Publications
2025 |
Zhang, Weidong; Xiong, Chenwei; Chen, Peng; Fu, Bing; Mao, Xianwen Elucidating Energy Conversion Pathways at Biotic/Abiotic Interfaces in Microbe-Semiconductor Hybrids Journal Article JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2025, ISSN: 0002-7863. @article{ISI:001504342600001, title = {Elucidating Energy Conversion Pathways at Biotic/Abiotic Interfaces in Microbe-Semiconductor Hybrids}, author = {Weidong Zhang and Chenwei Xiong and Peng Chen and Bing Fu and Xianwen Mao}, doi = {10.1021/jacs.5c02838}, times_cited = {0}, issn = {0002-7863}, year = {2025}, date = {2025-06-07}, journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Biotic/abiotic hybrid systems integrating microbes with light-absorbing semiconductor materials offer promising solutions for sustainable energy conversion and value-added chemical production. In this Perspective, we discuss the mechanistic insights into upstream energy conversion processes at the biotic-abiotic interfaces, underscoring their pivotal roles in determining biohybrid performance. We explore how biological, physicochemical, and electrochemical characterization techniques have advanced our understanding of energy conversion pathways and electron transport mechanisms within these complex systems. Moreover, we emphasize the growing importance of spatiotemporally resolved imaging in linking biological activity to physicochemical dynamics at the single-cell level. Moving forward, we propose that interdisciplinary collaborations and innovative methodologies will be critical in deepening the mechanistic understanding and unlocking the full potential of artificial photosynthetic biohybrid systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Biotic/abiotic hybrid systems integrating microbes with light-absorbing semiconductor materials offer promising solutions for sustainable energy conversion and value-added chemical production. In this Perspective, we discuss the mechanistic insights into upstream energy conversion processes at the biotic-abiotic interfaces, underscoring their pivotal roles in determining biohybrid performance. We explore how biological, physicochemical, and electrochemical characterization techniques have advanced our understanding of energy conversion pathways and electron transport mechanisms within these complex systems. Moreover, we emphasize the growing importance of spatiotemporally resolved imaging in linking biological activity to physicochemical dynamics at the single-cell level. Moving forward, we propose that interdisciplinary collaborations and innovative methodologies will be critical in deepening the mechanistic understanding and unlocking the full potential of artificial photosynthetic biohybrid systems. |
Swain, Nyayabanta; Tang, Ho-Kin; Foo, Darryl Chuan Wei; Khor, Brian J J; Lemarie, Gabriel; Assaad, Fakher F; Sengupta, Pinaki; Adam, Shaffique Engineering many-body quantum Hamiltonians with nonergodic properties using quantum Monte Carlo Journal Article PHYSICAL REVIEW B, 111 (22), 2025, ISSN: 2469-9950. @article{ISI:001511184900009, title = {Engineering many-body quantum Hamiltonians with nonergodic properties using quantum Monte Carlo}, author = {Nyayabanta Swain and Ho-Kin Tang and Darryl Chuan Wei Foo and Brian J J Khor and Gabriel Lemarie and Fakher F Assaad and Pinaki Sengupta and Shaffique Adam}, doi = {10.1103/PhysRevB.111.224201}, times_cited = {0}, issn = {2469-9950}, year = {2025}, date = {2025-06-02}, journal = {PHYSICAL REVIEW B}, volume = {111}, number = {22}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {We present a computational framework to identify Hamiltonians of interacting quantum many-body systems that host nonergodic excited states. We combine quantum Monte Carlo simulations with the recently proposed eigenstate-to-Hamiltonian construction, which maps the ground state of a specified parent Hamiltonian to a single nonergodic excited state of a new derived Hamiltonian. This engineered Hamiltonian contains nontrivial, systematically-obtained, and emergent features that are responsible for its nonergodic properties. We demonstrate this approach by applying it to quantum many-body scar states where we discover a previously unreported family of Hamiltonians with spatially oscillating spin exchange couplings that host scar-like properties, including revivals in the quantum dynamics, and towers in the inverse participation ratio; and to many-body localization, where we find a two-dimensional Hamiltonian with correlated disorder that exhibits nonergodic scaling of the participation entropy and inverse participation ratios of order unity. The method can be applied to other known ground states to discover new quantum many-body systems with nonergodic excited states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a computational framework to identify Hamiltonians of interacting quantum many-body systems that host nonergodic excited states. We combine quantum Monte Carlo simulations with the recently proposed eigenstate-to-Hamiltonian construction, which maps the ground state of a specified parent Hamiltonian to a single nonergodic excited state of a new derived Hamiltonian. This engineered Hamiltonian contains nontrivial, systematically-obtained, and emergent features that are responsible for its nonergodic properties. We demonstrate this approach by applying it to quantum many-body scar states where we discover a previously unreported family of Hamiltonians with spatially oscillating spin exchange couplings that host scar-like properties, including revivals in the quantum dynamics, and towers in the inverse participation ratio; and to many-body localization, where we find a two-dimensional Hamiltonian with correlated disorder that exhibits nonergodic scaling of the participation entropy and inverse participation ratios of order unity. The method can be applied to other known ground states to discover new quantum many-body systems with nonergodic excited states. |
