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| 2. |
- Choi, Jae Won, et al.
(författare)
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Interface-driven seebeck effect in two-dimensional trilayer-stacked PtTe2/MoS2/MoS2 heterostructures via electron-electron interactions
- 2023
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) platinum telluride (PtTe2), which is one of the promising metallic transition metal dichalcogenides, has been proven as an essential candidate for electronic devices, magnetic devices, type-II Dirac fermions, topological superconductors, and other optoelectronic applications. However, the formation and thermal transport as important thermoelectric (TE) device applications have not been realized in large-area 2D PtTe2 films due to their semi-metallic properties. Here, we report an innovative approach to enhance the in-plane TE power factors by piling the metallic PtTe2 films on high-resistance (> 10 MO) intrinsic MoS2 films to form bilayer-PtTe2/MoS2 (5 nm/7 nm)//sapphire and trilayer-PtTe2/MoS2/MoS2 (5 nm/7 nm/7 nm)//sapphire heterostructures via wet-transfer stacking method. Such approaches can be achieved by utilizing 2D/2D heterostructure to increase the electron effective mass due to the strong electron-electron interaction at interface under temperature gradient along the samples and ultimately increase Seebeck coefficients via interface-driven Seebeck effect along with a metallic high-conductivity top-PtTe2 films. The trilayer-stacked PtTe2/MoS2/MoS2 heterostructures exhibit an extremely high Seebeck coefficient of 21.6 mu V/K and power factor of similar to 0.2 mW/m.K-2, which are 231 % and similar to 727 %, higher than those of the metallic 5-nm-thick single PtTe2 film on the sapphire substrate, respectively. Our new physics and observation can pave the way toward an effective strategy for understating 2D/2D TMDC heterostructure materials for high Fig.-of-merit TE energy harvesting devices.
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| 3. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 4. |
- Choi, Jae Won, et al.
(författare)
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Observation of a Strong Decoupling Phenomenon in Pt/Si Hybrid Structures for In-Plane Thermoelectric Properties
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:40, s. 17283-17290
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Tidskriftsartikel (refereegranskat)abstract
- The performance of thermoelectric (TE) materials is limited by the intrinsic coupling of the Seebeck coefficient and the electrical conductivity such that an increase in one leads to a decrease in the other with respect to the carrier concentration. This coupling makes it particularly difficult to enhance the TE power factor in TE materials. In this study, we added a Pt top layer over a silicon wafer, forming a hybridized Pt/Si structure to drive a strong decoupling of the Seebeck coefficient and electrical conductivity. The results show that the electrical resistance in the Pt/Si hybrid structure decreased by ∼94 times compared to that of a single-layer lightly doped Si substrate at 300 K, while the Seebeck coefficient in the hybrid structure decreased slightly compared to that of the single layer. The remarkably high TE performance of the Pt/Si hybrid structure is brought about by the hybridization of the intrinsic high-conductivity Pt layer and the high-Seebeck coefficient Si substrate. In addition, we demonstrate that this novel and effective decoupling method enables the assessment of the in-plane intrinsic Seebeck coefficient of a lightly doped Si wafer, which typically has an electrical resistance that is extremely high to measure the Seebeck coefficient even with a high-resolution voltmeter. These results represent a significant advancement in the understanding of electrical transport in TE materials, which will invigorate further research on Si-based devices for realizing large-area watt-scale TE generation at room temperature.
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| 5. |
- Kang, Min-Sung, et al.
(författare)
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Enhanced Transverse Seebeck Coefficients in 2D/2D PtSe2/MoS2 Heterostructures Using Wet-Transfer Stacking
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:46, s. 51881-51888
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Tidskriftsartikel (refereegranskat)abstract
- It is very challenging to estimate thermoelectric (TE) properties when applying millimeter-scale two-dimensional (2D) transition metal dichalcogenide (TMDC) materials to TE device applications, particularly their Seebeck coefficient due to their high intrinsic electrical resistance. This paper proposes an innovative approach to measure large transverse (i.e., in-plane) Seebeck coefficients for 2D TMDC materials by placing a low resistance (LR) semimetallic PtSe2 film on high-resistance (HR) semiconducting MoS2 (>10 M omega), whose internal resistance is too high to measure the Seebeck coefficient, forming a heterojunction structure using wet-transfer stacking. The vertically stacked LRPtSe2 (3 nm)/HR-MoS2 (12 nm) heterostructure film exhibits a high Seebeck coefficient > 190 mu V/K up to 5 K temperature difference. This unusual behavior can be explained by an additional Seebeck effect induced at the interface between the LR-2D/HR2D heterostructure. The proposed stacked LR-PtSe2/HR-MoS2 heterostructure film offers promising phenomena 2D/2D materials that enable innovative TE device applications.
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| 6. |
- Kim, Min-Jeong, et al.
