Xingxing Zhang

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01 Dec 03:07

[ASAP] Tuning the Band Structure of MoS2 via Co9S8@MoS2 Core–Shell Structure to Boost Catalytic Activity for Lithium–Sulfur Batteries

by Boyu Li, Qingmei Su, Lintao Yu, Jun Zhang, Gaohui Du, Dong Wang, Di Han, Miao Zhang, Shukai Ding, and Bingshe Xu

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ACS Nano
DOI: 10.1021/acsnano.0c07332
01 Dec 03:06

[ASAP] cm2-Scale Synthesis of MoTe2 Thin Films with Large Grains and Layer Control

by David J. Hynek, Raivat M. Singhania, Shiyu Xu, Benjamin Davis, Leizhi Wang, Milad Yarali, Joshua V. Pondick, John M. Woods, Nicholas C. Strandwitz, and Judy J. Cha

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ACS Nano
DOI: 10.1021/acsnano.0c08069
01 Dec 03:06

[ASAP] Scalable Integration of Coplanar Heterojunction Monolithic Devices on Two-Dimensional In2Se3

by Subhrajit Mukherjee, Debopriya Dutta, Pranab K. Mohapatra, Lital Dezanashvili, Ariel Ismach, and Elad Koren

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ACS Nano
DOI: 10.1021/acsnano.0c08146
01 Dec 03:06

[ASAP] Area-Selective Atomic Layer Deposition Patterned by Electrohydrodynamic Jet Printing for Additive Manufacturing of Functional Materials and Devices

by Tae H. Cho, Nazanin Farjam, Christopher R. Allemang, Christopher P. Pannier, Eric Kazyak, Carli Huber, Mattison Rose, Orlando Trejo, Rebecca L. Peterson, Kira Barton, and Neil P. Dasgupta

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ACS Nano
DOI: 10.1021/acsnano.0c07297
01 Dec 03:00

[ASAP] Metalated Graphyne-Based Networks as Two-Dimensional Materials: Crystallization, Topological Defects, Delocalized Electronic States, and Site-Specific Doping

by Zechao Yang, Tim Sander, Julian Gebhardt, Tobias A. Schaub, Jörg Schönamsgruber, Himadri R. Soni, Andreas Görling, Milan Kivala, and Sabine Maier

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ACS Nano
DOI: 10.1021/acsnano.0c05865
01 Dec 02:59

[ASAP] Two-Dimensional Silicon/Carbon from Commercial Alloy and CO2 for Lithium Storage and Flexible Ti3C2Tx MXene-Based Lithium–Metal Batteries

by Yongling An, Yuan Tian, Yuchan Zhang, Chuanliang Wei, Liwen Tan, Chenghui Zhang, Naxin Cui, Shenglin Xiong, Jinkui Feng, and Yitai Qian

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ACS Nano
DOI: 10.1021/acsnano.0c08336
01 Dec 02:58

[ASAP] Flux Tunable Superconducting Quantum Circuit Based on Weyl Semimetal MoTe2

by Kuei-Lin Chiu, Degui Qian, Jiawei Qiu, Weiyang Liu, Dian Tan, Vahid Mosallanejad, Song Liu, Zongteng Zhang, Yue Zhao, and Dapeng Yu

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Nano Letters
DOI: 10.1021/acs.nanolett.0c02267
01 Dec 02:57

[ASAP] Second-Harmonic Young’s Interference in Atom-Thin Heterocrystals

by Wontaek Kim, Je Yhoung Ahn, Juseung Oh, Ji Hoon Shim, and Sunmin Ryu

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Nano Letters
DOI: 10.1021/acs.nanolett.0c03763
01 Dec 02:56

[ASAP] Precise Tuning of Band Structures and Electron Correlations by van der Waals Stacking of One-dimensional W6Te6 Wires

by Jinghao Deng, Da Huo, Yusong Bai, Yanping Guo, Zemin Pan, Shuangzan Lu, Ping Cui, Zhenyu Zhang, and Chendong Zhang

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Nano Letters
DOI: 10.1021/acs.nanolett.0c03897
01 Dec 02:55

