Niobium oxide dihalides NbOX<sub>2</sub>: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

Jia, Yinglu; Zhao, Min; Gou, Gaoyang; Zeng, Xiao Cheng; Li, Ju

doi:10.1039/c9nh00208a

Cited by 69 publications

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References 64 publications

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“…demonstrated theoretically that niobium oxide dihalides NbOX 2 (X = Cl, Br, and I) show intrinsic room temperature in‐plane ferroelectricity and antiferroelectricity induced by Nb cations polar displacement (Figure 12e,f). [ 203 ]…”

Section: Ferroelectric Materials and Fe‐gated Heterostructuresmentioning

confidence: 99%

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2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

Chu

Wang

et al. 2020

Advanced Materials

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The emergence of 2D polarized materials, including ferromagnetic, ferrovalley, and ferroelectric materials, has demonstrated unique quantum behaviors at atomic scales. These polarization behaviors are tightly bonded to the new degrees of freedom (DOFs) for next generation information storage and processing, which have been dramatically developed in the past few years. Here, the basic 2D polarized materials system and related devices’ application in spintronics, valleytronics, and electronics are reviewed. Specifically, the underlying physical mechanism accompanied with symmetry broken theory and the modulation process through heterostructure engineering are highlighted. These summarized works focusing on the 2D polarization would continue to enrich the cognition of 2D quantum system and promising practical applications.

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Section: Ferroelectric Materials and Fe‐gated Heterostructuresmentioning

confidence: 99%

Section: Ferroelectric Materials and Fe‐gated Heterostructuresmentioning

confidence: 99%

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

Chu

Wang

et al. 2020

Advanced Materials

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“…Additionally, the conduction and valence bands reveal anisotropic dispersion, and the valence and conduction bands around the Fermi surface are almost dispersed along the crystallographic b-axis. [34] Therefore, the electrons would migrate more easily along the b-axis because there exist more electrons in this direction. According to the anisotropy in electrical transport of 2D NbOI 2 flake, angle-resolved electrical www.advmat.de www.advancedsciencenews.com resistance measurements can be used to determine its in-plane structural orientation.…”

Section: Introductionmentioning

confidence: 99%

“…The simulated optical absorption coefficient along the c-axis (α c ) is an order of magnitude higher than that along the b-axis (α b ). [34] Consequently, the NbOI 2 is expected to exhibit unique in-plane anisotropy. However, until now, the preparation and basic properties of 2D NbOI 2 crystals have not been thoroughly investigated, and in particular, the in-plane anisotropy caused by its low-symmetry structure is still unclear.Here, we introduce a kind of transition metal oxide dihalides, NbOI 2 , into the 2D materials family with experimental demonstration of strong in-plane anisotropy.…”

