Publications
2025 |
Verzhbitskiy, Ivan A; Mishra, Abhishek; Mitra, Sanchali; Zhang, Zhepeng; Das, Sarthak; Lau, Chit Siong; Lee, Rainer; Huang, Ding; Eda, Goki; Ang, Yee Sin; Goh, Kuan Eng Johnson Low-Temperature Contacts and the Coulomb Blockade Effect in Layered Nanoribbons with In-Plane Anisotropy Journal Article ACS NANO, 2025, ISSN: 1936-0851. @article{ISI:001445756900001, title = {Low-Temperature Contacts and the Coulomb Blockade Effect in Layered Nanoribbons with In-Plane Anisotropy}, author = {Ivan A Verzhbitskiy and Abhishek Mishra and Sanchali Mitra and Zhepeng Zhang and Sarthak Das and Chit Siong Lau and Rainer Lee and Ding Huang and Goki Eda and Yee Sin Ang and Kuan Eng Johnson Goh}, doi = {10.1021/acsnano.4c15086}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-03-13}, journal = {ACS NANO}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {One-dimensional (1D) nanoribbons (NRs) constitute rapidly advancing nanotechnology with significant potential for emerging applications such as quantum sensing and metrology. TiS3 nanoribbons exhibit strong in-plane crystal anisotropy, enabling robust 1D confinement and resilience to edge disorder. Nevertheless, charge transport in 1D TiS3 remains relatively unexplored, particularly at low temperatures, where high contact resistance impacts device performance and fundamentally limits its applications. Here, we engineer electrical contacts between a bulk metal and a 1D NR and explore the low-temperature characteristics of the 1D field-effect devices. We report ohmic contacts for 1D TiS3 with temperature-independent contact resistances as low as 2.7 +/- 0.3 k Omega keywords = {}, pubstate = {published}, tppubtype = {article} } One-dimensional (1D) nanoribbons (NRs) constitute rapidly advancing nanotechnology with significant potential for emerging applications such as quantum sensing and metrology. TiS3 nanoribbons exhibit strong in-plane crystal anisotropy, enabling robust 1D confinement and resilience to edge disorder. Nevertheless, charge transport in 1D TiS3 remains relatively unexplored, particularly at low temperatures, where high contact resistance impacts device performance and fundamentally limits its applications. Here, we engineer electrical contacts between a bulk metal and a 1D NR and explore the low-temperature characteristics of the 1D field-effect devices. We report ohmic contacts for 1D TiS3 with temperature-independent contact resistances as low as 2.7 +/- 0.3 k Omega |
Liu, Xiongfang; Yang, Tong; Chen, Shanquan; Wu, Jing; Tang, Chi Sin; Ning, Yuanjie; Chen, Zuhuang; Dai, Liang; Sun, Mengxia; Chen, Mingyao; Han, Kun; Zhou, Difan; Zeng, Shengwei; Sun, Shuo; Li, Sensen; Yang, Ming; Breese, Mark B H; Cai, Chuanbing; Venkatesan, Thirumalai; Wee, Andrew T S; Yin, Xinmao Small polarons mediated near-room-temperature metal-insulator transition in vanadium dioxide and their hopping dynamics Journal Article APPLIED PHYSICS REVIEWS, 12 (1), 2025, ISSN: 1931-9401. @article{ISI:001403236800001, title = {Small polarons mediated near-room-temperature metal-insulator transition in vanadium dioxide and their hopping dynamics}, author = {Xiongfang Liu and Tong Yang and Shanquan Chen and Jing Wu and Chi Sin Tang and Yuanjie Ning and Zuhuang Chen and Liang Dai and Mengxia Sun and Mingyao Chen and Kun Han and Difan Zhou and Shengwei Zeng and Shuo Sun and Sensen Li and Ming Yang and Mark B H Breese and Chuanbing Cai and Thirumalai Venkatesan and Andrew T S Wee and Xinmao Yin}, doi = {10.1063/5.0236807}, times_cited = {0}, issn = {1931-9401}, year = {2025}, date = {2025-03-01}, journal = {APPLIED PHYSICS REVIEWS}, volume = {12}, number = {1}, publisher = {AIP Publishing}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {Researchers pursuing advanced photoelectric devices have discovered near room-temperature metal-insulator transitions (MIT) in nonvolatile VO2. Despite theoretical investigations suggesting that polaron dynamics mediate the MIT, direct experimental evidence remains scarce. In this study, we present direct evidence of the polaron state in insulating VO2 through high-resolution spectroscopic ellipsometry measurements and first-principles calculations. We illustrate the complementary role of polaron dynamics in facilitating Peierls and Mott transitions, thereby contributing to the MIT processes. Furthermore, our observations and characterizations of conventional metallic and correlated plasmons in the respective phases of the VO2 film offer valuable insight into their electron structures. This investigation enhances comprehension of the MIT mechanism in correlated systems and underscores the roles of polarons, lattice distortions, and electron correlations in facilitating phase transition processes in strongly correlated systems. Additionally, the detailed detection of small polarons and plasmons serves as inspiration for the development of new device functionalities.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Researchers pursuing advanced photoelectric devices have discovered near room-temperature metal-insulator transitions (MIT) in nonvolatile VO2. Despite theoretical investigations suggesting that polaron dynamics mediate the MIT, direct experimental evidence remains scarce. In this study, we present direct evidence of the polaron state in insulating VO2 through high-resolution spectroscopic ellipsometry measurements and first-principles calculations. We illustrate the complementary role of polaron dynamics in facilitating Peierls and Mott transitions, thereby contributing to the MIT processes. Furthermore, our observations and characterizations of conventional metallic and correlated plasmons in the respective phases of the VO2 film offer valuable insight into their electron structures. This investigation enhances comprehension of the MIT mechanism in correlated systems and underscores the roles of polarons, lattice distortions, and electron correlations in facilitating phase transition processes in strongly correlated systems. Additionally, the detailed detection of small polarons and plasmons serves as inspiration for the development of new device functionalities. |
Loh, Leyi; Ning, Shoucong; Kieczka, Daria; Chen, Yuan; Yang, Jianmin; Wang, Zhe; Pennycook, Stephen J; Eda, Goki; Shluger, Alexander L; Bosman, Michel Electron Ptychography for Atom-by-Atom Quantification of 1D Defect Complexes in Monolayer MoS2 Journal Article ACS NANO, 19 (6), pp. 6195-6208, 2025, ISSN: 1936-0851. @article{ISI:001416560700001, title = {Electron Ptychography for Atom-by-Atom Quantification of 1D Defect Complexes in Monolayer MoS_{2}}, author = {Leyi Loh and Shoucong Ning and Daria Kieczka and Yuan Chen and Jianmin Yang and Zhe Wang and Stephen J Pennycook and Goki Eda and Alexander L Shluger and Michel Bosman}, doi = {10.1021/acsnano.4c14988}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-02-07}, journal = {ACS NANO}, volume = {19}, number = {6}, pages = {6195-6208}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Defect complexes can induce beneficial functionalities in two-dimensional (2D) semiconductors. However, understanding their formation mechanism with single-atom sensitivity has proven to be challenging for light elements using conventional transmission electron microscopy (TEM) techniques. Here, we demonstrate the atom-resolved formation of various one-dimensional (1D) defect complexes-consisting of rhenium dopants, sulfur interstitials, and sulfur vacancies-in monolayer MoS2 by applying electron ptychography to our four-dimensional scanning transmission electron microscopy (4D-STEM) data sets. Our image resolution of 0.35 angstrom and a spatial precision of 2 pm allow us to achieve accurate matching between experimental structures and density functional theory (DFT) simulations at the atomic level. Additionally, we utilize out-of-focus ptychography to observe defect formation processes at dose rates comparable to those used in conventional TEM imaging, while maintaining a large field of view. This study demonstrates the systematic application of electron ptychography to extensive 4D-STEM data sets for quantitative defect imaging in 2D materials. We provide direct, atomically precise evidence that critical defect densities govern the formation of extended 1D defect complexes. For instance, we show that sulfur single-vacancy lines form when the vacancy density reaches 5 x 1013 cm-2 and transform into double-vacancy lines beyond 8 x 1013 cm-2. Rhenium-dopant lines emerge at a dopant concentration higher than 3 x 1013 cm-2, where metastable sulfur interstitial-vacancy lines also form as the cumulative electron dose reaches 3 x 105 e/angstrom 2, initiating a local nucleation of the 1T ' phase. Our results highlight the potential of electron ptychography for high-precision defect characterization and engineering in ultrathin 2D materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Defect complexes can induce beneficial functionalities in two-dimensional (2D) semiconductors. However, understanding their formation mechanism with single-atom sensitivity has proven to be challenging for light elements using conventional transmission electron microscopy (TEM) techniques. Here, we demonstrate the atom-resolved formation of various one-dimensional (1D) defect complexes-consisting of rhenium dopants, sulfur interstitials, and sulfur vacancies-in monolayer MoS2 by applying electron ptychography to our four-dimensional scanning transmission electron microscopy (4D-STEM) data sets. Our image resolution of 0.35 angstrom and a spatial precision of 2 pm allow us to achieve accurate matching between experimental structures and density functional theory (DFT) simulations at the atomic level. Additionally, we utilize out-of-focus ptychography to observe defect formation processes at dose rates comparable to those used in conventional TEM imaging, while maintaining a large field of view. This study demonstrates the systematic application of electron ptychography to extensive 4D-STEM data sets for quantitative defect imaging in 2D materials. We provide direct, atomically precise evidence that critical defect densities govern the formation of extended 1D defect complexes. For instance, we show that sulfur single-vacancy lines form when the vacancy density reaches 5 x 1013 cm-2 and transform into double-vacancy lines beyond 8 x 1013 cm-2. Rhenium-dopant lines emerge at a dopant concentration higher than 3 x 1013 cm-2, where metastable sulfur interstitial-vacancy lines also form as the cumulative electron dose reaches 3 x 105 e/angstrom 2, initiating a local nucleation of the 1T ' phase. Our results highlight the potential of electron ptychography for high-precision defect characterization and engineering in ultrathin 2D materials. |
Jiang, Yingying; Wong, Zicong Marvin; Yan, Hongwei; Tan, Teck Leong; Mirsaidov, Utkur Revealing Multistep Phase Separation in Metal Alloy Nanoparticles with In Situ Transmission Electron Microscopy Journal Article ACS NANO, 19 (3), pp. 3886-3894, 2025, ISSN: 1936-0851. @article{ISI:001396476700001, title = {Revealing Multistep Phase Separation in Metal Alloy Nanoparticles with \textit{In Situ} Transmission Electron Microscopy}, author = {Yingying Jiang and Zicong Marvin Wong and Hongwei Yan and Teck Leong Tan and Utkur Mirsaidov}, doi = {10.1021/acsnano.4c16095}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-01-14}, journal = {ACS NANO}, volume = {19}, number = {3}, pages = {3886-3894}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Phase separation plays a crucial role in many natural and industrial processes, such as the formation of clouds and minerals and the distillation of crude oil. In metals and alloys, phase separation is an important approach often utilized to improve their mechanical strength for use in construction, automobile, and aerospace manufacturing. Despite its importance in many processes, the atomic details of phase separation are largely unknown. In particular, it is unclear how a different crystal phase emerges from the parent alloy. Here, using real-time in situ transmission electron microscopy, we describe the stages of the phase separation in face-centered cubic (fcc) AuRu alloy nanoparticles, resulting in a Ru phase with a hexagonal close-packed (hcp) crystal structure. Our observation reveals that the hcp Ru phase forms in two steps: the spinodal decomposition of the alloy produces metastable fcc Ru clusters, and as they grow larger, these clusters transform into hcp Ru domains. Our calculations indicate that the primary reason for the fcc-to-hcp transformation is the size-dependent competition between the interfacial and bulk energies of Ru domains. These insights into elusive, transient steps in the phase separation of alloys can aid in engineering nanomaterials with unconventional phases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Phase separation plays a crucial role in many natural and industrial processes, such as the formation of clouds and minerals and the distillation of crude oil. In metals and alloys, phase separation is an important approach often utilized to improve their mechanical strength for use in construction, automobile, and aerospace manufacturing. Despite its importance in many processes, the atomic details of phase separation are largely unknown. In particular, it is unclear how a different crystal phase emerges from the parent alloy. Here, using real-time in situ transmission electron microscopy, we describe the stages of the phase separation in face-centered cubic (fcc) AuRu alloy nanoparticles, resulting in a Ru phase with a hexagonal close-packed (hcp) crystal structure. Our observation reveals that the hcp Ru phase forms in two steps: the spinodal decomposition of the alloy produces metastable fcc Ru clusters, and as they grow larger, these clusters transform into hcp Ru domains. Our calculations indicate that the primary reason for the fcc-to-hcp transformation is the size-dependent competition between the interfacial and bulk energies of Ru domains. These insights into elusive, transient steps in the phase separation of alloys can aid in engineering nanomaterials with unconventional phases. |
Carrio, Juan A G; Donato, Ricardo K; Carvalho, Alexandra; Koon, Gavin K W; Donato, Katarzyna Z; Yau, Xin Hui; Kosiachevskyi, Dmytro; Lim, Karen; Ravi, Vedarethinam; Joy, Josny; Goh, Kelda; Emiliano, Jose Vitorio; Lombardi, Jerome E; Neto, Castro A H From 2D kaolinite to 3D amorphous cement Journal Article SCIENTIFIC REPORTS, 15 (1), 2025, ISSN: 2045-2322. @article{ISI:001396241000050, title = {From 2D kaolinite to 3D amorphous cement}, author = {Juan A G Carrio and Ricardo K Donato and Alexandra Carvalho and Gavin K W Koon and Katarzyna Z Donato and Xin Hui Yau and Dmytro Kosiachevskyi and Karen Lim and Vedarethinam Ravi and Josny Joy and Kelda Goh and Jose Vitorio Emiliano and Jerome E Lombardi and Castro A H Neto}, doi = {10.1038/s41598-024-81882-1}, times_cited = {0}, issn = {2045-2322}, year = {2025}, date = {2025-01-11}, journal = {SCIENTIFIC REPORTS}, volume = {15}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Kaolinite is a single 2D layer of kaolin or metakaolin (MK), common clays that can be characterized as layered 3D materials. We show that because of its chemical composition, kaolinite can be converted into an amorphous 3D material by chemical means. This dimensional transformation is possible due to the large surface to volume ratio and chemical reactivity of kaolinite. We investigate the formation and influence of quasi- or nanocrystalline phases in MK-based alkali-activated materials (AAM) that are related to the Si/Al ratio. We analyze the formation of an AAM from a MK precursor, which is a 3D bonded network that preserves the layered structure at the nanometer scale. We also exfoliate the remaining layered phase to examine the effects of the alkali-activation in the final sheet structures embedded within the amorphous network. The final material can be used as a cement with no carbon dioxide produced by the transformation reaction.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Kaolinite is a single 2D layer of kaolin or metakaolin (MK), common clays that can be characterized as layered 3D materials. We show that because of its chemical composition, kaolinite can be converted into an amorphous 3D material by chemical means. This dimensional transformation is possible due to the large surface to volume ratio and chemical reactivity of kaolinite. We investigate the formation and influence of quasi- or nanocrystalline phases in MK-based alkali-activated materials (AAM) that are related to the Si/Al ratio. We analyze the formation of an AAM from a MK precursor, which is a 3D bonded network that preserves the layered structure at the nanometer scale. We also exfoliate the remaining layered phase to examine the effects of the alkali-activation in the final sheet structures embedded within the amorphous network. The final material can be used as a cement with no carbon dioxide produced by the transformation reaction. |