Zhang, Hongji; Grebenko, Artem K; Iakoubovskii, Konstantin V; Zhang, Hanning; Yamaletdinov, Ruslan; Makarova, Anna; Fedorov, Alexander; Rejaul, S K; Shivajirao, Ranjith; Tong, Zheng Jue; Grebenchuk, Sergey; Karadeniz, Ugur; Shi, Lu; Vyalikh, Denis V; He, Ya; Starkov, Andrei; Alekseeva, Alena A; Tee, Chuan Chu; Orofeo, Carlo Mendoza; Lin, Junhao; Suenaga, Kazutomo; Bosman, Michel; Koperski, Maciej; Weber, Bent; Novoselov, Kostya S; Yazyev, Oleg V; Toh, Chee-Tat; Ozyilmaz, Barbaros Superior Adhesion of Monolayer Amorphous Carbon to Copper Journal Article ADVANCED MATERIALS, 2025, ISSN: 0935-9648. @article{ISI:001498039100001, title = {Superior Adhesion of Monolayer Amorphous Carbon to Copper}, author = {Hongji Zhang and Artem K Grebenko and Konstantin V Iakoubovskii and Hanning Zhang and Ruslan Yamaletdinov and Anna Makarova and Alexander Fedorov and S K Rejaul and Ranjith Shivajirao and Zheng Jue Tong and Sergey Grebenchuk and Ugur Karadeniz and Lu Shi and Denis V Vyalikh and Ya He and Andrei Starkov and Alena A Alekseeva and Chuan Chu Tee and Carlo Mendoza Orofeo and Junhao Lin and Kazutomo Suenaga and Michel Bosman and Maciej Koperski and Bent Weber and Kostya S Novoselov and Oleg V Yazyev and Chee-Tat Toh and Barbaros Ozyilmaz}, doi = {10.1002/adma.202419112}, times_cited = {0}, issn = {0935-9648}, year = {2025}, date = {2025-05-29}, journal = {ADVANCED MATERIALS}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {The single-atom thickness of graphene holds great potential for device scaling, but its effectiveness as a thin metal-ion diffusion barrier in microelectronics and a corrosion barrier for plasmonic devices is compromised by weak van der Waals interactions with copper (Cu), leading to delamination issues. In contrast, monolayer amorphous carbon (MAC), a recently reported single-atom-thick carbon film with a disordered sp2 hybridized structure, demonstrates superior adhesion properties. This study reveals that MAC exhibits an adhesion energy of 85 J m-2 on Cu, which is 13 times greater than that of graphene. This exceptional adhesion is attributed to the formation of covalent-like Cu & horbar;C bonds while preserving its sp2 structure, as evidenced by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Density functional theory (DFT) calculations further elucidate that the corrugated structure of MAC facilitates the hybridization of C 2pz orbitals with Cu 4s and 3dz2 orbitals, promoting strong bonding. These insights indicate that the amorphous structure of MAC significantly enhances adhesion while preserving its elemental composition, providing a pathway to improve the mechanical reliability and performance of two-dimensional (2D) materials on metal substrates in various technological applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The single-atom thickness of graphene holds great potential for device scaling, but its effectiveness as a thin metal-ion diffusion barrier in microelectronics and a corrosion barrier for plasmonic devices is compromised by weak van der Waals interactions with copper (Cu), leading to delamination issues. In contrast, monolayer amorphous carbon (MAC), a recently reported single-atom-thick carbon film with a disordered sp2 hybridized structure, demonstrates superior adhesion properties. This study reveals that MAC exhibits an adhesion energy of 85 J m-2 on Cu, which is 13 times greater than that of graphene. This exceptional adhesion is attributed to the formation of covalent-like Cu & horbar;C bonds while preserving its sp2 structure, as evidenced by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Density functional theory (DFT) calculations further elucidate that the corrugated structure of MAC facilitates the hybridization of C 2pz orbitals with Cu 4s and 3dz2 orbitals, promoting strong bonding. These insights indicate that the amorphous structure of MAC significantly enhances adhesion while preserving its elemental composition, providing a pathway to improve the mechanical reliability and performance of two-dimensional (2D) materials on metal substrates in various technological applications. |
Yuan, Yue; Pazos, Sebastian; Li, Junzhu; Tian, Bo; Alharbi, Osamah; Zhang, Xixiang; Akinwande, Deji; Lanza, Mario On-chip atomristors Journal Article MATERIALS SCIENCE & ENGINEERING R-REPORTS, 165 , 2025, ISSN: 0927-796X. @article{ISI:001490397100001, title = {On-chip atomristors}, author = {Yue Yuan and Sebastian Pazos and Junzhu Li and Bo Tian and Osamah Alharbi and Xixiang Zhang and Deji Akinwande and Mario Lanza}, doi = {10.1016/j.mser.2025.101006}, times_cited = {0}, issn = {0927-796X}, year = {2025}, date = {2025-05-07}, journal = {MATERIALS SCIENCE & ENGINEERING R-REPORTS}, volume = {165}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {Resistive random access memories (RRAM) have shown interesting electrical performance and are relatively easy to fabricate, but their use is still restricted to a few applications due to limited reliability. The microelectronics industry has explored the fabrication of RRAM devices, but only a few amorphous metal-oxides have been tested on-chip, which are mainly TaOX, HfO2, Al2O3, CuXO, SiO2, ZrO2 and NiO. However, in these materials controlling accurately resistive switching through defect generation/recombination is very challenging because the positions of the atoms and the strengths of their bonds are unknown. Here we explore the use of defect-free monolayer hexagonal boron nitride (hBN) as insulating film in RRAM devices - often referred to as atomristors. In this crystalline material the number of atoms is 36.97 nm-2, they are arranged in-plane in a hexagonal lattice with covalent bonding, and the minimum energy to form a defect is 7.43 eV. This lower amount of uncertainties and the absence of local defects allows us to better adjust the electrical stresses to be applied for write, erase and read events, resulting in highly-reproducible non-volatile bipolar resistive switching (on-chip) with high endurance up to millions of cycles in multiple devices. These results represent a very significant advancement compared to previous atomristors patterned on SiO2 substrates. Unlike in previous atomristors, the switching is not produced by native defects, but it is produced by field-driven defects, which exhibit high potential for device ultraminiaturization.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Resistive random access memories (RRAM) have shown interesting electrical performance and are relatively easy to fabricate, but their use is still restricted to a few applications due to limited reliability. The microelectronics industry has explored the fabrication of RRAM devices, but only a few amorphous metal-oxides have been tested on-chip, which are mainly TaOX, HfO2, Al2O3, CuXO, SiO2, ZrO2 and NiO. However, in these materials controlling accurately resistive switching through defect generation/recombination is very challenging because the positions of the atoms and the strengths of their bonds are unknown. Here we explore the use of defect-free monolayer hexagonal boron nitride (hBN) as insulating film in RRAM devices - often referred to as atomristors. In this crystalline material the number of atoms is 36.97 nm-2, they are arranged in-plane in a hexagonal lattice with covalent bonding, and the minimum energy to form a defect is 7.43 eV. This lower amount of uncertainties and the absence of local defects allows us to better adjust the electrical stresses to be applied for write, erase and read events, resulting in highly-reproducible non-volatile bipolar resistive switching (on-chip) with high endurance up to millions of cycles in multiple devices. These results represent a very significant advancement compared to previous atomristors patterned on SiO2 substrates. Unlike in previous atomristors, the switching is not produced by native defects, but it is produced by field-driven defects, which exhibit high potential for device ultraminiaturization. |
Zhu, Jing; Mao, Xianwen Elucidating ionic liquids-mediated electrochemical interfaces for energy storage and electrocatalysis Journal Article MATERIALS TODAY ENERGY, 51 , 2025, ISSN: 2468-6069. @article{ISI:001487375000001, title = {Elucidating ionic liquids-mediated electrochemical interfaces for energy storage and electrocatalysis}, author = {Jing Zhu and Xianwen Mao}, doi = {10.1016/j.mtener.2025.101908}, times_cited = {1}, issn = {2468-6069}, year = {2025}, date = {2025-05-05}, journal = {MATERIALS TODAY ENERGY}, volume = {51}, publisher = {ELSEVIER SCI LTD}, address = {125 London Wall, London, ENGLAND}, abstract = {Ionic liquids (ILs) composed entirely of organic and/or inorganic ions exhibit diverse and tunable properties, serving as versatile energy-related functional materials. They are viable alternatives and supplements to traditional aqueous and organic electrolytes in electrochemical energy storage and conversion systems due to thermal stability, wide electrochemical windows, high ionic conductivity, and low flammability. This review aims to offer a fundamental understanding of the ion structure-electrical double layers (EDLs) relationship of emerging ILs in charge storage and transfer processes. We focused on modeling and simulation studies that connect microscopic interfacial structures and macroscopic charge-functional properties. The review starts with introducing IL types and molecular structures, then revisits physicochemical theories and computational approaches used to describe dense IL-based EDLs, with comparisons with dilute electrolytes. We summarize theoretical models for describing equilibrium EDL structures and associated capacitance behavior response to electrode polarization. We discuss recent molecular level insights into electrolyte ion adsorption and redox reactions in IL-based EDLs. Key findings include EDL structures, i.e., ion overscreening/crowing, and bilayer nanostructures, and interfacial phenomena, e.g., electrostatic shielding and local electric field effects, which critically influence performance in supercapacitors, batteries, and electrocatalysis, offering valuable guidance for the design of IL-enabled energy devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ionic liquids (ILs) composed entirely of organic and/or inorganic ions exhibit diverse and tunable properties, serving as versatile energy-related functional materials. They are viable alternatives and supplements to traditional aqueous and organic electrolytes in electrochemical energy storage and conversion systems due to thermal stability, wide electrochemical windows, high ionic conductivity, and low flammability. This review aims to offer a fundamental understanding of the ion structure-electrical double layers (EDLs) relationship of emerging ILs in charge storage and transfer processes. We focused on modeling and simulation studies that connect microscopic interfacial structures and macroscopic charge-functional properties. The review starts with introducing IL types and molecular structures, then revisits physicochemical theories and computational approaches used to describe dense IL-based EDLs, with comparisons with dilute electrolytes. We summarize theoretical models for describing equilibrium EDL structures and associated capacitance behavior response to electrode polarization. We discuss recent molecular level insights into electrolyte ion adsorption and redox reactions in IL-based EDLs. Key findings include EDL structures, i.e., ion overscreening/crowing, and bilayer nanostructures, and interfacial phenomena, e.g., electrostatic shielding and local electric field effects, which critically influence performance in supercapacitors, batteries, and electrocatalysis, offering valuable guidance for the design of IL-enabled energy devices. |
Ng, Joseph J Q; Tkachev, Sergey; Sim, Glendon C F; de Lima, Luiza Felippi; Koon, Gavin K W; Lima, Alexandre P; Neto, Antonio Castro H Non-Invasive Hydration Monitoring with a Graphene Dual Sweat Sensor Journal Article APPLIED SCIENCES-BASEL, 15 (9), 2025. @article{ISI:001486021400001, title = {Non-Invasive Hydration Monitoring with a Graphene Dual Sweat Sensor}, author = {Joseph J Q Ng and Sergey Tkachev and Glendon C F Sim and Luiza Felippi de Lima and Gavin K W Koon and Alexandre P Lima and Antonio Castro H Neto}, doi = {10.3390/app15094970}, times_cited = {0}, year = {2025}, date = {2025-04-30}, journal = {APPLIED SCIENCES-BASEL}, volume = {15}, number = {9}, publisher = {MDPI}, address = {MDPI AG, Grosspeteranlage 5, CH-4052 BASEL, SWITZERLAND}, abstract = {Maintaining optimal hydration is critical for physiological function, particularly during intense physical activities, in which dehydration or overhydration can impair performance and recovery. Traditional methods for monitoring hydration status, such as body weight changes, bioelectrical impedance, and urine specific gravity, are limited by inconvenience and lack of real-time capability. This study introduces a novel graphene-based dual-sensing electrochemical sensor for the rapid and non-invasive quantification of sodium and potassium concentrations in human sweat, key biomarkers of hydration status. Leveraging graphene's exceptional conductivity and functionalization potential, the sensor employs open-circuit potentiometry (OCP) to achieve high sensitivity and selectivity in detecting sodium and potassium. The sensor performance was validated against that of a commercial analyzer and ICP-OES, demonstrating a near-Nernstian response (61.93 mV/decade for sodium and 61.21 mV/decade for potassium detection) and a linear detection range spanning from 0.1 mM to 100 mM for both sodium and potassium monitoring in sweat. Sweat samples from an athlete during endurance exercise confirmed the sensor's reliability, with results closely matching those of ICP-OES and outperforming the commercial analyzer in regards to accuracy and sample efficiency. This work represents a cross-validated study of a sweat-based sensor with a second analytical technique, highlighting its potential as a real-time hydration monitoring tool for use in sports and beyond.