Gas Sensitivity of Poly (3, 4-ethylene dioxythiophene) Prepared by a Modified LB Film Method

An arachidic acid/poly （3, 4-ethylene dioxythiophene） （AA/PEDOT） multilayer Langmuir-Blodgett （LB） film was prepared by a modified LB film method. The theories were utilized to explain the effects between HCl molecule and LB film. The gas sensitivity mechanism of poly （3, 4-ethylene dioxythiophene） （PEDOT） multilayer film can be explained by the charge transfer between p system of PEDOT and oxidization HCl system. The gas sensitivity of PEDOT LB film deposited interdigital electrode to HCl was tested. The results showed that film thickness, treating temperature, deposition speed had different influence on film gas sensitivity. The AA/PEDOT film deposited device exhibited nonlinear behavior to HCl gas at lower concentration （20-60 ppm） and linear response behavior at higher gas concentration was observed. The time of the compound LB film of the AA/PEDOT responding to the 30 ppm HCl gas is about 20 seconds, which is far quicker than the time of the film to the PEDOTPRESS film（about 80 seconds）. It is not higher film press to better film. When the film press attains 45 mNs/m, the sensitivity of the AA/PEDOT film on the contrary descends.

Synthesis and Structure of PEDOT Prepared through a Modified LB Film Method

Adopting LB film method, an arachidic acid （AA）/PEDOT multilayer LB film and polymerized EDOT monomers in hydrophilic group of LB were chosen to prepare the arachidic acid （AA）/PEDOT multilayer LB film. UV-Vis, FT-IR and XPS analyses implied that EDOT was effectively polymerized in film, and thus PEDOT conducting polymer was produced. Analyses of XRR and SIMS indicated that the film had a well-arranged lamella structure, and further research showed that polymerization of EDOT in AA film destroyed the orderliness of the original LB film. This phenomenon could be related to the destructive effect of polymerization on the layered structure. We used four-point probe and semiconductor instrument to study the conductivity property of the film, and observed that the conductivity of AA/PEDOT film had sudden changes with the changes of processing time in an effective conduction network, which was caused by ＂permeability＂ in conducting channel of multilayer film. The test results also indicated that the conductivity of AA/PEDOT film was obviously better than that of spin-coating PEDOT/PSS or ODA-SA/PEDOT-PSS film due to the higher π structure of PEDOT structure and ordered film structure.

Study on Conductivity Properties of PEDOT Prepared through a Modified LB Film Method

Adopting LB film method, an arachidic acid （AA）/PEDOT multilayer LB film was chosen, and polymerized EDOT monomers in hydrophilic group of LB to prepare arachidic acid （AA）/PEDOT multilayer LB film. UV-Vis, FT-IR and XPS analyses implied that EDOT was effectively polymerized in film, and thus PEDOT conducting polymer was produced. Analyses of XRR and SIMS indicated that film had a well-arranged lamella structure, and further research showed that polymerization of EDOT in AA film destroyed the orderliness of the original LB film. This phenomenon could be related to the destructive effect of polymerization on layered structure. We used four-point probe and semiconductor instrument to study the conductivity property of the film, and observed that the conductivity of AA/PEDOT film had sudden changes with the processing time of changes in effective conduction network. That was caused by ＂permeability＂ in conducting channel of multilayer film. The test results also indicated that the conductivity of AA/PEDOT film was obviously better than that of spin-coating PEDOT/PSS film or that of ODA-SA/PEDOT-PSS film, which was due to the higher π structure of PEDOT structure and ordered film structure.

PREPARATION OF TiO_2 THIN FILMS BY MOCVD METHOD

Preparation of TiO2 thin films by MOCVD method is presented in this paper. A MOCVD system has been designed and built. A wide range of processing conditions are investigated to deposit TiO2 films on Si wafers starting from metal-organic precursor tetrabutyl titanate. Activation energy of the film formation （E） is obtained to be 23.6 kJ/mol. Structure of films is pure anatase when deposit temperatures are low, rutile forms at 700℃. The films also exhibit preferred crystallographic orientations which strongly depend on deposit conditions. Refractive index increases with increasing of film thickness and decreasing of deposit temperature.

