| 1. |
- Dankert, André, 1986, et al.
(författare)
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Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide
- 2017
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 11:6, s. 6389-6395
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Tidskriftsartikel (refereegranskat)abstract
- The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5–2% has been observed, corresponding to spin polarization of 5–10% in the measured temperature range of 300–75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.
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| 2. |
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| 3. |
- Lei, Yu, et al.
(författare)
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Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices
- 2022
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Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:6, s. 450-485
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Forskningsöversikt (refereegranskat)abstract
- Since the isolation of graphene in 2004, two-dimensional (2D) materials research has rapidly evolved into an entire subdiscipline in the physical sciences with a wide range of emergent applications. The unique 2D structure offers an open canvas to tailor and functionalize 2D materials through layer number, defects, morphology, moiré pattern, strain, and other control knobs. Through this review, we aim to highlight the most recent discoveries in the following topics: theory-guided synthesis for enhanced control of 2D morphologies, quality, yield, as well as insights toward novel 2D materials; defect engineering to control and understand the role of various defects, including in situ and ex situ methods; and properties and applications that are related to moiré engineering, strain engineering, and artificial intelligence. Finally, we also provide our perspective on the challenges and opportunities in this fascinating field.
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| 4. |
- Reddy, S. R., et al.
(författare)
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High Strain Rate Superplastic Flow and Fracture Characteristics of a Fine-Grained Eutectic High Entropy Alloy
- 2024
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - 1073-5623. ; 55, s. 173-182
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Tidskriftsartikel (refereegranskat)abstract
- A fine-grained micro-duplex AlCoCrFeNi2.1 eutectic high entropy alloy exhibited high strain rate superplasticity with an elongation to failure of ~ 960 pct at 1173 K and a strain rate of 10-1 s-1. Optimum superplasticity was associated with a strain rate sensitivity of ~ 0.5, and there were transitions to non-superplastic flow with strain rate sensitivities of < 0.5 at both low and high strain rates. Superplasticity is attributed to grain boundary sliding with the observed retention of an equiaxed grain morphology, with some grain growth. Cavities with dimensions in the range of 1 to 5 μm were observed in specimens pulled to failure. Although analysis revealed that cavity nucleation is likely under the experimental conditions, cavity growth was slow because of control by a plasticity growth rate that was proportional to the cavity size. Graphical Abstract: [Figure not available: see fulltext.]
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| 5. |
- Dash, Saroj Prasad, 1975, et al.
(författare)
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Silicon spintronics at room temperature
- 2010
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - 0277-786X. ; 7760:77600J
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Gaur, A.P.S., et al.
(författare)
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Surface Energy Engineering for Tunable Wettability through Controlled Synthesis of MoS2
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:8, s. 4314-4321
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Tidskriftsartikel (refereegranskat)abstract
- MoS2 is an important member of the transition metal dichalcogenides that is emerging as a potential 2D atomically thin layered material for low power electronic and optoelectronic applications. However, for MoS2 a critical fundamental question of significant importance is how the surface energy and hence the wettability is altered at the nanoscale in particular, the role of crystallinity and orientation. This work reports on the synthesis of large area MoS2 thin films on insulating substrates (SiO2/Si and Al2O3) with different surface morphology via vapor phase deposition by varying the growth temperatures. The samples were examined using transmission electron microscopy and Raman spectroscopy. From contact angle measurements, it is possible to correlate the wettability with crystallinity at the nanoscale. The specific surface energy for few layers MoS2 is estimated to be about 46.5 mJ/m2. Moreover a layer thickness-dependent wettability study suggests that the lower the thickness is, the higher the contact angle will be. Our results shed light on the MoS2–water interaction that is important for the development of devices based on MoS2 coated surfaces for microfluidic applications.
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| 7. |
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| 8. |
- Sharma, S., et al.
