RSS
E-mail Alert
Search Advanced
Article navigation > Materials Lab > 2022 > 1, 220033
Next Article Previous Article

Weiting Xu, Shengxue Yang. Seeking Novel Low-symmetry 2D Materials with Strong In-plane Anisotropy. Materials Lab 2022, 1, 220033. doi: 10.54227/mlab.20220033
Citation: Weiting Xu, Shengxue Yang. Seeking Novel Low-symmetry 2D Materials with Strong In-plane Anisotropy. Materials Lab 2022, 1, 220033. doi: 10.54227/mlab.20220033
shu

Perspective

Seeking Novel Low-symmetry 2D Materials with Strong In-plane Anisotropy

Published as part of the Virtual Special Issue “Beihang University at 70”

More Information

  • School of Materials Science and Engineering, Beihang University, Beijing 100191, China

  • Corresponding author: sxyang@buaa.edu.cn
    Abstract

  • Low-symmetry 2D materials, such as black phosphorus (BP), ReS2, etc., usually exhibit unique characteristic of its in-plane anisotropy. Inspired by this, the searching for novel low-symmetry 2D materials beyond BP and ReS2 is essential for creating polarization dependent devices and will benefit the future explorations of heterojunction on low-symmetry 2D materials. This perspective reviews the research on structure, characterization and applications of low-symmetry 2D materials.


    • FullText(HTML)

  • Today, exploring two-dimensional (2D) materials with in-plane anisotropic structures has been most attractive. Compared to other materials with high-symmetry crystal structure, low-symmetry 2D materials presents a variety of novel optical, electrical, thermal, mechanical properties, such as anisotropic light absorption[1, 2], linear dichroism[3, 4], anisotropic thermal transfer[5, 6], providing another degree of freedom to design and modulate electronic and optoelectronic devices. As the representative of low-symmetry 2D materials, BP possess tunable band gap, high mobility, anisotropic collective electronic excitations, non-parabolic band, anisotropic in-plane optical conductivity and anisotropic effective mass of carriers, allowing the construction of high-performance plasmonic devices[7], mid-infrared polarizers[8] and the fabrication of quasi-ballistic transistors[9, 10]. Therefore, research on low-symmetry 2D materials not only play an imperative role in scientific fields, but also can promote important technical needs. In this perspective, we will review the studies on low-symmetry 2D materials, focusing on introducing new material systems and effective characterization methods of exploring different aspects of in-plane anisotropy. Then, we will discuss its potential for fabricating novel devices, challenges in novel low-symmetry 2D materials and functional devices with existing materials.

    As listed in Table 1, all the low-symmetry 2D materials, such as group VIII-VI-type compounds[1], group IV-V-type compounds[11], group III-VI-type compounds[12], group IV-VI-type compounds[13-19], transition metal oxyhalides[20, 21] and 2D alloy[22, 23], typically belong to low-symmetry crystal systems, such as orthorhombic, monoclinic, or tetragonal crystal systems, and with different space group. Such low-symmetry crystal structure of the material is the main reason for the anisotropy of the electronic band structure, which leads to anisotropic effective mass of electrons or holes, and the interaction of electrons-phonons. It gives rise to some in-plane anisotropic properties that are not available in isotropic materials, such as anisotropic conductance, anisotropic carrier transport, anisotropic thermal conductivity, anisotropic optical absorption, etc.