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Maintaining optimal hydration is critical for physiological function, particularly during intense physical activities, in which dehydration or overhydration can impair performance and recovery. Traditional methods for monitoring hydration status, such as body weight changes, bioelectrical impedance, and urine specific gravity, are limited by inconvenience and lack of real-time capability. This study introduces a novel graphene-based dual-sensing electrochemical sensor for the rapid and non-invasive quantification of sodium and potassium concentrations in human sweat, key biomarkers of hydration status. Leveraging graphene's exceptional conductivity and functionalization potential, the sensor employs open-circuit potentiometry (OCP) to achieve high sensitivity and selectivity in detecting sodium and potassium. The sensor performance was validated against that of a commercial analyzer and ICP-OES, demonstrating a near-Nernstian response (61.93 mV/decade for sodium and 61.21 mV/decade for potassium detection) and a linear detection range spanning from 0.1 mM to 100 mM for both sodium and potassium monitoring in sweat. Sweat samples from an athlete during endurance exercise confirmed the sensor's reliability, with results closely matching those of ICP-OES and outperforming the commercial analyzer in regards to accuracy and sample efficiency. This work represents a cross-validated study of a sweat-based sensor with a second analytical technique, highlighting its potential as a real-time hydration monitoring tool for use in sports and beyond. |
Wang, Chuanbin; Tian, Jingnan; Tan, Qian; Xie, Jin; Chen, Guanyi; Chen, Yan; Mao, Xianwen Uncovering Photocatalytic Mechanisms toward Water Treatment by Operando Super-Resolution Reaction Imaging Journal Article ENVIRONMENTAL SCIENCE & TECHNOLOGY, 59 (20), pp. 9865-9885, 2025, ISSN: 0013-936X. @article{ISI:001479292800001, title = {Uncovering Photocatalytic Mechanisms toward Water Treatment by Operando Super-Resolution Reaction Imaging}, author = {Chuanbin Wang and Jingnan Tian and Qian Tan and Jin Xie and Guanyi Chen and Yan Chen and Xianwen Mao}, doi = {10.1021/acs.est.5c00209}, times_cited = {0}, issn = {0013-936X}, year = {2025}, date = {2025-04-30}, journal = {ENVIRONMENTAL SCIENCE & TECHNOLOGY}, volume = {59}, number = {20}, pages = {9865-9885}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Photocatalytic reactions leveraging nanoscale catalyst particles are vital for sustainable environmental remediation but often involve highly complex mechanisms that are difficult to probe due to the pervasive spatiotemporal heterogeneities in the structure and reactivity of the constituent nanosized photocatalyst particles. Super-resolution reaction imaging, with its high spatial and temporal resolution under realistic operando conditions, enables the real-time observation of photocatalytic reaction kinetics and multifaceted charge carrier behaviors at the nanoscale. However, no comprehensive review has yet explored how state-of-the-art super-resolution reaction imaging techniques inform the photocatalyst design for water treatment. This review aims to bridge that gap by providing an overview of the principles and unique advantages of super-resolution catalysis microscopy and related operando imaging tools. We also highlight how these in situ operando techniques can be applied to investigate structure-property relationships in photocatalysts at the single particle and subparticle levels. Key aspects such as size effects, crystal facet effects, bimetallic effects, heterojunction interface effects, defect effects, and particle aggregation effects will be examined through recent case studies, focusing on their impact on photocatalytic water decontamination efficiency. Finally, we discuss the challenges and future directions of leveraging super-resolution microscopy to distill materials design principles in advancing photocatalytic water treatment.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Photocatalytic reactions leveraging nanoscale catalyst particles are vital for sustainable environmental remediation but often involve highly complex mechanisms that are difficult to probe due to the pervasive spatiotemporal heterogeneities in the structure and reactivity of the constituent nanosized photocatalyst particles. Super-resolution reaction imaging, with its high spatial and temporal resolution under realistic operando conditions, enables the real-time observation of photocatalytic reaction kinetics and multifaceted charge carrier behaviors at the nanoscale. However, no comprehensive review has yet explored how state-of-the-art super-resolution reaction imaging techniques inform the photocatalyst design for water treatment. This review aims to bridge that gap by providing an overview of the principles and unique advantages of super-resolution catalysis microscopy and related operando imaging tools. We also highlight how these in situ operando techniques can be applied to investigate structure-property relationships in photocatalysts at the single particle and subparticle levels. Key aspects such as size effects, crystal facet effects, bimetallic effects, heterojunction interface effects, defect effects, and particle aggregation effects will be examined through recent case studies, focusing on their impact on photocatalytic water decontamination efficiency. Finally, we discuss the challenges and future directions of leveraging super-resolution microscopy to distill materials design principles in advancing photocatalytic water treatment. |
