ITO及WO3在电解液中的交流阻抗特性

采用表面过程法拉第阻纳表达式方法与等效电路方法，研究透明ITO平面电极及带WO3薄膜层的ITO平面电极处于1mol LiClO4丙烯碳酸酯电解液中的电化学阻抗谱．分析显示WO3薄膜层有效地阻止了表面吸附参量对ITO电极反应的影响，使电极反应仅受电极电位的影响，并且随WO3薄膜在电解液中浸泡时间的增加，WO3薄膜的常相位角元件的特性最终回归为电容效应．     

Comparison of the dye-sensitized solar cells performances based on transparent conductive ITO and FTO

We investigated dye-sensitized solar cell (DSSC) performances with regard to transparent conducting oxide substrates: indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO). The DSSCs were in a standard configuration: a photoelectrode of TiO₂ nanoparticles (9 nm size, anatase phase) deposited on transparent and electrically conductive substrates, counter electrodes of Pt-coated glass, ruthenium 535 dye, and AN50 iodolyte electrolyte (Solaronix). The cells manufactured from ITO (FTO) had an open circuit voltage of 705 (763) mV and short-circuit current of 7.87 (34.3) mA/cm². A direct correlation was found between transparent conductive film resistivity and cell efficiency. Resistivities of 52 Ω/sq for ITO substrates and 8.5 Ω/sq for FTO led to major differences in internal global efficiency: from 2.24% for ITO to 9.6% for FTO.     

Improvement of resistive switching characteristics in ZrO2 film by embedding a thin TiOx layer

The stabilization of the resistive switching characteristics is important to resistive random access memory (RRAM) device development. In this paper, an alternative approach for improving resistive switching characteristics in ZrO(2)-based resistive memory devices has been investigated. Compared with the Cu/ZrO(2)/Pt structure device, by embedding a thin TiO(x) layer between the ZrO(2) and the Cu top electrode, the Cu/TiO(x)-ZrO(2)/Pt structure device exhibits much better resistive switching characteristics. The improvement of the resistive switching characteristics in the Cu/TiO(x)-ZrO(2)/Pt structure device might be attributed to the modulation of the barrier height at the electrode/oxide interfaces.     

Interface Engineering with MoS2–Pd Nanoparticles Hybrid Structure for a Low Voltage Resistive Switching Memory

Metal oxide‐based resistive random access memory (RRAM) has attracted a lot of attention for its scalability, temperature robustness, and potential to achieve machine learning. However, a thick oxide layer results in relatively high program voltage while a thin one causes large leakage current and a small window. Owing to these fundamental limitations, by optimizing the oxide layer itself a novel interface engineering idea is proposed to reduce the programming voltage, increase the uniformity and on/off ratio. According to this idea, a molybdenum disulfide (MoS₂)–palladium nanoparticles hybrid structure is used to engineer the oxide/electrode interface of hafnium oxide (HfO_x)‐based RRAM. Through its interface engineering, the set voltage can be greatly lowered (from ?3.5 to ?0.8 V) with better uniformity under a relatively thick HfO_x layer (≈15 nm), and a 30 times improvement of the memory window can be obtained. Moreover, due to the atomic thickness of MoS₂ film and high transmittance of ITO, the proposed RRAM exhibits high transparency in visible light. As the proposed interface‐engineering RRAM exhibits good transparency, low SET voltage, and a large resistive switching window, it has huge potential in data storage in transparent circuits and wearable electronics with relatively low supply voltage.     

室温下制备非晶ZnO薄膜及其电阻开关特性研究

室温下采用紫外固化的方法取代溶胶-凝胶方法中的高温退火制备了氧化锌薄膜, XRD分析结果表明薄膜为非晶的, XPS分析结果表明薄膜的主要成分是ZnO。在深紫外固化后的薄膜表面溅射Al作为顶电极获得Al/a-ZnO/FTO结构的器件,研究深紫外照射时间对器件电阻转变性能的影响, 进一步解释了深紫外固化的机制。研究表明: 经过充足时间(12 h)照射的器件表现出双极性电阻开关特性,阈值电压分布集中(-3.7 V<V_set<-2.9 V, 3.4 V< V_reset<4.3 V)且符合低电压工作的要求, 至少在4000 s内器件的高低阻态都没有发生明显的退化, 表现出了良好的存储器特性。Al/a-ZnO/FTO器件的这种电阻转变特性可以用空间电荷限制电流传导机制解释。     

Low power and stable resistive switching in graphene oxide-based RRAM embedded with ZnO nanoparticles for nonvolatile memory applications

