Investigation of polyaniline films produced by vacuum deposition method

Using FTIR and optical spectroscopy techniques, as well as electron scanning microscope, we investigated polyaniline films obtained by the method of fractional thermal vacuum deposition. The structure of produced polyaniline films depends essentially on the deposition temperature and molecular weight of the initial polymer. For a polymer with low molecular weight at temperature below 250°C a homogeneous oligomeric film is produced. At higher temperatures (higher than 300°C) linkages of oligomeric fragments occur leading to appearance of more complex structural formations. This is reflected in the morphology of films deposited at different temperatures. The films have a high transparency and relatively high, for polymers, index of refraction in the visible and near infrared ranges of spectrum.     

Polymerization of aniline on bacterial cellulose and characterization of bacterial cellulose/polyaniline nanocomposite films

Bacterial cellulose/polyaniline nanocomposite film was prepared by the chemical oxidative polymerization of aniline with bacterial cellulose. Polyaniline conducting polymer nanocomposite films with bacterial cellulose fibers was prepared and characterized. In nanocomposite film, the bacterial cellulose was fully encapsulated with polyaniline by direct polymerization of the respective monomers using the oxidant and dopant. These bacterial cellulose/polyaniline nanocomposite films materials exhibited the inherent properties of both components. The deposition of a polyaniline on the bacterial cellulose surface was characterized by SEM. XPS revealed a higher doping level of the nanocomposite films doped with p-TSA dopant. From the cyclic voltammetry results, the polyaniline polymer was thermodynamically stable because redox peaks of electrochemical transitions in the voltagrams were maintained in bacterial cellulose/polyaniline nanocomposite films.     

Electrical resistance response of polyaniline films to water, ethanol, and nitric acid solution

<正>This paper reports on electrical resistance vs.aging time for the response of polyanihne films under exposure to water,ethanol and nitric acid(HNO_3) solution.Camphor sulfonic acid-doped polyanihne films were prepared by a "doping-dedoping-redoping" method,the morphology and microstructures of the films were characterized by a scanning electron microscope and an x-ray diffractometer,the electrical resistance was measured by a four-probe method.It was found that a lower amount of water molecules infiltrating the film can decrease the film's resistance possibly due to an enhancement of charge carrier transfer between polyanihne chains,whereas excessive water molecules can swell inter-chain distances and result in a quick increase of resistance.The resistance of the film under exposure to ethanol increases and becomes much larger than the original value.However,HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid.These results can help to understand the conduction mechanism in polyaniline films,and also indicate that the films have potential application in chemical sensors.     

Fabrication and capacitive characteristics of conjugated polymer composite p-polyaniline/n-WO3 heterojunction

A nanocrystalline and porous p-polyaniline/n-WO₃ dissimilar heterojunction at ambient temperature is reported. The high-quality and well-reproducible conjugated polymer composite films have been fabricated by oxidative polymerization of anilinium ion on predeposited WO₃ thin film by chemical bath deposition followed by thermal annealing at 573 K for 1 h. Atomic force microscopy (AFM) analyses reveal a homogenous but irregular cluster of faceted spherically shaped grains with pores. The scanning electron microscopy confirms the porous network of grains, which is in good agreement with the AFM result. The optical absorption analysis of polyaniline/WO₃ hybrid films showed that direct optical transition exist in the photon energy range 3.50–4.00 eV with bandgap of 3.70 eV. The refractive index developed peak at 445 nm in the dispersion region while the high-frequency dielectric constant, ? _∞, and the carrier concentration to effective mass ratio, N/m^*, was found to be 1.58 and 1.10 × 10³⁹ cm^?3, respectively. The temperature dependence of electrical resistivity of the deposited films follows the semiconductor behavior while the C–V characteristics (Mott–Schottky plots) show that the flat band potential was ?791 and 830 meV/SCE for WO₃ and polyaniline.     