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confidence: 99%

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Fang

Wang

et al. 2021

Advanced Materials

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induced diodes, [23,24] polarization-sensitive photodetectors, [25,26] synaptic-neuromorphic devices, [27] etc. Although the research on anisotropic 2D materials is progressing rapidly, it is still in its infancy as a whole. Therefore, developing new materials and exploring their anisotropic physical properties and functional devices are of great significance to the development of science and technology.Recently, layered transition metal oxide dihalides MOX 2 (M = V, Nb, Ta, Mo; X = Cl, Br, I) have gained increasing attention among materials scientists due to their chiral crystal structure and unique physical properties. [28][29][30][31][32][33] Among them, NbOI 2 has a low-symmetry monoclinic structure (space group C2), in which Nb atoms shift away from the center of [NbO 2 I 4 ] octahedra connected by sharing I-I edges and cornered O atoms along the c-and b-axes. Various connection modes enable NbOI 2 strong anisotropic physical properties and highly dispersed band structure. The simulated optical absorption coefficient along the c-axis (α c ) is an order of magnitude higher than that along the b-axis (α b ). [34] Consequently, the NbOI 2 is expected to exhibit unique in-plane anisotropy. However, until now, the preparation and basic properties of 2D NbOI 2 crystals have not been thoroughly investigated, and in particular, the in-plane anisotropy caused by its low-symmetry structure is still unclear.Here, we introduce a kind of transition metal oxide dihalides, NbOI 2 , into the 2D materials family with experimental demonstration of strong in-plane anisotropy. Few-layer and monolayer NbOI 2 crystals were obtained through mechanical exfoliation, and these crystals showed large second harmonic generation (SHG) response, verifying its noncentrosymmetric crystal structure. The strong in-plane anisotropy of phonon vibration in 2D NbOI 2 crystals was observed by using angleresolved polarized Raman measurements. The anisotropic electronic dispersion around the Fermi surfaces leads to the strong anisotropy of optical absorbance with an anisotropic factor of 1.75. In addition, highly anisotropic in-plane electrical resistance with a factor of 1.34 and photoresponsivity with a factor of 1.7 were demonstrated in 2D NbOI 2 crystals. These findings indicate that the 2D NbOI 2 crystal can serve as a promising candidate in anisotropic electronic and optoelectronic devices. Results and DiscussionBulk NbOI 2 belongs to the monoclinic space group C2 (No. 5) with a = 15.18 Å, b = 3.92 Å, c = 7.52 Å, β = 105.5°. Figure 1a Exploring in-plane anisotropic 2D materials is of great significance to the fundamental studies and further development of polarizationsensitive optoelectronics. Herein, chiral niobium oxide diiodide (NbOI 2 ) is introduced into the intriguing anisotropic 2D family with the experimental demonstration of anisotropic optical and electrical properties. 2D NbOI 2 crystals exhibit highly anisotropic dispersed band structures around the Fermi surface and strong in-plane anisotropy of phonon vibrations owing to the diff...

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“…The van der Waals (vdW) family of layered oxide dichlorides M OX 2 (M = V, Ta, Nb, Os; X = Halogen element) [41,42] is known to display the required geometric structure, where the MO 2 X 4 octahedra are corner-sharing along the a-axis, while edge-sharing along the b-axis. Peierls distortions have been found along the b-axis [43][44][45], resulting in d xy molecular orbitals, but the d xz/yz orbitals are unoccupied because this material is in the d 1 configuration. Then, it only partially fulfills our requirements for OSPP.…”

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Orbital-selective Peierls phase in the metallic dimerized chain MoOCl$_2$

Zhang,

Lin,

Moreo

et al. 2021

Preprint

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Using ab initio density functional theory, here we systematically study the monolayer MoOCl2 with a 4d 2 electronic configuration. Our main results is that an orbital-selective Peierls phase (OSPP) develops in MoOCl2, resulting in the dimerization of the Mo chain along the b-axis. Specifically, the Mo-dxy orbitals form robust molecular-orbital states inducing localized dxy singlet dimers, while the Mo-d xz/yz orbitals remain delocalized and itinerant. Our study shows that MoOCl2 is globally metallic, with the Mo-dxy orbital bonding-antibonding splittings opening a gap and the Mo-d xz/yz orbitals contributing to the metallic conductivity. Overall, the results resemble the recently much discussed orbital-selective Mott phase but with the localized band induced by a Peierls distortion instead of Hubbard interactions. Finally, we also qualitatively discuss the possibility of OSPP in the 3d 2 configuration, as in CrOCl2.

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Niobium oxide dihalides NbOX₂: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

Abstract: A new group of two-dimensional layered materials with intrinsic ferroelectricity and antiferroelectricity are identified through first-principles calculations.

Cited by 69 publications

References 64 publications

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Orbital-selective Peierls phase in the metallic dimerized chain MoOCl$_2$

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Niobium oxide dihalides NbOX2: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

Abstract: A new group of two-dimensional layered materials with intrinsic ferroelectricity and antiferroelectricity are identified through first-principles calculations.

Cited by 69 publications

References 64 publications

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

2D Polarized Materials: Ferromagnetic, Ferrovalley, Ferroelectric Materials, and Related Heterostructures

2D NbOI2: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Orbital-selective Peierls phase in the metallic dimerized chain MoOCl$_2$

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Niobium oxide dihalides NbOX₂: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties