ZrSe2

/Tag: ZrSe2

Electrical Conduction at the Interface between Insulating van der Waals Materials

2019-03-13T12:32:48+00:00March 13th, 2019|Categories: Publications|Tags: , , , , , |

Highly conducting interfaces between insulating 2D materials are demonstrated in van der Waals heterostructures fabricated by molecular‐beam epitaxy. In situ growth monitoring by reflection high energy electron diffraction confirms layer‐by‐layer fabrication of the heterostructures and the formation of abrupt interfaces. Hall effect measurements reveal that the conducting carriers are holes, and their densities are as large as 1014 cm−2. Abstract Emergent properties of 2D materials attract considerable interest in condensed matter physics and materials science due to their distinguished features that are missing in their bulk counterparts. A mainstream in this research field is to broaden the scope of material to expand the horizons of the research area, while developing functional interfaces between different 2D materials is another indispensable research direction. Here, the emergence of electrical conduction at the interface between insulating 2D materials is demonstrated. A new class of van der Waals heterostructures consisting of two sets of insulating transition‐metal dichalcogenides, group‐VI WSe2 and group‐IV TMSe2 (TM = Zr, Hf), is developed via molecular‐beam epitaxy, and it is found that those heterostructures are highly conducting although all the constituent materials are highly insulating. The WSe2/ZrSe2 interface exhibits more conducting behavior than the WSe2/HfSe2 interface, which can be understood by considering the band alignments between constituent materials. Moreover, by increasing Se flux during heterostructure fabrication, the WSe2/ZrSe2 interface becomes more conducting, reaching nearly metallic behavior. Further improvement of the crystalline quality as well as exploring different material combinations are expected to lead to metallic conduction, providing a novel functionality emerging

Published in: "Advanced Functional Materials".

Electrical Conduction at the Interface between Insulating van der Waals Materials

2019-03-10T20:32:47+00:00March 10th, 2019|Categories: Publications|Tags: , , , , , |

Highly conducting interfaces between insulating 2D materials are demonstrated in van der Waals heterostructures fabricated by molecular‐beam epitaxy. In situ growth monitoring by reflection high energy electron diffraction confirms layer‐by‐layer fabrication of the heterostructures and the formation of abrupt interfaces. Hall effect measurements reveal that the conducting carriers are holes, and their densities are as large as 1014 cm−2. Abstract Emergent properties of 2D materials attract considerable interest in condensed matter physics and materials science due to their distinguished features that are missing in their bulk counterparts. A mainstream in this research field is to broaden the scope of material to expand the horizons of the research area, while developing functional interfaces between different 2D materials is another indispensable research direction. Here, the emergence of electrical conduction at the interface between insulating 2D materials is demonstrated. A new class of van der Waals heterostructures consisting of two sets of insulating transition‐metal dichalcogenides, group‐VI WSe2 and group‐IV TMSe2 (TM = Zr, Hf), is developed via molecular‐beam epitaxy, and it is found that those heterostructures are highly conducting although all the constituent materials are highly insulating. The WSe2/ZrSe2 interface exhibits more conducting behavior than the WSe2/HfSe2 interface, which can be understood by considering the band alignments between constituent materials. Moreover, by increasing Se flux during heterostructure fabrication, the WSe2/ZrSe2 interface becomes more conducting, reaching nearly metallic behavior. Further improvement of the crystalline quality as well as exploring different material combinations are expected to lead to metallic conduction, providing a novel functionality emerging

Published in: "Advanced Functional Materials".

Electrical Conduction at the Interface between Insulating van der Waals Materials

2019-03-07T10:32:37+00:00March 7th, 2019|Categories: Publications|Tags: , , , , , |

Highly conducting interfaces between insulating 2D materials are demonstrated in van der Waals heterostructures fabricated by molecular‐beam epitaxy. In situ growth monitoring by reflection high energy electron diffraction confirms layer‐by‐layer fabrication of the heterostructures and the formation of abrupt interfaces. Hall effect measurements reveal that the conducting carriers are holes, and their densities are as large as 1014 cm−2. Abstract Emergent properties of 2D materials attract considerable interest in condensed matter physics and materials science due to their distinguished features that are missing in their bulk counterparts. A mainstream in this research field is to broaden the scope of material to expand the horizons of the research area, while developing functional interfaces between different 2D materials is another indispensable research direction. Here, the emergence of electrical conduction at the interface between insulating 2D materials is demonstrated. A new class of van der Waals heterostructures consisting of two sets of insulating transition‐metal dichalcogenides, group‐VI WSe2 and group‐IV TMSe2 (TM = Zr, Hf), is developed via molecular‐beam epitaxy, and it is found that those heterostructures are highly conducting although all the constituent materials are highly insulating. The WSe2/ZrSe2 interface exhibits more conducting behavior than the WSe2/HfSe2 interface, which can be understood by considering the band alignments between constituent materials. Moreover, by increasing Se flux during heterostructure fabrication, the WSe2/ZrSe2 interface becomes more conducting, reaching nearly metallic behavior. Further improvement of the crystalline quality as well as exploring different material combinations are expected to lead to metallic conduction, providing a novel functionality emerging

