D.R. Redinger

University of California, Berkeley, Berkeley, MO, United States

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Publications (14)12.7 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Transparent conductive oxides are promising candidates for realization of transparent electronics for display applications. The use of solution-processing techniques allows for a dramatic reduction in cost per unit area of electronic functionality. As a result, there is tremendous interest in the use of solution-processed transparent conductive oxides for realization of low-cost transparent electronic systems. Zinc oxide is processable out of solution using a variety of routes, including the use of nanoparticles, nanowires, and chemical bath deposition. By optimizing the deposition processes, it is possible to realize solution-processed transparent semiconductor films offering performance that is comparable to or better than amorphous silicon, while offering the advantages of transparency. Here, techniques for fabrication of solution-processed ZnO-based transistors are reviewed, and the outlook for such technologies is discussed.
    Journal of Display Technology 01/2010; · 1.66 Impact Factor
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    ABSTRACT: In recent years, printing has received substantial interest as a technique for realizing low cost, large area electronic systems. Printing allows the use of purely additive processing, thus lowering process complexity and material usage. Coupled with the use of low-cost substrates such as plastic, metal foils, etc., it is expected that printed electronics will enable the realization of a wide range of easily deployable electronic systems, including displays, sensors, and RFID tags. We review our work on the development of technologies and applications for printed electronics. By combining synthetically derived inorganic nanoparticles and organic materials, we have realized a range of printable electronic ldquoinksrdquo, and used these to demonstrate printed passive components, multilayer interconnection, diodes, transistors, memories, batteries, and various types of gas and biosensors. By exploiting the ability of printing to cheaply allow for the integration of diverse functionalities and materials onto the same substrate, therefore, it is possible to realize printed systems that exploit the advantages of printing while working around the disadvantages of the same.
    Solid-State Circuits Conference, 2008. ESSCIRC 2008. 34th European; 10/2008
  • V. Subramanian, S. K. Volkman, D. R. Redinger
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    ABSTRACT: In this work, we review our progress developing techniques for printing transparent transistors using various routes to realize solution-processed zinc oxide. We demonstrate printable ZnO inks based on ZnO nanoparticles, and realize transistors using this material as the channel. Additionally, we demonstrate a novel process for fabricating ZnO devices using chemical bath deposition. Pre-patterning may be achieved using printing, and subsequent chemical bath deposition is used to realize transparent ZnO films. Thus, through a combination of materials and process development, we demonstrate important steps towards the realization of printed transparent electronics.
    01/2008;
  • D. Redinger, V. Subramanian
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    ABSTRACT: Solution-processed transparent zinc oxide (ZnO) transistors are demonstrated using a chemical bath deposition process for ZnO deposition. The process is glass compatible and amenable to producing fully transparent electronics. Mobility as high as 3.5 cm<sup>2</sup>/V ldr s with on-off ratios of ~10<sup>5</sup> is realized. The transparency of ZnO allows for complete coverage of the pixel by the pixel drive transistors; analysis shows that the performance achieved herein is sufficient even to drive high-brightness organic light-emitting diode (OLED) displays by exploiting the high mobility and optical transparency of these devices. This makes this technology extremely attractive for use in active-matrix OLED display applications.
    IEEE Transactions on Electron Devices 07/2007; · 2.06 Impact Factor
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    ABSTRACT: In this paper, we have discussed our development of various printed electronics technologies targeted at meeting the needs of various optimal applications for printed electronics. While several concerns remain, particularly related to stability and reliability, the potential for printed electronics is strong, and progress will continue, driven by development of new materials and processes designed to exploit the opportunities that exist at the intersection of economics and engineering through the benefits of printing
    VLSI Technology, Systems, and Applications, 2006 International Symposium on; 05/2006
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    ABSTRACT: Printed electronics holds promise for realizing ultra-low-cost RFID tags for item-level tracking of consumer goods. We report on our progress in developing all-printed RFID tags. We review the development of printable materials for these applications, summarize the characteristics of printed devices, and discuss the implications of these on circuit performance limits and needs. Based on this assessment, we discuss the outlook for all-printed RFID tags and identify the problems remaining to be solved and the efforts taking place in this regard.
    Proceedings of the IEEE International Conference on VLSI Design 01/2006;
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    ABSTRACT: Printed electronics is attractive as a pathway towards the realization of ultra-low-cost RFID tags for replacement of conventional optical barcodes. While this application has received tremendous attention in recent years, it also represents one of the most challenging applications for organic transistors, based on both the performance requirements and the process complexity and cost implications. Here, we report on our progress in developing materials and processes for the realization of printed transistors for low-cost RFID applications. Using inkjet printing of novel conductors, dielectrics, and organic semiconductors, we have realized printed transistors with mobilities >0.1cm2/V-s, which is approaching the requirements of certain RFID applications. We review the performance of these devices, and discuss optimization strategies for achieving the ultimate performance goals requisite for realizing printed RFID.
    Proc SPIE 08/2005;
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    [show abstract] [hide abstract]
    ABSTRACT: 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<sup>-1</sup> cm<sup>2</sup>/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.
    Proceedings of the IEEE 08/2005; · 6.91 Impact Factor
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    ABSTRACT: We report on the highest performance all-printed transistors reported to date. Using nanoparticle-based printed contact, polymer dielectrics, and a printed soluble pentacene precursor semiconductor, we demonstrate all-inkjetted devices with mobilities >0.1cm<sup>2</sup>/V-s and on-off ratios as high as 10<sup>4</sup>. The performance of these devices is comparable to control devices fabricated on silicon-substrates, and thus, these devices represent a significant step towards the realization of low-cost printed electronics.
    Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International; 01/2005
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    ABSTRACT: An all ink-jet-deposited process capable of creating high-quality passive devices suitable for an RFID front-end is described. Gold nanocrystals are printed to create conductive lines with sheet resistance as low as 23 mΩ per square. Optimal printing conditions are found for polyimide dielectric layers and films as thin as 340 nm are produced. These results are used to create spiral inductors, interconnect, and parallel plate capacitors.
    IEEE Transactions on Electron Devices 01/2005; · 2.06 Impact Factor
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    ABSTRACT: In this paper, we demonstrate an all-printed passive component technology on plastic, including inductors, capacitors, and multilevel interconnects. This represents an important step towards the development of ultra-low-cost RFID on plastic.
    Device Research Conference, 2003; 07/2003
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    ABSTRACT: Low resistance conductors are crucial for the development of ultra-low-cost electronic systems such as radio frequency identifi-cation tags. Low resistance conductors are required to enable the fabrication of high-Q inductors, capacitors, tuned circuits, and interconnects. The fabrication of these circuits by printing will enable a dramatic reduction in cost, through the elimination of lithography, vacuum processing, and the need for high-cost substrates. Solutions of organic-encapsulated gold nanoparticles many be printed and subsequently annealed to form low resistance conductor patterns. We describe a process to form the same, and discuss the optimization of the process to demonstrate plastic-compatible gold conductors for the first time. By optimizing both the size of the nanoparticle and the length of the alkanethiol encapsulant, it is possible to produce particles that anneal at low temperatures (150°C) to form continuous gold films having low resistivity. We demonstrate the printing of these materials using an inkjet printer to demonstrate a plastic-compatible low resistance conductor technology. In recent years, there has been tremendous interest in flexible electronics. Besides the obvious applications of flexible electronics in flat panel displays, 1 flexible circuits are also promising for use in such applications as radio frequency identification RFID tags, 2 low cost sensors, 3 and other disposable electronic devices. In particular, devices based on organic semiconductors are considered to be very promising for these applications since they may potentially be fab-ricated entirely using printing technologies, 4 eliminating the need for such major cost points as lithography, vacuum processing includ-ing physical vapor deposition, plasma etching, and chemical vapor deposition CVD, while simultaneously allowing the use of reel-to-reel processing, resulting in reduced substrate handling and clean-room costs as well. Furthermore, since printing is inherently addi-tive in nature, material and disposal costs are also expected to be reduced, resulting in an extremely low net system cost. Progress in organic semiconductor technology has been rapid, with carrier mobilities improving in a sustained fashion over the last decade. 5-7 Indeed, the performance of various solution processed organic semiconductor materials has reached a state where circuit demonstrations are now possible. While several demonstration circuits have been fabricated using organic semiconductors, includ-ing shift registers, multiplexers, display backplanes, and encoders, 2,8 little work has been done on the other piece of the circuit puzzle, namely, the passive components. The requirements for these com-ponents are tremendous, both in terms of performance and cost. RFID applications will require the printing of high-Q inductors, transformers, and tuned circuits. 9 Display applications including both active matrix liquid crystal displays AMLCDs and organic light emitting diode OLED displays will require the printing of low resistance interconnects. Furthermore, organic transistors re-quire work function-matched contacts. Evaporated gold is com-monly used for these circuits, but is too expensive for use in low cost reel-to-reel applications. What is required, therefore, is a low resistance conductor technology suitable for printing using such technologies as screen printing and inkjet printing. This technology must be compatible with organic electronic devices, in that it must be possible to fabricate these low resistance structures at low tem-peratures. Specifically, many common low cost plastics deform un-acceptably between 150 and 200°C. Therefore, any printed conduc-tor technology must have a maximum temperature excursion lower than this range. It has been known for some time that metal nanoclusters have reduced melting and sintering temperatures when compared to their bulk counterparts. 10 Monolayer protected clusters MPCs of gold protected by alkanethiols can be dissolved into common nonpolar solvents such as toluene, THF, and hexanes, and are therefore suit-able for printing. Their low sintering temperatures make them po-tentially suitable for use in electronics in plastic, since they may potentially be annealed at low temperatures to form low resistance conductor films. Thiol-derivatized gold nanoclusters have been used in numerous interdisciplinary applications ranging from biological marking to nanotechnology. 11,12 Unfortunately, the melting/sintering temperatures for all gold nanocrystals reported to date are greater than 200°C, making them unsuitable for use in electronics on plastic applications. In this paper, we demonstrate a thiol-derivatized gold nanocluster technology suitable for use in printed circuits on plastic. We demonstrate, for the first time, a plastic-compatible gold nano-crystal technology with a temperature excursion of less than 150°C. Using a systematic study of the nanoparticle synthesis parameters, we demonstrate the optimization of the same to achieve low anneal temperatures while maintaining low film resistance.
    Journal of The Electrochemical Society - J ELECTROCHEM SOC. 01/2003; 150(7).
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: In recent years, there has been tremendous interest in all-printed electronics as a means of achieving ultra-low-cost electronic circuits with uses in displays and disposable electronics applications such as RFID tags. While there have been a few demonstrations of printed organic transistors to date, there has been little work on the associated passive component and interconnection technologies required to enable the development of all-printed RFID circuits. In particular, low-resistance conductors are crucial to achieve the high-Q inductors necessary for RFID. Here, we demonstrate inkjetted nanoparticle-Au conductors on plastic with sheet resistances as low as 0.03 ohms/square. We describe the optimization of the jetting parameters, and their impact on final film morphology and electrical properties. We also demonstrate a bridging technology based on an inkjetted polyimide interlevel dielectric. Using this process, we demonstrate multilevel interconnect and passive component structures including conductor patterns, crossover bridges, and tapped planar spiral inductors. Together, these represent an important step towards the realization of all-printed RFID.
  • D. Redinger, R. Farshchi, V. Subramanian