Preferential regrowth of indium–tin oxide (ITO) films deposited on GaN (0001) by rf-magnetron sputter

Effects of thermal treatments on the electrical properties and microstructures of indium–tin oxide (ITO)/GaN contacts have been investigated using a rf-magnetron sputter deposition followed by rapid thermal annealing. ITO films annealed at 800 °C revealed Schottky contact characteristics with a barrier height corresponding to ITO’s work function of 4.62 eV. The evolution of electrical properties of ITO/GaN contacts was attributed to the preferential regrowth of In₂O₃ (222)//GaN (0001) with an ideal metal–semiconductor Schottky contact. The feasible use of ITO/GaN as a transparent Schottky contact would be realized by the enhanced regrowth of In₂O₃ at high temperature. Received: 1 September 2000 / Accepted: 15 November 2000 / Published online: 28 February 2001     

Optimization of transparent conductor-embedding front electrodes for efficient light management

An optically and electrically optimum designed front electrode is reported by using a transparent conductive oxide (TCO) film integration. A substantial enhancement of light absorption was achieved by reduction of silver (Ag) grid shading losses while holding a similar series resistance. This obviously improves the solar cell efficiency with a significant reduction in the use of Ag shading area by one fourth. Due to the optical and electrical excellent indium-tin-oxide (ITO), the TCO benefits to widen the light transparent surface and spontaneously works as an anti-reflection coating layer.We have demonstrated that a trade-off between the optical and the electrical aspects should be considered to transfer the optical benefit by ITO supporting transparent electrode to the practical electrical advantage of current enhancement. Transmission line method was applied to profile the variation of contact resistances and specific contact resistance for optimum design of ITO-integrated front electrodes.     

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/□.     

光学透明红外与雷达兼容隐身复合超表面

基于透明导电材料氧化铟锡(ITO)、高透光的聚对苯二甲酸乙二醇酯(PET),设计并实现了光学透明超宽带雷达与红外兼容隐身的复合超表面。该结构由两个专门设计的光学透明超表面组成,由内到外依次为雷达吸波层、红外低发射层。通过调节谐振器尺寸和ITO的方阻实现了微波段8.0~32.0 GHz频带内吸收率高于90%的宽带吸波。利用高ITO占空比的容性频率选择表面,实现了微波段高透过率与红外波段低发射率,并进一步研究了其红外辐射特性。该结构具备较好的超宽频雷达吸波性能、低红外发射率与光学透明特性。     

TCO/Ag/TCO transparent electrodes for solar cells application

Among transparent electrodes, transparent conductive oxides (TCO)/metal/TCO structures can achieve optical and electrical performances comparable to, or better than, single TCO layers and very thin metallic films. In this work, we report on thin multilayers based on aluminum zinc oxide (AZO), indium tin oxide (ITO) and Ag deposited by RF magnetron sputtering on soda lime glass at room temperature. The TCO/Ag/TCO structures with thicknesses of about 50/10/50 nm were deposited with all combinations of AZO and ITO as top and bottom layers. While the electrical conductivity is dominated by the Ag intralayer irrespective of the TCO nature, the optical transmissions show a dependence on the nature of the top and bottom TCOs, mainly due to the change in the reflectivity of the multilayers. Structural, electrical and optical properties are studied to optimize the structure for very thin transparent electrodes suitable for photovoltaic applications.     

Optical, electrical and photovoltaic properties of thermally annealed PPHT:DDE blend thin films

We have investigated the optical, electrical and photovoltaic properties of devices based on 1,2-diazoamino diphenyl ethane (DDE) and poly(3-phenyl hydrazone thiophene) (PPHT):DDE blend. It is observed from the J-V characteristics of the Al/DDE/ITO (ITO—indium tin oxide) device that the electron current injected from Al contact was shown to be space charge limited (SCL), indicating that Al forms nearly ohmic contact for electron injection into lowest unoccupied molecular orbital (LUMO) of DDE. The effect of thermal annealing and composition, on the optical, electrical and photovoltaic response of blend of PPHT and DDE sandwiched between a transparent ITO electrode and an Al back contact are investigated. The observed absorption quenching in the PPHT:DDE blend is attributed to the disordering of PPHT chains and charge transfer between PPHT and DDE as evidenced by FTIR spectra. The observed red shift in the absorption peak on thermal annealing is due to the improvement in the ordering and increases in conjugation length in PPHT. The observed dark current-voltage curves agree well with trap-controlled SCL transport theory. The photophysics of the blend material and influence of thermal annealing on the performance and morphology of these devices were discussed. Annealing process results in the formation of PPHT:DDE complex and increase in the ordering of polymer chain, that increases the incident photon to current efficiency (IPCE) and power conversion efficiency of the photovoltaic devices.     