(författare)
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Intrinsic Seebeck coefficients of 2D polycrystalline PtSe2 semiconducting films through two-step annealing
- 2023
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:11, s. 5714-5724
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Tidskriftsartikel (refereegranskat)abstract
- Because of the high contact resistance between a metal and a film, evaluating the intrinsic Seebeck coefficient of large-area two-dimensional (2D) semiconducting films with high-resistance is challenging. Here, we report a simple scheme to measure the large-area Seebeck coefficients of 2D polycrystalline platinum diselenide (PtSe2) thin films, whose electrical resistance (>2 M omega) is too high to measure the thermoelectric (TE) properties, by thermal annealing. As-prepared PtSe2 thin films deposited on sapphire substrates and treated by a two-step thermal annealing process at 574 K exhibited an intrinsic Seebeck coefficient > similar to 160 mu V K-1, which is 400% higher than that of the single-crystalline PtSe2 bulk, under a temperature gradient of up to 5 K along the samples. In addition, we confirm that the in-plane Seebeck coefficient of the two-step annealed samples was independent of the metal electrode. In addition, the role of thermal annealing in intrinsically-high-resistance 2D PtSe2 semiconducting films based on the atomic-scale crystallographic characteristics of these films and the measured contact resistance between the metal and PtSe2 layer is further discussed. Our finding represents an important achievement in understanding and measuring the Seebeck effect of high-TE-performance 2D layered transition metal dichalcogenide materials.
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| 7. |
- Kim, Yun-Ho, et al.
(författare)
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Barrier-free semimetallic PtSe2 contact formation in two-dimensional PtSe2/PtSe2 homostructure for high-performance field-effect transistors
- 2023
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Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 638
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Tidskriftsartikel (refereegranskat)abstract
- The search for low-resistance metal contacts on two-dimensional (2D) layered transition metal dichalcogenide (TMDC) materials for high-performance electronic devices remains challenging owing to the lack of interfacial bonding on the surface and a strong Fermi-level pinning effect. In this study, we demonstrate a high-performance 2D large-area homostructured PtSe2/PtSe2 field-effect transistor (FET) by introducing a Schottky-barrier-free and semimetallic PtSe2 film (top layer) as an ohmic contact to semiconducting 2D PtSe2 films (bottom layer) via the wet-transfer method. We successfully improved the current on/off ratio of homostructured 2D/2D PtSe2/PtSe2 FET by more than approximately twofold increase compared to the PtSe2 FET with Pt contacts owing to the barrier-free homojunction PtSe2 layer. Our finding represents a significant achievement in obtaining highperformance electronic devices with barrier-free contacts on homostructured PtSe2 FETs and paves the way toward a promising strategy for wafer-scale 2D TMDC electronic devices.
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| 8. |
- Lee, Won-Yong, et al.
(författare)
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Abnormal Seebeck Effect in Vertically Stacked 2D/2D PtSe2/PtSe2 Homostructure
- 2022
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Ingår i: Advanced Science. - : Wiley-VCH Verlagsgesellschaft. - 2198-3844. ; 9:36
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Tidskriftsartikel (refereegranskat)abstract
- When a thermoelectric (TE) material is deposited with a secondary TE material, the total Seebeck coefficient of the stacked layer is generally represented by a parallel conductor model. Accordingly, when TE material layers of the same thickness are stacked vertically, the total Seebeck coefficient in the transverse direction may change in a single layer. Here, an abnormal Seebeck effect in a stacked two-dimensional (2D) PtSe2/PtSe2 homostructure film, i.e., an extra in-plane Seebeck voltage is produced by wet-transfer stacking at the interface between the PtSe2 layers under a transverse temperature gradient is reported. This abnormal Seebeck effect is referred to as the interfacial Seebeck effect in stacked PtSe2/PtSe2 homostructures. This effect is attributed to the carrier-interface interaction, and has independent characteristics in relation to carrier concentration. It is confirmed that the in-plane Seebeck coefficient increases as the number of stacked PtSe2 layers increase and observed a high Seebeck coefficient exceeding ≈188 µV K−1 at 300 K in a four-layer-stacked PtSe2/PtSe2 homostructure.
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| 9. |
- Lee, Won-Yong, et al.
(författare)
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Alternatingly Stacked Low- and High-Resistance PtSe2/PtSe2 Homostructures Boost Thermoelectric Power Factors
- 2023
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Ingår i: Advanced Electronic Materials. - : John Wiley & Sons. - 2199-160X. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- 2D transition-metal dichalcogenide (TMDC) materials are promising candidates with excellent thermoelectric (TE) properties owing to their low dimensionality in electronic and phonon transport. However, the considerable coupling of the Seebeck coefficient and electrical conductivity in such TE materials eventually results in the limit of the TE power factor increase, which severely hinders potential TE device applications. Herein, an alternative approach is demonstrated for breaking the strong coupling between the Seebeck coefficient and electrical conductivity in single TE materials by adopting a novel stacked PtSe2/PtSe2 homostructure. By alternately piling low-resistance (LR) PtSe2 (3 nm) onto high-resistance (HR) PtSe2 (2 nm) as one unit, the Seebeck coefficient and electrical conductivity of such stacked homostructures can be greatly enhanced with slightly improved electrical conductivity, ultimately resulting in a TE power factor in three-unit-stacked homostructures that is approximate to 1,648% higher than that of a single PtSe2 (15 nm) layer with the same thickness. This enhancement is attributed to an independent increase in the Seebeck coefficient, which depends on the interface among the LR and HR PtSe2 layers. The findings pave the way for a method that, unlike power factor optimization in conventional thermoelectric materials, can only utilize the Seebeck coefficient and electrical conductivity of each layer in a stacked homostructure.
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| 10. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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