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Proceedings of the IEEE

Issue 7 • Date July 2005

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Displaying Results 1 - 25 of 27
  • [Front cover]

    Page(s): c1
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  • Put your technology leadership in writing

    Page(s): c2
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  • Table of contents

    Page(s): 1233
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  • Proceedings of the IEEE publication information

    Page(s): 1234
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  • Special Issue on Flexible Electronics Technology, Part 1: Systems and Applications

    Page(s): 1235 - 1238
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  • Macroelectronics: Perspectives on Technology and Applications

    Page(s): 1239 - 1256
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    Flexible, large area electronics - macroelectronics - using amorphous silicon, low-temperature polysilicon, or various organic and inorganic nanocrystalline semiconductor materials is beginning to show great promise. While much of the activity in macroelectronics has been display-centric, a number of applications where macroelectronics is needed to enable solutions that are otherwise not feasible are beginning to attract technical and/or commercial interest. In this paper, we discuss the application drivers and the technology needs and device performance requirements to enable high performance applications to include RF systems. View full abstract»

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  • Functional Pixel Circuits for Elastic AMOLED Displays

    Page(s): 1257 - 1264
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (980 KB) |  | HTML iconHTML  

    While fabrication of active matrix organic LED (AMOLED) displays on plastic substrates continues to face technological challenges, stable electrical operation of thin-film transistor (TFT) pixel circuits under mechanical stress induced by substrate bending remains a critical issue. This paper investigates strain-induced shifts in hydrogenated amorphous silicon TFT characteristics and the compound impact on TFT circuit behavior. Measurements show that the magnitude of the shifts is determined by the direction of current flow in the TFT with respect to the bending stress orientation as well as bias conditions. Physically based compact models are developed that relate device characteristics to material behavior for design and optimization of AMOLED pixel circuits that can maintain immunity to bending stress. In particular, current mirror-based pixel circuits are presented that compensate for the long term threshold voltage shift and instantaneous strain-induced shifts in device characteristics. View full abstract»

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  • Flexible Organic LED and Organic Thin-Film Transistor

    Page(s): 1265 - 1272
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (578 KB) |  | HTML iconHTML  

    In this paper, a plastic organic thin-film transistor (OTFT) with high mobility formed on the polymeric gate dielectrics is presented. Flexible organic LEDs (OLEDs) operated by an OTFT are fabricated with a novel lamination method and the results are also presented. Fabrication method and the performances of white (consisting of R, G, and B) OLEDs with high efficiency, stability, and good color purity are discussed. View full abstract»

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  • Organic LED Pixel Array on a Dome

    Page(s): 1273 - 1280
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    We fabricated an array of organic LED (OLED) pixels on a dome of clear polymer foil. The array is first formed on the flat polymer substrate and then is shaped to the dome. During the shaping process, the polymer substrate and the metal interconnect undergo plastic deformation while the OLED pixels remain intact. The OLED pixels have comparable I-V characteristics before and after deformation, but the luminous efficiency was reduced by the deformation, apparently as a consequence of fractures in the aluminum cathode. The demonstration of OLED displays on a spherical surface is an important advance in the fabrication of conformally shaped electronics. View full abstract»

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  • Flexible a-Si:H Position-Sensitive Detectors

    Page(s): 1281 - 1286
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    Flexible and large area (5 mm ×80 mm with an active length of 70 mm) position-sensitive detectors (PSDs) deposited onto polymeric substrates (polyimide-Kapton VN) have been fabricated. The optimized structure presented is based on a heterojunction of amorphous silicon (a-Si:H)/ZnO:Al. The sensors were characterized by spectral response, photocurrent dependence as a function of light intensity, and position detection measurements. The set of data obtained on one-dimensional PSDs based on the heterojunction show excellent performances with a maximum spectral response of 0.12 A/W at 500 nm and a nonlinearity of ±10% over 70-mm length. The produced sensors present a nonlinearity higher than those ones produced on glass substrates, due to the different thermal coefficients exhibited by the polymer and the a-Si:H film. In order to prove this behavior, it was measured the defect density obtained by the constant photocurrent method on a-Si:H thin films deposited on polymeric substrates and bent with different radii of curvature. View full abstract»