Polymer-based multi-layer conductive electrode film for plastic LCD applications

Thin films of polymer-based multi-layer conductive electrode to be used as a substrate for a plastic liquid crystal display (LCD) have been prepared by a DC magnetron roll-to-roll sputtering method. The conductive layer is composed of three layers, ITO/Ag/ITO or ITO/APC/ITO, where APC is Ag-Pd-Cu alloy, on the polymer substrate (Arton?), which has been treated with hard-coat and gas-barrier layers. The properties of the conductive electrode for the plastic LCD were the following: (1) sheet resistance is 6 Ω/square; (2) transparency is 88% at 550 nm; (3) H₂O gas permeation through the plastics is 0.35 g/m² in 24 h; (4) durability against solvents is good for 5% NaOH solution, IPA, methanol, NMP, acetone, etc.; (5) the irreversible shrinkage and the compaction rate are both less than 3 ppm/h after annealing for 100 h at 150 °C. Received: 22 January 2001 / Accepted: 30 January 2001 / Published online: 26 April 2001     

膜层厚度对蓝宝石衬底上生长的ITO薄膜性质的影响

采用磁控溅射的方法在蓝宝石衬底上制备了氧化铟锡(ITO)透明氧化物薄膜;研究了不同厚度薄膜的结构、光学和电学特性。经X射线衍射(XRD)测量,发现在蓝宝石衬底上生长的ITO薄膜呈现了较高的(222)择优取向;随着膜层厚度的增加,该衍射峰对应的2θ衍射角逐渐向大角度方向移动,同时该衍射峰的半峰全宽逐渐减小,平均晶粒尺寸增大。 经光学透射光谱测量,发现随着膜层厚度的增加,光学透过率逐渐减小。膜层厚度为0.2 μm时,可见光透过率超过80%,当膜层厚度为0.8 μm时,可见光透过率下降到60%。电学测量结果表明,随着膜层厚度的增加,薄膜电阻率逐渐减小。膜层厚度为0.2 μm时,电阻率为9×10^-4 Ω·cm, 膜层厚度为0.8 μm时,电阻率为5.5×10^-4 Ω·cm。     

Electrical properties of transparent carbon nanotube networks prepared through different techniques

Ultra‐thin, optically transparent and electrically conducting films of pure carbon nanotubes (CNTs) are widely studied thanks to their promise for broad applications. In the present work, we study and compare different deposition techniques for the production of these networks: dip‐coating, spray‐coating, vacuum filtration and electrophoretic deposition on a quartz glass using single‐walled carbon nanotubes (SWCNTs) produced by the HiPCo method. In order to optimize the networks, besides the various deposition techniques we also investigate how the optical and electrical properties vary if the networks are fabricated from different CNTs, all synthesized by the CVD method: SWCNTs, DWCNTs and MWCNTs. As the main criteria for evaluating the quality of these CNT networks we measure the electrical surface resistance at a certain optical transmittance and correlate it to the morphology (homogeneity and roughness) of the networks. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

紫外-可见多功能光谱电化学池的研制

利用研制的紫外－可见多功能光谱电化学池,以ＵＶ－Ｖｉｓ长光程薄层和光透支光谱电化学法的分别测定了Ｆｅ（ＣＮ）６＾３－／Ｆｅ（ＣＮ）６＾４－电对的反应电数ｎ;燕以ＵＶ－Ｖｉｓ光透半无限扩散和平行人射式光谱电学法分别测定了Ｆｅ（ＣＮ）６＾３－的扩散系数Ｄ。实验的结果均与文献值相近,从而表明了这种ＵＶ－Ｖｉｓ多功能光谱电化学池的可靠性。     

Transparent conducting indium-tin-oxide (ITO) film as full front electrode in III-V compound solar cell

The application of transparent conducting indium-tin-oxide (ITO) film as full front electrode replacing the conventional bus-bar metal electrode in III-V compound GaInP solar cell was proposed. A high-quality, non-rectifying contact between ITO and 10 nm N⁺-GaAs contact layer was formed, which is benefiting from a high carrier concentration of the terrilium-doped N⁺-GaAs layer, up to 2×10¹⁹ cm^-3. A good device performance of the GaInP solar cell with the ITO electrode was observed. This result indicates a great potential of transparent conducting films in the future fabrication of larger area flexible III-V solar cell.     