[ASAP] Chiral Spin Spirals at the Surface of the van der Waals Ferromagnet Fe3GeTe2

by Mariëlle J. Meijer, Juriaan Lucassen, Rembert A. Duine, Henk J.M. Swagten, Bert Koopmans, Reinoud Lavrijsen, and Marcos H. D. Guimarães

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Nano Letters
DOI: 10.1021/acs.nanolett.0c03111
01 Dec 02:54

[ASAP] Plasmon-Enhanced Near-Field Chirality in Twisted van der Waals Heterostructures

by Tobias Stauber, Tony Low, and Guillermo Gómez-Santos

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Nano Letters
DOI: 10.1021/acs.nanolett.0c03519
01 Dec 02:53

Criteria for Realizing Room‐Temperature Electrical Transport Applications of Topological Materials

by Matthew Brahlek
Criteria for Realizing Room‐Temperature Electrical Transport Applications of Topological Materials

What does it take to make a room‐temperature electronic device based on the unusual states found in topological materials? The answer is a materials‐redesign, which delicately balances bandgap, dielectric constant, and effective mass. Identifying this new generation of materials can pave the way to realistic quantum technologies.


Abstract

The unusual electronic states found in topological materials can enable a new generation of devices and technologies, yet a long‐standing challenge has been finding materials without deleterious parallel bulk conduction. This can arise either from defects or thermally activated carriers. Here, the criteria that materials need to meet to realize transport properties dominated by the topological states, a necessity for a topological device, are clarified. This is demonstrated for 3D topological insulators, 3D Dirac materials, and 1D quantum anomalous Hall insulators, though this can be applied to similar systems. The key parameters are electronic bandgap, dielectric constant, and carrier effective mass, which dictate under what circumstances (defect density, temperature, etc.) the unwanted bulk state will conduct in parallel to the topological states. As these are fundamentally determined by the basic atomic properties, simple chemical arguments can be used to navigate the phase space to ultimately find improved materials. This will enable rapid identification of new systems with improved properties, which is crucial to designing new material systems and push a new generation of topological technologies.

01 Dec 02:52

Charge–Ferroelectric Transition in Ultrathin Na0.5Bi4.5Ti4O15 Flakes Probed via a Dual‐Gated Full van der Waals Transistor

by Xiaochi Liu, Xuefan Zhou, Yuchuan Pan, Junqiang Yang, Haiyan Xiang, Yahua Yuan, Song Liu, Hang Luo, Dou Zhang, Jian Sun
Charge–Ferroelectric Transition in Ultrathin Na0.5Bi4.5Ti4O15 Flakes Probed via a Dual‐Gated Full van der Waals Transistor

A dual‐gated MoS2 ferroelectric field‐effect transistor in full van der Waals structure is demonstrated with a thin Na0.5Bi4.5Ti4O15 flake as the ferroelectric gate dielectric. Hysteresis behaviors can be electrostatically controlled by dual‐gating from charge dynamic (clockwise) to ferroelectric (counterclockwise). This allows a multifunctional device with its operation switchable from short‐term memory to nonvolatile ferroelectric memory.


Abstract

Ferroelectric field‐effect transistors (FeFETs) have recently attracted enormous attention owing to their applications in nonvolatile memories and low‐power logic electronics. However, the current mainstream thin‐film‐based ferroelectrics lack good compatibility with the emergent 2D van der Waals (vdW) heterostructures. In this work, the synthesis of thin ferroelectric Na0.5Bi4.5Ti4O15 (NBIT) flakes by a molten‐salt method is reported. With a dry‐transferred NBIT flake serving as the top‐gate dielectric, dual‐gate molybdenum disulfide (MoS2) FeFETs are fabricated in a full vdW stacking structure. Barrier‐free graphene contacts allow the investigation of intrinsic carrier transport of MoS2 governed by lattice scattering. Thanks to the high dielectric constant of ≈94 in NBIT, a metal to insulator transition with a high electron concentration of 3.0 × 1013 cm−2 is achieved in MoS2 under top‐gate modulation. The electron field‐effect mobility as high as 182 cm2 V−1 s−1 at 88 K is obtained. The as‐fabricated MoS2 FeFET exhibits clockwise hysteresis transfer curves that originate from charge trapping/release with either top‐gate or back‐gate modulation. Interestingly, hysteresis behavior can be controlled from clockwise to counterclockwise using dual‐gate. A multifunctional device utilizing this unique property of NBIT, which is switchable electrostatically between short‐term memory and nonvolatile ferroelectric memory, is envisaged.

01 Dec 02:50

Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

by Azimkhan Kozhakhmetov, Bruno Schuler, Anne Marie Z. Tan, Katherine A. Cochrane, Joseph R. Nasr, Hesham El‐Sherif, Anushka Bansal, Alex Vera, Vincent Bojan, Joan M. Redwing, Nabil Bassim, Saptarshi Das, Richard G. Hennig, Alexander Weber‐Bargioni, Joshua A. Robinson
Scalable Substitutional Re‐Doping and its Impact on the Optical and Electronic Properties of Tungsten Diselenide

Substitutional rhenium (Re) doping of tungsten diselenide (WSe2) films is achieved via metal–organic chemical vapor deposition at front‐end‐of‐line (FEOL) and back‐end‐of‐line (BEOL) compatible temperatures, with a doping concentration of <0.001%. Trion concentration is increased as a function of dopant concentration and discrete donor levels that lie close to the conduction band are observed, confirming the n‐type dopant nature of the rhenium atoms.


Abstract

Reliable, controlled doping of 2D transition metal dichalcogenides will enable the realization of next‐generation electronic, logic‐memory, and magnetic devices based on these materials. However, to date, accurate control over dopant concentration and scalability of the process remains a challenge. Here, a systematic study of scalable in situ doping of fully coalesced 2D WSe2 films with Re atoms via metal–organic chemical vapor deposition is reported. Dopant concentrations are uniformly distributed over the substrate surface, with precisely controlled concentrations down to <0.001% Re achieved by tuning the precursor partial pressure. Moreover, the impact of doping on morphological, chemical, optical, and electronic properties of WSe2 is elucidated with detailed experimental and theoretical examinations, confirming that the substitutional doping of Re at the W site leads to n‐type behavior of WSe2. Transport characteristics of fabricated back‐gated field‐effect‐transistors are directly correlated to the dopant concentration, with degrading device performances for doping concentrations exceeding 1% of Re. The study demonstrates a viable approach to introducing true dopant‐level impurities with high precision, which can be scaled up to batch production for applications beyond digital electronics.

01 Dec 02:49

Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe2 Heterostructures

by Yu Chen, Lishu Wu, Hai Xu, Chunxiao Cong, Si Li, Shun Feng, Hongbo Zhang, Chenji Zou, Jingzhi Shang, Shengyuan A. Yang, Kian Ping Loh, Wei Huang, Ting Yu
Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe2 Heterostructures

Prominent suppression of the charge density wave (CDW) orders in graphene/NbSe2 heterostructures is observed by Raman spectroscopy and scanning tunneling microscopy/spectroscopy. The findings propose a new criterion to determine the T CDW through monitoring the line shape of the A1g mode. First‐principles calculations imply that interfacial electron doping suppresses the CDW states by impeding the lattice distortion of 2H‐NbSe2.


Abstract

Metallic layered transition metal dichalcogenides (TMDs) host collective many‐body interactions, including the competing superconducting and charge density wave (CDW) states. Graphene is widely employed as a heteroepitaxial substrate for the growth of TMD layers and as an ohmic contact, where the graphene/TMD heterostructure is naturally formed. The presence of graphene can unpredictably influence the CDW order in 2D CDW conductors. This work reports the CDW transitions of 2H‐NbSe2 layers in graphene/NbSe2 heterostructures. The evolution of Raman spectra demonstrates that the CDW phase transition temperatures (T CDW) of NbSe2 are dramatically decreased when capped by graphene. The induced anomalous short‐range CDW state is confirmed by scanning tunneling microscopy measurements. The findings propose a new criterion to determine the T CDW through monitoring the line shape of the A1g mode. Meanwhile, the 2D band is also discovered as an indicator to observe the CDW transitions. First‐principles calculations imply that interfacial electron doping suppresses the CDW states by impeding the lattice distortion of 2H‐NbSe2. The extraordinary random CDW lattice suggests deep insight into the formation mechanism of many collective electronic states and possesses great potential in modulating multifunctional devices.