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  • Organic Memory Device Fabricated Through Solution Processing

    Page(s): 1287 - 1296
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (996 KB) |  | HTML iconHTML  

    Novel organic memory devices including nonvolatile and write-once-read-many-times memory devices are reported. These devices were fabricated through a simple solution processing technique. Programmable electrical bistability was observed on a device made from a polymer film containing metal nanoparticles capped with saturated alkanethiol and small conjugated organic compounds sandwiched between two metal electrodes. The pristine device, which was in a low-conductivity state, exhibited an abrupt increase of current when the device was scanned up to a few volts. The high-conductivity state can be returned to the low-conductivity state by applying a certain voltage in the reverse direction. The device has a good stability in both states, and the transition from the low- to the high-conductivity state takes place in nanoseconds, so that the device can be used as a low-cost, high-density, high-speed, and nonvolatile memory. The electronic transition is attributed to the electric-field-induced charge transfer between the metal nanoparticles and small conjugated organic molecule. The electrical behavior of the device is strongly dependent on the materials in the polymer film. When gold nanoparticles capped with aromatic thiol were used, the device exhibited a transition from low- to high-conductivity state at the first voltage scan, and the device in the high-conductivity state cannot be returned to the low-conductivity state. This device can be used as a write-once-read-many-times memory device. View full abstract»

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  • Poly-Si TFT Fabricated at 150 deg C Using ICP-CVD and Excimer Laser Annealing

    Page(s): 1297 - 1305
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1790 KB) |  | HTML iconHTML  

    We fabricated poly-Si thin-film transistors at 150°C using inductively coupled plasma (ICP) chemical vapor deposition (CVD) and excimer laser annealing (ELA). An Si film deposited by ICP-CVD was recrystallized using ELA, and a poly-Si film with large grains exceeding 5000 Å in diameter was fabricated. An SiO2 film with a high breakdown field was deposited by ICP-CVD. A high mobility exceeding 100 cm2/Vs and a low subthreshold swing of 0.76 V/dec were successfully achieved. View full abstract»

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  • Extracting Contact Effects in Organic FETs

    Page(s): 1306 - 1311
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    Contact resistances between organic semiconductors and metal electrodes have been shown to play a dominant role in electronic charge injection properties of organic FETs (OFETs). These effects are more prevalent in short channel length devices and therefore should not be ignored when examining intrinsic properties such as the mobility and its dependence on temperature or gate voltage. Here we outline a general procedure to extract contact current-voltage characteristics and the true channel mobility from the transport characteristics in bottom-contact poly (3-hexylthiophene) FETs, for both ohmic and nonlinear charge injection, over a broad range of temperatures and gate voltages. Distinguishing between the contact and channel contributions in bottom-contact OFETs is an important step toward improved understanding and modeling of these devices. View full abstract»

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  • Photosensitive Polymer Thin-Film FETs Based on Poly(3-octylthiophene)

    Page(s): 1312 - 1320
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    The effects of white light on the electrical performance of polymer thin-film transistors (PTFTs) based on regioregular poly(3-octylthiophene) (P3OT) are investigated. Upon illumination, a significant increase in the PFET's drain current is observed with a maximum photosensitivity of 104 in the subthreshold operation and a broad-band responsivity with a maximum value of 160 mA/W at irradiance of 1.7 mW/cm2 and at low gate biases. The photosensitivity decreases with the increase in the absolute gate bias. The simultaneous control of the device with both the gate voltage and illumination is possible at low irradiances of <0.7 mW/cm2. It is found that the illumination effectively decreases the threshold voltage of the device, but it does not change the field-effect mobility. Using a trap model, it is shown that the narrow layers close to the drain and source contacts with high concentrations of defects are two possible regions for photogeneration of excitons and separation of charges. Using the theory of space-charge limited conduction, the extracted band mobility for P3OT is 0.08 cm2/V·s, while a mobility of 8×10-5cm2/V·s is found for the regions next to the source and drain contacts. The PTFT's high photosensitivity at zero gate voltage suggests a simple design of low-voltage, high-sensitivity two-terminal photodetectors for applications in large-area flexible optoelectronics. View full abstract»

