Pub Date : 2024-08-30DOI: 10.1088/2053-1583/ad70c8
Chhor Yi Ly, Chenda Vong, Tharith Sriv, Hyeonsik Cheong
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 (<50 cm−1) that are helpful for identifying the number of layers. The in-plane Eg and out-of-plane A1g modes of HfSe2 are located at ∼150 cm−1 and ∼200 cm−1, respectively. In HfS2, in-plane Eg and out-of-plane A1g 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).
{"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 HfX<sub>2</sub> (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<sup>−6</sup>Torr). We observed interlayer modes in HfSe<sub>2</sub> when the 2.54 eV excitation energy was used. The low-frequency Raman spectra reveal a series of shear and breathing modes (<50 cm<sup>−1</sup>) that are helpful for identifying the number of layers. The in-plane <italic toggle=\"yes\">E</italic><sub>g</sub> and out-of-plane <italic toggle=\"yes\">A</italic><sub>1g</sub> modes of HfSe<sub>2</sub> are located at ∼150 cm<sup>−1</sup> and ∼200 cm<sup>−1</sup>, respectively. In HfS<sub>2</sub>, in-plane <italic toggle=\"yes\">E</italic><sub>g</sub> and out-of-plane <italic toggle=\"yes\">A</italic><sub>1g</sub> optical phonons are observed at ∼260 cm<sup>−1</sup> and ∼337 cm<sup>−1,</sup> respectively. The in-plane and out-of-plane force constants of atomically thin HfSe<sub>2</sub> are obtained to be 1.87 × 10<sup>19</sup>N m<sup>−3</sup> and 6.55 × 10<sup>19</sup>N m<sup>−3</sup>, 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 HfX<sub>2</sub> (X = S, Se).","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"45 1","pages":""},"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}
Pub Date : 2024-08-30DOI: 10.1088/2053-1583/ad70c9
Tong Tong, Yongli He, Yuan Gao, Yukang Liu, Kan Liao, Weisheng Li
Hybrid systems coupling two-dimensional (2D) semiconductors with functional ferroelectrics are attracting increasing attention owing to their excellent electronic/optoelectronic properties and new functionalities through the multiple heterointerface interactions. In our device architecture, interfacial states are introduced on the ferroelectric Hf0.5Zr0.5O2 thin film as a gate dielectric layer for the charge trapping effect. Utilizing the collaborative effects of charge trapping and ferroelectric polarization behavior, a multifunctional 2D WSe2/HZO memtransistor is demonstrated with an ultra-low off-state (dark) current of 10−13 A, high on/off ratio of 106 and linear conductance update. This device exhibits reliable memory properties and tunable synaptic functions including short-term plasticity/long-term plasticity, paired pulse facilitation, spike-timing dependent plasticity, synaptic potentiation/depression, and filtering in a single device. Extensive endurance tests ensure robust stability (1000 switching cycles, 2000 s holding time) and the synaptic weight update in the device exhibits excellent linearity. Based on the experimental data, our devices eventually achieve an accuracy of 94.8% in artificial neural network simulations. These results highlight a new approach for constructing hybrid systems coupling 2D semiconductors with functional ferroelectrics in a single device to tune synaptic weight, optimize circuit design, and build artificial neuromorphic computing systems.
{"title":"Reconfigurable dielectric engineered WSe2/HZO mem-transistor","authors":"Tong Tong, Yongli He, Yuan Gao, Yukang Liu, Kan Liao, Weisheng Li","doi":"10.1088/2053-1583/ad70c9","DOIUrl":"https://doi.org/10.1088/2053-1583/ad70c9","url":null,"abstract":"Hybrid systems coupling two-dimensional (2D) semiconductors with functional ferroelectrics are attracting increasing attention owing to their excellent electronic/optoelectronic properties and new functionalities through the multiple heterointerface interactions. In our device architecture, interfacial states are introduced on the ferroelectric Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> thin film as a gate dielectric layer for the charge trapping effect. Utilizing the collaborative effects of charge trapping and ferroelectric polarization behavior, a multifunctional 2D WSe<sub>2</sub>/HZO memtransistor is demonstrated with an ultra-low off-state (dark) current of 10<sup>−13</sup> A, high on/off ratio of 10<sup>6</sup> and linear conductance update. This device exhibits reliable memory properties and tunable synaptic functions including short-term plasticity/long-term plasticity, paired pulse facilitation, spike-timing dependent plasticity, synaptic potentiation/depression, and filtering in a single device. Extensive endurance tests ensure robust stability (1000 switching cycles, 2000 s holding time) and the synaptic weight update in the device exhibits excellent linearity. Based on the experimental data, our devices eventually achieve an accuracy of 94.8% in artificial neural network simulations. These results highlight a new approach for constructing hybrid systems coupling 2D semiconductors with functional ferroelectrics in a single device to tune synaptic weight, optimize circuit design, and build artificial neuromorphic computing systems.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"294 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198541","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}
Pub Date : 2024-08-29DOI: 10.1088/2053-1583/ad70c7
Na Xin
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.