01 Dec 02:48

Air‐Stable Low‐Symmetry Narrow‐Bandgap 2D Sulfide Niobium for Polarization Photodetection

by Yang Wang, Peisong Wu, Zhen Wang, Man Luo, Fang Zhong, Xun Ge, Kun Zhang, Meng Peng, Yan Ye, Qing Li, Haonan Ge, Jiafu Ye, Ting He, Yunfeng Chen, Tengfei Xu, Chenhui Yu, Yueming Wang, Zhigao Hu, Xiaohao Zhou, Chongxin Shan, Mingsheng Long, Peng Wang, Peng Zhou, Weida Hu
Air‐Stable Low‐Symmetry Narrow‐Bandgap 2D Sulfide Niobium for Polarization Photodetection

Novel 2D anisotropic sulfide niobium (NbS3) is introduced into the material family by demonstrating its in‐plane structure, phonon vibrations, and electrical and optical anisotropies. Meaningfully, NbS3 Schottky photodetectors exhibit broadband detection sensitivity (400–10 600 nm), excellent response time (as fast as 11 µs), photoelectrical dichroic ratio (1.84), and high‐quality polarization imaging.


Abstract

Low‐symmetry 2D materials with unique anisotropic optical and optoelectronic characteristics have attracted a lot of interest in fundamental research and manufacturing of novel optoelectronic devices. Exploring new and low‐symmetry narrow‐bandgap 2D materials will be rewarding for the development of nanoelectronics and nano‐optoelectronics. Herein, sulfide niobium (NbS3), a novel transition metal trichalcogenide semiconductor with low‐symmetry structure, is introduced into a narrowband 2D material with strong anisotropic physical properties both experimentally and theoretically. The indirect bandgap of NbS3 with highly anisotropic band structures slowly decreases from 0.42 eV (monolayer) to 0.26 eV (bulk). Moreover, NbS3 Schottky photodetectors have excellent photoelectric performance, which enables fast photoresponse (11.6 µs), low specific noise current (4.6 × 10−25 A2 Hz−1), photoelectrical dichroic ratio (1.84) and high‐quality reflective polarization imaging (637 nm and 830 nm). A room‐temperature specific detectivity exceeding 107 Jones can be obtained at the wavelength of 3 µm. These excellent unique characteristics will make low‐symmetry narrow‐bandgap 2D materials become highly competitive candidates for future anisotropic optical investigations and mid‐infrared optoelectronic applications.

01 Dec 02:42

Recent Advances in Growth of Large‐Sized 2D Single Crystals on Cu Substrates

by Yixuan Fan, Lin Li, Gui Yu, Dechao Geng, Xiaotao Zhang, Wenping Hu
Recent Advances in Growth of Large‐Sized 2D Single Crystals on Cu Substrates

Recent advances in the growth and production of wafer‐scale and single‐crystal 2D materials on Cu substrates by chemical vapor deposition are presented. The features and roles of Cu in making 2D crystals are comprehensively demonstrated. The daunting quest for mass production of single‐crystal 2D materials poses great potential in electronics and other applications.


Abstract

Large‐scale and high‐quality 2D materials have been an emerging and promising choice for use in modern chemistry and physics owing to their fascinating property profile. The past few years have witnessed inspiringly progressing development in controlled fabrication of large‐sized and single‐crystal 2D materials. Among those production methods, chemical vapor deposition (CVD) has drawn the most attention because of its fine control over size and quality of 2D materials by modulating the growth conditions. Meanwhile, Cu has been widely accepted as the most popular catalyst due to its significant merit in growing monolayer 2D materials in the CVD process. Herein, very recent advances in preparing large‐sized 2D single crystals on Cu substrates by CVD are presented. First, the unique features of Cu will be given in terms of ultralow precursor solubility and feasible surface engineering. Then, scaled growth of graphene and hexagonal boron nitride (h‐BN) crystals on Cu substrates is demonstrated, wherein different kinds of Cu surfaces have been employed. Furthermore, the growth mechanism for the growth of 2D single crystals is exhibited, offering a guideline to elucidate the in‐depth growth dynamics and kinetics. Finally, relevant issues for industrial‐scale mass production of 2D single crystals are discussed and a promising future is expected.