Li, Tianbo; Lin, Min; Dale, Stephen G; Shi, Zekun; Neto, Castro A H; Novoselov, Kostya S; Vignale, Giovanni Diagonalization without Diagonalization: A Direct Optimization Approach for Solid-State Density Functional Theory Journal Article JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 21 (9), pp. 4730-4741, 2025, ISSN: 1549-9618. @article{ISI:001478048300001, title = {Diagonalization without Diagonalization: A Direct Optimization Approach for Solid-State Density Functional Theory}, author = {Tianbo Li and Min Lin and Stephen G Dale and Zekun Shi and Castro A H Neto and Kostya S Novoselov and Giovanni Vignale}, doi = {10.1021/acs.jctc.4c01551}, times_cited = {0}, issn = {1549-9618}, year = {2025}, date = {2025-04-28}, journal = {JOURNAL OF CHEMICAL THEORY AND COMPUTATION}, volume = {21}, number = {9}, pages = {4730-4741}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {We present a novel approach to address the challenges of variable occupation numbers in direct optimization of density functional theory (DFT). By parametrizing both the eigenfunctions and the occupation matrix, our method minimizes the free energy with respect to these parameters. As the stationary conditions require the occupation matrix and the Kohn-Sham Hamiltonian to be simultaneously diagonalizable, this leads to the concept of "self-diagonalization," where, by assuming a diagonal occupation matrix without loss of generality, the Hamiltonian matrix naturally becomes diagonal at stationary points. Our method incorporates physical constraints on both the eigenfunctions and the occupations into the parametrization, transforming the constrained optimization into an fully differentiable unconstrained problem, which is solvable via gradient descent. Implemented in JAX, our method was tested on aluminum and silicon, confirming that it achieves efficient self-diagonalization, produces the correct Fermi-Dirac distribution of the occupation numbers and yields band structures consistent with those obtained with SCF eigensolver methods in Quantum Espresso.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present a novel approach to address the challenges of variable occupation numbers in direct optimization of density functional theory (DFT). By parametrizing both the eigenfunctions and the occupation matrix, our method minimizes the free energy with respect to these parameters. As the stationary conditions require the occupation matrix and the Kohn-Sham Hamiltonian to be simultaneously diagonalizable, this leads to the concept of "self-diagonalization," where, by assuming a diagonal occupation matrix without loss of generality, the Hamiltonian matrix naturally becomes diagonal at stationary points. Our method incorporates physical constraints on both the eigenfunctions and the occupations into the parametrization, transforming the constrained optimization into an fully differentiable unconstrained problem, which is solvable via gradient descent. Implemented in JAX, our method was tested on aluminum and silicon, confirming that it achieves efficient self-diagonalization, produces the correct Fermi-Dirac distribution of the occupation numbers and yields band structures consistent with those obtained with SCF eigensolver methods in Quantum Espresso. |
Shen, Yaqing; Pazos, Sebastian; Zheng, Wenwen; Yuan, Yue; Ping, Yue; Alharbi, Osamah; Liu, Hang; Lu, Xu; Lanza, Mario MoS2 Transistors with 4 nm hBN Gate Dielectric and 0.46 V Threshold Voltage Journal Article ACS NANO, 19 (17), pp. 16903-16912, 2025, ISSN: 1936-0851. @article{ISI:001474827200001, title = {MoS_{2} Transistors with 4 nm hBN Gate Dielectric and 0.46 V Threshold Voltage}, author = {Yaqing Shen and Sebastian Pazos and Wenwen Zheng and Yue Yuan and Yue Ping and Osamah Alharbi and Hang Liu and Xu Lu and Mario Lanza}, doi = {10.1021/acsnano.5c02341}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-04-24}, journal = {ACS NANO}, volume = {19}, number = {17}, pages = {16903-16912}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {The use of two-dimensional (2D) semiconducting materials (MoS2, WS2) as a channel in field-effect transistors may help extend Moore's law and produce devices beyond the complementary metal-oxide-semiconductor (CMOS) technology. Traditional dielectrics used in microelectronics (SiO2, HfO2, Al2O3) form a defective interface with the 2D semiconductor & horbar;because the latter does not have dangling bonds & horbar;leading to multiple device reliability issues and premature failure. Using 2D hexagonal boron nitride (hBN) as the gate dielectric sounds like a potential solution because it can form a clean van der Waals interface with the 2D semiconductor. However, its relative permittivity is only 3.6, which has raised concerns: it is believed that a MoS2 transistor with hBN gate dielectric cannot be switched ON without the apparition of gate leakage current. Here, we show that transistors with a Pt/4 nm-hBN/MoS2 vertical structure can exhibit ON/OFF current ratios above 10(5), low threshold voltage of 0.46 V, and low gate leakage current density (J(G)) of 10(-4) A/cm(2). Moreover, our Pt/hBN/MoS2 transistors show acceptable performance even after 1000 switching cycles: ON/OFF current ratio is above 10(4) and J(G) below 10(-4) A/cm(2). Our study indicates that hBN may be a suitable gate dielectric for some types of nanosized MoS2 transistors.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The use of two-dimensional (2D) semiconducting materials (MoS2, WS2) as a channel in field-effect transistors may help extend Moore's law and produce devices beyond the complementary metal-oxide-semiconductor (CMOS) technology. Traditional dielectrics used in microelectronics (SiO2, HfO2, Al2O3) form a defective interface with the 2D semiconductor & horbar;because the latter does not have dangling bonds & horbar;leading to multiple device reliability issues and premature failure. Using 2D hexagonal boron nitride (hBN) as the gate dielectric sounds like a potential solution because it can form a clean van der Waals interface with the 2D semiconductor. However, its relative permittivity is only 3.6, which has raised concerns: it is believed that a MoS2 transistor with hBN gate dielectric cannot be switched ON without the apparition of gate leakage current. Here, we show that transistors with a Pt/4 nm-hBN/MoS2 vertical structure can exhibit ON/OFF current ratios above 10(5), low threshold voltage of 0.46 V, and low gate leakage current density (J(G)) of 10(-4) A/cm(2). Moreover, our Pt/hBN/MoS2 transistors show acceptable performance even after 1000 switching cycles: ON/OFF current ratio is above 10(4) and J(G) below 10(-4) A/cm(2). Our study indicates that hBN may be a suitable gate dielectric for some types of nanosized MoS2 transistors. |
Zhu, Yiru; Zhang, Zhepeng; Wang, Ye; Sarkar, Soumya; Li, Yang; Yan, Han; Ishibe-Veiga, Larissa; Bagri, Anita; Yang, Ziwei Jeffrey; Ramsden, Hugh; Eda, Goki; Hoye, Robert L Z; Wang, Yan; Chhowalla, Manish Effect of Substrate on Sulfur Vacancy Defect-Mediated Photoluminescence in Two-Dimensional MoS2 Journal Article JOURNAL OF PHYSICAL CHEMISTRY C, 129 (17), pp. 8294-8302, 2025, ISSN: 1932-7447. @article{ISI:001470681000001, title = {Effect of Substrate on Sulfur Vacancy Defect-Mediated Photoluminescence in Two-Dimensional MoS_{2}}, author = {Yiru Zhu and Zhepeng Zhang and Ye Wang and Soumya Sarkar and Yang Li and Han Yan and Larissa Ishibe-Veiga and Anita Bagri and Ziwei Jeffrey Yang and Hugh Ramsden and Goki Eda and Robert L Z Hoye and Yan Wang and Manish Chhowalla}, doi = {10.1021/acs.jpcc.4c08491}, times_cited = {0}, issn = {1932-7447}, year = {2025}, date = {2025-04-18}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {129}, number = {17}, pages = {8294-8302}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Chalcogen vacancy defects in monolayer transition metal dichalcogenides form in-gap states that can trap excitons, leading to defect-mediated photoluminescence (PL) emission. Here, we show that room-temperature (RT, 300 K) PL from sulfur vacancies in defective monolayer MoS2 is sensitive to doping from dielectric substrates such as SiO2 and HfO2. The defect-mediated PL is observed for monolayer MoS2 on untreated HfO2 but is quenched on untreated SiO2, which is attributed to electron doping of MoS2 on SiO2. Electron doping of MoS2 is confirmed by Raman and synchrotron X-ray photoelectron spectroscopy. Annealing of the SiO2 substrate modifies its surface states, which is reflected in the recovery of the defect-mediated PL emission. The role of substrate-induced doping on sulfur vacancy-mediated PL is further supported by gate-dependent PL measurements. Our results suggest that excess electrons fill the defect energy states from sulfur vacancies in MoS2, reducing the probability of photoexcited carrier occupation and subsequent defect-mediated emission.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Chalcogen vacancy defects in monolayer transition metal dichalcogenides form in-gap states that can trap excitons, leading to defect-mediated photoluminescence (PL) emission. Here, we show that room-temperature (RT, 300 K) PL from sulfur vacancies in defective monolayer MoS2 is sensitive to doping from dielectric substrates such as SiO2 and HfO2. The defect-mediated PL is observed for monolayer MoS2 on untreated HfO2 but is quenched on untreated SiO2, which is attributed to electron doping of MoS2 on SiO2. Electron doping of MoS2 is confirmed by Raman and synchrotron X-ray photoelectron spectroscopy. Annealing of the SiO2 substrate modifies its surface states, which is reflected in the recovery of the defect-mediated PL emission. The role of substrate-induced doping on sulfur vacancy-mediated PL is further supported by gate-dependent PL measurements. Our results suggest that excess electrons fill the defect energy states from sulfur vacancies in MoS2, reducing the probability of photoexcited carrier occupation and subsequent defect-mediated emission. |
Freeman, Charlie W F; Youel, Harry; Budniak, Adam K; Xue, Zekun; Libero, Henry De; Thomson, Thomas; Bosman, Michel; Eda, Goki; Kurebayashi, Hidekazu; Cubukcu, Murat Tunable Ultrastrong Magnon-Magnon Coupling Approaching the Deep-Strong Regime in a van der Waals Antiferromagnet Journal Article ACS NANO, 19 (16), pp. 16024-16031, 2025, ISSN: 1936-0851. @article{ISI:001469180000001, title = {Tunable Ultrastrong Magnon-Magnon Coupling Approaching the Deep-Strong Regime in a van der Waals Antiferromagnet}, author = {Charlie W F Freeman and Harry Youel and Adam K Budniak and Zekun Xue and Henry De Libero and Thomas Thomson and Michel Bosman and Goki Eda and Hidekazu Kurebayashi and Murat Cubukcu}, doi = {10.1021/acsnano.5c02576}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-04-17}, journal = {ACS NANO}, volume = {19}, number = {16}, pages = {16024-16031}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Antiferromagnetic (AFM) magnons in van der Waals (vdW) materials offer substantial potential for applications in magnonics and spintronics. In this study, we demonstrate ultrastrong magnon-magnon coupling in the GHz regime within a vdW AFM, achieving a maximum coupling rate of 0.91. Our investigation shows the tunability of coupling strength through temperature-dependent magnetic anisotropies. We compare coupling strength values derived from the gap size from the measured spectrum with those calculated directly through the coupling parameter and show that the gap size as a measure of coupling strength is limited for the ultrastrong coupling regime. Additionally, analytical calculations show the possibility to reach the deep-strong coupling regime by engineering the magnetic anisotropy. These findings highlight the potential of vdW AFMs as a model case to study magnetization dynamics in low-symmetry magnetic materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Antiferromagnetic (AFM) magnons in van der Waals (vdW) materials offer substantial potential for applications in magnonics and spintronics. In this study, we demonstrate ultrastrong magnon-magnon coupling in the GHz regime within a vdW AFM, achieving a maximum coupling rate of 0.91. Our investigation shows the tunability of coupling strength through temperature-dependent magnetic anisotropies. We compare coupling strength values derived from the gap size from the measured spectrum with those calculated directly through the coupling parameter and show that the gap size as a measure of coupling strength is limited for the ultrastrong coupling regime. Additionally, analytical calculations show the possibility to reach the deep-strong coupling regime by engineering the magnetic anisotropy. These findings highlight the potential of vdW AFMs as a model case to study magnetization dynamics in low-symmetry magnetic materials. |
