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Kang MS, Lee WY, Yoon YG, Choi JW, Kim GS, Kim SH, Park NW, Lee SK. Enhanced Transverse Seebeck Coefficients in 2D/2D PtSe 2/MoS 2 Heterostructures Using Wet-Transfer Stacking. ACS Appl Mater Interfaces 2022; 14:51881-51888. [PMID: 36355622 DOI: 10.1021/acsami.2c14065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
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 MΩ), whose internal resistance is too high to measure the Seebeck coefficient, forming a heterojunction structure using wet-transfer stacking. The vertically stacked LR-PtSe2 (3 nm)/HR-MoS2 (12 nm) heterostructure film exhibits a high Seebeck coefficient > 190 μV/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/HR-2D 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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Affiliation(s)
- Min-Sung Kang
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - Won-Yong Lee
- Division of Solid-State Electronics, Department of Electrical Engineering, Uppsala University, Uppsala75103, Sweden
| | - Young-Gui Yoon
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - Jae Won Choi
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - Si-Hoo Kim
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - No-Won Park
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics and Center for Berry Curvature Based New Phenomena, Chung-Ang University, Seoul06974, Republic of Korea
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Lee WY, Kang MS, Kim GS, Choi JW, Park NW, Sim Y, Kim YH, Seong MJ, Yoon YG, Saitoh E, Lee SK. Interface-Induced Seebeck Effect in PtSe 2/PtSe 2 van der Waals Homostructures. ACS Nano 2022; 16:3404-3416. [PMID: 35133142 DOI: 10.1021/acsnano.2c00359] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The Seebeck effect refers to the production of an electric voltage when different temperatures are applied on a conductor, and the corresponding voltage-production efficiency is represented by the Seebeck coefficient. We report a Seebeck effect: thermal generation of driving voltage from the heat flowing in a thin PtSe2/PtSe2 van der Waals homostructure at the interface. We refer to the effect as the interface-induced Seebeck effect. By exploiting this effect by directly attaching multilayered PtSe2 over high-resistance PtSe2 thin films as a hybridized single structure, we obtained the highly challenging in-plane Seebeck coefficient of the PtSe2 films that exhibit extremely high resistances. This direct attachment further enhanced the in-plane thermal Seebeck coefficients of the PtSe2/PtSe2 van der Waals homostructure on sapphire substrates. Consequently, we successfully enhanced the in-plane Seebeck coefficients for the PtSe2 (10 nm)/PtSe2 (2 nm) homostructure approximately 42% compared to that of a pure PtSe2 (10 nm) layer at 300 K. These findings represent a significant achievement in understanding the interface-induced Seebeck effect and provide an effective strategy for promising large-area thermoelectric energy harvesting devices using two-dimensional transition metal dichalcogenide materials, which are ideal thermoelectric platforms with high figures of merit.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jae Won Choi
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yumin Sim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yun-Ho Kim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Maeng-Je Seong
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Young-Gui Yoon
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Eiji Saitoh
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
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Lee WY, Park NW, Kang MS, Kim GS, Yoon YG, Lee S, Choi KY, Kim KS, Kim JH, Seong MJ, Kikkawa T, Saitoh E, Lee SK. Extrinsic Surface Magnetic Anisotropy Contribution in Pt/Y 3Fe 5O 12 Interface in Longitudinal Spin Seebeck Effect by Graphene Interlayer. ACS Appl Mater Interfaces 2021; 13:45097-45104. [PMID: 34496563 DOI: 10.1021/acsami.1c13180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A recent study found that magnetization curves for Y3Fe5O12 (YIG) slab and thick films (>20 μm thick) differed from bulk system curves by their longitudinal spin Seebeck effect in a Pt/YIG bilayer system. The deviation was due to intrinsic YIG surface magnetic anisotropy, which is difficult to adopt extrinsic surface magnetic anisotropy even when in contact with other materials on the YIG surface. This study experimentally demonstrates evidence for extrinsic YIG surface magnetic anisotropy when in contact with a diamagnetic graphene interlayer by observing the spin Seebeck effect, directly proving intrinsic YIG surface magnetic anisotropy interruption. We show the Pt/YIG bilayer system graphene interlayer role using large area single and multilayered graphenes using the longitudinal spin Seebeck effect at room temperature, and address the presence of surface magnetic anisotropy due to magnetic proximity between graphene and YIG layer. These findings suggest a promising route to understand new physics of spin Seebeck effect in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Young-Gui Yoon
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Suheon Lee
- Deopartment of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kwang-Yong Choi
- Deopartment of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Keun Soo Kim
- Department of Physics and Astronomy, Sejong University, Seoul 05006, Republic of Korea
| | - Jin-Hyuk Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Maeng-Je Seong
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Takashi Kikkawa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Eiji Saitoh
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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Park NW, Kim H, Lee WY, Kim GS, Kang DY, Kim TG, Saitoh E, Yoon YG, Rho H, Lee SK. Giant Thermoelectric Seebeck Coefficients in Tellurium Quantum Wires Formed Vertically in an Aluminum Oxide Layer by Electrical Breakdown. J Phys Chem Lett 2021; 12:8212-8219. [PMID: 34415767 DOI: 10.1021/acs.jpclett.1c01842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
High efficiency thermoelectric (TE) materials still require high thermopower for energy harvesting applications. A simple elemental metallic semiconductor, tellurium (Te), has been considered critical to realize highly efficient TE conversion due to having a large effective band valley degeneracy. This paper demonstrates a novel approach to directly probe the out-of-plane Seebeck coefficient for one-dimensional Te quantum wires (QWs) formed locally in the aluminum oxide layer by well-controlled electrical breakdown at 300 K. Surprisingly, the out-of-plane Seebeck coefficient for these Te QWs ≈ 0.8 mV/K at 300 K. This thermopower enhancement for Te QWs is due to Te intrinsic nested band structure and enhanced energy filtering at Te/AO interfaces. Theoretical calculations support the enhanced high Seebeck coefficient for elemental Te QWs in the oxide layer. The local-probed observation and detecting methodology used here offers a novel route to designing enhanced thermoelectric materials and devices in the future.
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Affiliation(s)
- No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hanul Kim
- Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Dae Yun Kang
- School of Electrical Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Tae Geun Kim
- School of Electrical Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Young-Gui Yoon
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Heesuk Rho
- Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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5
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Lee WY, Kang MS, Kim GS, Park NW, Choi KY, Le CT, Rashid MU, Saitoh E, Kim YS, Lee SK. Role of Ferromagnetic Monolayer WSe 2 Flakes in the Pt/Y 3Fe 5O 12 Bilayer Structure in the Longitudinal Spin Seebeck Effect. ACS Appl Mater Interfaces 2021; 13:15783-15790. [PMID: 33769783 DOI: 10.1021/acsami.0c22345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spin Seebeck effect (SSE) has attracted renewed interest as a promising phenomenon for energy harvesting systems. A noteworthy effort has been devoted to improving the SSE voltage by inserting ultrathin magnetic layers including Fe70Cu30 interlayers in Pt/Y3Fe5O12 (Pt/YIG) systems with increased spin-mixing conductance at the interfaces. Nevertheless, the responsible underlying physics associated with the role of the interlayer in Pt/YIG systems in the SSE is still unknown. In this paper, we demonstrate that with a monolayer tungsten diselenide (ML WSe2) interlayer in the Pt/YIG bilayer system, the longitudinal SSE (LSSE) voltage is significantly increased by the increased spin accumulation in the Pt layer; the spin fluctuation in ML WSe2 amplifies the spin current transmission because the in-plane-aligned WSe2 spins are coupled to thermally pumped spins under nonequilibrium magnetization conditions in the LSSE configuration at room temperature. The thermopower (VLSSE/ΔT) improves by 323% with respect to the value of the reference Pt/YIG bilayer sample in the LSSE at room temperature. In addition, the induced ferromagnetic properties of the ML WSe2 flakes on YIG increase the LSSE voltage (VLSSE) of the sample; the ferromagnetic properties are a result of the improved magnetic moment density in the ML WSe2 flakes and their two-dimensional (2D) ML nature in the LSSE under nonequilibrium magnetization conditions. The results can extend the application range of the materials in energy harvesting and provide important information on the physics of the LSSE with a transition metal dichalcogenide intermediate layer in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Kwang-Yong Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Chinh Tam Le
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Mamoon Ur Rashid
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Yong Soo Kim
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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6
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Lee WY, Park NW, Kim GS, Kang MS, Choi JW, Choi KY, Jang HW, Saitoh E, Lee SK. Enhanced Spin Seebeck Thermopower in Pt/Holey MoS 2/Y 3Fe 5O 12 Hybrid Structure. Nano Lett 2021; 21:189-196. [PMID: 33274946 DOI: 10.1021/acs.nanolett.0c03499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We first observed the spin-to-charge conversion due to both the inverse Rashba-Edelstein effect (IREE) and inverse spin-Hall effect in a holey multilayer molybdenum disulfide (MoS2) intermediate layer in a Pt/YIG structure via LSSE measurements under nonequilibrium magnetization. We found an enhancement of approximately 238%, 307%, and 290% in the longitudinal spin Seebeck effect (LSSE) voltage, spin-to-charge current, and thermoelectric (TE) power factor, respectively, compared with the monolayer MoS2 interlayer in a Pt/YIG structure. Such an enhancement in the LSSE performance of Pt/holey MoS2/YIG can be explained by the improvement of spin accumulation in the Pt layer by induced spin fluctuation as well as increased additional spin-to-charge conversion due to in-plane IREE. Our findings represent a significant achievement in the understanding of spin transport in atomically thin MoS2 interlayers and pave the way toward large-area TE energy-harvesting devices in two-dimensional transition metal dichalcogenide materials.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jae Won Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Kwang-Yong Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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Lee WY, Park NW, Kang MS, Kim GS, Jang HW, Saitoh E, Lee SK. Surface Coverage Dependence of Spin-to-Charge Current across Pt/MoS 2/Y 3Fe 5O 12 Layers via Longitudinal Spin Seebeck Effect. J Phys Chem Lett 2020; 11:5338-5344. [PMID: 32558573 DOI: 10.1021/acs.jpclett.0c01502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The voltage induced by the inverse spin Hall effect (ISHE) is affected by several factors, including the spin Hall angle of the normal metal (NM), the quality and magnetic properties of the ferromagnetic material (FM), and the interface conditions between the NM and FM bilayers in longitudinal spin Seebeck effect (LSSE) measurement. Specifically, the interface conditions in NM/FM systems via LSSE devices play a crucial role in determining the efficiency of spin current injection into the NM layer. In this letter, we report a new approach to controlling the efficiency of spin current injection into a Pt layer across a Pt/Y3Fe5O12 (YIG) interface by surface coverage of the intermediate layer. A continuous, large-area multilayer molybdenum dichalcogenide (MoS2) thin film grown by chemical vapor deposition is inserted between the Pt and YIG layers