Jin, Shangjian; Foo, Darryl C W; Qu, Tingyu; Ozyilmaz, Barbaros; Adam, Shaffique Unified theoretical framework for Kondo superconductors: Periodic Anderson impurities with attractive pairing and Rashba spin-orbit coupling Journal Article PHYSICAL REVIEW B, 111 (1), 2025, ISSN: 2469-9950. @article{ISI:001416427700003, title = {Unified theoretical framework for Kondo superconductors: Periodic Anderson impurities with attractive pairing and Rashba spin-orbit coupling}, author = {Shangjian Jin and Darryl C W Foo and Tingyu Qu and Barbaros Ozyilmaz and Shaffique Adam}, doi = {10.1103/PhysRevB.111.014505}, times_cited = {0}, issn = {2469-9950}, year = {2025}, date = {2025-01-08}, journal = {PHYSICAL REVIEW B}, volume = {111}, number = {1}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {Magnetic superconductors manifest a fascinating interplay between their magnetic and superconducting properties. This becomes evident, for example, in the significant enhancement of the upper critical field observed in uranium-based superconductors, or the destruction of superconductivity well below the superconducting transition temperature Tc in cobalt-doped NbSe2. In this work, we argue that the Kondo interaction plays a pivotal role in governing these behaviors. By employing a periodic Anderson model, we study the Kondo effect in superconductors with either singlet or triplet pairing. In the regime of small impurity energies and high doping concentrations, we find the emergence of a Kondo resistive region below Tc. While a magnetic field suppresses singlet superconductivity, it stabilizes triplet pairing through the screening of magnetic impurities, inducing reentrant superconductivity at high fields. Moreover, introducing an antisymmetric spin-orbital coupling suppresses triplet superconductivity. This framework provides a unified picture to understand the observation of Kondo effect in NbSe2 as well as the phase diagrams in Kondo superconductors such as UTe2 and URhGe.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Magnetic superconductors manifest a fascinating interplay between their magnetic and superconducting properties. This becomes evident, for example, in the significant enhancement of the upper critical field observed in uranium-based superconductors, or the destruction of superconductivity well below the superconducting transition temperature Tc in cobalt-doped NbSe2. In this work, we argue that the Kondo interaction plays a pivotal role in governing these behaviors. By employing a periodic Anderson model, we study the Kondo effect in superconductors with either singlet or triplet pairing. In the regime of small impurity energies and high doping concentrations, we find the emergence of a Kondo resistive region below Tc. While a magnetic field suppresses singlet superconductivity, it stabilizes triplet pairing through the screening of magnetic impurities, inducing reentrant superconductivity at high fields. Moreover, introducing an antisymmetric spin-orbital coupling suppresses triplet superconductivity. This framework provides a unified picture to understand the observation of Kondo effect in NbSe2 as well as the phase diagrams in Kondo superconductors such as UTe2 and URhGe. |
Carrio, Juan A G; Talluri, Vssl Prasad; Toolahalli, Swamy T; Echeverrigaray, Sergio G; Neto, Antonio Castro H Cross-Linked Self-Standing Graphene Oxide Membranes: A Pathway to Scalable Applications in Separation Technologies Journal Article MEMBRANES, 15 (1), 2025. @article{ISI:001404434600001, title = {Cross-Linked Self-Standing Graphene Oxide Membranes: A Pathway to Scalable Applications in Separation Technologies}, author = {Juan A G Carrio and Vssl Prasad Talluri and Swamy T Toolahalli and Sergio G Echeverrigaray and Antonio Castro H Neto}, doi = {10.3390/membranes15010031}, times_cited = {0}, year = {2025}, date = {2025-01-01}, journal = {MEMBRANES}, volume = {15}, number = {1}, publisher = {MDPI}, address = {ST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND}, abstract = {The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe2O3, Al2O3, CaSO4, Nb2O5, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m2 and 0.090 m2 and thicknesses from 0.6 mu m to 20 mu m, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties-the Nb2O5 cross-linked membranes present distinct performance characteristics-creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The large-scale implementation of 2D material-based membranes is hindered by mechanical stability and mass transport control challenges. This work describes the fabrication, characterisation, and testing of self-standing graphene oxide (GO) membranes cross-linked with oxides such as Fe2O3, Al2O3, CaSO4, Nb2O5, and a carbide, SiC. These cross-linking agents enhance the mechanical stability of the membranes and modulate their mass transport properties. The membranes were prepared by casting aqueous suspensions of GO and SiC or oxide powders onto substrates, followed by drying and detachment to yield self-standing films. This method enabled precise control over membrane thickness and the formation of laminated microstructures with interlayer spacings ranging from 0.8 to 1.2 nm. The resulting self-standing membranes, with areas between 0.002 m2 and 0.090 m2 and thicknesses from 0.6 mu m to 20 mu m, exhibit excellent flexibility and retain their chemical and physical integrity during prolonged testing in direct contact with ethanol/water and methanol/water mixtures in both liquid and vapour phases, with stability demonstrated over 24 h and up to three months. Gas permeation and chemical characterisation tests evidence their suitability for gas separation applications. The interactions promoted by the oxides and carbide with the functional groups of GO confer great stability and unique mass transport properties-the Nb2O5 cross-linked membranes present distinct performance characteristics-creating the potential for scalable advancements in cross-linked 2D material membranes for separation technologies. |
