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| 2. |
- Choi, A., et al.
(författare)
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Suppression of the magneto resistance in high electric fields of polyacetylene nanofibers
- 2010
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Ingår i: SYNTHETIC METALS. - 0379-6779. ; 160:11-12, s. 1349-1353
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Tidskriftsartikel (refereegranskat)abstract
- We present results of non-linear magneto resistance (MR) of polyacetylene nanofibers in high magnetic field up to H = 30 T at low temperature T = 1.5 K. The MR was proven to be of the spin origin; it reaches 16% at highest H. Unexpectedly, the MR was suppressed by increasing electric field E, vanishing at E ≳ 5 × 104 V/cm. It is understood that the doping induced spinless charged soliton pairs, which are initially confined to a certain distance because of the interchain phase correlations, and are deconfined in high electric fields, resulting in a vanishing magneto resistance (VMR). The role of the specific, degenerate ground state of the polyacetylene is confirmed by parallel studies of the different magneto resistances of polyaniline nanofibers which contrarily is not affected by the electric field. © 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Degerman, Johan, 1976, et al.
(författare)
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Extended Target Tracking using Principal Components
- 2011
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Ingår i: Proceedings of the 14th International Conference on Information Fusion. - 9781457702679 ; , s. Art. no. 5977659-
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Konferensbidrag (refereegranskat)abstract
- The increased resolution in today’s radar systemsenables tracking of small targets. However, tracking both smalland large targets in a dense target scenario raises considerablechallenges. The data association of tracks to measurement groupsis highly dependent on good target extension models for filteringand likelihood computation. In our attempt to design a trackerfor extended targets, we start by adopting the results from thetechnique referred to as random matrices, which enables us toseparate the filtering into an extension and a kinematical part.We re-define the measurement model and discard the assumptionof independent Gaussian-distributed plots. Instead we assume theprincipal components to be Gaussian distributed. Then, througha heuristic approach, we create a two-stage Kalman filter, wherethe first stage estimates the principal components, and the secondstage estimates the centre of gravity, using the output fromthe first stage as measurement uncertainty. The advantage ofhaving a Kalman filter with data-driven measurement noise overa standard Kalman filter is demonstrated using simulated data,where a significant improvement in terms of smaller errors andreduced track loss is shown.
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| 4. |
- Dey, Anil, et al.
(författare)
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Combining axial and radial nanowire heterostructures: Radial Esaki diodes and tunnel field-effect transistors
- 2013
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:12, s. 5919-5924
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Tidskriftsartikel (refereegranskat)abstract
- The ever-growing demand on high-performance electronics has generated transistors with very impressive figures of merit. The continued scaling of the supply voltage of field-effect transistors, such as tunnel field-effect transistors (TFETs), requires the implementation of advanced transistor architectures including FinFETs and nanowire devices. Moreover, integration of novel materials with high electron mobilities, such as III-V semiconductors and graphene, are also being considered to further enhance the device properties. In nanowire devices, boosting the drive current at a fixed supply voltage or maintaining a constant drive current at a reduced supply voltage may be achieved by increasing the cross-sectional area of a device, however at the cost of deteriorated electrostatics. A gate-all-around nanowire device architecture is the most favorable electrostatic configuration to suppress short channel effects, however, the arrangement of arrays of parallel vertical nanowires to address the drive current predicament will require additional chip area. The use of a core-shell nanowire with a radial heterojunction in a transistor architecture provides an attractive means to address the drive current issue without compromising neither chip area nor device electrostatics. In addition to design advantages of a radial transistor architecture, we in this work illustrate the benefit in terms of drive current per unit chip area and compare the experimental data for axial GaSb/InAs Esaki diodes and TFETs to their radial counterparts and normalize the electrical data to the largest cross-sectional area of the nanowire, i.e. the occupied chip area, assuming a vertical device geometry. Our data on lateral devices show that radial Esaki diodes deliver almost 7 times higher peak current, Jpeak = 2310 kA/cm2, than the maximum peak current of axial GaSb/InAs(Sb) Esaki diodes per unit chip area. The radial TFETs also deliver high peak current densities Jpeak = 1210 kA/cm2 while their axial counterparts at most carry Jpeak = 77 kA/cm2, normalized to the largest cross-sectional area of the nanowire.
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| 5. |
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| 6. |
- Dey, Anil, et al.
(författare)
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GaSb nanowire pFETs for III-V CMOS
- 2013
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Ingår i: IEEE Device Research Conference. Proceedings. - 1548-3770. ; , s. 13-14
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Konferensbidrag (refereegranskat)
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| 7. |
- Dey, Anil, et al.
(författare)
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Single InAs/GaSb Nanowire Low-Power CMOS Inverter
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984.
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Tidskriftsartikel (refereegranskat)abstract
- III − V semiconductors have so far predom- inately been employed for n-type transistors in high-frequency applications. This development is based on the advantageous transport properties and the large variety of heterostructure combinations in the family of III − V semiconductors. In contrast, reports on p-type devices with high hole mobility suitable for complementary metal − oxide − semiconductor (CMOS) circuits for low-power operation are scarce. In addition, the di ffi culty to integrate both n- and p-type devices on the same substrate without the use of complex bu ff er layers has hampered the development of III − V based digital logic. Here, inverters fabricated from single n-InAs/p-GaSb hetero- structure nanowires are demonstrated in a simple processing scheme. Using undoped segments and aggressively scaled high- κ dielectric, enhancement mode operation suitable for digital logic is obtained for both types of transistors. State-of-the-art on- and o ff -state characteristics are obtained and the individual long-channel n- and p-type transistors exhibit minimum subthreshold swings of SS = 98 mV/dec and SS = 400 mV/dec, respectively, at V ds = 0.5 V. Inverter characteristics display a full signal swing and maximum gain of 10.5 with a small device-to-device variability. Complete inversion is measured at low frequencies although large parasitic capacitances deform the waveform at higher frequencies.
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| 8. |
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| 9. |
- Engström, Anders, et al.
(författare)
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The Importance of Representing Mixed-Phase Clouds for Simulating Distinctive Atmospheric States in the Arctic
- 2014
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 27:1, s. 265-272
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Tidskriftsartikel (refereegranskat)abstract
- Observations from the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) suggest that the Arctic Basin is characterized by two distinctly different preferred atmospheric states during wintertime. These states appear as two peaks in the frequency distribution of surface downwelling longwave radiation (LWD), representing radiatively clear and opaque conditions. Here, the authors have investigated the occurrence and representation of these states in the widely used ECMWF Interim Re-Analysis (ERA-Interim) dataset. An interannually recurring bimodal distribution of LWD values is not a clearly observable feature in the reanalysis data. However, large differences in the simulated liquid water content of clouds in ERA-Interim compared to observations are identified and these are linked to the lack of a radiatively opaque peak in the reanalysis. Using a single-column model, dynamically controlled by data from ERA-Interim, the authors show that, by tuning the glaciation speed of supercooled liquid clouds, it is possible to reach a very good agreement between the model and observations from the SHEBA campaign in terms of LWD. The results suggest that the presence of two preferred Arctic states, as observed during SHEBA, is a recurring feature of the Arctic climate system during winter [December–March (DJFM)]. The mean increase in LWD during the Arctic winter compared to ERA-Interim is 15 W m−2. This has a substantial bearing on climate model evaluation in the Arctic as it indicates the importance of representing Arctic states in climate models and reanalysis data and that doing so could have a significant impact on winter ice thickness and surface temperatures in the Arctic.
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| 10. |
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