2D Materials最新文献

{"title":"Raman spectroscopy of atomically thin HfX2 (X=S, Se)","authors":"Chhor Yi Ly, Chenda Vong, Tharith Sriv, Hyeonsik Cheong","doi":"10.1088/2053-1583/ad70c8","DOIUrl":"https://doi.org/10.1088/2053-1583/ad70c8","url":null,"abstract":"We investigated interlayer modes of few-layer HfX₂ (X = S, Se) by using low-frequency micro-Raman spectroscopy with three excitation energies (1.96 eV, 2.33 eV, 2.54 eV) under vacuum condition (∼10⁻⁶Torr). We observed interlayer modes in HfSe₂ when the 2.54 eV excitation energy was used. The low-frequency Raman spectra reveal a series of shear and breathing modes (&lt;50 cm⁻¹) that are helpful for identifying the number of layers. The in-plane <italic toggle=\"yes\">E</italic>_g and out-of-plane <italic toggle=\"yes\">A</italic>_1g modes of HfSe₂ are located at ∼150 cm⁻¹ and ∼200 cm⁻¹, respectively. In HfS₂, in-plane <italic toggle=\"yes\">E</italic>_g and out-of-plane <italic toggle=\"yes\">A</italic>_1g optical phonons are observed at ∼260 cm⁻¹ and ∼337 cm^−1, respectively. The in-plane and out-of-plane force constants of atomically thin HfSe₂ are obtained to be 1.87 × 10¹⁹N m⁻³ and 6.55 × 10¹⁹N m⁻³, respectively, by fitting the observed interlayer modes using the linear chain model. These results provide valuable information on materials parameters for device designs using atomically-thin layered HfX₂ (X = S, Se).","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetoresistance in two-dimensional materials and van der Waals heterostructures","authors":"Na Xin","doi":"10.1088/2053-1583/ad70c7","DOIUrl":"https://doi.org/10.1088/2053-1583/ad70c7","url":null,"abstract":"Magnetoresistance (MR) refers to the alteration in electrical resistance within a material when influenced by a magnetic field. Studying MR at the atomic level holds a significant interest both in fundamental research and practical applications. Atomically thin two-dimensional (2D) van der Waals materials and their heterostructures offer an unprecedented platform to investigate MR, thanks to the very broad range of properties and no requirement for lattice matching. Here, we review the various mechanisms of MR effect in 2D materials and their heterostructures, including tunneling MR, extremely large unsaturated MR, layer MR, and colossal MR, as well as explore their potential in device applications. Furthermore, we discuss the limitations and main challenges that still exist for the development of practical devices based on MR and provide our considerations towards real applications.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropic effects in two-dimensional materials","authors":"Alexander N Rudenko, Mikhail I Katsnelson","doi":"10.1088/2053-1583/ad64e1","DOIUrl":"https://doi.org/10.1088/2053-1583/ad64e1","url":null,"abstract":"Among a huge variety of known two-dimensional (2D) materials, some of them have anisotropic crystal structures; examples include different systems such as a few-layer black phosphorus (phosphorene), beryllium nitride BeN₄, the van der Waals magnet CrSBr, and rhenium dichalcogenides ReX₂. As a consequence, their optical and electronic properties are highly anisotropic as well. In some cases, the anisotropy results in not only smooth renormalization of observable properties in comparison with the isotropic case, but in the appearance of dramatically new physics. The examples are hyperbolic plasmons and excitons, strongly anisotropic ordering of adatoms at the surface of 2D or van der Waals materials, and essential changes in transport and superconducting properties. Here, we present a systematic review of the electronic structure, transport, and optical properties of several representative groups of anisotropic 2D materials, including semiconductors, anisotropic Dirac and semi-Dirac materials, and superconductors.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optical control of berry curvature in gated WSe2 bilayers","authors":"Majeed Ur Rehman, Zia Ur Rahman, Azizur Rahman, Waqas Ahmad, Sadeeq Ullah","doi":"10.1088/2053-1583/ad6ba2","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6ba2","url":null,"abstract":"Unlike single layers of 2H transition metal dichalcogenides (TMDCs), bilayers of 2H TMDCs maintain inversion and time reversal (TR) symmetries, resulting in a vanishing Berry curvature (<inline-formula>\u0000<tex-math><?CDATA $Omega(k)sim0)$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">Ω</mml:mi><mml:mo stretchy=\"false\">(</mml:mo><mml:mi>k</mml:mi><mml:mo stretchy=\"false\">)</mml:mo><mml:mo>∼</mml:mo><mml:mn>0</mml:mn><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href=\"tdmad6ba2ieqn1.gif\"></inline-graphic></inline-formula> that inhibits various potential transport phenomena. A nonzero Berry curvature <inline-formula>\u0000<tex-math><?CDATA $(Omega(k)neq0)$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mo stretchy=\"false\">(</mml:mo><mml:mi mathvariant=\"normal\">Ω</mml:mi><mml:mo stretchy=\"false\">(</mml:mo><mml:mi>k</mml:mi><mml:mo stretchy=\"false\">)</mml:mo><mml:mo>≠</mml:mo><mml:mn>0</mml:mn><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href=\"tdmad6ba2ieqn2.gif\"></inline-graphic></inline-formula> is imperative for the occurrence of several unconventional transport phenomena, including the anomalous Hall effect and the anomalous Nernst effect. To overcome this limitation, we break these symmetries in bilayer TMDCs using electrostatic gating and circularly polarized light as external means. For non-gated WSe₂ bilayers, circularly polarized light breaks TR symmetry, creating a finite Berry curvature signal in both conduction and valence bands, controllable by light intensity and its polarity. In gated WSe₂ bilayers, where inversion symmetry is also broken, we observe a sign reversal in Berry curvature within the conduction bands, the extent of which depends on the relative strengths of the electric gating and light intensity. Overall, under finite bias and light intensity, the 2H bilayers of WSe₂ exhibits finite spin Hall, valley Hall, and anomalous Hall conductivities, which depend on the strengths of the applied perturbations.