Rapid communication Preparation of TiO_2 nanometer thin films with high photocatalytic activity by reverse micellar method

Two kinds of TiO_2 nanometer thin films were prepared on stainless steel bythe reverse micellar and sol-gel methods, respectively. The calcined TiO_ 2 thin films werecharacterized by X-ray diffraction (XRD), atomic force microscopy (AFM), BET surface area and X-rayphotoelectron spectroscopy (XPS). Photocatalytic activity was evaluated by photocatalyticdecoloration of methyl orange aqueous solution. The results showed that the TiO_2 thin filmsprepared by reverse micellar method (designated as RM-TiO_2 films) showed higher photocatalyticactivity than those by sol-gel method (designated as SG-TiO_2 films). This is attributed to the factthat the former is composed of smaller monodispersed spherical particles with a size of about 15 nmand possesses higher surface areas.

Rapid communication Ruthenium disulfide thin films prepared by the successive ionic layer adsorption and reaction (SILAR) method

RuS_2 thin films were prepared by the cost-effective chemicalmethod―successive ionic layer adsorption and reaction (SILAR). The structural, optical, andelectrical properties were investigated using X-ray diffraction, scanning electron microscopy,optical transmittance, and electrical resistivity methods. The results indicate that the films arehomogeneous and dense; the structure of the as-deposited films is amorphous and they crystallizeafter annealed at 500℃ for 30 min. The band gap of the as-deposited films is found to be 1.85 eV,and the electrical resistivity of them is in the order of 10~5 Ω·cm.

Effect of Wafer Size on the Film Internal Stress Measurement by Wafer Curvature Method

Wafer curvature method has been applied to determine the internal stress in the films using Stoney＇s equation.During the film deposition,the wafer fixation on the sample holder will restrict the deformation of the rectangle-shaped wafer,which may result in the stress datum difference along length and width direction.In this paper,the effect of wafer size and the wafer fixation on the TiN film internal stress measured by wafer curvature method was discussed.The rectangle-shaped wafers with different length/width ratios（L/W=1：1,2：1,3：1 and 4：1） were fixed as a cantilever beam.After the TiN films deposition,the profiles of the film/wafer were measured using a stylus profilometer and then the internal stress was calculated using the Stoney equation in the film.The results showed that the fixed end of the wafers limited to some degree the curvature of the wafers along the width direction.For film internal stress measured by wafer curvature method,the wafer profile should be scanned along the length direction and the scan distance should be greater than or equal to half of wafer length.When the length/width ratio of the wafer reached 3：1,the wafer curvature and the calculated stress were basically the same at different positions along the length direction.For film internal stress measured by wafer curvature method,it was recommended that the length/width ratio of wafer should be considered to be greater than or equal to 3：1,and the deformed profile was scanned along the length direction.

Structural, Optical and Luminescence Properties of ZnO Thin Films Prepared by Sol-Gel Spin-Coating Method： Effect of Precursor Concentration

Transparent zinc oxide（ZnO） thin films are fabricated by a simple sol-gel spin-coating technique on glass substrates with different solution concentrations（0.3-1.2 M） using zinc acetate dehydrate [Zn（CH_3COO）_2·2H_2O] as precursor and isopropanol and monoethanolamine（MEA） as solvent and stabilizer, respectively. The molar ratio of zinc acetate dehydrate to MEA is 1.0. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of solution concentration on the structural and optical properties of the ZnO thin films. The obtained results of all thin films are discussed in detail and are compared with other experimental data.

Effect of Annealing on Ferroelectric Properties of Bi_ (3.25)La_(0.75)Ti_3O_ (12) Thin Films Prepared by the Sol-gel Method

Bi3.25La0.75Ti3O12（BLT）thin films were prepared on Pt/Ti/SiO2/Si substrate by the sol-gel method.The effect of annealing on their structures and ferroelectric properties was investigated.The XRD patterns indicate that the BLT films annealed at different temperatures are randomly orientated and the single perovskite phase is obtained at 550℃.The remmant polarization increnses and the coercive field decreases with the annealing temperature increasing.The leakage current density of the BLT films annealed at 700℃ is about 5.8×10^-8A/cm^2 at the electrie field of 250kv/cm.