    Table 1.  The crystal structure and basic parameters of low-symmetry 2D materials.
    New material systemsMaterialsatomsSide viewTop viewCrystal systemSpace group
    group VIII-VI-type compoundsPdSe2orthorhombicPbca
    group IV-VI-type compoundsSnSeorthorhombicPnma
    GeSeorthorhombicPnma
    GeS2monoclinicP21/c
    GeSe2monoclinicP21/c
    transition metal oxyhalidesCrOClorthorhombicPmmn
    group III-VI-type compoundsTlSetetragonalI4/mcm
    group IV-V-type compoundsGeAsmonoclinicC2/m
    2D alloyNb(1−x)TixS3monoclinicP21/m
    Ge(1−x)SnxSe2monoclinicP21/c
     | Show Table
    DownLoad: CSV

    As a rare anisotropic material in group VIII-VI-type compounds, PdSe2 possesses an orthorhombic structure with space group Pbca[1]. As displayed in Table 1 (second row fourth column and second row fifth column), one Pd atom and four Se atoms form an asymmetric pentagonal structure which different from honeycomb structure of graphene.

    SnSe possesses an orthorhombic structure with space group Pnma[14]. As displayed in Table 1 (third row fourth column), each layer of SnSe exhibits a puckered crystal structure similar to BP[8], thus also owns unusual in-plane anisotropic physical properties. It is worth mentioning that different from single element composition in BP, SnSe have Sn and Se elements with different electronegativity, and inversion symmetry broken will occurs in its odd numbered layers, which will make the symmetry even lower, thus shows stronger anisotropy than BP and bring richer physical properties.

    Group Ge-VI type compounds usually have a low-symmetry crystal structure, such as GeS2, GeSe, GeSe2. As displayed in Table 1 (fourth row fourth column), GeSe possesses an orthorhombic structure with space group Pnma[16] and shows similar crystal structure with SnSe. Different from GeSe, GeS2 and GeSe2 possesses a monoclinic structure with space group P21/c[15, 19]. As displayed in Table 1 (fifth row fourth column and sixth row fourth column), the basic building blocks of GeX2 (X=S, Se) are a tetrahedron consisting of one Ge atom and four X atoms which results in two inequivalent in-plane directions and thus leads to a low-symmetry crystal structure.

    GeAs possesses a monoclinic structure with space group C2/m[11]. As displayed in Table 1 (ninth row fourth column), the side view of GeAs shows that monolayer GeAs consists of one twisted hexagon and two twisted pentagons, which are bonded by Ge atoms and As atoms. Interestingly, there are two type of Ge-Ge bonds, parallel and perpendicular to the layer plane, respectively, which caused in-plane anisotropy of GeAs and enriched the structure types of low-symmetry 2D materials.

    2D alloys, like Nb(1−x)TixS3 and Ge(1−x)SnxSe2, as displayed in Table 1 (tenth row fourth column and eleventh row fourth column), also possess low-symmetry crystal structures, because their crystal structures are formed by partially replacing the metal atoms in TiS3 and β-GeSe2, respectively. Especially, the quasi-one-dimensional structure of TiS3 has been demonstrated that has direct band gap[24] and presents a larger anisotropic absorption ratio[25], which endows Nb(1−x)TixS3 alloys with optical in-plane anisotropy. In order to expand the applications of low-symmetry 2D materials, it is significant to use innovative methods to detect the anisotropy properties of low-symmetry 2D materials and to discovery novel low-symmetry 2D material systems with more potential properties.

    As mentioned in “Crystal structure of low-symmetry 2D materials” part, low-symmetry structures often lead to anisotropic band structures. For better explaining the carrier transport or the interaction of electron phonons, we calculated the band structure of some low-symmetry 2D materials including SnSe, TlSe, CrOCl and Nb(1−x)TixS3 (Fig. 1). In the band structures of above low-symmetry 2D materials, valence and conduction band curves exhibit highly anisotropic dispersions. Taking SnSe as an example, the calculated band structure demonstrates electron−photon interactions along zigzag direction and armchair direction and shows distinctly linear dichroism along two directions (Fig. 1a), similar anisotropy also observed in band structure of TlSe, CrOCl and Nb(1−x)TixS3 (Fig. 1b-1d), but there is difference in band dispersions along the two crystal orientations. By systematically analyze crystal structure and calculated band structure of low-symmetry 2D materials, we can screen the properties of low-symmetry 2D materials, particularly anisotropic electrical properties and anisotropic optical properties, thus the simulation is essential and provides a solid theoretical foundation for subsequent experimental research.