in the LSSE configuration. We found that, when the large-area multilayer MoS2 film was present, the measured ISHE-induced voltage and theoretically calculated spin current in the Pt/MoS2/YIG trilayer increased by ∼510% and 470%, respectively, compared to those of a Pt/YIG bilayer. The induced voltage and spin current were very sensitive to the surface conductance, which was affected by the surface coverage of the multilayer MoS2 films in the LSSE measurement. Furthermore, the theoretically calculated spin current and spin mixing conductance in the trilayer geometry are in qualitatively good agreement with the experimental observations. These measurements enable us to explain the effect of the interface conditions on the spin Seebeck effect in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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Tahir Z, Kim S, Ullah F, Lee S, Lee JH, Park NW, Seong MJ, Lee SK, Ju TS, Park S, Bae JS, Jang JI, Kim YS. Highly Efficient Solar Steam Generation by Glassy Carbon Foam Coated with Two-Dimensional Metal Chalcogenides. ACS Appl Mater Interfaces 2020; 12:2490-2496. [PMID: 31840505 DOI: 10.1021/acsami.9b18589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Steam generation by eco-friendly solar energy has immense potential in terms of low-cost power generation, desalination, sanitization, and wastewater treatment. Herein, highly efficient steam generation in a bilayer solar steam generator (BSSG) is demonstrated, which is comprised of a large-area SnSe-SnSe2 layer deposited on a glassy carbon foam (CF). Both CF and SnSe-SnSe2 possess high photothermal conversion capabilities and low thermal conductivities. The combined bilayer system cumulatively converts input solar light into heat through phonon-assisted transitions in the indirect band gap SnSe-SnSe2 layer, together with trapping of sunlight via multiple scattering due to the porous morphology of the CF. This synergistic effect leads to efficient broadband solar absorption. Moreover, the low out-of-plane thermal conductivities of SnSe-SnSe2 and CF confine the generated heat at the evaporation surface, resulting in a significant reduction of heat losses. Additionally, the hydrophilic nature of the acid-treated CF offers effective water transport via capillary action, required for efficient solar steam generation in a floating form. A high evaporation rate (1.28 kg m-2 h-1) and efficiency (84.1%) are acquired under 1 sun irradiation. The BSSG system shows high recyclability, stability, and durability under repeated steam-generation cycles, which renders its practical device applications possible.
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Affiliation(s)
- Zeeshan Tahir
- Department of Physics and Energy Harvest Storage Research Center , University of Ulsan , Ulsan 44610 , South Korea
| | - Sungdo Kim
- Department of Physics and Energy Harvest Storage Research Center , University of Ulsan , Ulsan 44610 , South Korea
| | - Farman Ullah
- Department of Physics and Energy Harvest Storage Research Center , University of Ulsan , Ulsan 44610 , South Korea
| | - Sunghan Lee
- Department of Physics and Energy Harvest Storage Research Center , University of Ulsan , Ulsan 44610 , South Korea
| | - Je-Ho Lee
- Department of Physics , Chung-Ang University , Seoul 06794 , South Korea
| | - No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06794 , South Korea
| | - Maeng-Je Seong
- Department of Physics , Chung-Ang University , Seoul 06794 , South Korea
| | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06794 , South Korea
| | - Tae-Seong Ju
- Department of Physics , Pusan National University , Busan 46241 , South Korea
| | - Sungkyun Park
- Department of Physics , Pusan National University , Busan 46241 , South Korea
| | - Jong-Seong Bae
- Busan Center , Korea Basic Science Institute , Busan 46742 , South Korea
| | - Joon Ik Jang
- Department of Physics , Sogang University , Seoul 04107 , South Korea
| | - Yong Soo Kim
- Department of Physics and Energy Harvest Storage Research Center , University of Ulsan , Ulsan 44610 , South Korea
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9
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Park NW, Lee WY, Yoon YS, Kim GS, Yoon YG, Lee SK. Achieving Out-of-Plane Thermoelectric Figure of Merit ZT = 1.44 in a p-Type Bi 2Te 3/Bi 0.5Sb 1.5Te 3 Superlattice Film with Low Interfacial Resistance. ACS Appl Mater Interfaces 2019; 11:38247-38254. [PMID: 31542917 DOI: 10.1021/acsami.9b11042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Recently, low-dimensional superlattice films have attracted significant attention because of their low dimensionality and anisotropic thermoelectric (TE) properties such as the Seebeck coefficient, electrical conductivity, and thermal conductivity. For these superlattice structures, both electrons and phonons show highly anisotropic behavior and exhibit much stronger interface scattering in the out-of-plane direction of the films compared to the in-plane direction. However, no detailed information is available in the literature for the out-of-plane TE properties of the superlattice-based films. In this report, we present the out-of-plane Seebeck coefficient, thermal conductivity, and electrical properties of p-type Bi2Te3/Bi0.5Sb1.5Te3 (bismuth telluride/bismuth antimony telluride, BT/BST) superlattice films in the temperature range of 77-500 K. Because of the synergistic combination of the energy filtering effect and low interfacial resistance of the superlattice structure, an impressively high ZT of 1.44 was achieved at 400 K for the 200 nm-thick p-type BT/BST superlattice film, corresponding to a 43% ZT enhancement compared to the pristine p-BST films with the same thickness.
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Affiliation(s)
- No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Won-Yong Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Yo-Seop Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Gil-Sung Kim
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Young-Gui Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
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10
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Park NW, Kang DY, Lee WY, Yoon YS, Kim GS, Saitoh E, Kim TG, Lee SK. Controllable Seebeck Coefficients of a Metal-Diffused Aluminum Oxide Layer via Conducting Filament Density and Energy Filtering. ACS Appl Mater Interfaces 2019; 11:23303-23312. [PMID: 31184861 DOI: 10.1021/acsami.9b01289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigate the intrinsic thermoelectric (TE) properties of the metal-diffused aluminum oxide (AO) layer in metal/AO/metal structures, where the metallic conducting filaments (CFs) were locally formed in the structures via an electrical breakdown (EBD) process as shown by resistive switching memory devices, by directly measuring cross-plane Seebeck coefficients on the CF-containing insulating AO layers. The results showed that the Seebeck coefficients of the CF-containing AO layer in metal/AO/metal structures were influenced by the generation of the metallic CFs, which is due to the diffusion of the metal into the insulating AO layers when exposed to a temperature gradient in the direction of the cross plane of the sample. In addition, the increase in the Seebeck coefficients of the CF-containing AO layer when the number of EBD-processed patterns was increased is satisfactorily explained by the low-energy carrier (i.e., minority carriers) filtering through the metal-oxide interfacial barriers in the metal/AO/metal structures.
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Affiliation(s)
- No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Dae Yun Kang
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Won-Yong Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Yo-Seop Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Gil-Sung Kim
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Eiji Saitoh
- Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
- WPI Advanced Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
- Department of Applied Physics , The University of Tokyo , Tokyo 113-8656 , Japan
| | - Tae Geun Kim
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
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11
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Park NW, Lee WY, Yoon YS, Ahn JY, Lee JH, Kim GS, Kim TG, Choi CJ, Park JS, Saitoh E, Lee SK. Direct Probing of Cross-Plane Thermal Properties of Atomic Layer Deposition Al 2O 3/ZnO Superlattice Films with an Improved Figure of Merit and Their Cross-Plane Thermoelectric Generating Performance. ACS Appl Mater Interfaces 2018; 10:44472-44482. [PMID: 30507128 DOI: 10.1021/acsami.8b15997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, have not been performed from these semiconducting superlattice films because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present a technique using a structure of sandwiched superlattice films between two embedded heaters as the heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al2O3/ZnO superlattice films, prepared by the atomic layer deposition method. Used in combination with the promising cross-plane four-point probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al2O3/ZnO superlattice films in the temperature range of 80 to 500 K. Our experimental methodology and the obtained results represent a significant advancement in the understanding of phonons and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.
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Affiliation(s)
- No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Won-Yong Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Yo-Seop Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Jay-Young Ahn
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Jung-Hoon Lee
- Division of Materials Science and Engineering , Hanyang University , Seoul 04763 , Republic of Korea
| | - Gil-Sung Kim
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Tae Geun Kim
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Chel-Jong Choi
- Department of Semiconductor Science and Technology , Chonbuk National University , Jeonju 54896 , Republic of Korea
| | - Jin-Seong Park
- Division of Materials Science and Engineering , Hanyang University , Seoul 04763 , Republic of Korea
| | | | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
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12
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Cho SH, Cho K, Park NW, Park S, Koh JH, Lee SK. Multi-Layer SnSe Nanoflake Field-Effect Transistors with Low-Resistance Au Ohmic Contacts. Nanoscale Res Lett 2017; 12:373. [PMID: 28549378 PMCID: PMC5445061 DOI: 10.1186/s11671-017-2145-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 05/14/2017] [Indexed: 06/07/2023]
Abstract
We report p-type tin monoselenide (SnSe) single crystals, grown in double-sealed quartz ampoules using a modified Bridgman technique at 920 °C. X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) measurements clearly confirm that the grown SnSe consists of single-crystal SnSe. Electrical transport of multi-layer SnSe nanoflakes, which were prepared by exfoliation from bulk single crystals, was conducted using back-gated field-effect transistor (FET) structures with Au and Ti contacts on SiO2/Si substrates, revealing that multi-layer SnSe nanoflakes exhibit p-type semiconductor characteristics owing to the Sn vacancies on the surfaces of SnSe nanoflakes. In addition, a strong carrier screening effect was observed in 70-90-nm-thick SnSe nanoflake FETs. Furthermore, the effect of the metal contacts to multi-layer SnSe nanoflake-based FETs is also discussed with two different metals, such as Ti/Au and Au contacts.
