水和乙醇对纳米管结构聚苯胺电阻率的影响

研究了水和无水乙醇对萘磺酸掺杂的纳米管结构聚苯胺的电阻率-温度依赖关系的影响（测量温区为80—300K）.实验结果表明，水分子和乙醇分子的进入均使样品的电导率升高.利用电荷能量限制隧道模型结合纳米管粉末压片的结构特点，认为样品电阻主要来源于纳米管间接触电阻.水或乙醇分子在纳米管聚苯胺中通过与分子链的相互作用，增加了链间与链上非局域化载流子的数量，增大管间接触界面，降低了载流子的隧穿势垒，进而提高了导电能力.但水和乙醇对样品导电性质影响程度是不同的，主要是因为水分子和乙醇分子在结构和物理化学性质上的不同. 关键词： 聚苯胺 纳米管 电阻率     

Effect of cross-linkable polymer on the morphology and properties of transparent multi-walled carbon nanotube conductive films

In this study, we fabricated optically transparent and electrically conductive multi-walled carbon nanotube (MWCNT) thin films using a spray-coating technique. The transparency and the electrical resistance of thin film are dependent on the nanotube content deposited on the polyethylene terephthalate (PET) substrate. Poly(acrylic acid) (PAA) and poly(N-vinyl pyrrolidone) (PVP) were used as adhesion promoters to improve MWCNT coating more significantly. The cross-linked polymer resulted in a superior bond between the MWCNTs and the substrates. The surface electrical resistance was significantly lower than the original sheet after nitric acid (HNO₃) treatment because of the removed surfactant and the increased interconnecting networks of MWCNT bundles, thus improving the electrical and optical properties of the films. Stronger interaction between the MWCNTs and the substrates resulted in lower decomposition of the polymer chain and less amounts of MWCNTs separated into the HNO₃ solution. The lower sheet electrical resistance of PVP/PAA-g-MWCNT conductive films on the PET substrate was because of a more complete conductive path with the cross-linked polymer than that without. Such an improved sheet of electrical resistance varied from 8.83 × 10⁴ Ω/□ to 2.65 × 10³ Ω/□ with 5.0 wt.% PVP/PAA-g-MWCNT sprayed on the PET after acid treatment.     

A comparative analysis of graphene oxide films as proton conductors

The electrical conductivity of graphene oxide (GO) films in vapors of water and acid solutions is found to be close to the conductivity of a film formed after drying the solution of phenol-2,4-disulfonic acid in polyvinyl alcohol, which is known to be a proton conductor. We found that the conductivity of a GO film in vapors of the H₂O–H₂SO₄ electrolyte possesses a sharp maximum at ~1 % by weight of sulfuric acid. The highest conductivity of GO films can be expected when placing the films over acid vapors where the acid concentration is essentially lower than in the acid solutions at their maximum conductivity. Since the conductivity of the H₂O–H₂SO₄ electrolyte itself has a maximum at ~30 % by weight of sulfuric acid, the use of intermediate concentrations of H₂SO₄ is recommended in practical applications. The GO films permeated with water or acid solution in water are expected to possess the proton-exchange properties similar to those of other proton-exchanging membranes.     

The influence of incorporating organic molecules or inorganic nanoparticles on the optical and electrical properties of carbon nanotube films

Organic molecules and inorganic nanoparticles were incorporated into transparent and conductive single- or double-wall carbon nanotube (SWNT or DWNT) films, and their electrical and optical properties were measured. When organic tetrafluoro-tetracyanoquinodimethane (F₄TCNQ) molecules were incorporated into the nanotube films, sheet resistance was reduced to ∼50% of those from the pristine SWNT and DWNT films. Larger improvements were observed with Au nanoparticle decoration or HNO₃/SOCl₂ dipping processes. The sheet resistances were measured to be at 75% of transmittance for HNO₃/SOCl₂-treated DWNT films and at 77% for Au-incorporated DWNT films, making their electrical conductivities 200%-300% better than those of the pristine DWNT films. It was observed that DWNTs have better electrical/optical performance than SWNTs. The relative influence of various dopants, F₄TCNQ, Au, and HNO₃/SOCl₂ as well as microwave irradiation on the optical and electrical properties was identified by using Raman and UV-vis-NIR spectra.     