    Fig. 1  Anisotropic band structure of low-symmetry 2D materials. (a) Band structure of SnSe[14]. Copyright 2017, Springer Nature. (b) Band structure of TlSe[12]. Copyright 2018, American Chemical Society. (c) Band structure of Nb(1−x)TixS3[23]. Copyright 2019, American Chemical Society. (d) Band structure of CrOCl[20]. Copyright 2019, American Chemical Society.
    DownLoad: Full-Size Img PowerPoint

    4.1   Anisotropic Optical Properties

    Due to the optical absorption involves only electron-photon interaction, and electronic structures of low-symmetry 2D materials is anisotropy, the optical absorption in low-symmetry 2D materials is highly orientation-dependent. For example, By measuring the polarization-dependent transmission spectrum (PDTS) on few-layers TlSe in a wide photon energy range from 1.25 to 2.5 eV (Fig. 2a), the TlSe shows stronger absorption along zigzag direction than armchair direction[12]. Similarly, Nb(1−x)TixS3 shows the same anisotropic optical absorption behavior whose absorption along zigzag direction is more severe than along armchair direction (Fig. 2b)[23]. In contrast to TlSe which has a stronger absorption along zigzag direction, SnSe and Ge(1−x)SnxSe2 show a stronger absorption along armchair direction than zigzag direction (Fig. 2c and 2d)[14, 22], since the different spatial structure of the wave functions of bands near the conduction band minimum (CBM) and valence band maximum (VBM) along armchair and zigzag directions.

    Fig. 2  Anisotropic optical absorption of low-symmetry 2D materials. (a) Anisotropic absorption spectra of TlSe. The polarization angle of 0° and 90° correspond to the zigzag and armchair directions, respectively[12]. Copyright 2018, American Chemical Society. (b) Anisotropic absorption spectra of Nb(1−x)TixS3. The b-axis and a-axis correspond to zigzag and armchair directions, respectively[23]. Copyright 2019, American Chemical Society. (c) Anisotropic absorption spectra of SnSe[14]. Copyright 2017, Springer Nature. (d) Anisotropic absorption spectra of Ge(1−x)SnxSe2. The polarization angle of 0° and 90° correspond to the zigzag and armchair directions, respectively[22]. Copyright 2019, RSC Pub.
    DownLoad: Full-Size Img PowerPoint

    In addition to anisotropic optical absorption, optical reflection has also been demonstrated to be orientation-dependent. Azimuth-dependent reflectance difference microscopy (ADRDM) as an imaging detection method that displays the N(θ) value simultaneously for all samples and even substrates under the same field of view, so that the reflectance anisotropic contrast of the material along different crystal orientations can be visualized in situ and non-destructively. Early low-symmetry 2D materials example of this measurement was GeAs[11], when change the polarization of incident light, there is a change in reflectance contrast in the ADRDM image of GeAs and the maximum and minimum of reflectance difference (RD) values appeared at two nearly vertical angles which indicates armchair and zigzag direction.

    Beyond the widely explored anisotropic linear optical properties of low-symmetry 2D materials, anisotropy has also been observed in nonlinear optic. For instance, by employing polarization-resolved second-harmonic generation (PRSHG), the nonlinear optical anisotropy in CrOCl has been characterized[20]. The polarization diagram of SHG intensity fitting at different angles exhibits two different periodic variations under parallel and perpendicular configuration. Besides, the calculated second-order susceptibility χCrOCl can reach 2.24 × 10−11 m/V, comparable to χGdSe, which is commonly used in nonlinear optics[26], confirming the strong in-plane nonlinear optical anisotropy in CrOCl. The above materials exhibit unique optical anisotropy and demonstrated that new low-symmetry 2D material systems open up possibilities for the fabrication of orientation-dependent linear and nonlinear optical detectors.