IPTO薄膜制备及其在有机光电器件中的应用

新型IPTO(Pr Ti O3掺杂In2O3)薄膜的可见光透过率及导电性可与商业化的ITO薄膜媲美。采用双源电子束设备制备了一种新型的IPTO透明导电薄膜,通过开尔文探针法测试,其功函数为5.14 e V。为验证新型IPTO透明导电阳极对有机电致发光器件性能的影响,将IPTO替代商业化ITO作为阳极制备了有机电致发光器件。基于IPTO阳极的器件的亮度最大值为85 140 cd/m2,外量子效率最大值为3.16%,分别为以ITO为阳极的器件的3倍及1.13倍。这种性能的改善是由于IPTO具有较小的表面粗糙度及较高的功函数,可以降低阳极的注入势垒,有利于电荷向有机层注入,改善了器件内的空穴及电子的注入平衡。     

Performance analysis and comparison of MWCNT loaded ITO and TIO based optically transparent patch antennas for terahertz communications

Multiwalled carbon nanotube (MWCNT) loaded transparent conducting oxide materials (TCOMs) based optically transparent antennas are designed to resonate at 750 GHz. TCOMs such as indium-doped tin oxide (ITO) and titanium-doped tin oxide (TIO) are used for designing the transparent terahertz patch antennas. Shorting pin technique is used to improve the impedance performances of the transparent antennas. The MWCNT is used for shorting the microstrip line with the ground plane of the antenna. By varying the position of short with respect to the antenna patch, the resonant frequency of the antennas are optimized to resonate at 750 GHz. The impedance and radiation performances of the MWCNT loaded transparent antennas are compared. A broad impedance bandwidth (−10 dB) is achieved for both the proposed antennas. The MWCNT shorting pin effect on radiation performances of the transparent antennas are discussed in detail. The antennas are simulated using finite element method (FEM) based electromagnetic solver, Ansys-HFSS.     

Fiber laser annealing of indium-tin-oxide nanoparticles for large area transparent conductive layers and optical film characterization

Indium tin oxide (ITO) coatings are widely used as transparent electrodes for optoelectronic devices. The most common preparation methods are sputtering, evaporation, and wet chemical deposition. ITO coatings can also be manufactured by solution deposition of ITO nanoparticles followed by furnace thermal annealing with the major motivation to reduce equipment investment. However, conventional furnace annealing is energy intensive, slow, and limited by the peak processing temperature. To overcome these constraints, we suggest using a laser beam for ITO nanoparticle annealing over a large area. It is shown in the present study that a low cost, high power, and high efficiency laser can yield large area functional ITO films in a process that carries substantial promise for potential industrial implementation. Furthermore, laser annealing generates higher electrical conductivity than conventional, thermally annealed nanoparticle films. The optical and electrical properties of the annealed ITO films can also be altered by adjusting laser parameters and environmental gases.     

Adsorption and electrically stimulated desorption of the triblock copolymer poly(propylene sulfide-bl-ethylene glycol) (PPS-PEG) from indium tin oxide (ITO) surfaces

Protein-resistant triblock copolymers, poly(propylene sulfide-bl-ethylene glycol) (PPS-PEG) have been previously demonstrated to chemisorb onto gold surfaces forming monolayers that resist non-specific protein adsorption and are stable against oxidation. In this paper, we report on the adsorption of PPS-PEG onto a transparent and electrically conductive substrate, indium tin oxide (ITO). In addition, we demonstrate the controlled desorption of PPS-PEG by applying an electrical stimulus. We have used three complementary surface characterization techniques: variable angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze the adsorption and electro-desorption of PPS-PEG from an ITO surface. All three methods confirmed the formation of PPS-PEG adlayers on the ITO surfaces. Based on our experimental XPS and ToF-SIMS results as well as former publications, we postulate that the chemisorption of the PPS-PEG on ITO involves direct sulfide-indium (or tin) interactions. When an ascending anodic electrical stimulus was applied to the surface of the modified samples, a gradual and steady polymer removal was observed, with complete loss of the polymeric monolayer at a potential of 2000 mV (referenced to Ag electrode). Anodic polarization did not result in oxidation of the thioether function of the PPS-PEG adlayers, indicating excellent oxidation resistance of PPS-PEG on ITO surfaces. This work is focused on exploiting electrical stimuli for the in situ surface modification under dynamic control.     