Surface modification of polyacrylonitrile film by anchoring conductive polyaniline and determination of uricase adsorption capacity and activity

Polyacrylonitrile (PAN) films were modified with chemical polymerization of conductive polyaniline (PANI) in the presence of potassium dichromate as an oxidizing agent. The effect of aniline concentration on the grafting efficiency and on the electrical surface resistance of PAN and (PAN/PANI)-1-3 composite film was investigated. The surface resistances of the conductive composite films were found to be between 6.32 and 0.97 kΩ/cm. As the amount of grafted PANI increased on the PAN films, the electrical resistance of composite film decreased. The PAN/PANI composite films were also characterized using SEM and FTIR. The changes in the surface properties of the films were characterized by contact angle measurements. As expected, the PAN, PAN/PANI and PAN/PANI-uricase immobilized films, exhibited different contact angle values and surface free energy due to different interactive functional groups of the films.The conductive films were well characterized and used for immobilization of uricase. The amount of adsorbed enzyme increases with the increase of surface concentration of grafted fibrous polyaniline polymer. The maximum amount of immobilized enzyme onto composite film containing 2.4% PANI was about 216 μg/cm² (i.e., PAN/PANI-3). The immobilized uricase was reused 24 times in batch wise assay in a day. Finally, the immobilized uricase enzyme system was successfully fabricated and applied to determine the uric acid level in human serum samples.     

Influence of Cu electroplating solutions on boron carbon nitride (BCN) film

Cu electroplating is required for the fabrication of Cu/low-k interconnections. The permeation of a plating solution into low-k films during Cu electroplating is a serious challenge for 45-nm nodes and more complex devices. We investigated the influence of Cu electroplating solutions on boron carbon nitride (BCN) as a low-k film. After dipping it into a Cu electroplating solution that contained additives, the BCN film's hydrophilic surface changed to a hydrophobic surface, and the incorporation of water into the BCN film was suppressed by surfactant adsorption. Sulfuric residue was detected on the BCN sample by thermal desorption spectroscopy after treatment in the Cu electroplating solution with additives; however, it was found through electrical measurements that this solution did not affect the leakage current or the dielectric constant of the BCN film. We successfully fabricated an electroplating Cu layer on a BCN film with good adhesion, and we believe that this BCN film is a sufficiently useful material for Cu/BCN integration in LSI.     

Effect of displacement on resistance and capacitance of polyaniline film

This paper investigates the properties of displacement sensors based on polyaniline (PANI) films. About 1 wt% of PANI micropowder is mixed and stirred in a solution of 90 wt% water and 10 wt% alcohol at room temperature. The films of PANI are deposited from solution by drop-casting on Ag electrodes,which are preliminary deposited on glass substrates. The thicknesses of the PANI films are in the range of 20 μm-80 μm. A displacement sensor with polyaniline film as an active material is designed and fabricated. The investigations showed that,on average,the AC resistance of the sensor decreases by 2 times and the capacitance accordingly increases by 1.6 times as the displacement changes in the range of 0 mm-0.5 mm. The polyaniline is the only active material of the displacement sensor. The resistance and capacitance of the PANI changes under the pressure of spring and elastic rubber,and this pressure is created by the downward movement of the micrometer.     

Water vapour sorption by mim systems

In studying the properties of the sandwich system Al-Al₂O₃-Au(Al) the capacitance of the system was found to depend on the humidity of the environment. The humidity induced capacitance change is reversible and can be explained assuming a process of physical sorption of water vapours by Al₂O₃ dielectric film. The sorption rate is independent of the oxide film thickness, which leads to a conclusion that mainly the sorption in the surface layer of the oxide is involved in the process. The sorption rate is, however, decreasing with increasing thickness of the upper evaporated electrode, which can be taken as an evidence of the fact that the water molecules penetrate to the oxide films through the upper metal layer whose coverage is not complete due to the porosity of the oxide film underneath.On the basis of our experimental results we come to a conclusion that even when the Al₂O₃ films are prepared by oxidation in a 3% solution of tartaric acid, their structure is porous. Proceeding from a simplified picture of the dielectric structure we propose an equivalent electrical scheme of the Al-Al₂O₃-Au Al system. The frequency characteristics measured at different environment humidities correspond to the dependences calculated for the proposed equivalent circuit.     

Degradation and protection of polyaniline from exposure to ultraviolet radiation

The effect of UV radiation on both pure and additive-containing polyaniline thin films is described. Experimental investigations included optical transmittance spectroscopy and electrical conductivity measurements. Exposure to UV radiation in the range of 380 to 400 nm was seen to increase film transmittance by 4% through photobleaching. Different gas ambients were employed for this experiment and progressively more photobleaching was observed for nitrogen, air and oxygen atmospheres. This effect arises due to the destruction of quinoid and benzenoid chromophores on the polymer backbone. Concomitantly, a decrease in film resistivity was also observed and this can be attributed to increased oxidative doping of the film material. The addition of controlled amounts of Tinuvin 213—an ultraviolet absorber (UVA) material—was seen to reduce the UV-induced degradation of polyaniline thin films by absorption of UV photons through regenerative intramolecular photolysis.     

Influence of the thickness on structural,magnetic and electrical properties of La0.7Ca0.3MnO3 thin film

We have studied the effect of thickness on the structural, magnetic and electrical properties of La_0.7Ca_0.3MnO₃ thin films prepared by pulsed laser deposition method using X-ray diffraction, electrical transport, magneto-transport and dc magnetization. X-ray diffraction pattern reflects that all films have c-axis epitaxial growth on LaAlO₃ substrate. The decrease in out-of-plane cell parameter specifies a progressive relaxation of in the plane compressive strain as the film thickness is increases. From the dc magnetization measurements, it is observed that ferromagnetic to paramagnetic transition temperature increases with increase in the film thickness. Magneto-resistance and temperature coefficient of resistance increases with film thickness and have maximum value near its metal to insulator transition temperature.     

Investigation of heat-treatment and pre-treatment on microstructure and electrochemical properties of cerium nano-oxide films on AA7020-T6 by sol-gel methods

In this paper cerium nano-oxide films were applied on AA7020-T6 alloy by sol-gel method. Potentiodynamic polarization and EIS studies have been used to study the corrosion behavior of cerium oxide nano films in 3.5% NaCl. Microstructural and phase properties of cerium oxide were investigated by SEM and XRD. The results showed that heat-treatment temperature and pre-treatment have an important effect on microstructure and electrochemical properties of cerium nano-oxide films. It can be seen from the results that with increasing heat-treatment temperature from 150 to 300 °C, the corrosion resistance of the films increased. It is related to increase the condensation of the films with adding temperature. Also, it can be seen that with adding temperature from 300 to 400 °C, the corrosion resistance of the films decrease. This is an important case related to crystallization of the cerium oxide films between 300 and 400 °C which showed that crystallized ceria films illustrate less corrosion resistance with respect to an amorphous film. Although with applying cerium oxide films the corrosion resistance of the films increased but still the passive region of the ceria films was tiny. So that in this research especially pre-treatment (etching in NaOH solution for 1 min, washing with deionized water for 5 min, etching with acid solution which contained several acids (H₂SO₄, HF, HCl, H₃PO₄), washing with deionized water for 5 min and after that following the samples in boiling deionized water for 1 h) was applied on samples before ceria treatment. The results showed that after applying this pre-treatment the passive region of the films increased extremely. It is related to formation of the thick and porous alumina films after applying pre-treatment which are similar to millepore.     