Published in: "Advanced Functional Materials".

Emergence of conduction band-induced semiconductor-to-metal transition in ZrSe2 through Hf substitution. (arXiv:1812.00157v1 [cond-mat.mtrl-sci])

2018-12-04T02:29:16+00:00December 4th, 2018|Categories: Publications|Tags: , |

Two-dimensional (2D) layered materials are very important and versatile platform for exploring novel electronic properties in different phases. The chemical doping in two-dimensional (2D) layered materials can engineer the electronic structure with useful physical properties which are distinct in comparison with the pristine one. Herein, we employed angle-resolved photoemission spectroscopy (ARPES) combined with first-principles density functional theory (DFT) calculations, to show the possible phase engineering of ZrSe2 via Hafnium (Hf) atoms substitution, which manifests a semiconducting-to-metallic transition. The emergence of conduction band at high symmetry M point around the Brillouin zone boundary due to extra charge doping, clearly demonstrates the conceivable evidence of semiconductor to metal transition in ZrSe2, through Hf substitution (about 12.5 percent) at room temperature. Similarly, the electrical resistance measurements further revealed the decrease of resistance with increasing temperature for ZrSe2 that confirms the semiconducting behavior, while the resistance increases with increasing temperature for Hf doped ZrSe2 that in an indication of the metallic behavior. This study further demonstrates the possibility of the band gap engineering through heavily doped metal in 2D materials thereby modulating the electronic properties of layered materials for next-generation electronic applications.

Published in: "arXiv Material Science".

Localized Surface Plasmon Resonance on Two-Dimensional HfSe2 and ZrSe2. (arXiv:1810.04829v1 [cond-mat.mtrl-sci])

2018-10-12T02:29:39+00:00October 12th, 2018|Categories: Publications|Tags: , , , |

HfSe2 and ZrSe2 are newly discovered two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) with promising properties for future nanoelectronics and optoelectronics. We theoretically revealed the electronic and optical properties of these two emerging 2D semiconductors, and evaluated their performance for the application of localized surface plasmon resonance (LSPR) at extreme conditions: in-plane direction versus out-of-plane direction and monolayer versus multilayer. First, the energy band structure and dielectric constants were calculated for both the monolayer and multilayer structures using Kohn-Sham density functional theory (KS-DFT) with van der Waals (vdW) corrections. A parallel-band effect observed in the monolayer band structure indicates a strong light-matter interaction. Then, based on the calculated dielectric constants, the performance of the LSPR excited by Au sphere nanoparticles (NPs) was quantitatively characterized, including polarizability, scattering and absorption cross-sections, and radiative efficiency using Mie theory. For the multilayer HfSe2 and ZrSe2, the LSPR showed very comparable intensities in both the in-plane and out-of-plane directions, suggesting an isotropy-like light-matter interaction. In a comparison, the LSPR excited on the monolayer HfSe2 and ZrSe2 was clearly observed in the in-plane direction but effectively suppressed in the out-of-plane direction due to the unique anisotropic nature. In addition to this extraordinary anisotropy-to-isotropy transition as the layer number increases, a red-shift of the LSPR wavelength was also found. Our work has predicated the thickness-dependent anisotropic light-matter interaction on the emerging 2D semiconducting HfSe2 and ZrSe2, which holds great potential for broad optoelectronic applications such as sensing and energy conversion.

Published in: "arXiv Material Science".

HfSe2 and ZrSe2: Two-dimensional semiconductors with native high-{kappa} oxides

2017-08-11T18:31:41+00:00August 11th, 2017|Categories: Publications|Tags: , |

The success of silicon as a dominant semiconductor technology has been enabled by its moderate band gap (1.1 eV), permitting low-voltage operation at reduced leakage current, and the existence of SiO2 as a high-quality “native” insulator. In contrast, other mainstream semiconductors lack stable oxides and must rely on deposited insulators,

Published in: "Science Advances".

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