Efficient visible light-induced photoelectrocatalytic degradation of rhodamine B by polyaniline-sensitized TiO<Subscript>2</Subscript> nanotube arrays

Self-organized anodic TiO₂ nanotube arrays were sensitized with polyaniline by a simple electrodeposite method. The morphological and structural properties studied by scanning electron microscopy and fourier transform infrared spectroscopy reveal the successful deposition of polyaniline on the nanotube arrays. The polyaniline-sensitized TiO₂ nanotube arrays exhibit a distinguishable red shift on the absorption spectrum. Electrochemical impedance investigation attested to a significant improvement of the interfacial electron-transfer kinetics for promoted electron–hole effective separation. The as-prepared samples showed a high efficiency for the photoelectrocatalytic degradation of rhodamine B under visible-light irradiation (λ > 400 nm). The enhanced photoelectrocatalytic activity could be attributed to the extended absorption in the visible-light region by the polyaniline and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the polyaniline/TiO₂ nanotube arrays interface.     

La0.5Sr0.5CoO3薄膜的外延生长及其机理研究

利用脉冲激光制膜法,在多种衬底和温度条件下,系统研究了La_0.5Sr_0.5CoO₃(LSCO)薄膜的结构和外延生长特性,在LaAlO₃,SrTiO₃和MgO衬底上实现了LSCO薄膜的外延生长.外延生长的薄膜具有低的电阻率和金属性导电特征.研究表明,外延生长的最佳温度范围为700—800℃,最佳衬底为LaAlO₃.并着重探讨了衬底材料和淀积温度等多种因素对LSCO薄膜的生长与性 关键词：     

Growth and characterization of silicon nitride films on various underlying materials

Characteristics of silicon nitride (SiN_x:H) films, grown by plasma enhanced chemical vapor deposition (PECVD) on various metals such as Ta, IrMn, NiFe, Cu, and CoFe at various temperatures down to 100 °C, were studied using measurements of BHF etch rate, surface roughness and Auger electron spectroscopy (AES). The results were compared with those obtained for SiN_x:H films on Si. The deposition rate of SiN_x:H films increased slightly as deposition temperature decreased, and showed a weak dependence on the underlying materials. The surface of the nitride films deposited on all underlying materials at lower temperatures (below 150 °C) became rougher. In particular, a bubble-like surface was observed on the nitride film deposited on NiFe at 100 °C. At higher deposition temperatures (above 200 °C), SiN_x:H films on all the above metals had small RMS values, except for films on Cu which cracked at 250 °C. BHF (10:1) etch rate increased dramatically for nitride films deposited below 150 °C. For different underlying films, the BHF etch rate was quite different, but exhibited the same trend with decrease in deposition temperature. AES measurements showed that Si and N concentrations in the SiN_x:H films were only slightly different for the various deposition temperatures and underlying materials. AES depth profile of nitride films indicated that both surface O content and the depth of oxygen penetrating into SiN_x:H increased for low temperature-deposited films. However, there was no observed oxygen signal from within the films, even for films deposited at 100 °C, and both Si and N concentrations were uniform throughout the film. Received: 26 October 2001 / Accepted: 2 March 2001 / Published online: 20 June 2001     

Effects of crystallinity on laser-induced voltage effect from Zn0.9Co0.1O thin film

Co-doped ZnO epilayer films were grown by pulsed laser deposition (PLD) on vicinal cut silicon and sapphire substrates. Changes in deposition time were observed as a moderate effect on the quality of the films, and the influence of the thickness on thermoelectric signals from Zn_0.9Co_0.1O thin films were discussed. The effect of one of the main deposition parameters, the deposition time, on the crystallinity and electron mobility properties of the Zn_0.9Co_0.1O thin films grown on sapphire was investigated by means of X-ray diffraction (XRD) and laser-induced voltage (LIV) effect. It shown that the XRD rocking curve full-width half-maximun (FWHM) decreased as time increasing, and the LIV signals were observed along the tilting angle of the substrate orientation when the pulsed KrF excimer laser of 248 nm were irradiated on the films. When the films illuminated in pulse lasers, the highest signals occurred in the films with best crystalline quality, and the signals were higher in the films grown on sapphire than those on silicon substrates. It suggested that the electrical resistivity and electron mobility have close relations with not only the crystallinity but also with the interface of the thin films.     

