| 1. |
- Berggren, Magnus, 1968-, et al.
(författare)
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Commentary: Organic materials for printed electronics : Editorial in Nature Materials, vol 6, pp 3-5
- 2007
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 6, s. 3-5
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Organic materials can offer a low-cost alternative for printed electronics and flexible displays. However, research in these systems must exploit the differences - via molecular-level control of functionality - compared with inorganic electronics if they are to become commercially viable
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| 2. |
- Berggren, Magnus, 1968-, et al.
(författare)
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Organic materials for printed electronics
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:1, s. 3-5
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Tidskriftsartikel (refereegranskat)abstract
- Organic materials can offer a low-cost alternative for printed electronics and flexible displays. However, research in these systems must exploit the differences — via molecular-level control of functionality — compared with inorganic electronics if they are to become commercially viable. Introduction Conducting and semiconducting organic materials, both polymers and molecules, are being considered for a vast array of electronic applications. The first examples, such as displays in mobile appliances, have found their way to market as replacements for traditional components in existing products. Organic electronics distinguishes itself from traditional electronics because one can define functionality at the molecular level, process the materials from solution, and make displays and circuits that are completely flexible. So far, very little of the uniqueness of organic electronics is expressed in the products promoted as manufacturable; why? One important opportunity for organic electronics is the area of radiofrequency identification (RFID) manufactured using an all-in-line printing process. This technology comprises fast-switching transistors, antennas operating at frequencies above 100 kHz, memory, and so on, all integrated into a plastic foil. The present target in many organic electronics labs around the world is to develop the high-speed (>10 kHz) transistors critical for such devices. The use of organic transistors instead of their inorganic equivalents is motivated by cost. So far, little effort has been devoted to exploring organic electronics in terms of its true unique electronic functionality and the possibility to add electronics to surfaces previously considered electronically inactive. For instance, paper is produced at speeds exceeding 100 km h-1 and is converted into packages and printed media at manufacturing flows typically above 100 m min-1. Adding organic electronics onto, for instance, the paper surface during the paper conversion process would demonstrate the true uniqueness of organic electronics, both from a manufacturing and an application point of view. Retail chains and transportation companies desperately seek a printed electronic technology to provide better safety and security features on packages and automatically track and trace products all the way from the manufacturer to the end customer. The financial losses related to counterfeiting, failure in transportation and damaged packages is comparable to the overall profits made on the product contained in the package. In addition, printed electronics could potentially guide the end-user to properly use the product and to guarantee brand authenticity, for example through an interactive user's guide, and electronic features to replace existing security devices such as the holographic stickers commonly used in packages and bank notes today. It turns out that, for many of these applications, high-frequency signal-processing is not required; 10 ms to 1 s response times are appropriate. These are goals that a very simple printed electronics technology may be able to fill. Silicon-based RFID devices are currently used in high-end products, but are prohibitively expensive for commodities such as food at the consumer package level. Thus, the potential value for printed organic electronics seems to exist if the expense can be kept down. For instance, TetraPak, who produces more than 100 billion packages every year, estimates that the costs for additional security and safety features cannot exceed about 0.2 Eurocents per package (Istvan Ulvros, TetraPak, private communication). Much of the research in organic electronics aims to optimise inherent charge transport and efficiency characteristics of the materials already in use in individual devices. This work has pushed the solar energy-to-electricity power-conversion efficiency in organic solar cells close to 5% (ref. 1) and the luminous efficiency of plastic luminescent devices to around 25 cd A-1 (ref. 2). Organic electrochromic displays now perform extraordinarily well in terms of colour contrast, memory and stability3, and polymer transistors easily run at speeds beyond 100 kHz (ref.4). These results have been achieved by improving the performance at the individual device level. Rarely are integrated circuits or high-volume manufacturing conditions considered in the research. Typically, a series of more than ten patterning, material deposition and post-processing steps are required to make one kind of device. The tradition has been to develop specific materials that exclusively function well in only one device type. RFID circuits (for example) typically require rectifiers, antennas, powering devices, transistors for signal processing, encapsulation layers and in some cases also displays. Merging today's efforts conducted at the organic electronics device level would then result in a production route that would include perhaps 50 (or even more) discrete manufacturing steps. Unfortunately, the cost for a label requiring several tens of patterning steps including exotic organic electronic materials is not compatible with the value and costs of packages. In traditional printers, typically five to ten printing stations are available in series (Fig. 1). Each station also includes one or two convection, infrared or ultraviolet curing steps. At ordinary printing speeds (10 to 200 m min-1) the substrate spends on the order of a tenth to several seconds in each printing station. During this time, registration, material deposition and post-processing must take place. The value structure in printing technology means that the cost for printing scales at least linearly with the number of printing steps. The yield and systematic errors in printing technology becomes a nightmare beyond ten printing steps. The cost for materials such as inks, substrates and coatings is a considerable part of the entire product value. Our own calculations indicate that each individual RFID label would cost more than 10 Eurocents (Lars-Olov Hennerdal, Acreo, private communication).