Transparent,photocatalytic, titania thin films formed at low temperature

A convenient method for the preparation of transparent, photocatalytic titania thin films is described. The films do not require annealing or thermal processing to develop photoactivity, thus can be applied to many thermally-sensitive substrates. Oxalic acid is used in place of the usual mineral acids to peptize the precipitated hydrous titania formed from the hydrolysis of titanium iso-propoxide. This leaves no inorganic residues in the film resulting in a higher quality film. The mineral phase and the photocatalytic activity produced are strongly influenced by the ratio of oxalic acid:titanium iso-propoxide employed. The peptization is carried out at 65 °C with vigorous stirring for 1 h in water containing 15% v/v ethanol, followed by a hydrothermal step at 95 °C. High oxalic acid:Ti molar ratios (0.5:1) result in rutile free sols, while lower ratios (0.25:1) result in anatase, rutile, brookite and TiO₂(B) in varying proportions. The films were exposed to low level UV light to cure, and photodecompose the residual organic components in the film. The photodecomposition of residual oxalic acid in the cast films were monitored using infrared spectroscopy. Photo-activity of the UV-cured films was compared by monitoring the decoloration of methylene blue stains on the film, by UV–Vis spectroscopy. Transmission was greater than 99% across the visible light region (400–800 nm).     

多层溅射制备Wsix/Si薄膜的电阻率特性研究

利用多层溅射技术制备了ＷＳｉ_x／Ｓｉ薄膜，然后测量其平面电阻的退火行为，发现平面电阻在６００－７００℃之间退火后有陡降，这对应于非晶ＷＳｉ_x薄膜中Ｗ₅Ｓｉ₃四角相的形成。ｘ射线衍射和慢正电子湮没测量也证实了这一点。认为薄膜电阻率的突变反映了导电机制的变化，它和薄膜结构的变化有很好的对应关系。 关键词：     

用于彩色滤光片的低阻低应力ITO透明导电膜

探讨了用于彩色滤光片的低电阻和低压应力的ITO透明导电膜工艺。用磁控溅射方法在不同温度的衬底上制备了ITO薄膜。研究了膜形衬底温度与膜结晶化程度的关系,以及膜形衬底温度对膜电阻和压应力的影响。对不同衬底温度下形成的ITO薄膜进行了退火处理,并对退火后的ITO薄膜的电阻和压应力特性进行了分析。结果表明,采用室温沉积非晶态ITO膜,在真空退火下可获得低电阻、低压应力的多晶相ITO膜。     

CO2 laser-induced crystallization of sol–gel-derived indium tin oxide films

Indium tin oxide (ITO) thin films prepared by the sol–gel method have been deposited by the dip-coating process on silica substrates. CO₂ laser is used for annealing treatments. The electrical resistivity of sol–gel-derived ITO thin films decreased following crystallization after exposure to CO₂ laser beam. The topological and electrical properties of the irradiated surfaces have been demonstrated to be strongly related to the coating solution and to the laser processing parameters. Optimal results have been obtained for 5 dip-coating layers film from 0.4 mol/l solution irradiated by 0.6 W/m² laser power density. In this case, homogeneous and optically transparent traces were obtained with a measured sheet resistance of 1.46×10² Ω/□.     

The across-plane conductivity and microstructure of SrZr0.95Y0.05O3 − δ thin films

The across-plane electrical conductivity of the proton-conducting SrZr_0.95Y_0.05O_3???δ thin films fabricated by chemical solution deposition on single-crystalline ZrO₂ doped by 10 mol% of Y₂O₃ (YSZ) substrates was investigated using impedance spectroscopy. The average grain size of the films was found to increase considerably with thermal treatment. This change in grain size has a strong effect on the electrical behavior of films. Our results show that the electrochemical performance of the cell is strongly affected by the potential difference at the film/substrate interface. Coarse-grain film microstructure was proved to be preferable for the reduction of both the film resistance and interfacial barrier.     