The present study reports the role of zinc oxide nanoparticles (ZnO NPs) embedded in graphene oxide (GO)-based RRAM for non-volatile memory applications. GO thin film embedded with different concentrations of ZnO NPs was deposited on bottom electrode, i.e., indium tin oxide (ITO) coated glass. Thermal evaporation technique was used for the fabrication of top electrodes for electrical measurements. Structural and morphological studies of synthesized GO and ZnO NPs were done by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Switching characteristics of the RRAM devices were investigated using electrical measurements. It has been observed that the optimized concentration of ZnO NPs (20%) shows stable switching behavior with low SET (??0.61 V) and RESET (+?0.65 V) voltages as compared to pure GO devices. The switching of the fabricated memory devices from high resistance state (HRS) to low resistance state (LRS) has been found due to conductive filament formed between top and bottom electrodes. This conductive filament has been confirmed by the change in resistance as a function of temperature. The Al/GO-ZnO(20%)/ITO devices show stable endurance behavior for >?50 cycles and retention behavior for >?4?×?10³ s. In HRS, the dominated conduction mechanism was found to be space-charge limited conduction (SCLC), whereas in LRS, the Ohmic conduction mechanism was observed. The incorporation of ZnO NPs increased the number of oxygen vacancies in switching layer which eventually enhanced the formation of conductive filament. This phenomenon has been confirmed using XPS characterization of the switching layer. These optimized concentrations of ZnO embedded in GO switching layers provide a way for future low power non-volatile memory devices.

     

Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property

Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.     

电色膜和电色器件的光电特性

介绍了电子束蒸发沉积WO3膜在0．5mol/LH2SO4溶液和NiOx膜在1molKOH溶液中的电色性能；介绍了沉积到玻璃片上的ITO膜作透明导电电极、光学上活性的WO3阴极变色膜作工作电极、光学上活性的NiOx阳极变色膜作反电极（贮存电荷试样的贮存器）和1molLiClO4丙酮溶液的电解质作锂离子导体组成的互补型电色器件的光电特性。     

Influence of surface electrode on luminescent properties of nanocrystalline silicon electroluminescent device

We describe the electrical and luminescence properties of nanocrystalline silicon (nc-Si) based red electroluminescent (EL) devices using an indium tin oxide (ITO) and/or gold (Au) films as a surface electrode, and the variation in the transmittance and resistivity of two electrodes with various film thicknesses. The increase in the film thickness from 50 to 200 nm of the ITO electrode led to the lowering of resistivity from 2.0 x 10(-3) to 9.1 x 10(-4) omega cm and almost the same value (83-92%) of transmittance in the red region. On the other hand, the Au electrode was lowered the resistivity from 1.8 x 10(-4) to 1.6 x 10(-5) omega cm and the transmittance in the red region from 42 to 1.8% with increasing the film thickness from 10 to 80 nm. Moreover, the red luminescence from the EL devices using the ITO and/or Au electrodes having thickness of 200 and 10 nm, respectively, obtained by applying the direct current forward voltage above 4.5 and 2.5 V and/or by flowing the forward current density above 53 and 38 mA/cm2, respectively. However, the luminescence intensity of EL device with the ITO electrode strengthened more than about one order of magnitude in comparison to that of the EL device with the Au electrode. This was due to the high value of transmittance in the red region of the ITO electrode. We suggest that the ITO electrode is an optimum surface electrode for the realization of nc-Si based EL device with the high brightness.     

HFCVD grown graphene like carbon–nickel nanocomposite thin film as effective counter electrode for dye sensitized solar cells

The two step processes of hot filament chemical vapor deposition (HFCVD) and DC sputtering were used to grow graphene like carbon (GLC)–nickel (Ni) nanocomposite thin film on fluorine-doped tin oxide (FTO) glass and applied as counter electrode (CE) for dye sensitized solar cells (DSSCs). The morphological and absorption properties revealed uniform GLC–Ni thin film with reasonable transmittance. The GLC–Ni thin film showed enhanced electrical conductivity as compared to FTO. The good electrocatalytic activity towards iodide ions in redox electrolyte was showed by the prepared GLC–Ni/FTO thin film electrode. The fabricated DSSC with GLC–Ni/FTO counter electrode (CE) presented relatively moderate solar-to-electrical conversion efficiency of ∼3.1% with high short-circuit current density (J_SC) of ∼10.03 mA/cm², open circuit voltage (V_OC) of ∼0.663 V with fill factor (FF) of ∼0.45, which might attribute to enhanced electrical conductivity and the electrocatalytic activity of GLC–Ni/FTO CE.     