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  • Large Area Electronics Using Printing Methods

    Page(s): 1321 - 1329
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    After the demonstration of the first organic FET in 1986, a new era in the field of electronic began: the era of organic electronics. Although the reported performance of organic transistors is still considerably lower compared to that of silicon transistors, a new market is open for organic devices, where the excellent performance of silicon technology is not required. Several commercial applications for organic electronics have been suggested: organic RFID tags, electronic papers, imagers, sensors, organic LED drivers, etc. The main advantage of organic technologies over silicon technologies is the possibility of making low-cost, large area electronics. The main processes which allow patterning with suitable resolution on a large areas are printing methods. Here we will provide an overview of methods that can be useful in the low-cost production of large area electronics. View full abstract»

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  • Progress Toward Development of All-Printed RFID Tags: Materials, Processes, and Devices

    Page(s): 1330 - 1338
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    Printed electronics provides a promising potential pathway toward the realization of ultralow-cost RFID tags for item-level tracking of consumer goods. Here, we report on our progress in developing materials, processes, and devices for the realization of ultralow-cost printed RFID tags. Using printed nanoparticle patterns that are subsequently sintered at plastic-compatible temperatures, low-resistance interconnects and passive components have been realized. Simultaneously, printed transistors with mobilities >10-1 cm2/V-s have been realized using novel pentacene and oligothiophene precursors for pMOS and ZnO nanoparticles for nMOS. AC performance of these devices is adequate for 135-kHz RFID, though significant work remains to be done to achieve 13.56-MHz operation. View full abstract»

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  • Printed Electrochemical Devices Using Conducting Polymers as Active Materials on Flexible Substrates

    Page(s): 1339 - 1347
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    This paper reports some of our initial works in pursuit of a simple and low-cost method of fabricating all-organic electrochemical diodes, triodes, and transistors on flexible plastic or paper substrates. Conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT : PSS), utilized as an active component, is deposited by spin-coating or printing techniques. The devices are directly fabricated from design without the need for masks, patterns, or dies. The output characteristics of both half-wave and full-wave rectifier circuits from two-terminal diodes show stable performances at frequencies below 5 Hz. In three-terminal tunable triodes, threshold voltage can be tuned in the range between 0.25 and 1.6 V. In four-terminal transistors, ambipolar operation function can be realized in one single device. ION/IOFF current ratios of 103-104 have been achieved in the triode and transistor at operating voltages below 3 V. In addition, the device applications in electrochromic displays, logical circuits, as well as the switching speed of the circuits and device stability, are discussed. View full abstract»

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  • Printed Organic Semiconducting Devices

    Page(s): 1348 - 1356
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    Recent improvements in carrier mobility, environmental stability, and advancements in p- and n-type organic semiconductor materials have resulted in reports of device operation suitable for low-functionality, low-cost products. Deposition of solution-processable materials that enable the use of low-cost, high-speed deposition techniques such as screen printing, spin coating, and conventional graphic arts printing technologies have also recently been demonstrated. The material requirements necessary to realize these products, an organic transistor device structure that can be fabricated with these materials via printing processes, and the resulting device performance are presented and discussed. The use of standards and their impact on driving technology to commercialization are also addressed. View full abstract»

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  • High-Performance Nanowire Electronics and Photonics and Nanoscale Patterning on Flexible Plastic Substrates