Lanza, Mario; Pazos, Sebastian; Aguirre, Fernando; Sebastian, Abu; Gallo, Manuel Le; Alam, Syed M; Ikegawa, Sumio; Yang, Joshua J; Vianello, Elisa; Chang, Meng-Fan; Molas, Gabriel; Naveh, Ishai; Ielmini, Daniele; Liu, Ming; Roldan, Juan B The growing memristor industry Journal Article NATURE, 640 (8059), pp. 613-622, 2025, ISSN: 0028-0836. @article{ISI:001508375400027, title = {The growing memristor industry}, author = {Mario Lanza and Sebastian Pazos and Fernando Aguirre and Abu Sebastian and Manuel Le Gallo and Syed M Alam and Sumio Ikegawa and Joshua J Yang and Elisa Vianello and Meng-Fan Chang and Gabriel Molas and Ishai Naveh and Daniele Ielmini and Ming Liu and Juan B Roldan}, doi = {10.1038/s41586-025-08733-5}, times_cited = {2}, issn = {0028-0836}, year = {2025}, date = {2025-04-17}, journal = {NATURE}, volume = {640}, number = {8059}, pages = {613-622}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {The semiconductor industry is experiencing an accelerated transformation to overcome the scaling limits of the transistor and to adapt to new requirements in terms of data storage and computation, especially driven by artificial intelligence applications and the Internet of Things. In this process, new materials, devices, integration strategies and system architectures are being developed and optimized. Among them, memristive devices and circuits-memristors are two-terminal memory devices that can also mimic some basic bioelectronic functions-offer a potential approach to create more compact, energy-efficient or better-performing systems. The memristor industry is growing quickly, raising abundant capital investment, creating new jobs and placing advanced products in the market. Here we analyse the status and prospects of the memristor industry, focusing on memristor-based products that are already commercially available, prototypes with a high technological readiness level that might affect the market in the near future, and discuss obstacles and pathways to their implementation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The semiconductor industry is experiencing an accelerated transformation to overcome the scaling limits of the transistor and to adapt to new requirements in terms of data storage and computation, especially driven by artificial intelligence applications and the Internet of Things. In this process, new materials, devices, integration strategies and system architectures are being developed and optimized. Among them, memristive devices and circuits-memristors are two-terminal memory devices that can also mimic some basic bioelectronic functions-offer a potential approach to create more compact, energy-efficient or better-performing systems. The memristor industry is growing quickly, raising abundant capital investment, creating new jobs and placing advanced products in the market. Here we analyse the status and prospects of the memristor industry, focusing on memristor-based products that are already commercially available, prototypes with a high technological readiness level that might affect the market in the near future, and discuss obstacles and pathways to their implementation. |
Lin, Guoming; Mirsaidov, Utkur Encapsulation of Metal Nanoparticles by Metal-Organic Framework Imaged with In Situ Liquid Phase Transmission Electron Microscopy Journal Article ADVANCED SCIENCE, 2025. @article{ISI:001468850000001, title = {Encapsulation of Metal Nanoparticles by Metal-Organic Framework Imaged with In Situ Liquid Phase Transmission Electron Microscopy}, author = {Guoming Lin and Utkur Mirsaidov}, doi = {10.1002/advs.202500984}, times_cited = {0}, year = {2025}, date = {2025-04-17}, journal = {ADVANCED SCIENCE}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {Metal nanoparticle@metal-organic framework (NP@MOF) composites hold promise for potential applications in gas storage, catalysis, sensing, environmental monitoring, and biomedicine. Despite their importance, details of how MOFs encapsulate the NPs to form NP@MOF hybrid nanostructures are largely unexplored. Here, using ultra-low electron-flux in situ liquid phase transmission electron microscopy (LP-TEM), the encapsulation of Au NPs with zeolitic imidazolate framework-8 (ZIF-8) is visualized. These observations reveal that the speeds at which MOFs nucleate on the NP's surface impact the shell's shape. At low concentrations of MOF precursor, NPs are encapsulated with well-defined single-crystalline MOF shells, while at high concentrations, MOFs tend to nucleate and grow from multiple sites on the NP surface, resulting in irregularly shaped polycrystalline MOF shells. This approach, which uses a very low electron flux to image the synthesis of Au@ZIF-8 nanostructures, can be extended to imaging crucial processes in many other beam-sensitive materials and help design hybrid systems for a broad range of applications.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Metal nanoparticle@metal-organic framework (NP@MOF) composites hold promise for potential applications in gas storage, catalysis, sensing, environmental monitoring, and biomedicine. Despite their importance, details of how MOFs encapsulate the NPs to form NP@MOF hybrid nanostructures are largely unexplored. Here, using ultra-low electron-flux in situ liquid phase transmission electron microscopy (LP-TEM), the encapsulation of Au NPs with zeolitic imidazolate framework-8 (ZIF-8) is visualized. These observations reveal that the speeds at which MOFs nucleate on the NP's surface impact the shell's shape. At low concentrations of MOF precursor, NPs are encapsulated with well-defined single-crystalline MOF shells, while at high concentrations, MOFs tend to nucleate and grow from multiple sites on the NP surface, resulting in irregularly shaped polycrystalline MOF shells. This approach, which uses a very low electron flux to image the synthesis of Au@ZIF-8 nanostructures, can be extended to imaging crucial processes in many other beam-sensitive materials and help design hybrid systems for a broad range of applications. |
Cheng, Nicholas Lin Quan; Ulman, Kanchan Ajit; Quek, Su Ying Defect Engineering in Hexagonal Boron Nitride: Optical Properties of Stable Defect Complexes Arising from Boron Interstitials Journal Article ACS APPLIED MATERIALS & INTERFACES, 17 (16), pp. 24058-24070, 2025, ISSN: 1944-8244. @article{ISI:001466592300001, title = {Defect Engineering in Hexagonal Boron Nitride: Optical Properties of Stable Defect Complexes Arising from Boron Interstitials}, author = {Nicholas Lin Quan Cheng and Kanchan Ajit Ulman and Su Ying Quek}, doi = {10.1021/acsami.4c19034}, times_cited = {0}, issn = {1944-8244}, year = {2025}, date = {2025-04-14}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {17}, number = {16}, pages = {24058-24070}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor that is promising as a host material for solid-state quantum technologies through defect engineering. It has been shown that boron atoms can be removed from the lattice upon irradiation by electrons or light ions, creating boron vacancies and boron interstitials. While the optical properties of boron-vacancy-derived defects have been studied extensively, little is known about the optical properties of boron-interstitial-derived defects. In this work, we