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The importance of interlaboratory studies for robust measurements of graphene and other 2D materials","authors":"Keith R Paton, Andrew J Pollard","doi":"10.1088/2053-1583/ad6911","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6911","url":null,"abstract":"This perspective article presents the current state of interlaboratory studies in graphene and other 2D materials. These interlaboratory studies are mostly coordinated via the Versailles Project on Advanced Materials and Standards and are crucial in establishing robust and validated protocols for measuring key properties of these materials. These protocols can then be included in international documentary standards. We summarise the key findings of completed studies and outline the approach of those that are currently underway. An outline of future needs is also presented, highlighting gaps in the current scope of activities and therefore where the focus of future studies should be.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orbital magnetization in two-dimensional materials from high-throughput computational screening","authors":"Martin Ovesen, Thomas Olsen","doi":"10.1088/2053-1583/ad6ba3","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6ba3","url":null,"abstract":"We calculate the orbital magnetization of 822 two-dimensional magnetic materials from the Computational 2D Materials Database (C2DB). For compounds containing 5<italic toggle=\"yes\">d</italic> elements we find orbital moments of the order of 0.3–0.5 <inline-formula>\u0000<tex-math><?CDATA $mu_{mathrm{B}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>μ</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">B</mml:mi></mml:mrow></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"tdmad6ba3ieqn1.gif\"></inline-graphic></inline-formula>, which points to the necessity of including these in any type of magnetic modeling and comparison with experiments. It is also shown that the alignment of orbital moments with respect to the spin largely follows the predictions from Hund’s rule and that deviations may be explained by the <italic toggle=\"yes\">d</italic>-band splitting originating from the crystal field—for example in the important case of CrI₃. Finally, we show that for certain insulators, Hubbard corrections may lead to large and fully unquenched orbital moments that are pinned to the lattice rather than the spin and that these moments can lead to enormous magnetic anisotropies. Such unquenched ground states are only found from density functional theory calculations that include both Hubbard corrections and self-consistent spin–orbit coupling and largely invalidates the use of the magnetic force theorem for calculating magnetic anisotropies.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Perspectives on 2D materials for hybrid and beyond-Si image sensor applications","authors":"Haochuan Wan, Zhihao Xu, Yiheng Zhang, Junyi Zhao, Chuan Wang","doi":"10.1088/2053-1583/ad6912","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6912","url":null,"abstract":"The complementary metal–oxide–semiconductor (CMOS) image sensor has become essential and ubiquitous in our daily lives as it is present in almost every pocket. As demand for compact, multifunction, and high-efficiency Internet of Things applications continues to rise, novel configuration designs and manufacturing methods, such as neural network integration and 3D stacking have been implemented to enhance the CMOS image sensor’s (CIS) performance. However, the progress of image sensors based on silicon CMOS technology would eventually be limited by the intrinsic optical, electrical, and mechanical properties of silicon material. This has led to the exploration of two-dimensional materials (2DMs) and the emergence of 2DMs as promising candidates for the next generation of optoelectronic devices. In this article, we discuss the current advancements and challenges associated with silicon CISs and the potential benefits of incorporating 2DMs in the image sensor. We highlight three critical opportunities for 2DMs, including Si CMOS/2DMs hybrid structure and direct growth techniques of 2DMs on Si for back-end-of-line integration, 2DMs-based neuromorphic photodetectors (PDs) and optical neural networks for in-image-sensor-processing, and curved image sensor based on 2DMs PDs for bionic detection. With the growing maturity of 2DM technologies, we anticipate that the device scaling and the increase of integration density of 2DM electronics in the image sensor will continue, leading to the development of highly efficient, compact, intelligent, and versatile 2DM image sensors in the near future.