Electrostatic spray deposition of Gd0.1Ce0.9O1.95 and La0.9Sr0.1Ga0.8Mg0.2O2.87 thin films

The deposition of gadolinia-doped ceria (CGO, Gd_0.1Ce_0.9O_1.95) and LaGaO₃-based perovskite oxides (LSGM, La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.87) thin films on a stainless steel substrate was studied using the electrostatic spray deposition (EDS) technique. The effect of process conditions, such as deposition temperature, deposition time and liquid flow rate, on the surface morphology and microstructure of thin films was examined with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The deposited CGO films with a highly porous and three-dimensional interconnected structure were obtained at a liquid flow rate of 0.5 ml/h, a deposition temperature of 503 K and a deposition time ranging from 0.5 to 1 h. On the other hand, the deposited LSGM thin films with porous microstructure were also obtained at the deposition time of 1 h, the deposition temperature of 533 K and the liquid flow rate of 0.5 ml/h. The deposited CGO and LSGM thin films were amorphous at the used deposition temperature. Subsequently, the samples were annealed at 1173 K for 2 h and the desired crystal structures were obtained. The chemical analysis of the thin films was investigated by energy dispersive X-ray (EDX) analysis. The observed chemical compositions of the samples were in a fair agreement with those of the starting solutions.     

Electrochemical responses of carbon nanotubes-based films printed on polymer substances

The electrochemical responses of novel thin films, which consist of multiwalled carbon nanotubes (MWCNTs) printed on polymer substrates, were investigated towards ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple in aqueous potassium chloride solutions. With this respect, MWCNT-based films were fabricated through transfer of water-dispersed MWCNTs onto the polymer substances polyethylene terephthalate (MWCNT-PET) and polycarbonate (MWCNT-PC) by means of mass flexographic printing process. For the electrochemical studies, the techniques of cyclic voltammetry and electrochemical impedance spectroscopy were employed. The findings reveal that the MWCNT-PC films exhibit better stability in solution, less oxidation overpotential, greater oxidation current density, and larger capacitance compared to MWCNT-PET films. In addition, the MWCNT-PC films provide fewer barriers for electron transfer process and faster electrode kinetics compared to MWCNT-PET films. The results are very promising and open the possibility of using mass-printing techniques for the construction of printed MWCNT-polymer films for electrochemical applications.     

Ionic conduction and phase separation studies in PEO-P(VdF-HFP)-LiClO4-dedoped polyaniline nanofiber composite polymer electrolytes — I

In the present work, dispersion of dedoped polyaniline nanofibers into PEO-LiClO₄ blended with P(VdF-HFP) has been discussed. Polyaniline nanofibres have been synthesized by a gentle interfacial polymerization route. The nanofibers are dedoped with base NaOH and films of PEO-P(VdF-HFP)-LiClO₄-dedoped polyaniline nanofibres are prepared by solution casting method with varying concentration of dedoped (insulating) nanofibers (from 5 wt. % to 25 wt. %). The synthesized polymer electrolyte films have been characterized by ac impedance analysis, XRD and SEM. The ionic conductivity of PEO-P(VdF-HFP)-LiClO₄ electrolyte system increases with increase in concentration of dedoped polyaniline nanofibers. The high aspect ratio (> 50) nanofibres prevent PEO-P(VdF-HFP)-LiClO₄ electrolyte matrix from reorganization resulting in increase in amorphicity that leads to enhancement in ionic conductivity. However, the XRD results show that at higher concentration (> 15 wt. %) the nanofibres get phase separated out from the polymer electrolyte phase and start forming insulating clusters which impedes the ion motion. SEM studies confirm the formation of domain like structure of nanofibres at higher concentration, which act as physical barrier for the conduction of Li⁺ ions.     