Grain Size and Photocatalytic Activity of Nanometer TiO_2 Thin Films Prepared by the Sol-gel Method

Transparent anatase TiO2 nanometer thin films with photocatalytic activity were prepared via the sol-gel method on soda-lime glass. The thickness , crystalline phase, grain size, surface hydroxyl amount and so on were characterized by scanning electron microscopy (SEM) , X-ray diffraction (XRD), transmission electron microscopy ( TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible spectrophotometer ( UV-VIS). The photocatalytic activity of TiO2 thin films was evaluated for the photocatalytic decolorization of aqueous methyl orange . The effects of film thickness on the crystalline phase, grain size, transmittance and photocatalytic activity of nanometer Ti02 thin films were discussed.

An overview of thermoelectric films:Fabrication techniques,classification,and regulation methods

Thermoelectric materials have aroused widespread concern due to their unique ability to directly convert heat to electricity without any moving parts or noxious emissions.Taking advantages of two-dimensional structures of thermoelectric films,the potential applications of thermoelectric materials are diversified,particularly in microdevices.Well-controlled nanostructures in thermoelectric films are effective to optimize the electrical and thermal transport,which can significantly improve the performance of thermoelectric materials.In this paper,various physical and chemical approaches to fabricate thermoelectric films,including inorganic,organic,and inorganic–organic composites,are summarized,where more attentions are paid on the inorganic thermoelectric films for their excellent thermoelectric responses.Additionally,strategies for enhancing the performance of thermoelectric films are also discussed.

Characterization of La-doped xBiInO_3(1-x)PbTiO_3 Piezoelectric Films Deposited by the Radio-Frequency Magnetron Sputtering Method

La-doped and undoped xBiIn03-（1 - x）PbTi03 （BI-PT） thin films are deposited on （101）SrRuO3/（lOO）Pt/（lO0） MgO substrates by the rf-magnetron sputtering method. The structures of the films are characterized by XRD and SEM, and the results indicate that the thin films are grown with mainly （100） oriented and columnar structures. The ferroelectricity and piezoelectricity of the BI-PT films are also measured, and the measured results illustrate that both performances are effectively improved by the La-doping with suitable concentrations. These results will open up wide potential applications of the films in electronic devices.

FABRICATION OF PIEZOELECTRIC BIMORPH USING LEAD ZIRCONATE TITANATE THIN FILM DEPOSITED BY HYDROTHERMAL METHOD

In order to describe the characteristics of piezoelectric bimorph, properties of lead zirconate titanate （LZT） film are studied by X-ray diffraction （XRD） and scanning eletron microscope （SEM）. The ratio of PbTiOJPbZrO3 in LZT is 53/47, which is around morphotropic phase boundary （MPB）. LZT film is composed of cubic particles with the average size of 5 ~ma. Density of thin film is figured out through the datum measured in experiments. The displacement model used to analyze the driving ability of bimorph is set up, and the effect of elastic intermediate layer is taken into account. Piezoelectric coefficient of LZT film is worked out by using the displacement model. Experiments of driving ability show that deformation of bimorph free end does not increase with times of crystal growth processes and the maximum deformation is obtained after two times crystal growth processes. Finally, the ferroelectric property of the bimorph is investigated and coercive voltage of the bimorph is obtained.

Preparation and properties of CdS thin films grown by ILGAR method

CdS thin films were deposited by the ion layer gas reaction (TLGAR) method.Structural, chemical, topographical development as well as optical and electrical properties ofas-deposited and annealed thin films were investigated by XRD, SEM, XPS, AFM and UV-VIS. The resultsshowed that the thin films are uniform, compact and good in adhesion to the substrates, and thegrowth of the films is 2.8 nm/cycle. The evolution of structure undergoes from the cubic structureto the hexagonal one with a preferred orientation along the (002) plane after annealing at 673 K. Anamount of C, O and Cl impurities can be reduced by increasing the drying temperature or byannealing in N2 atmosphere. It was found that the band gap of the CdS films shifts to higherwavelength after annealing or increasing film thickness. The electrical resistivity decreases withincreasing annealing temperature and film thickness.