{"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":"74 1","pages":""},"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}
Pub Date : 2024-08-27DOI: 10.1088/2053-1583/ad64e1
Alexander N Rudenko, Mikhail I Katsnelson
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.
{"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 BeN<sub>4</sub>, the van der Waals magnet CrSBr, and rhenium dichalcogenides ReX<sub>2</sub>. 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":"43 1","pages":""},"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}
Pub Date : 2024-08-27DOI: 10.1088/2053-1583/ad6ba2
Majeed Ur Rehman, Zia Ur Rahman, Azizur Rahman, Waqas Ahmad, Sadeeq Ullah
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 (Ω(k)∼0) that inhibits various potential transport phenomena. A nonzero Berry curvature (Ω(k)≠0) 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.
{"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 WSe<sub>2</sub> 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 WSe<sub>2</sub> 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 WSe<sub>2</sub> 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":"134 1","pages":""},"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}
Pub Date : 2024-08-23DOI: 10.1088/2053-1583/ad6911
Keith R Paton, Andrew J Pollard
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.
{"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":"14 1","pages":""},"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}
Pub Date : 2024-08-22DOI: 10.1088/2053-1583/ad6ba3
Martin Ovesen, Thomas Olsen
We calculate the orbital magnetization of 822 two-dimensional magnetic materials from the Computational 2D Materials Database (C2DB). For compounds containing 5d elements we find orbital moments of the order of 0.3–0.5 μB, 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 d-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.
{"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 CrI<sub>3</sub>. 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":"45 1","pages":""},"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}
Pub Date : 2024-08-14DOI: 10.1088/2053-1583/ad6912
Haochuan Wan, Zhihao Xu, Yiheng Zhang, Junyi Zhao, Chuan Wang
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.
{"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":"61 1","pages":""},"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}
Pub Date : 2024-08-14DOI: 10.1088/2053-1583/ad6b80
Shiwei Li, Xinyu Cao, Qi Zhang, Yan Huang, Guangli Kuang, Chuanying Xi, Kenji Watanabe, Takashi Taniguchi, Geliang Yu, Lei Wang
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 EZ/EN ≈ 4 and EZ/EN ≈ 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.
{"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":"WSe<sub>2</sub> 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 WSe<sub>2</sub> flake are weakly coupled. The electric displacement field can easily break the layer degeneracy of the bilayer WSe<sub>2</sub>. Together with the strong spin–orbit coupling, it exhibits many novel quantum physical properties. In this work, we fabricate high quality dual-gated bilayer WSe<sub>2</sub> 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 WSe<sub>2</sub> layers are filled independently and the bottom layer WSe<sub>2</sub> 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 WSe<sub>2</sub> 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 WSe<sub>2</sub> layers confirms the weak coupling between them. Our results show that the bilayer WSe<sub>2</sub> behave like two closely packed independent electronic systems under electric displacement fields.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"26 1","pages":""},"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}
Pub Date : 2024-08-08DOI: 10.1088/2053-1583/ad6910
Yan Dou, Rui Dai, Haofan Sun, Kun Bi, Xin Zhao and Qiong Nian
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.
熔融沉积建模三维打印技术为生产电化学传感器提供了一种经济高效的简化方法，克服了与材料选择、复杂制造工艺和可重复性问题相关的挑战。本研究介绍了一种利用双打印机设置简化传感器电极制造的创新方法。该工艺的一个关键改进是使用还原氧化石墨烯（rGO）进行表面改性，这不仅能改善电化学特性，还能在 3D 打印表面形成褶皱结构。这些皱纹大大增加了表面积，直接提高了电极的电化学性能。对电极表面进行的全面表征（包括 rGO 修饰前后）表明，电极的灵敏度大幅提高，过氧化氢（H2O2）安培测量的灵敏度提高了 40 倍。这一突破为 3D 打印电化学传感器的先进应用铺平了道路。
{"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":"22 1","pages":""},"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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：