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| 3. |
- Elgazzar, S, et al.
(författare)
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Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking
- 2009
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Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 8:4, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu2Si2, where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.
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| 4. |
- Forsblom, Mattias, et al.
(författare)
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How superheated crystals melt
- 2005
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 4:5, s. 388-390
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Tidskriftsartikel (refereegranskat)abstract
- The melting of superheated crystalline solids through the penetration of intense radiation within at a temperature above the equilibrium melting temperature was investigated. The atomistic simulations, relevant for aluminum, was used to show that the thermal fluctuation initiating melting is an aggregate typically with 6-7 interstitials and 3-4 vacancies. Vacancy-interstital pairs were created through thermal fluctuation and interstitial-vacancy pairs were created close to the interstitial aggregate. It was found that when a defect aggregate contains more than about 10 point defects, it usually grows rapidly and irreversibly.
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| 5. |
- Gambardella, P., et al.
(författare)
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Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface
- 2009
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Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 8:3, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic atoms at surfaces may provide the ultimate paradigm of a solid-state magnetic memory exhibiting either classical , or quantum , behaviour. Individual atoms, however, are difficult to arrange in regular patterns1,2,3,4, . Moreover, their magnetic properties are dominated by interaction with the substrate, which, as in the case of Kondo systems, often leads to a decrease or quench of their local magnetic moment , . Here we show that the supramolecular assembly of Fe and 1,4-benzenedicarboxylic acid molecules on a Cu surface results in ordered arrays of high-spin mononuclear Fe centres on a 1.5 nm square grid. Lateral coordination with the molecular ligands yields unsaturated yet stable coordination bonds, which allow for the chemical modification of the electronic and magnetic properties of the Fe atoms independently from the substrate. The easy magnetization direction of the Fe centres can be switched by oxygen adsorption, thus opening a way to control the magnetic anisotropy in supramolecular layers akin to that employed in metallic thin films , , , .
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| 6. |
- Hamedi, Mahiar, et al.
(författare)
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Towards woven logic from organic electronic fibres
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:5, s. 357-362
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Tidskriftsartikel (refereegranskat)abstract
- The use of organic polymers for electronic functions is mainly motivated by the low-end applications, where low cost rather than advanced performance is a driving force. Materials and processing methods must allow for cheap production. Printing of electronics using inkjets1 or classical printing methods has considerable potential to deliver this. Another technology that has been around for millennia is weaving using fibres. Integration of electronic functions within fabrics, with production methods fully compatible with textiles, is therefore of current interest, to enhance performance and extend functions of textiles2. Standard polymer field-effect transistors require well defined insulator thickness and high voltage3, so they have limited suitability for electronic textiles. Here we report a novel approach through the construction of wire electrochemical transistor (WECT) devices, and show that textile monofilaments with 10–100 m diameters can be coated with continuous thin films of the conducting polythiophene poly(3,4-ethylenedioxythiophene), and used to create micro-scale WECTs on single fibres. We also demonstrate inverters and multiplexers for digital logic. This opens an avenue for three-dimensional polymer micro-electronics, where large-scale circuits can be designed and integrated directly into the three-dimensional structure of woven fibres.