Influence of boron carbide on properties of CVD-diamond thin films at various deposition pressures

Microcrystalline boron-doped diamond (BDD) films are synthesized on the silicon substrate by the hot-filament chemical vapor deposition method under the gas mixture of hydrogen and methane in the presence of boron carbide (B₄C) placed in front of filaments. The observed results of scanning electron microscopy, Raman spectroscopy and X-ray diffraction show the morphologies. Microstructures for various deposition pressures of as-grown diamond films are found to be dependent on the change of deposition pressure. These results reveal that with the increase of deposition pressure, resistivity decreases and increase in the grain size is noted in the presence of B₄C. Resistivity shows a sudden fall of about three orders of magnitude by the addition of boron in the diamond films. This is due to the crystal integrity induced by B-atoms in the structure of diamond in the presence of B₄C. These results are also significant for the conventional applications of BDD materials. The effects of deposition pressure on the overall films morphology and the doping level dependence of the diamond films have also been discussed.     

Growth and thermoelectric properties of FeSb<Subscript>2</Subscript> films produced by pulsed laser deposition

Thermoelectric FeSb₂ films were produced by pulsed laser deposition on silica substrates in a low-pressure Ar environment. The growth conditions for near phase-pure FeSb₂ films were confirmed to be optimized at a substrate temperature of 425°C, an Ar pressure of 2 Pa, and deposition time of 3 h by ablating specifically prepared compound targets made of Fe and Sb powders in atomic ratio of 1:4. The thermoelectric transport properties of FeSb₂ films were investigated. Pulsed laser deposition was demonstrated as a method for production of good-quality FeSb₂ films.     

First nucleation steps of vanadium oxide thin films studied by XPS inelastic peak shape analysis

The initial states of deposition of vanadium oxide thin films have been studied by analysis of the peak shape (both inelastic background and elastic contributions) of X-ray photoemission spectra (XPS) after successive deposition experiments. This study has permitted to assess the type of nucleation and growth mechanisms of the films. The experiments have been carried out in situ in the preparation chamber of a XPS spectrometer. Thin films of vanadium oxide have been prepared on Al₂O₃ and TiO₂ by means of thermal evaporation, ion beam assisted deposition and plasma enhanced chemical vapour deposition. The thin films prepared by the first two procedures consisted of V₂O₄, while those prepared by the latter had a V₂O₅ stoichiometry. The analysis of the inelastic background of the photoemission spectra has shown that the films prepared by thermal evaporation on Al₂O₃ are formed by big particles that only cover completely the surface of the substrate when their height reaches 16 nm. By contrast, the thin films prepared with assistance of ions on Al₂O₃ or with plasma on TiO₂ consist of smaller particles that succeed in covering the substrate surface already for a height of approximately 4 nm. Thin films prepared by plasma-assisted deposition on Al₂O₃ depict an intermediate situation where the substrate is completely covered when the particles have a height of approximately 6 nm. The type of substrates, differences in the deposition procedure or the activation of the adatoms by ion bombardment are some of the factors that are accounted for by to explain the different observed behaviours.     

离子束增强沉积制备p型氧化锌薄膜及其机理研究

采用离子束增强沉积方法在Si和SiO₂/Si衬底上制备In-N共掺杂ZnO薄膜(INZO)，溅射靶是用ZnO和2 atm% In₂O₃粉体均匀混合并压制而成，在氩离子溅射ZnO靶的同时，氮、氩混合离子束垂直注入沉积的薄膜.实验结果显示INZO薄膜具有(002)的择优取向，并且为p型导电，电阻率最低为0.9Ωcm.薄膜在氮气、氧气气氛下退火，对薄膜的结构和电学特性与成膜和退火条件的关系进行了分析. 关键词： 氧化锌薄膜 p型掺杂 离子束增强沉积     

Microstructure and properties of manganese dioxide films prepared by electrodeposition

Nanostructured manganese dioxide films were obtained by galvanostatic, pulse and reverse pulse electrodeposition from 0.01 to 0.1 M KMnO₄ solutions. The deposition yield was investigated by in situ monitoring the deposit mass using a quartz crystal microbalance (QCM). Obtained films were studied by electron microscopy, X-ray diffraction analysis, energy dispersive spectroscopy, thermogravimetric and differential thermal analysis. The QCM and electron microscopy data were utilized for the investigation of deposition kinetics and film formation mechanism. It was shown that the deposition rate and film microstructure could be changed by variation of deposition conditions. The method allowed the fabrication of dense or porous films. The thickness of dense films was limited to ∼0.1 μm due to the insulating properties of manganese dioxide and film cracking, attributed to drying shrinkage. Porous and crack-free 1-2 μm films were obtained using galvanostatic or reverse pulse deposition from 0.02 M KMnO₄ solutions. It was shown that film porosity is beneficial for the charge transfer during deposition and crack prevention in thick films. Moreover, porous nanostructured films showed good capacitive behavior for applications in electrochemical supercapacitors. The porous nanostructured films prepared in the reverse pulse regime showed higher specific capacitance (SC) compared to the SC of the galvanostatic films. The highest SC of 279 F/g in a voltage window of 1 V was obtained in 0.1 M Na₂SO₄ solutions at a scan rate of 2 mV/s.     