    Page(s): 1357 - 1363
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    The introduction of an ambient-temperature route for integrating high-mobility semiconductors on flexible substrates could enable the development of novel electronic and photonic devices with the potential to impact a broad spectrum of applications. Here we review our recent studies demonstrating that high-quality single-crystal nanowires (NWs) can be assembled onto flexible plastic substrates under ambient conditions to create FETs and light-emitting diodes. We also show that polymer substrates can be patterned through the use of a room temperature nanoimprint lithography technique for the general fabrication of hundred-nanometer scale features, which can be hierarchically patterned to the millimeter scale and integrated with semiconductor NWs to make high-performance FETs. The key to our approach is the separation of the high-temperature synthesis of single-crystal NWs from room temperature solution-based assembly, thus enabling fabrication of single-crystal devices on virtually any substrate. Silicon NW FETs on plastic substrates display mobilities of 200 cm2-V-1-s-1, rivaling those of single-crystal silicon and exceeding those of state-of-the-art amorphous silicon and organic transistors currently used for flexible electronics. Furthermore, the generality of this bottom-up assembly approach suggests the integration of diverse nanoscale building blocks on a variety of substrates, potentially enabling far-reaching advances in lightweight display, mobile computing, and information storage applications. View full abstract»

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  • Low-Temperature Deposition of Hydrogenated Amorphous Silicon in an Electron Cyclotron Resonance Reactor for Flexible Displays

    Page(s): 1364 - 1373
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    Electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) is investigated as a technique for depositing hydrogenated amorphous silicon (a-Si : H) at a temperature of 80°C, which is compatible with the use of transparent, plastic substrates. The ECR-PECVD reactor is described and the principles underlying its operation explained. In particular, the factors controlling the deposition of a-Si : H by this technique are investigated, and it is shown that control of gas phase reactions between silane and hydrogen species is essential. High-quality a-Si : H is deposited in a narrow processing window with a photosensitivity greater than 106. Thin-film transistors (TFTs) fabricated at 125°C incorporating low-temperature a-Si : H as the channel layer have a switching ratio of almost 105. With further optimization of the other material layers, such TFTs could be used for the active matrix transistors in flexible liquid crystal displays on plastic substrates. View full abstract»

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  • Realization of Flexible Plasma Display Panels on PET Substrates

    Page(s): 1374 - 1378
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    DC plasma display panels are fabricated on flexible polyethylene terephtalate (PET) substrates. Each pixel consists of laterally placed anode and cathode electrodes. All electrical elements are formed on a single PET substrate, whereas a second substrate is needed to encapsulate the panel. Silver is used as the metal for each electrode and standard photolithography is used to form each cell. A 150-μm-thick layer of a UV-curable polymeric adhesive was used to form barrier ribs to both electrically isolate neighboring cells and to encapsulate the plasma. Conversion of vacuum UV into visible light is possible by blast-embedding of proper phosphor grains into the top substrate. The current-voltage and turn-on voltage versus pressure characteristics are examined. Effect of curvature on turn-on voltage is addressed. View full abstract»

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  • Scanning Our Past from Madrid: Leonardo Torres Quevedo

    Page(s): 1379 - 1382
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    Leonardo Torres Quevedo is a world-renowned Spanish engineer. His fields of interest were very extensive and included mechanics, aeronautics, and automatics. During his life, he received numerous awards and scientific honors. He was a member of the Spanish Royal Academy of Sciences (1901), a member of the Spanish Society of Physics and Chemists (1916), a member of the Spanish Royal Academy of Language (1920), an associate member of the French Academy of Sciences (1927), and an honorary member of the Geneva Society of Physics and Natural History. He also received the Echegaray Gold Medal from the Spanish Royal Academy of Sciences in 1916 and was appointed president of this prestigious institution in 1928. View full abstract»

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  • Future Special Issues/Special Sections of the IEEE Proceedings

    Page(s): 1383 - 1385
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  • Have you visited lately? www.ieee.org [advertisement]

    Page(s): 1386
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  • Proceedings of the IEEE information for authors

    Page(s): 1387 - 1388
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