and optical properties of the ATO thin films is mainly investigated.It is suggested that the transition degree of Sb~(3+) towards Sb~(5+)(Sb~(5+)/Sb~(3+) ratio) is determined by Sb content.When the Sb content is increased to 12 at%,the Sb~(5+)/Sb~(3+) ratio reaches the highest value of 2.05,corresponding to the resistivity of 2.70×10~(-3) Ω·cm.Meanwhile,the Burstein-Moss effect caused by the increase of carrier concentration is observed and the band gap of the ATO thin films is broadened to 4.0 eV when the Sb content is increased to 12 at%,corresponding to the highest average optical transmittance of 92%.Comprehensively considering the combination of electrical and optical properties,the ATO thin films deposited with Sb content of 12 at%exhibit the best properties with the highest "figure of merit" of 3.85×10~(-3) Ω~(-1).Finally,an antimony selenide(Sb_2Se_3) heterojunction solar cell prototype with the ATO thin film as the anode has been prepared,and a power conversion efficiency of 0.83%has been achieved.     

Preparation of V-doped TiO2 photocatalysts by the solution combustion method and their visible light photocatalysis activities

A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM, Raman, XPS and UV-Vis DRS. The effects of V doping concentration on the phase structure and photocatalytic properties were investigated. XRD, Raman, and XPS show that V doping diffuses into TiO2 crystal lattice mainly in the form of V5＋ and causes a phase transition from anatase to mille. V doping can widen the light absorption range of TiO2, with the absorption threshold wavelength shifting from 425 to 625 nm. The photocatalytic activity of V-doped TiO2 powders were evaluated by the photocatalytic degradation of methyl orange （MO） under visible light irradiation. It is found that V doping enhances the photoeatalyilc activity under visible light irradiation and the optimal degradation rate of MO is about 95.8% with 1.0 at% V-doped TiO2.     

Remarkable improvement of ferroelectric properties and leakage current in BiFeO<Subscript>3</Subscript> thin films by nd modification

Ferroelectric and leakage properties are important for ferroelectric applications. Pure and Nd-doped (x=0.05-0.20) BiFeO3 thin films were fabricated by sol-gel method on FTO substrates. The phase structure, surface morphology, leakage current, ferroelectric properties, and optical properties of BiFeO₃^- based thin films were investigated. The substitution of Nd³⁺ ions for the Bi3+ site converts the structure from rhombohedral to coexisting tetragonal and orthorhombic. Nd doping improves the crystallinity of BiFeO₃ thin films. The leakage current of Nd-doped BiFeO₃ decreases by two to three orders of magnitude compared with that of pure BiFeO₃. Among the samples, 15% Nd-doped BiFeO₃ exhibits the strongest ferroelectric polarization of 17.96 μC/cm². Furthermore, the absorption edges of Bi_1-xNd _x FeO₃ thin films show a slight red-shift after Nd doping.     

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.     

Self-assembled SnO<Subscript>2</Subscript> colloidal particles and their gas sensing performance to H<Subscript>2</Subscript>, C<Subscript>2</Subscript>H<Subscript>5</Subscript>OH and LPG

Using organo-tin Sn(OC4H9)4 as precursor, sodium dodecyl sulfonate (SDS) and SDS-gelatin (SDS-G) complex as template, two tin dioxide colloidal particles were prepared by a self-assembly method. Both SnO2 products were respectively labelled SnO2-B particles with SDS and SnO2-C particles with SDS-G, which are applied in fabricating SnO2 gas sensors corresponding to SnO2-B’ and SnO2-C’ sensors. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermo-gravimetry and different thermal analysis (TG/DTA) were used for characterizations. The experimental results show that SnO2-B colloidal particles are composed of mesoporous piece-like particles, while SnO2-C particles mainly consist of spherical particles. Gas sensing measurements show that SnO2-B’ sensor performs the best sensing response to all target gases, including H2, C2H5OH and liquid petroleum gas (LPG). In particular, the sensing response of SnO2-B’ sensor is achieved at 32 in H2 atmosphere at the concentration of 1000×10-6 M. The gas sensing mechanism was purposely discussed from the electron transfer process and the microstructures of the as-prepared SnO2 products. It is found that serious agglomerations in SnO2-B’ particles facilitate the high gas sensing performance of SnO2-B’ sensor, while mesoporous structures in SnO2-C’ particles decrease the gas sensing response of SnO2-C’ sensor.     

Mechanism and behaviors of Cr3+-doped TiO2

TiO₂ powder and TiO₂ thin film on the surface of glazed ceramic tile were prepared by sol-gel method. The influences of different doping Cr³⁺ concentration on the photocatalytic activity of TiO₂ were discussed, UV-visible and X-ray diffraction analysis were used to test the performance of TiO₂ powder and film. The results indicate that photocatalytic activity of doping Cr³⁺-TiO₂ thin film is higher than that of powder, and the interaction between Cr³⁺-doped and substrate can greatly enhance the photocatalytic activity. The results of X-ray diffraction and photoabsorption show that the Cr³⁺-doped energy level in TiO₂ is 0.62 eV high from the top of valence band, which belongs to the type of deep energy level doping. On the basis of the semiconductor energy level theory and Cr³⁺ dopant energy level, the semiconductor energy level model of Cr³⁺ in TiO₂ powder and thin film were established, and the doping mechanisms of Cr³⁺-doped in TiO₂ powder and thin film were analyzed. Foundation item: Project (20466001) supported by the National Natural Science Foundation of China     

Surface characteristics and structure of oxide films containing Ca and P on Ti substrate

The oxide films were obtained in an electrolyte of calcium glyeerphosphate (Ca-GP) and calcium acetate (CA) by mieroare oxidation (MAO). The oxide films displayed a porous and rough structure on the film surface, and the roughness tended to increase with inereasing voltage of mieroare oxidation. The oxide film exhibited a uniform coating and tends to be well boned to the substrate. The thiekness of oxide films depended on the final voltage at a eonstant concentration of eleetrolyte solution. Ca and P were also incorporated into the oxide film during the mieroarc oxidation process, It was found that the electrolyte of ealeium glyeerphosphate ( Ca-GP) and ealeium acetate (CA) was suitable for microarc oxidation to form oxide film eontaining Ca and P on Ti substrate. The eoneentration of Ca and P were 11.6 at% and 6. 4 at% , respectively, when microare oxidation was performed in the electrolyte of 0. 06 M Ca-GP and 0. 25 M CA at current density 50 A/m^2 and final voltage 350 V. The composition of the Ca, P and Ti changed during depth profiling. The crystalline phases were only anatase when final voltage was below 300 V and rutile was presented when voltage was up to 350V. The microstructure, phase structure and phase composition were investigated by scanning electron microscopy (SEM) , atomic foree microscope (AFM) , energy dispersive X-ray mieroanalyser (EDX) , and X-ray diffraction (XRD),     

Preparation of AgSnO2 composite powders by hydrothermal process

Silver-tin oxide powders were synthesized by the hydrothermal method with Ag（NH3）2^＋ solution and Na2SnO3 solution as raw materials and Na2SO3 as reductant. The precipitation conditions of Na2SnO3 solution and the reduction conditions of Ag（NH3）2^＋ were also investigated. The powders prepared were characterized by differential thermal analysis （DTA）, X-ray diffraction analysis （XRD）, scanning electron microscope （SEM） and energy spectrum analysis, The results show that pH value of the solution is a key parameter in the formation of Sn（OH）4 precipitate and the reduction reaction of Ag（NH3）2^＋ can release H^＋ ions, which results in synchronous precipitation of Sn（OH）6^2- as Sn（OH）4. The reduction of Ag（NH3）2^＋ and precipitation of Na2SnO3 occur simultaneously and the coprecipitation of silver and tin oxide is reached by the hydrothermal method. The silver-tin oxide composite powders have mainly flake shape of about 0.3 μm in thickness and there exists homogeneous distribution of tin oxide and silver in the powder synthesized.     

Enhanced Photoelectric Property of Mo-C Codoped TiO_2 Films Deposited by RF Magnetron Cosputtering

Mo-C codoped TiO_2 films were prepared by RF magnetron cosputtering. Ultraviolet-visible spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray Analysis and X-Ray Diffraction were used to study the influences of codoping on energy gap, surface morphology, valence states of elements, ions content and crystal structure, respectively. The concentration of photogenerated carriers was measured by studying photocurrent density, while catalytic property was evaluated by observing degradation rate of methylene blue under visible light. A Mo-doped TiO_2 film, whose content of Mo had been optimized in advance, was prepared and later used for subsequent comparisons with codoped samples. The result indicates that Mo-C codoping could curtail the energy gap and shift the absorption edge toward visible range. Under the illumination of visible light, codoped TiO_2 films give rise to stronger photocurrent due to smaller band gaps. It is also found that Mo, C codoping results in a porous surface, whose area declines gradually with increasing carbon content. Carbon and Molybdenum doses were delicately optimized. Under the illumination of visible light, sample doped with 9.78at% carbon and 0.36at% Mo presents the strongest photocurrent which is about 8 times larger than undoped TiO_2 films, and about 6 times larger than samples doped with Mo only.     

Synthesis ofNanocrystalline RuO2（60%）-SnO2（40%） Powders by Amorphous Citrate Route

Nanometer RuO2-SnO2 was synthesized by the citrate-gel method using RuCl3, SnCl4 as cation sources, citric acid as complexing agent and anhydrous ethanol as solvent. The structures of the derived powders were characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, transmission electron microscope, and Brunauer-Emmett-Teller surface area measurement. The pure, fine and amorphous powders was obtained at 160℃. The materials calcined at above 400 ℃ were composed of rutile-type oxide phases having particle sizes of fairly narrow distribution and good thermal resistant properties. By adding SnO2 to RuO2, the Ru metallic phase can be effectively controlled under a traditional temperature of preparation for dimensional stable anode.     

Electronic structure and transport coefficients of the thermoelectric materials Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> from first-principles calculations

The electronic structures of bulk Bi₂Te₃ crystals were investigated by the first-principles calculations. The transport coefficients including Seeback coefficient and power factor were then calculated by the Boltzmann theory, and further evaluated as a function of chemical potential assuming a rigid band picture. The results suggest that p-type doping in the Bi₂Te₃ compound may be more favorable than n-type doping. From this analysis results, doping effects on a material will exhibit high ZT. Furthermore, we can also find the right doping concentration to produce more efficient materials, and present the “advantage filling element map” in detail.     

Influence of Yttrium Ion-implantation on Oxidation Kinetics of Co-40Cr Alloy and Property of Oxide/Substrate Interface

The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） was used to examine the Cr203 oxide film＇s morphology after oxidation. Secondary ion mass spectroscopy （SIMS） method was used to examine the binding energy change of chromium caused by yttrium doping. Acoustic emission （AE） method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvements are mainly that implanted yttrium reduces the grain size of Cr2O3 oxide, increases the high temperature plasticity of oxide film, and remarkably reduces the number and size of Cr2O3/Co-40Cr interfacial defects.     

Tensile properties of an aluminum matrix composite reinforced by SnO<Subscript>2</Subscript>-coated Al<Subscript>18</Subscript>B<Subscript>4</Subscript>O<Subscript>33</Subscript> whisker

Al18B4O33 whisker was coated by SnO2 particles using a chemical precipitation method, and an aluminum matrix composite reinforced by the coated whisker was fabricated by squeeze casting technique. It is found that the SnO2 coating can react with aluminum matrix during squeeze casting process, and Sn particles are induced near the interface between Al18B4O33 whisker and matrix. The tensile test at room temperature indicated that the tensile strength of Al18B4O33 whisker reinforced aluminum matrix composite can be enhanced by suitable content of SnO2 coating. The composites with various whisker coating contents exhibit maximum tensile plasticity at about 300 ℃, and the composite with a suitable whisker coating content could enhance its tensile plasticity evidently, which suggest that an Al18B4O33 whisker-Al composite with both high strength at room temperature and high formability at elevated temperature can be designed.     

Effect of Na concentrations on microstructure and optical properties of ZnO films

Na-doped ZnO thin films were deposited on the glass substrates using sol-gel method. The effect of Na concentrations on the structural and optical properties of ZnO films was studied. As Na concentration increases from 0.0 at% to 16.0 at%, preferential c-axis orientation becomes more and more obvious, and the intensity of the diffraction peaks from (103) increases. The optical band gap Eg value increases from 3.261 to 3.286 eV first and then decreases as Na concentration increases from 0.0 to 2.0 at% and th...     

掺氮3C-SiC电子结构的第一性原理研究

采用广义梯度近似方案处理电子间相互作用的交换关联能量泛函,电子波函数采用平面波基矢展开,并采用超软赝势近似离子实与价电子间相互作用,对掺氮(3×3×3)3C-SiC超晶胞电子结构进行了第一性原理研究．对不同掺氮浓度3C-SiC超晶胞的能带结构和态密度进行计算,结果表明氮原子的2p态和2s态分别占据价带顶和导带底,随着掺杂浓度的增加,导带底和价带顶的位置逐渐向低能端移动,导带底移动速度要大于价带顶,导致禁带宽度减小．