A Novel Method of Fabricating Flexible Transparent Conductive Large Area Graphene Film

We fabricate flexible conductive and transparent graphene films on position-emission-tomography substrates and prepare large area graphene films by graphite oxide sheets with the new technical process. The multi-layer graphene oxide sheets can be chemically reduced by HNO3 and HI to form a highly conductive graphene film on a substrate at lower temperature. The reduced graphene oxide sheets show a high conductivity sheet with resistance of 476Ω/sq and transmittance of 76% at 550nm （6 layers）. The technique used to produce the transparent conductive graphene thin film is facile, inexpensive, and can be tunable for a large area production applied for electronics or touch screens.

Preparation of Nanometer-structured TiO_2 Thin Films by Sol-Gel Method

The transparent anatase TiO 2 nanometer thin films were prepared by the sol-gel method on soda-lime glass.X-ray diffraction,thermal analysis and UV-visible spectrophotometer were used to analyze the formation of the phases.Only increasing the heat-treatment time,the average grain size has no obvious change.The mechanism of grain growth in TiO 2 thin film is probably as follows:the grain of coating will become grain core later;TiO 2 sol constantly deposited on the surface of TiO 2 grain and formed membrane with increasing of coating cycle times;TiO 2 grain in the film grow steadily.

BIMORPH-TYPE PIEZOELECTRIC THIN FILM BENDING ACTUATORS SYNTHESIZED BY HYDROTHERMAL METHOD

Lead zirconate titanium solid-solution (PZT) thin films with variousthickness are synthesized on titanium substrates by repeated hydrothermal treatments. Young modulus,electric-field-induced displacement and the density of the PZT film are measured respectively.Bimorph- type bending actuators are fabricated using these films. The model, which is used toanalyze the driving ability of bimorph-type bending actuators by hydrothermal method, is set up. Itcan be seen that the driving ability of bimorph-type bending actuators can be greatly improved byoptimizing the thickness of PZT thin film and substrate from the theoretical analysis results. Themeasured values are expected to agree with the theoretical values calculated by the above model.

Preparation,Growth Mechanisms and Characterizations of ZnSe Films via the Solvothermal Method

With diethylamine as a solvent, ZnSe films were formed on the Si substrate directly from zinc and selenium through the modified solvothermal method. The effects of holding temperature, deposition time and substrate surface treatment on the quality and morphologies of the ZnSe films were investigated. The growth mechanism of ZnSe films was proved to be a layer-nucleation growth process, which was tied in with the Stranski-Krastanov （SK） model. ZnSe films were identified by the X-ray diffraction pattern （XRD）, the scanning electron microscope （SEM）, the X-ray photoelectron spectroscope （XPS） and the photoluminescence （PL） techniques. The results indicate that the modified solvothermal method with diethylamine as a solvent is suitable to prepare high quality ZnSe films.

Gap States of ZnO Thin Films by New Methods:Optical Spectroscopy,Optical Conductivity and Optical Dispersion Energy

The optical reflectance and transmittance spectra in the wavelength range of 300-2500 nm are used to compute the absorption coefficient of zinc oxide films annealed at different post-annealing temperatures 400, 500 and 600°C.The values of the cross point between the curves of the real and imaginary parts of the optical conductivity ɑ_1 and ɑ_1 with energy axis of films exhibit values that correspond to optical gaps and are about 3.25-3.3 eV. The maxima of peaks in plots dR/dλ and dT/dλ versus wavelength of films exhibit optical gaps at about 3.12-3.25 eV.The values of the fundamental indirect band gap obtained from the Tauc model are at about 3.14-3.2 eV. It can be seen that films annealed at 600°C have the minimum indirect optical band gap at about 3.15 eV. The films annealed at 600°C have Urbach＇s energy minimum of 1.38 eV and hence have minimum disorder. The dispersion energy d of films annealed at 500°C has the minimum value of 43 eV.

Thermal Characteristics of PVA-PANI-ZnS Nanocomposite Film Synthesized by Gamma Irradiation Method

Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic（PA） setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.