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Affiliation(s)
- Sang-Hyeok Cho
- Department of Physics, Chung-Ang University, Seoul, 06974 Republic of Korea
| | - Kwanghee Cho
- Department of Physics, Chung-Ang University, Seoul, 06974 Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul, 06974 Republic of Korea
| | - Soonyong Park
- Department of Physics, Chung-Ang University, Seoul, 06974 Republic of Korea
| | - Jung-Hyuk Koh
- School of Electrical and Electronics Engineering, Chung-Ang University, Seoul, 06974 Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul, 06974 Republic of Korea
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13
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Park NW, Ahn JY, Park TH, Lee JH, Lee WY, Cho K, Yoon YG, Choi CJ, Park JS, Lee SK. Control of phonon transport by the formation of the Al 2O 3 interlayer in Al 2O 3-ZnO superlattice thin films and their in-plane thermoelectric energy generator performance. Nanoscale 2017; 9:7027-7036. [PMID: 28368061 DOI: 10.1039/c7nr00690j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Recently, significant progress has been made in increasing the figure-of-merit (ZT) of various nanostructured materials, including thin-film and quantum dot superlattice structures. Studies have focused on the size reduction and control of the surface or interface of nanostructured materials since these approaches enhance the thermopower and phonon scattering in quantum and superlattice structures. Currently, bismuth-tellurium-based semiconductor materials are widely employed for thermoelectric (TE) devices such as TE energy generators and coolers, in addition to other sensors, for use at temperatures under 400 K. However, new and promising TE materials with enhanced TE performance, including doped zinc oxide (ZnO) multilayer or superlattice thin films, are also required for designing solid-state TE power generating devices with the maximum output power density and for investigating the physics of in-plane TE generators. Herein, we report the growth of Al2O3/ZnO (AO/ZnO) superlattice thin films, which were prepared by atomic layer deposition (ALD), and the evaluation of their electrical and TE properties. All the in-plane TE properties, including the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ), of the AO/ZnO superlattice (with a 0.82 nm-thick AO layer) and AO/ZnO films (with a 0.13 nm-thick AO layer) were evaluated in the temperature range 40-300 K, and the measured S, σ, and κ were -62.4 and -17.5 μV K-1, 113 and 847 (Ω cm)-1, and 0.96 and 1.04 W m-1 K-1, respectively, at 300 K. Consequently, the in-plane TE ZT factor of AO/ZnO superlattice films was found to be ∼0.014, which is approximately two times more than that of AO/ZnO films (ZT of ∼0.007) at 300 K. Furthermore, the electrical power generation efficiency of the TE energy generator consisting of four couples of n-AO/ZnO superlattice films and p-Bi0.5Sb1.5Te3 (p-BST) thin-film legs on the substrate was demonstrated. Surprisingly, the output power of the 100 nm-thick n-AO/ZnO superlattice film/p-BST TE energy generator was determined to be ∼1.0 nW at a temperature difference of 80 K, corresponding to a significant improvement of ∼130% and ∼220% compared to the 100 nm-thick AO/ZnO film/p-BST and n-BT/p-BST film generators, respectively, owing to the enhancement of the TE properties, including the power factor of the superlattice film.
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Affiliation(s)
- No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea.
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Lee WY, Lee JH, Ahn JY, Park TH, Park NW, Kim GS, Park JS, Lee SK. Anisotropic temperature-dependent thermal conductivity by an Al 2O 3 interlayer in Al 2O 3/ZnO superlattice films. Nanotechnology 2017; 28:105401. [PMID: 28145279 DOI: 10.1088/1361-6528/aa5985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The thermal conductivity of superlattice films is generally anisotropic and should be studied separately in the in-plane and cross-plane directions of the films. However, previous works have mostly focused on the cross-plane thermal conductivity because the electrons and phonons in the cross-plane direction of superlattice films may result in much stronger interface scattering than that in the in-plane direction. Nevertheless, it is highly desirable to perform systematic studies on the effect of interface formation in semiconducting superlattice films on both in-plane and cross-plane thermal conductivities. In this study, we determine both the in-plane and cross-plane thermal conductivities of Al2O3 (AO)/ZnO superlattice films grown by atomic layer deposition (ALD) on SiO2/Si substrates in the temperature range of 50-300 K by the four-point-probe 3-ω method. Our experimental results indicate that the formation of an atomic AO layer (0.82 nm) significantly contributes to the decrease of the cross-plane thermal conductivity of the AO/ZnO superlattice films compared with that of AO/ZnO thin films. The cross-plane thermal conductivity (0.26-0.63 W m-1 K-1 of the AO/ZnO superlattice films (with an AO layer of ∼0.82 nm thickness) is approximately ∼150%-370% less than the in-plane thermal conductivity (0.96-1.19 W m-1 K-1) of the corresponding film, implying significant anisotropy. This indicates that the suppression of the cross-plane thermal conductivity is mainly attributed to the superlattice, rather than the nanograin columnar structure in the films. In addition, we theoretically analyzed strong anisotropic behavior of the in-plane and cross-plane thermal conductivities of the AO/ZnO superlattice films in terms of temperature dependence.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea
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Park NW, Park SI, Lee SK. Effect of Thickness of Single-Phase Antimony and Tellurium Thin Films on Their Thermal Conductivities. J Nanosci Nanotechnol 2015; 15:6729-6733. [PMID: 26716236 DOI: 10.1166/jnn.2015.11589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present the effects of film thickness and grain size on the out-of-plane thermal conductivities of single-phase Sb and Te thin films, which are of great interest for thermoelectric device applications. The thermal conductivities of the films were measured by the four-point-probe 3Ωo method, at room temperature. For this study, 50-, 100-, and 200-nm-thick Sb and Te thin films were prepared by electron-beam evaporation at room temperature. From the measured thermal conductivities, we evaluated that the average thermal conductivities of the Sb and Te thin films were 5.9-10.2 W/(m x K) and 0.8-1.2 W/(m x K), respectively, at room temperature. This result reveals that the thickness and grain size of each thin film strongly affect the modulation of its thermal conductivity at room temperature.