    4.2   Anisotropic Electronic Transport

    Low-symmetry structure results in an anisotropic band dispersion relation and anisotropic carrier effective mass, eventually leading to electrical anisotropic transport. The carrier mobility of 2D anisotropic material shows orientation-dependence, which can be studied by angle-resolved electrical transport measurements though fabricating four or more diagonal pairs of electrodes. Taking SnSe as an example, the carrier mobility along armchair direction is much larger than that along zigzag direction, with the anisotropy ratio of 5.8, exhibiting strong dependency on crystal orientation (Fig. 3a and 3b)[14]. Unlike SnSe, GeAs possesses higher mobility along zigzag direction which demonstrated zigzag direction is more mobile direction (Fig. 3c and 3d). The anisotropic mobility ratio of GeAs is calculated to be 4.6[11], which is slightly higher than BP and lower than SnSe[8, 14]. The remarkable and tunable electrical anisotropy of low-symmetry 2D material enable the future blossoming of novel electronic devices.

    Fig. 3  Anisotropic electronic transport properties of SnSe and GeAs. (a) Transfer curves of anisotropic SnSe transistors. (b) Polar plot of normalized field-effect mobility for SnSe transistors[14]. Copyright 2017, Springer Nature. (c) Transfer curves of anisotropic GeAs transistors. (d) Polar plot of normalized field-effect mobility for GeAs transistors[11]. Copyright 2018, John Wiley and Sons.
    DownLoad: Full-Size Img PowerPoint

    Based on the anisotropic optical and electrical properties, low-symmetry 2D materials can achieve high-precision detection of incident light information and obtain polarimetric signals of incident light, which can be useful for assembly of navigation, optical switches, and high-contrast polarizers. Thus, low-symmetry 2D materials show great application potential in designing polarization-sensitive photodetectors. For instance, by fabricating only one pairs of electrodes and employing a polarized incident 633 nm laser, the photocurrent of TlSe was obviously observed to be linear dichroic that maximum and minimum photocurrent appeared when the incident laser polarized along zigzag direction and armchair direction, respectively (Fig. 4a and 4b)[12]. Then, we obtained a dichroic ratio of 2.65. We also fabricated similar polarization-sensitive photodetector on 2D alloy Nb(1−x)TixS3, with the same illumination under incident 633 nm laser, and found the maximum photocurrent when the polarization paralleled to zigzag direction (Fig. 4c and 4d) and with a dichroic ratio up to 1.75 which is comparable to TlSe[23]. Therefore, the emergence of novel 2D anisotropic materials is crucial for future design of new polarized-sensitive photodetectors.

    Fig. 4  Optoelectronics application of TlSe and Nb(1−x)TixS3. (a) Schematic diagram of TlSe photodetection device. (b) 2D colormap of anisotropic photocurrent of TlSe[12]. Copyright 2018, American Chemical Society. (c) Schematic diagram of Nb(1−x)TixS3 photodetection device. (d) 2D colormap of anisotropic photocurrent of Nb(1−x)TixS3[23]. Copyright 2019, American Chemical Society.
    DownLoad: Full-Size Img PowerPoint

    In-depth understanding of the complementary relationship between the physical properties and structures of materials is an important prerequisite for opening up the application prospects of low-symmetry 2D materials. Where we expect, anisotropic materials will bring exciting opportunities for various fields. On the one hand, owing to anisotropic transport and high mobility characteristics, anisotropic materials can be utilized as modulators and inverters in high-frequency thin-film electronics. In addition, this feature also extends to bionic electronics, which could implement the functions similar to synapses that heterogeneous signal transmissions in biological neural networks. Furthermore, the relative angle between the layers of low-symmetry 2D materials offer multitude of extraordinary properties to some special stacked structures, such as twisted BP homojunction. The effective masses along different orientation is varying in low-symmetry BP, thus there is a new “orientation barrier” in twisted BP to turn different rectification ratios[27], and the designed twisted homojunction based on low-symmetry 2D materials has great potential for realizing new orientation-induced optoelectronic devices. On the other hand, utilizing the absorption of polarized light, anisotropic materials can serve as promising alternative materials for polarization reflectors and optical waveplates. Finally, in optoelectronics, the high sensitivity to polarized light enable better capture of rich information from incident light, such as surface roughness, crystal orientation, etc., which is highly valuable in the fabrication of polarization-sensitive photodetectors. Furthermore, designing photodetectors by building heterostructure based on anisotropic materials, the built-in electric field can effectively accelerate the separation and transportation of photogenerated electron-hole pairs so that the photoresponse is expected to enhanced.