Hao, Qi; Liu, Yijun; Zou, Ren; Shi, Ge; Yang, Shilian; Zhong, Linxin; Yang, Wu; Chi, Xiao; Liu, Yunpeng; Admassie, Shimelis; Peng, Xinwen g-C3N4 nanosheets coupled with CoSe2 as co-catalyst for efficient photooxidation of xylose to xylonic acid Journal Article GREEN ENERGY & ENVIRONMENT, 10 (1), pp. 231-238, 2025, ISSN: 2096-2797. @article{ISI:001395719700001, title = {\textit{g}-C_{3}N_{4} nanosheets coupled with CoSe_{2} as co-catalyst for efficient photooxidation of xylose to xylonic acid}, author = {Qi Hao and Yijun Liu and Ren Zou and Ge Shi and Shilian Yang and Linxin Zhong and Wu Yang and Xiao Chi and Yunpeng Liu and Shimelis Admassie and Xinwen Peng}, doi = {10.1016/j.gee.2024.04.004}, times_cited = {0}, issn = {2096-2797}, year = {2025}, date = {2025-01-01}, journal = {GREEN ENERGY & ENVIRONMENT}, volume = {10}, number = {1}, pages = {231-238}, publisher = {KEAI PUBLISHING LTD}, address = {16 DONGHUANGCHENGGEN NORTH ST, Building 5, Room 411, BEIJING, DONGCHENG DISTRICT 100009, PEOPLES R CHINA}, abstract = {Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products. CoSe2 is a promising non-precious, efficient cocatalyst for photooxidation, which can facilitate the separation of photogenerated electron-holes, increase the reaction rates, and enhance photocatalytic efficiency. In this work, we synthesized a stable and efficient photocatalysis system of CoSe2/g-C3N4 through attaching CoSe2 on g-C3N4 sheets, with a yield of 50.12% for the selective photooxidation of xylose to xylonic acid. Under light illumination, the photogenerated electrons were prone to migrating from g-C3N4 to CoSe2 due to the higher work function of CoSe2, resulting in the accelerated separation of photogenerated electron-holes and the promoted photooxidation. Herein, this study reveals the unique function of CoSe2, which can significantly promote oxygen adsorption, work as an electron sink and accelerate the generation of center dot O-2, thereby improving the selectivity toward xylonic acid over other by-products. This work provides useful insights into the design of selective photocatalysts by engineering g-C3N4 for biomass high-value utilization. (c) 2025 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Photocatalysis has emerged as an effective approach to sustainably convert biomass into value-added products. CoSe2 is a promising non-precious, efficient cocatalyst for photooxidation, which can facilitate the separation of photogenerated electron-holes, increase the reaction rates, and enhance photocatalytic efficiency. In this work, we synthesized a stable and efficient photocatalysis system of CoSe2/g-C3N4 through attaching CoSe2 on g-C3N4 sheets, with a yield of 50.12% for the selective photooxidation of xylose to xylonic acid. Under light illumination, the photogenerated electrons were prone to migrating from g-C3N4 to CoSe2 due to the higher work function of CoSe2, resulting in the accelerated separation of photogenerated electron-holes and the promoted photooxidation. Herein, this study reveals the unique function of CoSe2, which can significantly promote oxygen adsorption, work as an electron sink and accelerate the generation of center dot O-2, thereby improving the selectivity toward xylonic acid over other by-products. This work provides useful insights into the design of selective photocatalysts by engineering g-C3N4 for biomass high-value utilization. (c) 2025 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. |
2024 |
Ezzi, Mohammed Al M; Pallewela, Gayani N; Beule, Christophe De; Mele, E J; Adam, Shaffique Analytical Model for Atomic Relaxation in Twisted Moire PHYSICAL REVIEW LETTERS, 133 (26), 2024, ISSN: 0031-9007. @article{ISI:001386385200014, title = {Analytical Model for Atomic Relaxation in Twisted Moire author = {Mohammed Al M Ezzi and Gayani N Pallewela and Christophe De Beule and E J Mele and Shaffique Adam}, doi = {10.1103/PhysRevLett.133.266201}, times_cited = {1}, issn = {0031-9007}, year = {2024}, date = {2024-12-23}, journal = {PHYSICAL REVIEW LETTERS}, volume = {133}, number = {26}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {By virtue of being atomically thin, the electronic properties of heterostructures built from twodimensional materials are strongly influenced by atomic relaxation. The atomic layers behave as flexible membranes rather than rigid crystals. Here we develop an analytical theory of lattice relaxation in twisted moire keywords = {}, pubstate = {published}, tppubtype = {article} } By virtue of being atomically thin, the electronic properties of heterostructures built from twodimensional materials are strongly influenced by atomic relaxation. The atomic layers behave as flexible membranes rather than rigid crystals. Here we develop an analytical theory of lattice relaxation in twisted moire |
Zhang, Lishu; Yuan, Zhengping; Yang, Jie; Zhou, Jun; Jiang, Yanyan; Li, Hui; Cai, Yongqing; Tsymbal, Evgeny Y; Feng, Yuan Ping; Zhu, Zhifeng; Shen, Lei Van der Waals spin-orbit torque antiferromagnetic memory Journal Article PHYSICAL REVIEW B, 110 (22), 2024, ISSN: 2469-9950. @article{ISI:001389463600001, title = {Van der Waals spin-orbit torque antiferromagnetic memory}, author = {Lishu Zhang and Zhengping Yuan and Jie Yang and Jun Zhou and Yanyan Jiang and Hui Li and Yongqing Cai and Evgeny Y Tsymbal and Yuan Ping Feng and Zhifeng Zhu and Lei Shen}, doi = {10.1103/PhysRevB.110.L220409}, times_cited = {1}, issn = {2469-9950}, year = {2024}, date = {2024-12-20}, journal = {PHYSICAL REVIEW B}, volume = {110}, number = {22}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {The technique of conventional ferromagnet/heavy-metal spin-orbit torque (SOT) offers significant potential for enhancing the efficiency of magnetic memories. However, it faces fundamental physical limitations, including shunting effects from the metallic layer, broken symmetry for enabling antidamping switching, spin scattering caused by interfacial defects, and sensitivity to stray magnetic fields. To address these issues, we here propose a van der Waals (vdW) field-free SOT antiferromagnetic memory using a vdW bilayer LaBr2 (an antiferromagnet with perpendicular magnetic anisotropy) and a monolayer Td phase WTe2 (a Weyl semimetal with broken inversion symmetry). By systematically employing density functional theory in conjunction with nonequilibrium Green's function methods and macrospin simulations, we demonstrate that the proposed vdW SOT devices exhibit remarkably low critical current density approximately 10 MA/cm2 and rapid field-free magnetization switching in 250 ps. This facilitates excellent write performance with extremely low energy consumption. Furthermore, the device shows a significantly low read error rate, as evidenced by a high tunnel magnetoresistance ratio of up to 4250%. The superior write and read performance originates from the unique strong on-site (insulating phase) and off-site (magnetic phase) Coulomb interactions in electride LaBr2, a large nonzero z-component polarization in WTe2, and the proximity effect between them.