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Kim DJ, Lee WY, Park NW, Kim GS, Lee KM, Kim J, Choi MK, Lee GH, Han W, Lee SK. Drug response of captured BT20 cells and evaluation of circulating tumor cells on a silicon nanowire platform. Biosens Bioelectron 2015; 67:370-8. [DOI: 10.1016/j.bios.2014.08.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/16/2014] [Accepted: 08/22/2014] [Indexed: 12/16/2022]
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Park NW, Lee WY, Hong JE, Park TH, Yoon SG, Im H, Kim HS, Lee SK. Effect of grain size on thermal transport in post-annealed antimony telluride thin films. Nanoscale Res Lett 2015; 10:20. [PMID: 25852318 PMCID: PMC4384892 DOI: 10.1186/s11671-015-0733-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 01/05/2015] [Indexed: 06/04/2023]
Abstract
The effects of grain size and strain on the temperature-dependent thermal transport of antimony telluride (Sb2Te3) thin films, controlled using post-annealing temperatures of 200°C to 350°C, were investigated using the 3-omega method. The measured total thermal conductivities of 400-nm-thick thin films annealed at temperatures of 200°C, 250°C, 300°C, 320°C, and 350°C were determined to be 2.0 to 3.7 W/m · K in the 20 to 300 K temperature range. We found that the film grain size, rather than the strain, had the most prominent effect on the reduction of the total thermal conductivity. To confirm the effect of grain size on temperature-dependent thermal transport in the thin films, the experimental results were analyzed using a modified Callaway model approach.
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Affiliation(s)
- No-Won Park
- />Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea
| | - Won-Yong Lee
- />Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea
| | - Ji-Eun Hong
- />Department of Materials Engineering, Chungnam National University, Daejeon, 305-764 Republic of Korea
| | - Tae-Hyun Park
- />Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea
| | - Soon-Gil Yoon
- />Department of Materials Engineering, Chungnam National University, Daejeon, 305-764 Republic of Korea
| | - Hyunsik Im
- />Department of Semiconductor Science and Physics, Dongguk University, Seoul, 100-715 Republic of Korea
| | - Hyung Sang Kim
- />Department of Semiconductor Science and Physics, Dongguk University, Seoul, 100-715 Republic of Korea
| | - Sang-Kwon Lee
- />Department of Physics, Chung-Ang University, Seoul, 156-756 Republic of Korea
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Kim DJ, Kim GS, Seol JK, Hyung JH, Park NW, Lee MR, Lee MK, Fan R, Lee SK. Filopodial Morphology Correlates to the Capture Efficiency of Primary T-Cells on Nanohole Arrays. J Biomed Nanotechnol 2014; 10:1030-40. [DOI: 10.1166/jbn.2014.1814] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Khurelbaatar Z, Hyung JH, Kim GS, Park NW, Shim KH, Lee SK. Electrical transport characterization of PEDOT:PSS/n-Si Schottky diodes and their applications in solar cells. J Nanosci Nanotechnol 2014; 14:4394-4399. [PMID: 24738402 DOI: 10.1166/jnn.2014.7937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate locally contacted PEDOT:PSS Schottky diodes with excellent rectifying behavior, fabricated on n-type Si substrates using a spin-coating process and a reactive-ion etching process. Electrical transport characterizations of these Schottky diodes were investigated by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. We found that these devices exhibit excellent modulation in the current with an on/off ratio of - 10(6). Schottky junction solar cells composed of PEDOT:PSS and n-Si structures were also examined. From the current density-voltage (J-V) measurement of a solar cell under illumination, the short circuit current (I(sc)), open circuit voltage (V(oc)), and conversion efficiency (eta) were - 19.7 mA/cm2, - 578.5 mV, and - 6.5%, respectively. The simple and low-cost fabrication process of the PEDOT:PSS/n-Si Schottky junctions makes them a promising candidate for further high performance solar cell applications.