    However, currently, many challenges remain unaddressed that limit the development of anisotropic materials. First, degree of current in-plane anisotropy in low-symmetry 2D materials is not high enough for practical applications, thus we need to focus on developing new technologies to improve anisotropic ratio, such as carrier mobility ratio and polarized photocurrent ratio. Second, in order to promote the process of practical application, we also expect to solve the difficulty of the controllable large-scale preparation of 2D anisotropic materials in the future. Additionally, it is equally important to achieve regulation of the number of layers, which is conducive to further studying the influence of different band structures on anisotropy properties at different thickness. Overall, we hope to excavate more novel 2D anisotropic materials that as candidate materials for designing new electronic devices, optoelectronic devices, anisotropic magnetic devices, providing new possibilities for fundamental studies and achieving unprecedented structure-related device performance (Fig. 5).

    Fig. 5  Schematic of recent progress, future development and possible challenges in low-symmetry 2D materials.
    DownLoad: Full-Size Img PowerPoint

  • This work was supported by the National Natural Science Foundation of China (No. 51972007).

  • The authors declare no conflicts of interest.

  • The manuscript was drafted by Dr. Weiting Xu and revised by Prof. Shengxue Yang. All authors had approved the final version of the manuscript.

    • Author Biographies
  • Weiting Xu is currently a Ph.D. candidate under the supervision of Professor Shengxue Yang in the School of Materials Science and Engineering, Beihang University. She received her B.S. degree from Nanning Normal University in 2018 and her M.S. degree from Hunan University in 2021. Her research focuses on the synthesis of 2D materials and complex heterostructures, nanoelectronics.
    Shengxue Yang is currently a full professor of Beihang University. She received her Ph.D. degree in 2013 from Northeast Normal University. She was a postdoctoral fellow in the State Key Laboratory of Superlattice, Institute of Semiconductors, Chinese Academy of Sciences (2013–2015). Then, she was a visiting postdoctoral fellow at the University of California, Los Angeles with Prof. Xiangfeng Duan (2016–2017). She has authored over 50 peer-reviewed publications in international journals with an h-index of 30. Her research focuses on the synthesis, characterization, and device application of low-dimensional materials.
    • References
  • 1. L. Pi, C. Hu, W. Shen, L. Li, P. Luo, X. Hu, P. Chen, D. Li, Z. Li, X. Zhou, T. Zhai, Adv. Funct. Mater., 2021, 31, 2006774

    CrossRef Google Scholar

    2. Z. Shu, Q. Peng, P. Huang, Z. Xu, A. A. Suleiman, X. Zhang, X. Bai, X. Zhou, T. Zhai, Matter, 2020, 2, 977

    CrossRef Google Scholar

    3. H. Yuan, X. Liu, F. Afshinmanesh, W. Li, G. Xu, J. Sun, B. Lian, A. G. Curto, G. Ye, Y. Hikita, Z. Shen, S. C. Zhang, X. Chen, M. Brongersma, H. Y. Hwang, Y. Cui, Nat. Nanotechnol., 2015, 10, 707