Novel type of indium oxide thin films sputtering for opto-electronic applications

Transparent conductive oxide (TCO) thin films play a significant role in recent optical technologies. Displays of various types, photovoltaic systems, and opto-electronic devices use these films as transparent signal electrodes. They are used as heating surfaces and active control layers. Oxides of TCO materials such as: tin, indium, zinc, cadmium, titanium and the like, exhibit their properties. However, indium oxide and indium oxide doped with tin (ITO) coatings are the most used in this technology.In this work, we present conductive transparent indium oxide thin films which were prepared using a novel triode sputtering method. A pure In₂O₃ target of 2 in. in diameter was used in a laboratory triode sputtering system. This system provided plane plasma discharge at a relatively low pressure 0.5-5 mTorr of pure argon. The substrate temperature was varied during the experiments from room temperature up to 200 °C. The films were deposited on glass, silicon, and flexible polyimide substrates. The films were characterized for optical and electrical properties and compared with the indium oxide films deposited by magnetron sputtering.     

Electrical conduction and bipolar switching properties in transparent vanadium oxide resistive random access memory (RRAM) devices

In this study, the electrical conduction and bipolar switching properties in transparent vanadium oxide thin films are investigated and discussed. (110)-oriented vanadium oxide thin films were well deposited onto transparent ITO substrates for the possible development of applications in the structure of system-on-panel devices. For the as-deposited vanadium oxide thin films, they were prepared for 1 h by a rf magnetron sputtering method of rf power 130 W, chamber pressure 10 mTorr, substrate temperature 550 °C, and different oxygen concentrations. In addition, the Al/V₂O₅/ITO device presents reliable and bipolar switching behavior. The on/off ratio and switching cycling of two stable states are found and discussed. We suggest that the current–voltage characteristics are governed by ohmic contact and Poole?Frankel emission transport model mechanisms in low- and high-voltage regions, respectively.     

Plasma-based sputtering of indium tin oxide for the application of photovoltaic cells

Transparent and conducting indium tin oxide (ITO) thin films were deposited on soda lime glass substrates by RF plasma magnetron sputtering at room temperature. The effect of thickness (100, 200 and 300?nm) on the physical (structural, optical, electrical) properties of ITO thin films was investigated systematically. It is observed that with an increase in thickness, the X-ray diffraction data indicate polycrystalline films with grain orientations predominantly along (222) and (400) directions; the average grain size increases from 10 to 30?nm; the optical band gap increases from 3.68 to 3.73?eV and the transmission decrease from 80% to 70% . Four-point probes show a low resistivity (2.4×10^?5?Ω?cm) values for film with a thickness 300?nm. Present work shows that the ITO is a promising transparent conductive oxide material for the solar cell application.     

Dependence of intermediated noble metals on the optical and electrical properties of ITO/metal/ITO multilayers

Sn doped In₂O₃ (ITO) single layer and a sandwich structure of ITO/metal/ITO (IMI) multilayer films were deposited on a polycarbonate substrate using radio-frequency and direct-current magnetron sputtering process without substrate heating. The intermediated metal films in the IMI structure were Au and Cu films and the thickness of each layer in the IMI films was kept constant at 50 nm/10 nm/40 nm. In this study, the ITO/Au/ITO films show the lowest resistivity of 5.6 × 10⁻⁵ Ω cm.However the films show the lower optical transmission of 71% at 550 nm than that (81%) of as deposited ITO films. The ITO/Cu/ITO films show an optical transmittance of 54% and electrical resistivity of 1.5 × 10⁻⁴ Ω cm. Only the ITO/Au/ITO films showed the diffraction peaks in the XRD pattern. The figure of merit indicated that the ITO/Au/ITO films performed better in a transparent conducting electrode than in ITO single layer films and ITO/Cu/ITO films.     

Properties of ITO films prepared by rf magnetron sputtering

Recently, a detailed study of the properties of ITO thin films deposited under various preparation conditions using the rf magnetron sputtering technique (from ITO target in pure Ar gas) has been undertaken in our laboratory. The effect of substrate temperature has been studied in a previous paper. Here the results of a study of the structural, electrical and optical properties of the ITO films with different thickness are presented. The figure of merit for the films, which is a measure of the quality of the films as transparent conductive layers for photovoltaic applications, has been evaluated.