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| 7. |
- Iota, Valentin, et al.
(författare)
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Six-fold coordinated carbon dioxide VI
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- Under standard conditions, carbon dioxide (CO2) is a simple molecular gas and an important atmospheric constituent, whereas silicon dioxide (SiO2) is a covalent solid, and one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO2 transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO2 tridymite. Here, we present the discovery of an extended-solid phase of CO2: a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO2-II (refs 1,2) above 50 GPa at 530–650 K. Together with the previously reported CO2-V (refs 3–5) and a-carbonia6, this extended phase indicates a fundamental similarity between CO2 (a prototypical molecular solid) and SiO2 (one of Earth's fundamental building blocks). We present a phase diagram with a limited stability domain for molecular CO2-I, and suggest that the conversion to extended-network solids above 40–50 GPa occurs via intermediate phases II (refs 1,2), III (refs 7,8) and IV (refs 9,10). The crystal structure of phase VI suggests strong disorder along the c axis in stishovite-like P42/mnm, with carbon atoms manifesting an average six-fold coordination within the framework of sp3 hybridization.
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| 8. |
- Isaksson, Joakim, et al.
(författare)
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Electronic Control of Ca2+ Signalling in Neuronal Cells using an Organic Electronic Ion Pump
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:9, s. 673-679
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Tidskriftsartikel (refereegranskat)abstract
- Cells and tissues use finely regulated ion fluxes for their intra- and intercellular communication. Technologies providing spatial and temporal control for studies of such fluxes are however, limited. We have developed an electrophoretic ion pump made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) to mediate electronic control of the ion homeostasis in neurons. Ion delivery from a source reservoir to a receiving electrolyte via a PEDOT:PSS thin-film channel was achieved by electronic addressing. Ions are delivered in high quantities at an associated on/off ratio exceeding 300. This induces physiological signalling events that can be recorded at the single-cell level. Furthermore, miniaturization of the device to a 50-um-wide channel allows for stimulation of individual cells. As this technology platform allows for electronic control of ion signalling in individual cells with proper spatial and temporal resolution, it will be useful in further studies of communication in biological systems.
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| 9. |
- Johansson, Jonas, et al.
(författare)
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Structural properties of (111)B-oriented III-V nanowires
- 2006
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 5:7, s. 574-580
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Tidskriftsartikel (refereegranskat)abstract
- Controlled growth of nanowires is an important, emerging research field with many applications in, for example, electronics, photonics, and life sciences. Nanowires of zinc blende crystal structure, grown in the left fence111right fenceB direction, which is the favoured direction of growth, usually have a large number of twin-plane defects. Such defects limit the performance of optoelectronic nanowire-based devices. To investigate this defect formation, we examine GaP nanowires grown by metal-organic vapour-phase epitaxy. We show that the nanowire segments between the twin planes are of octahedral shape and are terminated by {111} facets, resulting in a microfaceting of the nanowires. We discuss these findings in a nucleation context, where we present an idea on how the twin planes form. This investigation contributes to the understanding of defect formation in nanowires. One future prospect of such knowledge is to determine strategies on how to control the crystallinity of nanowires.
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| 10. |
- Linnros, Jan
(författare)
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Optoelectronics - Nanocrystals brighten transistors
- 2005
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 4:2, s. 117-119
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Tidskriftsartikel (refereegranskat)abstract
- Silicon nanocrystals provide efficient means of generating light that is both tunable and compatible with conventional microelectronics. However, progress has been hampered by difficulties in achieving efficient carrier injection. A new approach could provide the solution.
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