    CrossRef Google Scholar

    4. R. Wang, F. Zhou, L. Lv, S. Zhou, Y. Yu, F. Zhuge, H. Li, L. Gan, T. Zhai, CCS Chem., 2019, 1, 268

    CrossRef Google Scholar

    5. Y. Zhang, H.-L. Yi, H.-P. Tan, ACS Photonics, 2018, 5, 3739

    CrossRef Google Scholar

    6. L. Li, W. Han, L. Pi, P. Niu, J. Han, C. Wang, B. Su, H. Li, J. Xiong, Y. Bando, T. Zhai, InfoMat., 2019, 1, 54

    CrossRef Google Scholar

    7. T. Low, R. Roldan, H. Wang, F. Xia, P. Avouris, L. M. Moreno, F. Guinea, Phys. Rev. Lett., 2014, 113, 106802

    CrossRef Google Scholar

    8. F. Xia, H. Wang, Y. Jia, Nat. Commun., 2014, 5, 4458

    CrossRef Google Scholar

    9. J. Qiao, X. Kong, Z. X. Hu, F. Yang, W. Ji, Nat. Commun., 2014, 5, 4475

    CrossRef Google Scholar

    10. H. Liu, A. T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tomanek, P. D. Ye, ACS Nano, 2014, 8, 4033

    CrossRef Google Scholar

    11. S. Yang, Y. Yang, M. Wu, C. Hu, W. Shen, Y. Gong, L. Huang, C. Jiang, Y. Zhang, P. M. Ajayan, Adv. Funct. Mater., 2018, 28, 1707379

    CrossRef Google Scholar

    12. S. Yang, C. Hu, M. Wu, W. Shen, S. Tongay, K. Wu, B. Wei, Z. Sun, C. Jiang, L. Huang, Z. Wang, ACS Nano, 2018, 12, 8798

    CrossRef Google Scholar

    13. S. Liu, Y. Chen, S. Yang, C. Jiang, Nano Res., 2022, 15, 1532

    CrossRef Google Scholar

    14. S. Yang, Y. Liu, M. Wu, L.-D. Zhao, Z. Lin, H.-c. Cheng, Y. Wang, C. Jiang, S.-H. Wei, L. Huang, Y. Huang, X. Duan, Nano Res., 2018, 11, 554

    CrossRef Google Scholar

    15. Y. Yang, S. C. Liu, X. Wang, Z. Li, Y. Zhang, G. Zhang, D. J. Xue, J. S. Hu, Adv. Funct. Mater., 2019, 29, 1900411

    CrossRef Google Scholar

    16. Y. Yang, S.-C. Liu, Y. Wang, M. Long, C.-M. Dai, S. Chen, B. Zhang, Z. Sun, Z. Sun, C. Hu, S. Zhang, L. Tong, G. Zhang, D.-J. Xue, J.-S. Hu, Adv. Optical Mater., 2019, 7, 1801311

    CrossRef Google Scholar

    17. Y. Yang, X. Wang, S. C. Liu, Z. Li, Z. Sun, C. Hu, D. J. Xue, G. Zhang, J. S. Hu, Adv. Sci., 2019, 6, 1801810

    CrossRef Google Scholar

    18. Y. Yang, S. C. Liu, Z. Li, D. J. Xue, J. S. Hu, Chem. Commun., 2021, 57, 565

    CrossRef Google Scholar

    19. Y. Yang, S. C. Liu, W. Yang, Z. Li, Y. Wang, X. Wang, S. Zhang, Y. Zhang, M. Long, G. Zhang, D. J. Xue, J. S. Hu, L. J. Wan, J. Am. Chem. Soc., 2018, 140, 4150

    CrossRef Google Scholar

    20. T. Zhang, Y. Wang, H. Li, F. Zhong, J. Shi, M. Wu, Z. Sun, W. Shen, B. Wei, W. Hu, X. Liu, L. Huang, C. Hu, Z. Wang, C. Jiang, S. Yang, Q. M. Zhang, Z. Qu, ACS Nano, 2019, 13, 11353