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20
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Park NW, Lee WY, Kim JA, Song K, Lim H, Kim WD, Yoon SG, Lee SK. Reduced temperature-dependent thermal conductivity of magnetite thin films by controlling film thickness. Nanoscale Res Lett 2014; 9:96. [PMID: 24571956 PMCID: PMC3938477 DOI: 10.1186/1556-276x-9-96] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 02/19/2014] [Indexed: 06/03/2023]
Abstract
We report on the out-of-plane thermal conductivities of epitaxial Fe3O4 thin films with thicknesses of 100, 300, and 400 nm, prepared using pulsed laser deposition (PLD) on SiO2/Si substrates. The four-point probe three-omega (3-ω) method was used for thermal conductivity measurements of the Fe3O4 thin films in the temperature range of 20 to 300 K. By measuring the temperature-dependent thermal characteristics of the Fe3O4 thin films, we realized that their thermal conductivities significantly decreased with decreasing grain size and thickness of the films. The out-of-plane thermal conductivities of the Fe3O4 films were found to be in the range of 0.52 to 3.51 W/m · K at 300 K. For 100-nm film, we found that the thermal conductivity was as low as approximately 0.52 W/m · K, which was 1.7 to 11.5 order of magnitude lower than the thermal conductivity of bulk material at 300 K. Furthermore, we calculated the temperature dependence of the thermal conductivity of these Fe3O4 films using a simple theoretical Callaway model for comparison with the experimental data. We found that the Callaway model predictions agree reasonably with the experimental data. We then noticed that the thin film-based oxide materials could be efficient thermoelectric materials to achieve high performance in thermoelectric devices.
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Affiliation(s)
- No-Won Park
- Department of Physics, Chung-Ang University, Seoul, 156–756, Republic of Korea
| | - Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul, 156–756, Republic of Korea
| | - Jin-A Kim
- Department of Materials Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea
| | - Kyungjun Song
- Department of Nature-Inspired Nanoconvergence Systems, Korean Institute of Machinery and Materials (KIMM), Daejeon 305-343, Republic of Korea
| | - Hyuneui Lim
- Department of Nature-Inspired Nanoconvergence Systems, Korean Institute of Machinery and Materials (KIMM), Daejeon 305-343, Republic of Korea
| | - Wan-Doo Kim
- Department of Nature-Inspired Nanoconvergence Systems, Korean Institute of Machinery and Materials (KIMM), Daejeon 305-343, Republic of Korea
| | - Soon-Gil Yoon
- Department of Materials Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul, 156–756, Republic of Korea
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Lee SY, Lee MR, Park NW, Kim GS, Choi HJ, Choi TY, Lee SK. Temperature-dependent thermal conductivities of 1D semiconducting nanowires via four-point-probe 3-ω method. Nanotechnology 2013; 24:495202. [PMID: 24231523 DOI: 10.1088/0957-4484/24/49/495202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on a systematic study of the thermal transport characteristics of both as-grown zinc oxide and gallium nitride nanowires (NWs) via the four-point-probe 3-ω method in the temperature range 130-300 K. Both as-grown NWs were synthesized by a vapor-liquid-solid growth mechanism, and show clear n-type semiconducting behavior without any defects, which enables both the NWs to be promising candidates for thermoelectric materials. To measure the thermal conductivities of both NWs with lower heat loss and measurement errors, the suspended structures were formed by a combination of an e-beam lithography process and a random dispersion method. The measured thermal conductivities of both NWs are greatly reduced compared to their bulk materials due to the enhanced phonon scattering via the size effect and dopants (impurities). Furthermore, we observed that the Umklapp peaks of both NWs are shifted to a higher temperature than those of their bulk counterparts, indicating that phonon-boundary scattering dominates over other phonon scattering due to the size effect.
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Affiliation(s)
- Seung-Yong Lee
- Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore
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Kim GS, Lee MR, Lee SY, Hyung JH, Park NW, Lee ES, Lee SK. Reduction in thermal conductivity of Bi thin films with high-density ordered nanoscopic pores. Nanoscale Res Lett 2013; 8:371. [PMID: 24001222 PMCID: PMC3766660 DOI: 10.1186/1556-276x-8-371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Accepted: 08/21/2013] [Indexed: 05/04/2023]
Abstract
We prepared two-dimensional Bi thin films with high-density ordered nanoscopic pores by e-beam evaporation of Bi metal. For this structure, we used polystyrene beads ranging from 200 to 750 nm in diameter as an etch mask. The typical hole and neck sizes of the Bi thin films with approximately 50 nm in thickness on SiO2/Si substrates were in the range of 135 to 490 nm and 65 to 260 nm, respectively. By measuring the thermal characteristics through a 3ω technique, we found that the thermal conductivities of nanoporous Bi thin films are greatly suppressed compared with those of corresponding bulk materials. With a decrease in pore size to approximately 135 nm, the thermal conductivity decreased significantly to approximately 0.46 W/m·K at 300 K.
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Affiliation(s)
- Gil-Sung Kim
- Basic Research Laboratory (BRL), Department of Semiconductor Science and Technology, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Mi-Ri Lee
- Basic Research Laboratory (BRL), Department of Semiconductor Science and Technology, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Seung-Yong Lee
- Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore
| | - Jung-Hwan Hyung
- Basic Research Laboratory (BRL), Department of Semiconductor Science and Technology, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Eun Sun Lee
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA 22904, USA
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea
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Abstract
The efficacy of attention rehabilitation after an acquired brain injury was examined meta-analytically. Thirty studies with a total of 359 participants met the authors' selection criteria. Studies were categorized according to whether training efficacy was evaluated by comparing pre- and posttraining scores only or included a control condition as well. Performance improved significantly (using the d+ statistic) after training in pre-post only studies but not in pre-post with control studies. Further analyses showed that specific-skills training significantly improved performance of tasks requiring attention but that the cognitive-retraining methods included in the meta-analysis did not significantly affect outcomes. These findings demonstrate that acquired deficits of attention are treatable using specific-skills training. Implications of these results for rehabilitation theory and future research are discussed.
