scholarly journals Large enhancement of thermoelectric performance in MoS2/h-BN heterostructure due to vacancy-induced band hybridization

2020 ◽  
Vol 117 (25) ◽  
pp. 13929-13936 ◽  
Author(s):  
Jing Wu ◽  
Yanpeng Liu ◽  
Yi Liu ◽  
Yongqing Cai ◽  
Yunshan Zhao ◽  
...  
Keyword(s):  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Resonant Scattering ◽  
Defect Engineering ◽  
Thermoelectric Power Factor ◽  
Kondo Insulator ◽  
Large Enhancement ◽  
External Fluctuations ◽  
2D Nanosheets ◽  
Thermoelectric Parameters

Local impurity states arising from atomic vacancies in two-dimensional (2D) nanosheets are predicted to have a profound effect on charge transport due to resonant scattering and can be used to manipulate thermoelectric properties. However, the effects of these impurities are often masked by external fluctuations and turbostratic interfaces; therefore, it is challenging to probe the correlation between vacancy impurities and thermoelectric parameters experimentally. In this work, we demonstrate that n-type molybdenum disulfide (MoS2) supported on hexagonal boron nitride (h-BN) substrate reveals a large anomalous positive Seebeck coefficient with strong band hybridization. The presence of vacancies on MoS2with a large conduction subband splitting of 50.0 ± 5.0 meV may contribute to Kondo insulator-like properties. Furthermore, by tuning the chemical potential, the thermoelectric power factor can be enhanced by up to two orders of magnitude to 50 mW m−1K−2. Our work shows that defect engineering in 2D materials provides an effective strategy for controlling band structure and tuning thermoelectric transport.

scholarly journals Chemical potential and quantum Hall ferromagnetism in bilayer graphene

Science ◽  
2014 ◽  
Vol 345 (6192) ◽  
pp. 58-61 ◽  
Author(s):  
Kayoung Lee ◽  
Babak Fallahazad ◽  
Jiamin Xue ◽  
David C. Dillen ◽  
Kyounghwan Kim ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Quantum Hall ◽  
Bilayer Graphene ◽  
Zero Magnetic Field ◽  
High Magnetic Fields ◽  
Complex Interplay ◽  
Electron Hole ◽  
Quantum Hall State

Bilayer graphene has a distinctive electronic structure influenced by a complex interplay between various degrees of freedom. We probed its chemical potential using double bilayer graphene heterostructures, separated by a hexagonal boron nitride dielectric. The chemical potential has a nonlinear carrier density dependence and bears signatures of electron-electron interactions. The data allowed a direct measurement of the electric field–induced bandgap at zero magnetic field, the orbital Landau level (LL) energies, and the broken-symmetry quantum Hall state gaps at high magnetic fields. We observe spin-to-valley polarized transitions for all half-filled LLs, as well as emerging phases at filling factors ν = 0 and ν = ±2. Furthermore, the data reveal interaction-driven negative compressibility and electron-hole asymmetry in N = 0, 1 LLs.

Enhancement of thermoelectric power factor in CrSi2 film via Si:B addition

2015 ◽  
Vol 29 (27) ◽  
pp. 1550189
Author(s):  
Q. R. Hou ◽  
B. F. Gu ◽  
Y. B. Chen
Keyword(s):  
Electrical Resistivity ◽  
Thermoelectric Power ◽  
Raman Spectra ◽  
Power Factor ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
Thermoelectric Power Factor ◽  
X Ray ◽  
Large Enhancement ◽  
Diffraction Patterns

In this paper, we report a large enhancement in the thermoelectric power factor in CrSi2 film via Si:B (1 at.% B content) addition. The Si:B-enriched CrSi2 films are prepared by co-sputtering CrSi2 and heavily B-doped Si targets. Both X-ray diffraction patterns and Raman spectra confirm the formation of the crystalline phase CrSi2. Raman spectra also indicate the crystallization of the added Si:B. With the addition of Si:B, the electrical resistivity [Formula: see text] decreases especially at low temperatures while the Seebeck coefficient [Formula: see text] increases above 533 K. As a result, the thermoelectric power factor, [Formula: see text], is greatly enhanced and can reach [Formula: see text] at 583 K, which is much larger than that of the pure CrSi2 film.

Photon Tunneling via Coupling Graphene Plasmons With Phonon Polaritons of Hexagonal Boron Nitride in Reststrahlen Bands

2021 ◽  
Author(s):  
Ruiyi Liu ◽  
Xiaohu Wu ◽  
Zheng Cui
Keyword(s):  
Boron Nitride ◽  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Tunneling Probability ◽  
Coupling Mechanism ◽  
Work Study ◽  
Photon Tunneling ◽  
Phonon Polaritons ◽  
Graphene Plasmons

Abstract The photon tunneling probability is the most important thing in near-field radiative heat transfer (NFRHT). This work study the photon tunneling via coupling graphene plasmons with phonon polaritons in hexagonal boron nitride (hBN). We consider two cases of the optical axis of hBN along z-axis and x-axis, respectively. We investigate the NFRHT between graphene-covered bulk hBN, and compare it with that of bare bulk hBN. Our results show that in Reststrahlen bands, the coupling of graphene plasmons and phonon polaritons in hBN can either suppress or enhance the photon tunneling probability, depending on the chemical potential of graphene and frequency. This conclusion holds when the optiacal axis of hBN is either along z-axis or x-axis. The findings in this work not only deepen our understanding of coupling mechanism between graphene plasmons with phonon polaritons, but also provide a theoretical basis for controlling photon tunneling in graphene covered hyperbolic materials.

scholarly journals Hexagonal boron nitride: a review on selfstanding crystals synthesis towards 2D nanosheets

2021 ◽  
Author(s):  
Camille Maestre ◽  
Bérangère Toury ◽  
Philippe Steyer ◽  
Vincent Garnier ◽  
Catherine Journet
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
2D Nanosheets

scholarly journals DEFECT ENGINEERING OF 2D MONATOMIC-LAYER MATERIALS

2013 ◽  
Vol 27 (23) ◽  
pp. 1330017 ◽  
Author(s):  
QING PENG ◽  
JARED CREAN ◽  
ALBERT K. DEARDEN ◽  
CHEN HUANG ◽  
XIAODONG WEN ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Two Dimensional ◽  
Defect Engineering ◽  
Two Dimensional Materials ◽  
And Behavior

Atomic-thick monolayer two-dimensional materials present advantageous properties compared to their bulk counterparts. The properties and behavior of these monolayers can be modified by introducing defects, namely defect engineering. In this paper, we review a group of common two-dimensional crystals, including graphene, graphyne, graphdiyne, graphn-yne, silicene, germanene, hexagonal boron nitride monolayers and MoS2monolayers, focusing on the effect of the defect engineering on these two-dimensional monolayer materials. Defect engineering leads to the discovery of potentially exotic properties that make the field of two-dimensional crystals fertile for future investigations and emerging technological applications with precisely tailored properties.

scholarly journals Preparation of PP/2D-Nanosheet Composites Using MoS2/MgCl2- and BN/MgCl2-Bisupported Ziegler–Natta Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 596
Author(s):  
He-xin Zhang ◽  
Byeong-Gwang Shin ◽  
Dong-Eun Lee ◽  
Keun-Byoung Yoon
Keyword(s):  
Thermal Stability ◽  
In Situ Polymerization ◽  
Hexagonal Boron Nitride ◽  
Interfacial Interaction ◽  
Catalyst Preparation ◽  
Two Dimensional ◽  
2D Nanosheets ◽  
Thermal Stability Of ◽  
Ziegler Natta Catalysts

Polypropylene/molybdenum disulfied (PP/MoS2) and Polypropylene/hexagonal boron nitride (PP/hBN) nanocomposites with varying concentration (0–6 wt %) were fabricated via in situ polymerization using two-dimensional (2D)-nanosheet/MgCl2-supported Ti-based Ziegler–Natta catalysts, which was prepared through a novel coagglomeration method. For catalyst preparation and interfacial interaction, MoS2 and hBN were modified with octadecylamine (ODA) and octyltriethoxysilane (OTES), respectively. Compared with those of pristine PP, thermal stability of composites was 70 °C higher and also tensile strength and Young’s modulus of the composites were up to 35% and 60% higher (even at small filler contents), respectively. The alkyl-modified 2D nanofillers were characterized by strong interfacial interactions between the nanofiller and the polymer matrix. The coagglomeration method employed in this work allows easy introduction and content manipulation of various 2D-nanosheets for the preparation of 2D-nanosheet/MgCl2-supported Ti-based Ziegler–Natta catalysts.

scholarly journals Boron Vacancy: A strategy to boost the Oxygen Reduction Reaction of hexagonal boron nitride nanosheet in hBN-2H-MoS2 heterostructure

2021 ◽  
Author(s):  
Dipayan Roy ◽  
Karamjyoti Panigrahi ◽  
Uday Kumar Ghorui ◽  
Bikram Kumar Das ◽  
Souvik Bhattacharjee ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Active Sites ◽  
Hexagonal Boron Nitride ◽  
Reduction Reaction ◽  
Two Dimensional ◽  
Defect Engineering ◽  
Boron Nitride Nanosheet ◽  
Two Dimensional Materials ◽  
Surface Active ◽  
High Band

Incorporation of vacancies in a system considered as proficient defect engineering in general catalytic modulation. Among the two-dimensional materials, surface active sites’ deficiency and high band gap restrict hexagonal boron...

scholarly journals Spatially controlled epitaxial growth of 2D heterostructures via defect engineering using a focused He ion beam

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Martin Heilmann ◽  
Victor Deinhart ◽  
Abbes Tahraoui ◽  
Katja Höflich ◽  
J. Marcelo J. Lopes
Keyword(s):  
Defect Formation ◽  
Electron Tunneling ◽  
Hexagonal Boron Nitride ◽  
Ion Beam ◽  
High Density ◽  
Attractive Alternative ◽  
Defect Engineering ◽  
Selective Area ◽  
Nucleation Sites ◽  
Beam Parameters

AbstractThe combination of two-dimensional (2D) materials into heterostructures enables the formation of atomically thin devices with designed properties. To achieve a high-density, bottom-up integration, the growth of these 2D heterostructures via van der Waals epitaxy (vdWE) is an attractive alternative to the currently mostly employed mechanical transfer, which is problematic in terms of scaling and reproducibility. Controlling the location of the nuclei formation remains a key challenge in vdWE. Here, a focused He ion beam is used to deterministically place defects in graphene substrates, which serve as preferential nucleation sites for the growth of insulating, 2D hexagonal boron nitride (h-BN). Therewith a mask-free, selective-area vdWE (SAvdWE) is demonstrated, in which nucleation yield and crystal quality of h-BN are controlled by the ion beam parameters used for defect formation. Moreover, h-BN grown via SAvdWE is shown to exhibit electron tunneling characteristics comparable to those of mechanically transferred layers, thereby lying the foundation for a reliable, high-density array fabrication of 2D heterostructures for device integration via defect engineering in 2D substrates.

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