    CrossRef Google Scholar

    21. T. Zhang, Y. Zhang, M. Huang, B. Li, Y. Sun, Z. Qu, X. Duan, C. Jiang, S. Yang, Adv. Sci., 2022, 9, 2105483

    CrossRef Google Scholar

    22. Y. Liu, M. Wu, Z. Sun, S. Yang, C. Hu, L. Huang, W. Shen, B. Wei, Z. Wang, S. Yang, Y. Ye, Y. Li, C. Jiang, Nanoscale, 2019, 11, 23116

    CrossRef Google Scholar

    23. S. Yang, M. Wu, W. Shen, L. Huang, S. Tongay, K. Wu, B. Wei, Y. Qin, Z. Wang, C. Jiang, C. Hu, ACS Appl. Mater. Interfaces, 2019, 11, 3342

    CrossRef Google Scholar

    24. J. Dai, X. C. Zeng, Angew. Chem., 2015, 127, 7682

    CrossRef Google Scholar

    25. J. O. Island, R. Biele, M. Barawi, J. M. Clamagirand, J. R. Ares, C. Sanchez, H. S. van der Zant, I. J. Ferrer, R. D'Agosta, A. Castellanos-Gomez, Sci. Rep., 2016, 6, 22214

    CrossRef Google Scholar

    26. J. Shi, P. Yu, F. Liu, P. He, R. Wang, L. Qin, J. Zhou, X. Li, J. Zhou, X. Sui, S. Zhang, Y. Zhang, Q. Zhang, T. C. Sum, X. Qiu, Z. Liu, X. Liu, Adv. Mater., 2017, 29, 1701486

    CrossRef Google Scholar

    27. W. Xin, X. K. Li, X. L. He, B. W. Su, X. Q. Jiang, K. X. Huang, X. F. Zhou, Z. B. Liu, J. G. Tian, Adv. Mater., 2018, 30, 1704653

    CrossRef Google Scholar

    • Rights and permissions

  • This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

    • Relative Articles
  • Cited by
  • Supplements
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索
Export Citation
PDF view
DownLoad PDF 6474KB
XML

Figures(6)

Tables(1)

Information

Received Date:  30 April 2022
Revised Date:  27 June 2022
Accepted Date:  03 July 2022
Available Online:  18 July 2022
Publish Date:  26 December 2022

Article Metrics

Article views(3344) PDF downloads(1285) Citation(0)

Other Articles By Authors

2022 Vol. 1, No. 4
Article Contents
Abstract
1.   Introduction
2.   Crystal Structure of Low-symmetry 2D Materials
3.   Anisotropic Band Structure
4.   In-plane Anisotropic Physical Properties
5.   Optoelectronics Application
6.   Future Perspectives
Acknowledgements
Conflicts of interest
Author contributions
References

Catalog

Abstract
FullText(HTML)

  • 4.1   Anisotropic Optical Properties

  • 4.2   Anisotropic Electronic Transport

Author Biographies
References
Rights and permissions
Relative Articles
Cited by
Supplements

/

DownLoad:  Full-Size Img  PowerPoint
Return
  • Table 1.  The crystal structure and basic parameters of low-symmetry 2D materials.
    New material systemsMaterialsatomsSide viewTop viewCrystal systemSpace group
    group VIII-VI-type compoundsPdSe2orthorhombicPbca
    group IV-VI-type compoundsSnSeorthorhombicPnma
    GeSeorthorhombicPnma
    GeS2monoclinicP21/c
    GeSe2monoclinicP21/c
    transition metal oxyhalidesCrOClorthorhombicPmmn
    group III-VI-type compoundsTlSetetragonalI4/mcm
    group IV-V-type compoundsGeAsmonoclinicC2/m
    2D alloyNb(1−x)TixS3monoclinicP21/m
    Ge(1−x)SnxSe2monoclinicP21/c
     | Show Table
    DownLoad: CSV
qrcode