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Valley landau level crossings in weakly coupled bilayer WSe2","authors":"Shiwei Li, Xinyu Cao, Qi Zhang, Yan Huang, Guangli Kuang, Chuanying Xi, Kenji Watanabe, Takashi Taniguchi, Geliang Yu, Lei Wang","doi":"10.1088/2053-1583/ad6b80","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6b80","url":null,"abstract":"WSe₂ is a p-type 2D-semiconductor that can be mechanically exfoliated down to atomic layers. Unlike the Bernal stacked bilayer graphene, the two layers in a bilayer WSe₂ flake are weakly coupled. The electric displacement field can easily break the layer degeneracy of the bilayer WSe₂. Together with the strong spin–orbit coupling, it exhibits many novel quantum physical properties. In this work, we fabricate high quality dual-gated bilayer WSe₂ devices and observe twofold degenerate Landau levels(LLs) and density-dependent quantum Hall states which show transitions between even and odd filling. When introducing carriers into the system from the valence band edge by gating, two WSe₂ layers are filled independently and the bottom layer WSe₂ shows negative compressibility at the crossover point. Above 9 T, we observe the degeneracy of LLs is completely broken and there are two sets of LL crossings in the top WSe₂ layer at Zeeman-to-cyclotron energy ratio <inline-formula>\u0000<tex-math><?CDATA $E_Z/E_N$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>E</mml:mi><mml:mi>Z</mml:mi></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>E</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"tdmad6b80ieqn1.gif\"></inline-graphic></inline-formula> ≈ 4 and <inline-formula>\u0000<tex-math><?CDATA $E_Z/E_N$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>E</mml:mi><mml:mi>Z</mml:mi></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>E</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"tdmad6b80ieqn2.gif\"></inline-graphic></inline-formula> ≈ 5. The interplay between two LLs from the two WSe₂ layers confirms the weak coupling between them. Our results show that the bilayer WSe₂ behave like two closely packed independent electronic systems under electric displacement fields.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduced graphene oxide-modified electrodes via fused deposition modeling 3D printing for hydrogen peroxide sensor","authors":"Yan Dou, Rui Dai, Haofan Sun, Kun Bi, Xin Zhao and Qiong Nian","doi":"10.1088/2053-1583/ad6910","DOIUrl":"https://doi.org/10.1088/2053-1583/ad6910","url":null,"abstract":"Fused deposition modeling 3D printing provides a cost-effective and streamlined method for producing electrochemical sensors, overcoming the challenges associated with material selection, complex fabrication processes, and reproducibility issues. This study introduces an innovative approach utilizing a dual-printer setup to simplify the manufacturing of sensor electrodes. A critical enhancement in this process is the surface modification with reduced graphene oxide (rGO), which not only improves the electrochemical characteristics but also induces a wrinkled structure on the 3D printed surface. These wrinkles significantly increase the surface area, directly boosting the electrode’s electrochemical performance. Comprehensive characterization of the electrode surfaces, both before and after rGO modification, demonstrates a substantial increase in sensitivity, with a fortyfold improvement observed in hydrogen peroxide (H2O2) amperometric measurements. This breakthrough paves the way for advanced applications in 3D printed electrochemical sensors.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":5.5,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust large-gap quantum spin Hall states in stabilized bismuthene on Si(111)-α-√3×√3-Au","authors":"B. M. Llona, Hsin-Lei Chou, Liang-Wei Lan, Shih-Yu Wu, Chia-Hsiu Hsu, F. Chuang, Hsin Lin, Chien-Cheng Kuo","doi":"10.1088/2053-1583/ad64e4","DOIUrl":"https://doi.org/10.1088/2053-1583/ad64e4","url":null,"abstract":"\u0000 Bismuthene is a promising large-gap two-dimensional topological material with potential applications in quantum devices. However, fabricating a stable bismuthene on a substrate that preserves its edge states and large energy gap at room temperature has been challenging. In this study, we successfully stabilized bismuthene on the 2D electron gas Si(111)-α-√3×√3-Au surface despite its delicate atomic structures, enabling direct access to its quantum spin Hall states. Scanning tunneling microscopy (STM) with localized dI/dV mapping on in-situ prepared structures revealed that the bismuthene surface exhibits a stable, shallow-buckled, insulative interior and an almost planar metallic edge. We found a 0.75 eV-bandgap throughout the interior and a closing gap at the island’s boundary. By using island-based differential conductance mapping, we identified localized edge states and the Dirac point at an energy of −0.10 eV within the bandgap. These results support the 2D-TI nature of bismuthene in Au / Si(111), paving the way for the development of bismuthene-based quantum devices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":null,"pages":null},"PeriodicalIF":4.5,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141825415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}