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The technique of conventional ferromagnet/heavy-metal spin-orbit torque (SOT) offers significant potential for enhancing the efficiency of magnetic memories. However, it faces fundamental physical limitations, including shunting effects from the metallic layer, broken symmetry for enabling antidamping switching, spin scattering caused by interfacial defects, and sensitivity to stray magnetic fields. To address these issues, we here propose a van der Waals (vdW) field-free SOT antiferromagnetic memory using a vdW bilayer LaBr2 (an antiferromagnet with perpendicular magnetic anisotropy) and a monolayer Td phase WTe2 (a Weyl semimetal with broken inversion symmetry). By systematically employing density functional theory in conjunction with nonequilibrium Green's function methods and macrospin simulations, we demonstrate that the proposed vdW SOT devices exhibit remarkably low critical current density approximately 10 MA/cm2 and rapid field-free magnetization switching in 250 ps. This facilitates excellent write performance with extremely low energy consumption. Furthermore, the device shows a significantly low read error rate, as evidenced by a high tunnel magnetoresistance ratio of up to 4250%. The superior write and read performance originates from the unique strong on-site (insulating phase) and off-site (magnetic phase) Coulomb interactions in electride LaBr2, a large nonzero z-component polarization in WTe2, and the proximity effect between them. |
Lu, Bin; Niu, Yue; Chen, Qian; Wong, Ping Kwan Johnny; Guo, Qingjie; Jiang, Wei; Rath, Ashutosh; Pennycook, Stephen J; Wang, Lei; Xia, Ke; Zhai, Ya; Wee, Andrew Thye Shen; Zhang, Wen Is Semiconducting Transition-Metal Dichalcogenide Suitable for Spin Pumping? Journal Article NANO LETTERS, 25 (1), pp. 35-40, 2024, ISSN: 1530-6984. @article{ISI:001379965300001, title = {Is Semiconducting Transition-Metal Dichalcogenide Suitable for Spin Pumping?}, author = {Bin Lu and Yue Niu and Qian Chen and Ping Kwan Johnny Wong and Qingjie Guo and Wei Jiang and Ashutosh Rath and Stephen J Pennycook and Lei Wang and Ke Xia and Ya Zhai and Andrew Thye Shen Wee and Wen Zhang}, doi = {10.1021/acs.nanolett.4c03469}, times_cited = {0}, issn = {1530-6984}, year = {2024}, date = {2024-12-17}, journal = {NANO LETTERS}, volume = {25}, number = {1}, pages = {35-40}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Spin pumping has been reported on interfaces formed with ferromagnetic metals and layered transition-metal dichalcogenides (TMDs), as signified by enhanced Gilbert damping parameters extracted from magnetodynamics measurements. However, whether the observed damping enhancement purely arises from the pumping effect has remained debatable, given that possible extrinsic disturbances on the interfaces cannot be excluded in most of the experiments. Here, we explore an atomically clean interface formed with CoFeB and atomically thin MoSe2, achieved by an all in situ growth strategy based on molecular beam epitaxy. Taking advantage of ferromagnetic resonance analysis, we find that the Gilbert damping of the CoFeB/MoSe2 interface closely resembles that of CoFeB/SiO2, suggesting the absence of spin pumping. With similar findings demonstrated on a few more representative interfaces, this work clarifies the unsuitability of semiconducting TMDs for spin pumping and suggests that the observed damping enhancement in the previous reports may be predominantly attributed to extrinsic contributions during the experimental process.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Spin pumping has been reported on interfaces formed with ferromagnetic metals and layered transition-metal dichalcogenides (TMDs), as signified by enhanced Gilbert damping parameters extracted from magnetodynamics measurements. However, whether the observed damping enhancement purely arises from the pumping effect has remained debatable, given that possible extrinsic disturbances on the interfaces cannot be excluded in most of the experiments. Here, we explore an atomically clean interface formed with CoFeB and atomically thin MoSe2, achieved by an all in situ growth strategy based on molecular beam epitaxy. Taking advantage of ferromagnetic resonance analysis, we find that the Gilbert damping of the CoFeB/MoSe2 interface closely resembles that of CoFeB/SiO2, suggesting the absence of spin pumping. With similar findings demonstrated on a few more representative interfaces, this work clarifies the unsuitability of semiconducting TMDs for spin pumping and suggests that the observed damping enhancement in the previous reports may be predominantly attributed to extrinsic contributions during the experimental process. |
Morin, Julien Luc Paul; Dubey, Nileshkumar; Luong-Van, Emma Kim; Yu, Baiqing; Sabino, Clarice Ferreira; Silikas, Nick; Agarwalla, Shruti Vidhawan; Neto, Castro A H; Rosa, Vinicius Graphene nanocoating on titanium maintains structural and antibiofilm properties post-sterilization Journal Article DENTAL MATERIALS, 41 (1), pp. 7-15, 2024, ISSN: 0109-5641. @article{ISI:001391110500001, title = {Graphene nanocoating on titanium maintains structural and antibiofilm properties post-sterilization}, author = {Julien Luc Paul Morin and Nileshkumar Dubey and Emma Kim Luong-Van and Baiqing Yu and Clarice Ferreira Sabino and Nick Silikas and Shruti Vidhawan Agarwalla and Castro A H Neto and Vinicius Rosa}, doi = {10.1016/j.dental.2024.10.009}, times_cited = {0}, issn = {0109-5641}, year = {2024}, date = {2024-12-17}, journal = {DENTAL MATERIALS}, volume = {41}, number = {1}, pages = {7-15}, publisher = {ELSEVIER SCI LTD}, address = {125 London Wall, London, ENGLAND}, abstract = {Objective: To evaluate the impact of