Nanostructured WO₃/BiVO₄ heterojunction films for efficient photoelectrochemical water splitting

We report on a novel heterojunction WO(3)/BiVO(4) photoanode for photoelectrochemical water splitting. The heterojunction films are prepared by solvothermal deposition of a WO(3) nanorod-array film onto fluorine-doped tin oxide (FTO) coated glass, with subsequent deposition of a low bandgap, 2.4 eV, visible light responding BiVO(4) layer by spin-coating. The heterojunction structure offers enhanced photoconversion efficiency and increased photocorrosion stability. Compared to planar WO(3)/BiVO(4) heterojunction films, the nanorod-array films show significantly improved photoelectrochemical properties due, we believe, to the high surface area and improved separation of the photogenerated charge at the WO(3)/BiVO(4) interface. Synthesis details are discussed, with film morphologies and structures characterized by field emission scanning electron microscopy and X-ray diffraction.     

A new DRAM-type memory devices based on polymethacrylate containing pendant 2-methylbenzothiazole

A polymethacrylate containing pendant 2-methylbenzothiazole (pBVMA) with good thermal stability was synthesized by free radical polymerization. The devices based on pBVMA possess a sandwich structure comprising bottom indium-tin oxide (ITO) electrode and top Al electrode. The as-fabricated device exhibits the dynamic random access memory (DRAM) behavior with an ON/OFF current ratio up to 10⁵ and can endure 10⁸ read cycles under −1 V pulse voltage. The effect of the film thickness on the device performance was investigated and the devices fabricated with 75 nm and 45 nm thick pBVMA films were both found to exhibit DRAM type memory behaviors, which may indicate that the Al nanoparticles had no penetration into the thin film during the vacuum-deposition process. The molecular simulation and physical theoretical models were analyzed and the mechanism of the DRAM performance may be attributed to the weak electron withdrawing ability of the molecule.     

Poly(p-phenylene vinylene) light-emitting devices prepared via the precursor route onto indium tin oxide and fluorine-doped tin dioxide substrates

For the preparation of organic light-emitting devices (LEDs) an optically transparent and electrically conducting thin film is needed as anode. Usually, a glass substrate coated with indium tin oxide (ITO) is used. We show that ITO is unsuitable in the case of poly(p-phenylene vinylene) (PPV) prepared by the precursor route. We have found that a reaction in which hydrogen chloride is eliminated during the thermal conversion to PPV and the ITO takes place. Scanning electron microscopy investigations of the ITO-PPV interface demonstrates that indium chloride compounds, e.g., InCl3 crystals with dimensions up to 40 μm, are produced. Photoluminescence measurements reveal that the fluorescence efficiency is quenched by a factor of 2–23 in the case of ITO compared with PPV converted onto usual glass. In a second step we have investigated LEDs prepared from PPV in the ITO/PPV/Al configuration in order to obtain information about the process responsible for the degradation of these devices. We shall show that the formation of the above-mentioned indium chloride compounds is one possible degradation mechanism and is responsible for the relative short lifetimes of these LEDs. To overcome this problem we propose to use fluorine-doped tin dioxide (FTO) instead of ITO. Finally, we show the results obtained for LEDs in the FTO/PPV/Al configuration and compare them with ITO/PPV/Al devices. This revised version was published online in November 2006 with corrections to the Cover Date.     

A complementary electrochromic device with highly improved performance based on brick-like hydrated tungsten trioxide film

Uniform and well adhesive nanostructured hydrated tungsten trioxide (3WO3 x H2O) films were grown on fluorine doped tin oxide (FTO) substrate via a facile and template-free crystal-seed-assisted hydrothermal method by addition of ammonium sulfate ((NH4)2SO4) and hydrogen peroxide (H2O2). X-ray diffraction (XRD) studies indicated that the films are of orthorhombic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis showed that the film was composed of brick-like nanostructures with a preferred growing direction along (002). The influence of seed layer, (NH4)2SO4 and H2O2 on the products were also studied. The film showed good cyclic stability, comparable switching speed and coloration efficiency (30.1 cm2 C(-1)). A complementary electrochromic device based on the film and Prussian blue depicted highly improved color contrast, coloration/bleaching response (1.8 and 3.7 s respectively) and coloration efficiency (164.6 cm2 C(-1)).     

Conductivity mechanisms in poly(p-phenylene vinylene) light-emitting diodes at high and low bias

Polymer light-emitting diodes (LEDs) based on the structure ITO conducting glass /poly(p-phenylene vinylene)/metal (Al, In, Mg) have been investigated with particular emphasis on some anomalous and poorly understood features of the conduction mechanisms. At large forward bias (above 3 V, where electroluminescence is seen) the DC current is dominated by hole injection at the bottom ITO electrode and is not very sensitive to the top electrode metal or the fabrication conditions. It always increases exponentially with voltage at 20°C, but studies on operating voltages and apparent ideality factors as a function of thickness indicate that the conduction mechanism probably involves thermally assisted tunnelling rather than a simple Schottky diode mechanism. In contrast, the current at low forward bias (0.1–3 V) is exceptionally sensitive to the top electrode material, fabrication conditions, and operating history of the device. Anomalous behaviour is often seen, particularly with new devices and with Mg or In electrodes. With Al electrodes, particularly after a top electrode annealing step, the behaviour becomes much more stable and resistive, and logJ increases linearly with V^1/4 over 3 orders of magnitude of current. The overall behaviour at low bias is controlled by the barrier to holes at the top electrode, but the role of filamentary defects, dopants, and the insulating interfacial layer is also discussed.     