use state-of-the-art first-principles calculations to predict the electronic and optical properties of boron interstitials (Bint) and defect complexes comprising Bint and substitutional carbon impurities at boron and nitrogen sites (CB and CN). These carbon impurities can be present in as-grown hBN and can also be introduced intentionally. We demonstrate that these complexes are expected to be stable at room temperature. Our GW-Bethe-Salpeter equation (BSE) calculations show that Bint-CB and Bint-CN have low-energy optical transitions that are isolated in energy, making them suitable as single-photon emitters. Together with constrained density functional theory calculations to capture the red shift due to emission, we predict that Bint-CB and Bint-CN have zero phonon lines at similar to 2.0 eV and similar to 2.6 eV, respectively. Defects involving Bint are likely to be the source of blue emitters recently observed in regions several microns away from ion-irradiated parts of hBN. Our work sheds light on these recent experiments and introduces a fresh perspective to the field of quantum emitters in hBN-we show that defects related to Bint are potential single-photon emitters that can be intentionally created in hBN.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor that is promising as a host material for solid-state quantum technologies through defect engineering. It has been shown that boron atoms can be removed from the lattice upon irradiation by electrons or light ions, creating boron vacancies and boron interstitials. While the optical properties of boron-vacancy-derived defects have been studied extensively, little is known about the optical properties of boron-interstitial-derived defects. In this work, we use state-of-the-art first-principles calculations to predict the electronic and optical properties of boron interstitials (Bint) and defect complexes comprising Bint and substitutional carbon impurities at boron and nitrogen sites (CB and CN). These carbon impurities can be present in as-grown hBN and can also be introduced intentionally. We demonstrate that these complexes are expected to be stable at room temperature. Our GW-Bethe-Salpeter equation (BSE) calculations show that Bint-CB and Bint-CN have low-energy optical transitions that are isolated in energy, making them suitable as single-photon emitters. Together with constrained density functional theory calculations to capture the red shift due to emission, we predict that Bint-CB and Bint-CN have zero phonon lines at similar to 2.0 eV and similar to 2.6 eV, respectively. Defects involving Bint are likely to be the source of blue emitters recently observed in regions several microns away from ion-irradiated parts of hBN. Our work sheds light on these recent experiments and introduces a fresh perspective to the field of quantum emitters in hBN-we show that defects related to Bint are potential single-photon emitters that can be intentionally created in hBN. |
Liang, Haidong; Chen, Yuan; Loh, Leyi; Cheng, Nicholas Lin Quan; Litvinov, Dmitrii; Yang, Chengyuan; Chen, Yifeng; Zhang, Zhepeng; Watanabe, Kenji; Taniguchi, Takashi; Koperski, Maciej; Quek, Su Ying; Bosman, Michel; Eda, Goki; Bettiol, Andrew Anthony Site-Selective Creation of Blue Emitters in Hexagonal Boron Nitride Journal Article ACS NANO, 19 (15), pp. 15130-15138, 2025, ISSN: 1936-0851. @article{ISI:001465855100001, title = {Site-Selective Creation of Blue Emitters in Hexagonal Boron Nitride}, author = {Haidong Liang and Yuan Chen and Leyi Loh and Nicholas Lin Quan Cheng and Dmitrii Litvinov and Chengyuan Yang and Yifeng Chen and Zhepeng Zhang and Kenji Watanabe and Takashi Taniguchi and Maciej Koperski and Su Ying Quek and Michel Bosman and Goki Eda and Andrew Anthony Bettiol}, doi = {10.1021/acsnano.5c03423}, times_cited = {0}, issn = {1936-0851}, year = {2025}, date = {2025-04-12}, journal = {ACS NANO}, volume = {19}, number = {15}, pages = {15130-15138}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Hexagonal boron nitride (hBN) has been of great interest due to its ability to host several bright quantum emitters at room temperature. However, the identification of the observed emitters remains challenging due to spectral variability, as well as the lack of atomic defect structure information. In this work, we demonstrate the site-selective creation of blue emitters in exfoliated hBN flakes with high-energy ion irradiation. With the correlation analysis of cryogenic and temperature-dependent photoluminescence (PL) spectroscopy, we observe two zero phonon lines (ZPLs) at similar to 432.8 and 454.3 nm. Photoluminescence excitation (PLE) measurements further confirm the emission origins of the two prominent lines. Scanning transmission electron microscopy (STEM) reveals that the dominant defect structures present in ion-irradiated samples are vacancy-type (V x ) and adatom(intercalant)-type (A x ). Together with first-principles GW-BSE (Bethe-Salpeter equation) calculations, we deduce that the observed blue emissions are likely related to boron intercalants (Bint). Our results not only discover a group of blue emissions in hBN but also provide insights into the physical origin of the emissions with local atomic structures in hBN.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hexagonal boron nitride (hBN) has been of great interest due to its ability to host several bright quantum emitters at room temperature. However, the identification of the observed emitters remains challenging due to spectral variability, as well as the lack of atomic defect structure information. In this work, we demonstrate the site-selective creation of blue emitters in exfoliated hBN flakes with high-energy ion irradiation. With the correlation analysis of cryogenic and temperature-dependent photoluminescence (PL) spectroscopy, we observe two zero phonon lines (ZPLs) at similar to 432.8 and 454.3 nm. Photoluminescence excitation (PLE) measurements further confirm the emission origins of the two prominent lines. Scanning transmission electron microscopy (STEM) reveals that the dominant defect structures present in ion-irradiated samples are vacancy-type (V x ) and adatom(intercalant)-type (A x ). Together with first-principles GW-BSE (Bethe-Salpeter equation) calculations, we deduce that the observed blue emissions are likely related to boron intercalants (Bint). Our results not only discover a group of blue emissions in hBN but also provide insights into the physical origin of the emissions with local atomic structures in hBN. |