Formation of TiO2 film with lower electrical resistance by aerosol beam and fiber laser irradiation

Titanium dioxide (TiO₂) is a functional ceramic with unique photoconductive and photocatalytic properties. In our previous study, a TiO₂ film was formed by aerosol beam irradiation. The films were darkened by femtosecond laser irradiation in air. Then electrical resistance of the darkened area on the film decreased. The heating process is also a useful method to vary the TiO₂ film property. Local heating can be performed by using a continuous wave (CW) fiber laser. In this study, the film was irradiated with a commercial CW fiber laser in vacuum. Laser irradiated area on the film was also darkened after CW fiber laser irradiation. The electrical resistance of the darkened area on the films was decreased as laser fluence was increased. Electrical resistance of the darkened area after CW fiber laser irradiation in vacuum was much smaller than that after femtosecond laser irradiation.     

Influence of oxygen depletion layer on the properties of tin oxide gas-sensing films fabricated by atomic layer deposition

In this paper we report on the influence of film thickness on the electrical and gas-sensing properties of tin oxide thin films grown by atomic layer deposition (ALD) technique. The nature of the carrier and post-flow gases used in ALD was found to have a dramatic influence on the electrical conductance of the deposited films. Up to a film thickness of 50 nm the sheet conductance of the films increased with the thickness, and above 50 nm the sheet conductance was not significantly influenced by the film thickness. This effect was attributed to oxygen depletion at the film surface. When the depth of oxygen depletion (d _dep) was greater than or equal to the film thickness (t), the sheet conductance was thickness dependant. On the other hand, when d _dep≤t, the sheet conductance was independent of the film thickness but depended on the depth of the oxygen depletion. This proposed explanation was verified by subjecting the films to different lengths of post-annealing in an oxygen depleted atmosphere. Gas-sensing functionality of the films with various thicknesses was examined. It was observed that the film thickness had a significant influence on the gas-sensing property of the films. When the thickness was greater than 40 nm, the sensitivity of the films to ethanol was found to follow the widely reported trend, i.e., the sensitivity decreases when the film thickness increases. Below the film thickness of 40 nm the sensitivity decreases as film thickness decreases, and we propose a model to explain this observation based on the increase in resistance due to multiple grain boundaries.     

The effects of solvent nature on spray-deposited ZnO thin film prepared from Zn (CH3COO)2, 2H2O

Transparent conducting zinc oxide was deposited on glass substrate by ultrasonic spray method. The ZnO samples with concentration of 0.1 M were deposited at 300, 350 and 400 °C with 2 min of deposition time. The effects of substrate temperature, ethanol and methanol solution on the structural, electrical and optical properties were examined. The DRX analyses indicated that ZnO films have polycrystalline nature and hexagonal wurtzite structure with (1 0 0) and (0 0 2) preferential orientation corresponding to ZnO films resulting from methanol and ethanol, respectively. The crystallinity of the thin films improved with ethanol solution. All films exhibit an average optical transparency about 80%, in the visible range. The band gap energy of ZnO films obtained with methanol solution higher than of ethanol solution for all the films. The electrical resistivity decrease with ZnO obtained from ethanol indicated; due to the maximum crystallite size retched at this point.     

Fabrication of double- and multi-walled carbon nanotube transparent conductive films by filtration-transfer process and their property improvement by acid treatment

Double-walled carbon nanotubes (DWCNTs) and two kinds of vertically aligned multi-walled carbon nanotubes were employed as raw materials to fabricate transparent conductive films (TCFs). DWCNTs constructed the densest conductive network at the same transmittance, and the corresponding TCFs showed the best performance (320 Ω/□ at 75.0% T). The ratio of dc conductivity to optical conductivity (σ _dc/σ _op) of the as-dispersed DWCNTs was 3.88. The as-obtained TCFs were dipped in HNO₃ solution to improve their performances. Attributed to the removal of sodium dodecyl sulfate molecules, reduction of film thickness, and doping with electron acceptors (such as oxygen), the surface resistance after HNO₃ treatment decreased. The σ _dc/σ _op ratio of the DWCNTs was further increased to 5.24.