Preparing thick, defect-free films of anatase titania for dye-sensitized solar cells

Anatase titania (TiO₂) nanoparticle films were prepared on fluorine-doped tin oxide (FTO) and tin-doped indium oxide (ITO) substrates. The films were characterized by X-ray diffraction, scanning electron microscopy, profilometry, Raman spectroscopy, and optical microscopy. The results show that defects are initiated during the sintering step and continue to propagate once the film is cooled. The sintering and annealing steps were controlled by reducing the pressure and the rate of temperature change. These steps reduced the stresses generated during film preparation, allowing thick titania films on both FTO and ITO substrates to be prepared with minimal defects. Using the optimized conditions for film preparation, 20 μm thick films of titania on FTO and ITO substrates were obtained with calculated defect densities of 2.5 and 7.8%. Films as thick as 25 μm were prepared on FTO substrates with a defect density of only 6.0%. Dye-sensitized solar cells (DSSCs) were fabricated using the titania films prepared by both standard and vacuum sintering methods. DSSCs made with 20 μm titania films sintered at intermediate pressures show improvements to short-circuit current, open-circuit voltage, and device efficiency.     

直流磁控溅射沉积WO3薄膜电致变色性能研究

以金属钨为靶材,采用直流反应磁控溅射方法,在玻璃上制备电致变色WO3薄膜.利用X射线衍射(XRD)方法对薄膜的结构进行了分析,得出了WO3薄膜的沉积工艺.制备了WO3/TTO/Glass电致变色器件,并对其性能进行了研究.结果表明在Li+注入前后,薄膜的透射率平均变化约50%,具有较好的可逆变色特性;Li+注入后,WO3薄膜中的一部分W6+变为W5+,转化比例约为25%.     

Characterization of transparent conductive ITO, ITiO, and FTO films for application in photoelectrochemical cells

Transparent conductive In(2-x)Sn(x)O3 (ITO) and In(2-x)Ti(x)O3 (ITiO) films were prepared via RF magnetron sputtering on soda-lime glass substrates at 300 degrees C and investigated with respect to their photoelectric conversion performance compared with the commercial F:SnO2 (FTO) glass. The near infrared ray transmittance of ITiO was highest for wavelengths over 1000 nm compared with those of ITO and FTO. Photoelectrochemical cells (PECs) were fabricated using ITiO film, ITO film, and FTO glass. The photoelectric conversion efficiency (eta) of the PECs samples using ITiO was 5.64%, whereas 2.73% was obtained from the PEC samples with ITO, both at 100 mW/cm2 light intensity. The impedance measurement was also used to explain the electrochemical performance of the PECs with various TCO glasses.     

ITO用作铁电薄膜电极的研究

研究了sol-gel掺锡氧化铟（ITO溶胶在SiO2/Si衬底和光学玻璃衬底上的成膜及结晶性能,并与CVD法生长的ITO薄膜作了对比。结论是：sol-gelITO膜,虽然具有与CVD ITO膜相似的结晶性能和较高的导电性,但以sol-gel ITO膜作下电极,无法使PLT、PZT的sol-gel膜具有明显的结晶取向。因漏电太大,sol-gel ITO也无法作sol-gel铁电膜（如PLT,PZT）的上电极。但在CVD ITO膜上,sol-gel铁电膜能很好结晶,且Au/PLT/ITO电容,具有良好的电学性能。     

Preparation of inorganic solid state thin film for electrochromic application

All oxide solid state ITO (indium tin oxide)/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked structure was deposited on a silica glass substrate by pulsed laser deposition for its electrochromic application. The Li doped amorphous tungsten trioxide Li_yWO_3−x thin film prepared at room temperature and in oxygen pressure of 7 Pa got the color of blue due to the mixture valence state of tungsten. We found that the amorphous Li_1−zMn₂O₄ thin film was suitable for the electrochromic application in spite of the low ion conductivity along in-plane direction. The ITO electrode thin film deposited at room temperature showed the relatively high transmittance and the usable conductivity. The transmittance at a wavelength of 750 nm for the ITO/Li_yWO_3−x/Li_1−zMn₂O₄/ITO stacked film changed from 50% to 80% by the applied voltage, while the transmittance at around 450 nm did not change. The blue-colored electrochromic property could be observed for the all oxide solid state film.