(författare)
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Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium
- 2014
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 89:7
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Tidskriftsartikel (refereegranskat)abstract
- The magnitude of spin accumulation created in semiconductors by electrical injection of spin-polarized electrons from a ferromagnetic tunnel contact is investigated, focusing on how the spin signal detected in a Hanle measurement varies with the thickness of the tunnel oxide. An extensive set of spin-transport data for Si and Ge magnetic tunnel devices reveals a scaling with the tunnel resistance that violates the core feature of available theories, namely, the linear proportionality of the spin voltage to the injected spin current density. Instead, an anomalous scaling of the spin signal with the tunnel resistance is observed, following a power law with an exponent between 0.75 and 1 over 6 decades. The scaling extends to tunnel resistance values larger than 10(9) Omega mu m(2), far beyond the regime where the classical impedance mismatch or back flow into the ferromagnet play a role. This scaling is incompatible with existing theory for direct tunnel injection of spins into the semiconductor. It also demonstrates conclusively that the large spin signal does not originate from two-step tunneling via localized states near the oxide/semiconductor interface. Control experiments show that spin accumulation in localized states within the tunnel barrier or artifacts are also not responsible. Altogether, the scaling results suggest that, contrary to all existing descriptions, the spin signal is proportional to the applied bias voltage, rather than the (spin) current.
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| 9. |
- Barick, P., et al.
(författare)
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Effect of concentration and molecular weight of polyethylenimine on zeta potential, isoelectric point of nanocrystalline silicon carbide in aqueous and ethanol medium
- 2015
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Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 41:3, s. 4289-4293
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Tidskriftsartikel (refereegranskat)abstract
- The effect of dispersant concentration and its molecular weight on zeta potential of nanocrystalline silicon carbide in an aqueous medium was investigated. An increase in the concentration of the dispersant, such as polyethylenimine (PEI), in slurry prepared from nanosized silicon carbide, was found to augment the iso-electric point and zeta potential. However, the zeta potential was observed to decline as the pH of the slurry shifts towards the basic region. This aforementioned behavior is attributed to the enhanced mutual repulsion between the polymer chains of the dispersant adsorbed on the surfaces of SiC particles and those approaching the surfaces. The higher ionization potential of polymers in the acidic region compared to the basic region increases the adsorption. The relationship between zeta potential and pH is however, noted to remain virtually unchanged with molecular weight of PEI. Further, it is observed that zeta potential of SiC decreases with the increase in solid content of the slurry. Rheology study reveals that the ethanol based slurry has a lower viscosity than the water based slurry, making ethanol the preferred dispersing medium for colloidal processing of nanometric SiC powder. © 2014 Elsevier Ltd and Techna Group S.r.l.
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| 10. |
- Hokke, N H, et al.
(författare)
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RF Information Harvesting for Medium Access in Event-driven Batteryless Sensing
- 2022
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Ingår i: 2022 21st ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN). - : IEEE. - 9781665496247 - 9781665496254 ; , s. 377-389
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Konferensbidrag (refereegranskat)abstract
- We present radio-frequency (RF) information harvesting, a channel sensing technique that takes advantage of the energy in the wireless medium to detect channel activity at essentially no energy cost. RF information harvesting is essential for event-driven wireless sensing applications using battery-less devices that harvest tiny amounts of energy from impromptu events, such as operating a switch, and then transmit the event notification to a one-hop gateway. As multiple such devices may concurrently detect events, coordinating access to the channel is key. RF information harvesting allows devices to break the symmetry between concurrently-transmitting devices based on the harvested energy from the ongoing transmissions. To demonstrate the benefits of RF information harvesting, we integrate it in a tailor-made ultra lowpower hardware MAC protocol we call Radio Frequency-Distance Packet Queuing (RF-DiPaQ). We build a hardware/software prototype of RF-DiPaQ and use an established Markov framework to study its performance at scale. Comparing RF-DiPaQ against staple contention-based MAC protocols, we show that it outperforms pure Aloha and 1-CSMA by factors of 3.55 and 1.21 respectively in throughput, while it saturates at more than double the offered load compared to 1-CSMA. As traffic increases, the energy saving of RF-DiPaQ against CSMA protocols increases, consuming 36% less energy than np-CSMA at typical offered loads.
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