Tribological behavior of in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films

Multilayer polyelectrolyte films containing silver ions were obtained by molecular deposition method on a glass plate or a quartz substrate. The in situ Ag nanoparticles were synthesized in the multilayer polyelectrolyte films which were put into fresh NaBH₄ aqueous solution. The structure and surface morphology of composite molecular deposition films were observed by UV-vis spectrophotometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tribological characteristic was investigated by AFM and micro-tribometer. It was found that the in situ Ag nanoparticles/polyelectrolyte composite molecular deposition films have lower coefficient of friction and higher anti-wear life than pure polyelectrolyte molecular deposition films.     

Si基铁电Bi3.15Nd0.85Ti3O12多层薄膜的一致取向生长和性能的研究

采用脉冲激光沉积(PLD)技术，利用LSCO/CeO₂/YSZ多异质缓冲层，在Si(100)基 片上成功地制备了c轴一致取向的Bi_3.15Nd_0.85Ti₃O12(BNT)铁电薄膜.利用X射线衍射(XRD)和扫描电镜(SEM)分析测定了薄膜的相结构 、取向和形貌特征，考察了沉积温度和氧分压对BNT薄膜微结构、取向和形貌的影响，确定 了BNT薄膜的最佳沉积条件.对在优化的条件下制备得到的BNT薄膜的C-V曲线测试得到了典型 的蝴蝶形曲线，表明该薄膜具有较好的电极化反转存储特性.最后讨论了BNT薄膜铁电性能与 薄膜取向的相关性. 关键词： 3.15Nd_0.85Ti₃O₁₂')" href="#">Bi_3.15Nd_0.85Ti₃O₁₂ 铁电薄 膜 多层异质结 脉冲激光沉积     

Influence of deposition conditions on the microstructure of oxides thin films

Thin films of ZrO₂, HfO₂ and TiO₂ were deposited on kinds of substrates by electron beam evaporation (EB), ion assisted deposition (IAD) and dual ion beam sputtering (DIBS). Then some of them were annealed at different temperatures. X-ray diffraction (XRD) was applied to determine the crystalline phase and the grain size of these films, and the results revealed that their microstructures strongly depended on the deposition conditions such as substrate, deposition temperature, deposition method and annealing temperature. Theory of crystal growth and migratory diffusion were applied to explain the difference of crystalline structures between these thin films deposited and treated under various conditions.     

Growth and characterization of nanostructured anatase phase TiO<Subscript>2</Subscript> thin films prepared by DC reactive unbalanced magnetron sputtering

Titanium dioxide thin films were deposited on three different unheated substrates by unbalanced magnetron sputtering. The effects of the sputtering current and deposition time on the crystallization of TiO₂ thin films were studied. The TiO₂ thin films were deposited at three sputtering current values of 0.50, 0.75, and 1.00 A with different deposition times of 25, 35, and 45 min, respectively. The surface morphology of the films was investigated by atomic force microscopy (AFM). The structure was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The film thickness was determined by field emission scanning electron microscopy (FE-SEM), and the optical property was evaluated with spectroscopic ellipsometry. The results show that polycrystalline anatase films were obtained at a low sputtering current value. The crystallinity of the anatase phase increases as the sputtering current increases. Furthermore, nanostructured anatase phase TiO₂ thin films were obtained for all deposition conditions. The grain size of TiO₂ thin films was in the range 10–30 nm. In addition, the grain size increases as the sputtering current and deposition time increase.