sterilization methods on the structural integrity and antimicrobial properties of graphene nanocoating on titanium (GN). Methods: GN was transferred to titanium using wet (WT) or dry transfer (DT) techniques and sterilized using an autoclave (AC), glutaraldehyde (GA), or ethylene oxide (EtO). The GN structure was characterized using Raman spectroscopy before and after sterilization. Additional specimens were characterized by Raman after AC and water jetting. Biofilm formation was assessed before and after AC using colony-forming units (CFU), biofilm biomass, and SEM (uncoated titanium was the control). Three independent samples were used for structural characterization and biofilm quantification. Statistical analyses were conducted using one-way analysis of variance (ANOVA) and Tukey's test (alpha = 0.05). Results: WT and DT demonstrated high structural stability after sterilization and water jetting, with negligible coating quality or coverage loss. GN exhibited lower biofilm formation even after AC sterilization, as shown by the reduction in CFU counts, biofilm biomass, and SEM images compared to the control. Significance: GN demonstrated high resistance to the stresses imposed by all sterilization methods tested, maintaining its structural integrity, resistance to water-jet cleaning, and antibiofilm potential. The findings suggest that standard industrial practices can effectively sterilize highly resilient GN on titanium implants and possibly other biomaterials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Objective: To evaluate the impact of sterilization methods on the structural integrity and antimicrobial properties of graphene nanocoating on titanium (GN). Methods: GN was transferred to titanium using wet (WT) or dry transfer (DT) techniques and sterilized using an autoclave (AC), glutaraldehyde (GA), or ethylene oxide (EtO). The GN structure was characterized using Raman spectroscopy before and after sterilization. Additional specimens were characterized by Raman after AC and water jetting. Biofilm formation was assessed before and after AC using colony-forming units (CFU), biofilm biomass, and SEM (uncoated titanium was the control). Three independent samples were used for structural characterization and biofilm quantification. Statistical analyses were conducted using one-way analysis of variance (ANOVA) and Tukey's test (alpha = 0.05). Results: WT and DT demonstrated high structural stability after sterilization and water jetting, with negligible coating quality or coverage loss. GN exhibited lower biofilm formation even after AC sterilization, as shown by the reduction in CFU counts, biofilm biomass, and SEM images compared to the control. Significance: GN demonstrated high resistance to the stresses imposed by all sterilization methods tested, maintaining its structural integrity, resistance to water-jet cleaning, and antibiofilm potential. The findings suggest that standard industrial practices can effectively sterilize highly resilient GN on titanium implants and possibly other biomaterials. |
Guo, Qiangbing; Wu, Yun-Kun; Zhang, Di; Zhang, Qiuhong; Guo, Guang-Can; Alu, Andrea; Ren, Xi-Feng; Qiu, Cheng-Wei Polarization entanglement enabled by orthogonally stacked van der Waals NbOCl2 crystals Journal Article NATURE COMMUNICATIONS, 15 (1), 2024. @article{ISI:001376827800011, title = {Polarization entanglement enabled by orthogonally stacked van der Waals NbOCl_{2} crystals}, author = {Qiangbing Guo and Yun-Kun Wu and Di Zhang and Qiuhong Zhang and Guang-Can Guo and Andrea Alu and Xi-Feng Ren and Cheng-Wei Qiu}, doi = {10.1038/s41467-024-54876-w}, times_cited = {2}, year = {2024}, date = {2024-12-02}, journal = {NATURE COMMUNICATIONS}, volume = {15}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Polarization entanglement holds significant importance for photonic quantum technologies. Recently emerging subwavelength nonlinear quantum light sources, e.g., GaP and LiNbO3 thin films, benefiting from the relaxed phase-matching constraints and volume confinement, have shown intriguing properties, such as high-dimensional hyperentanglement and robust entanglement anti-degradation. Van der Waals (vdW) NbOCl2 crystal, with strong optical nonlinearities, has emerged as a potential candidate for ultrathin quantum light sources. However, polarization entanglement is inaccessible in the NbOCl2 crystal due to its unfavorable nonlinear susceptibility tensor. Here, by leveraging the twist-stacking degree of freedom inherently in vdW systems, we showcase the preparation of polarization entanglement and quantum Bell states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Polarization entanglement holds significant importance for photonic quantum technologies. Recently emerging subwavelength nonlinear quantum light sources, e.g., GaP and LiNbO3 thin films, benefiting from the relaxed phase-matching constraints and volume confinement, have shown intriguing properties, such as high-dimensional hyperentanglement and robust entanglement anti-degradation. Van der Waals (vdW) NbOCl2 crystal, with strong optical nonlinearities, has emerged as a potential candidate for ultrathin quantum light sources. However, polarization entanglement is inaccessible in the NbOCl2 crystal due to its unfavorable nonlinear susceptibility tensor. Here, by leveraging the twist-stacking degree of freedom inherently in vdW systems, we showcase the preparation of polarization entanglement and quantum Bell states. |