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Affiliation(s)
- N W Park
- Baycrest Centre for Geriatic Care, Kunin-Lunenfeld Applied Research Unit and Department of Psychology, Toronto, Ontario, Canada.
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Abstract
The efficacy of attention rehabilitation after an acquired brain injury was examined meta-analytically. Thirty studies with a total of 359 participants met the authors' selection criteria. Studies were categorized according to whether training efficacy was evaluated by comparing pre- and posttraining scores only or included a control condition as well. Performance improved significantly (using the d+ statistic) after training in pre-post only studies but not in pre-post with control studies. Further analyses showed that specific-skills training significantly improved performance of tasks requiring attention but that the cognitive-retraining methods included in the meta-analysis did not significantly affect outcomes. These findings demonstrate that acquired deficits of attention are treatable using specific-skills training. Implications of these results for rehabilitation theory and future research are discussed.
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Affiliation(s)
- N W Park
- Baycrest Centre for Geriatic Care, Kunin-Lunenfeld Applied Research Unit and Department of Psychology, Toronto, Ontario, Canada.
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Abstract
This study investigated social judgment problems of an individual (AM) with bilateral frontal and temporal lobe damage including damage to the amygdala. We hypothesized that AM could automatically process positive, but not negative evaluative information and could process both types of evaluative information using controlled processing. In Phase 1 of Experiment 1 AM and controls were shown a series of words one at a time and were required to make good/bad judgments as quickly as possible. Results showed that AM was more likely than controls to rate words as good, and was significantly slower to make good/bad judgments of negatively, but not positively, evaluated words. In Phase 2 AM was shown a prime (positive or negative) then target (positive or negative) and instructed to evaluate whether the target word was good or bad. Results showed that AM responded more quickly when prime and target were both positive, but not when prime and target were both negative, whereas controls showed both types of priming. Experiment 2 determined whether AM's impaired processing of negative evaluative information could be abolished under controlled processing. AM was explicitly instructed to generate positive and negative connotations of a series of single words and given essentially unlimited time. Under these conditions, AM and controls did not differ significantly in their ability to generate positive versus negative connotations of words. In Experiment 3 AM and controls both showed normal semantic priming effects. The results are interpreted within the component process model of memory.
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Affiliation(s)
- N W Park
- Kunin-Lunenfeld Applied Research Unit and Department of Psychology, Baycrest Centre for Geriatric Care, University of Toronto, 3560 Bathurst Street, Suite 2W-02, Ont., M6A 2E1, Toronto, Canada.
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Abstract
This research investigated whether people with severe traumatic brain injury (TBI) are impaired on divided attention tasks requiring working memory. In experiment 1, a severe TBI and control group performed two tasks requiring working memory separately and concurrently. Results showed that the TBI group had impaired divided attention when performing the two tasks concurrently, although the two groups did not differ in performance when these tasks were performed separately. Experiment 2 showed that performance on the paced auditory serial addition task improved with increases in the intertrial interval for both TBI and control groups. A meta-analysis showed that TBIs are impaired on divided attention when the tasks require controlled processing, but not when the tasks can be carried out relatively automatically.
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Affiliation(s)
- N W Park
- Department of Psychology, Baycrest Centre for Geriatric Care, Toronto, Ontario, Canada.
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Park NW, Rim C, Soh DS. Effect of rotation symmetry on Abelian Chern-Simons field theory and anyon equation on a sphere. Int J Clin Exp Med 1994; 50:5241-5251. [PMID: 10018173 DOI: 10.1103/physrevd.50.5241] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Park NW, Schechter J, Weigel H. Electromagnetic, axial-vector, and strange currents in the Skyrme model: Effects of symmetry breaking. Phys Rev D Part Fields 1991; 43:869-884. [PMID: 10013449 DOI: 10.1103/physrevd.43.869] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Johnson R, Park NW, Schechter J, Soni V, Weigel H. Singlet axial-vector current and the "proton-spin" question. Phys Rev D Part Fields 1990; 42:2998-3009. [PMID: 10013182 DOI: 10.1103/physrevd.42.2998] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Park NW, Schechter J, Weigel H. Symmetry breaking and hyperon decays in the Skyrme model. Phys Rev D Part Fields 1990; 41:2836-2843. [PMID: 10012677 DOI: 10.1103/physrevd.41.2836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Jain P, Johnson R, Park NW, Schechter J, Weigel H. Neutron-proton mass-splitting puzzle in Skyrme and chiral quark models. Phys Rev D Part Fields 1989; 40:855-865. [PMID: 10011885 DOI: 10.1103/physrevd.40.855] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Jain P, Johnson R, Meissner UG, Park NW, Schechter J. Realistic pseudoscalar-vector chiral Lagrangian and its soliton excitations. Phys Rev D Part Fields 1988; 37:3252-3266. [PMID: 9958616 DOI: 10.1103/physrevd.37.3252] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Meissner UG, Johnson R, Park NW, Schechter J. Bag formation in the presence of vector mesons. II. Inclusion of scalars. Phys Rev D Part Fields 1988; 37:1285-1288. [PMID: 9958808 DOI: 10.1103/physrevd.37.1285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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