Loh, Leyi; Ho, Yi Wei; Xuan, Fengyuan; del Aguila, Andres Granados; Chen, Yuan; Wong, See Yoong; Zhang, Jingda; Wang, Zhe; Watanabe, Kenji; Taniguchi, Takashi; Pigram, Paul J; Bosman, Michel; Quek, Su Ying; Koperski, Maciej; Eda, Goki Nb impurity-bound excitons as quantum emitters in monolayer WS2 Journal Article NATURE COMMUNICATIONS, 15 (1), 2024. @article{ISI:001360396900001, title = {Nb impurity-bound excitons as quantum emitters in monolayer WS_{2}}, author = {Leyi Loh and Yi Wei Ho and Fengyuan Xuan and Andres Granados del Aguila and Yuan Chen and See Yoong Wong and Jingda Zhang and Zhe Wang and Kenji Watanabe and Takashi Taniguchi and Paul J Pigram and Michel Bosman and Su Ying Quek and Maciej Koperski and Goki Eda}, doi = {10.1038/s41467-024-54360-5}, times_cited = {0}, year = {2024}, date = {2024-11-20}, journal = {NATURE COMMUNICATIONS}, volume = {15}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Point defects in crystalline solids behave as optically addressable individual quantum systems when present in sufficiently low concentrations. In two-dimensional (2D) semiconductors, such quantum defects hold potential as versatile single photon sources. Here, we report the synthesis and optical properties of Nb-doped monolayer WS2 in the dilute limit where the average spacing between individual dopants exceeds the optical diffraction limit, allowing the emission spectrum to be studied at the single-dopant level. We show that these individual dopants exhibit common features of quantum emitters, including narrow emission lines (with linewidths <1 meV), strong spatial confinement, and photon antibunching. These emitters consistently occur within a narrow spectral range across multiple samples, distinct from common quantum emitters in van der Waals (vdW) materials that show large ensemble broadening. Analysis of the Zeeman splitting reveals that they can be attributed to bound exciton complexes comprising dark excitons and negatively charged Nb.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Point defects in crystalline solids behave as optically addressable individual quantum systems when present in sufficiently low concentrations. In two-dimensional (2D) semiconductors, such quantum defects hold potential as versatile single photon sources. Here, we report the synthesis and optical properties of Nb-doped monolayer WS2 in the dilute limit where the average spacing between individual dopants exceeds the optical diffraction limit, allowing the emission spectrum to be studied at the single-dopant level. We show that these individual dopants exhibit common features of quantum emitters, including narrow emission lines (with linewidths <1 meV), strong spatial confinement, and photon antibunching. These emitters consistently occur within a narrow spectral range across multiple samples, distinct from common quantum emitters in van der Waals (vdW) materials that show large ensemble broadening. Analysis of the Zeeman splitting reveals that they can be attributed to bound exciton complexes comprising dark excitons and negatively charged Nb. |
Erofeev, Ivan; Hartanto, Antony Winata; Khan, Muhaimin Mareum; Deng, Kerong; Kumar, Krishna; Aabdin, Zainul; Tjiu, Weng Weei; Zhang, Mingsheng; Pacco, Antoine; Philipsen, Harold; Chowdhuri, Angshuman Ray; Huynh, Han Vinh; Holsteyns, Frank; Mirsaidov, Utkur Digital Etching of Molybdenum Interconnects Using Plasma Oxidation Journal Article ADVANCED MATERIALS INTERFACES, 12 (1), 2024, ISSN: 2196-7350. @article{ISI:001357050400001, title = {Digital Etching of Molybdenum Interconnects Using Plasma Oxidation}, author = {Ivan Erofeev and Antony Winata Hartanto and Muhaimin Mareum Khan and Kerong Deng and Krishna Kumar and Zainul Aabdin and Weng Weei Tjiu and Mingsheng Zhang and Antoine Pacco and Harold Philipsen and Angshuman Ray Chowdhuri and Han Vinh Huynh and Frank Holsteyns and Utkur Mirsaidov}, doi = {10.1002/admi.202400558}, times_cited = {1}, issn = {2196-7350}, year = {2024}, date = {2024-11-12}, journal = {ADVANCED MATERIALS INTERFACES}, volume = {12}, number = {1}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {Molybdenum (Mo) has a high potential of becoming the material of choice for sub-10 nm scale metal structures in future integrated circuits (ICs). Manufacturing at this scale requires exceptional precision and consistency, so many metal processing techniques must be reconsidered. In particular, present direct wet chemical etching methods produce anisotropic etching profiles with significant surface roughness, which can be detrimental to device performance. Here, it is shown that polycrystalline Mo nanowires can be etched uniformly using a cyclic two-step "digital" method: the metal surface is first oxidized with isotropic oxygen plasma to form a layer of MoO3, which is then selectively removed using either wet chemical or dry isotropic plasma etching. These two steps are repeated in cycles until the intended metal recess is achieved. High uniformity of plasma oxidation defines the etching uniformity, and small metal recess per cycle (typically 1-2 nm) provides precise control over the etching depth. This method can replace wet etching where high etching precision is needed, enabling the reliable manufacturing of nanoscale metal interconnects.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Molybdenum (Mo) has a high potential of becoming the material of choice for sub-10 nm scale metal structures in future integrated circuits (ICs). Manufacturing at this scale requires exceptional precision and consistency, so many metal processing techniques must be reconsidered. In particular, present direct wet chemical etching methods produce anisotropic etching profiles with significant surface roughness, which can be detrimental to device performance. Here, it is shown that polycrystalline Mo nanowires can be etched uniformly using a cyclic two-step "digital" method: the metal surface is first oxidized with isotropic oxygen plasma to form a layer of MoO3, which is then selectively removed using either wet chemical or dry isotropic plasma etching. These two steps are repeated in cycles until the intended metal recess is achieved. High uniformity of plasma oxidation defines the etching uniformity, and small metal recess per cycle (typically 1-2 nm) provides precise control over the etching depth. This method can replace wet etching where high etching precision is needed, enabling the reliable manufacturing of nanoscale metal interconnects. |