01 Dec 02:40

General Synthesis of Nanoporous 2D Metal Compounds with 3D Bicontinous Structure

by Dechao Chen, Shoucong Ning, Jiao Lan, Ming Peng, Huigao Duan, Anlian Pan, Yongwen Tan
General Synthesis of Nanoporous 2D Metal Compounds with 3D Bicontinous Structure

2D metal compounds with bicontinous nanoporous structure are successfully prepared by using a recyclable nanoporous gold assisted chemical vapor deposition process. The resulting 3D nanoporous MoSSe with tunable pore sizes and porosity exhibits excellent electrochemical N2 reduction reaction properties. This work opens up a promising avenue for fundamental studies and potential applications of a wide variety of nanoporous metal compounds.


Abstract

Although 2D layered metal compounds are widely exploited using various techniques such as exfoliation and vapor‐phase‐assisted growth, it is still challenging to construct the 2D materials in a 3D configuration with preservation of the unique physicochemical properties of the metal compounds. Herein, a general synthetic strategy is reported for a wide variety of 2D (atomic‐scale thickness) metal compounds with 3D bicontinous nanoporous structure. 19 binary compounds including sulfides, selenides, tellurides, carbides, and nitrides, and five alloyed compounds, are successfully prepared via a surface alloy strategy, which are readily created by using a recyclable nanoporous gold assisted chemical vapor deposition process. These 3D nanoporous metal compounds with preserved 2D physicochemical properties, tunable pore sizes, and compositions for electrocatalytic applications, show excellent catalytic performance in the electrochemical N2 reduction reaction. This work opens up a promising avenue for fundamental studies and potential applications of a wide variety of nanoporous metal compounds.

01 Dec 02:40

Programming Multiphase Media Superwetting States in the Oil–Water–Air System: Evolutions in Hydrophobic–Hydrophilic Surface Heterogeneous Chemistry

by Yihan Sun, Zhiguang Guo
Programming Multiphase Media Superwetting States in the Oil–Water–Air System: Evolutions in Hydrophobic–Hydrophilic Surface Heterogeneous Chemistry

A new conceptual insight, “multiphase media superwetting states” for superwettability is presented. Programming of multiphase media superwetting states can be manipulated by surface hydrophobic–hydrophilic heterogeneous chemistry by varying the spraying inks’ chemistry and external stimuli. In‐air superhydrophilicity–superoleophobicity and underoil superhydrophilicity can be realized via ammonia vapor exposure and ultraviolet light illumination, respectively.


Abstract

Studies toward tailoring macroscopic extreme wetting behaviors on a certain well‐defined surface in multiphase media are significant but still at an infant stage. Herein, superantiwetting evolutions in the oil–water–air system can be programmed from single to quadruple superrepellence by controlling the surface hydrophobic–hydrophilic heterogeneous chemistry. Ammonia vapor exposure makes the realization of challenging superhydrophilicity–superoleophobicity possible in air medium, causing the transition from quadruple to triple superantiwetting states in the oil–water–air system. Upon UV illumination, only single superrepellence–underwater superoleophobicity is maintained on titanium dioxide (TiO2, P25)‐based coatings. A reversible transition between underoil superhydrophilicity and superhydrophobicity via an alternating UV irradiation and heating process leads to a switching between “water‐absorbing” and “size‐sieving” effects in water‐in‐oil emulsion separation. A comparative study for investigating two such effects in emulsion separation is further investigated. The current conceptual insights not only extend superwetting states to multiphase media, but can also deepen the understanding of the relationship between macroscopic extreme wetting behaviors and surface chemistry.

01 Dec 02:39

A Novel Heterostructure Based on RuMo Nanoalloys and N‐doped Carbon as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

by Kejun Tu, Diana Tranca, Fermín Rodríguez‐Hernández, Kaiyue Jiang, Senhe Huang, Qi Zheng, Ming‐Xi Chen, Chenbao Lu, Yuezeng Su, Zhenying Chen, Haiyan Mao, Chongqing Yang, Jinyang Jiang, Hai‐Wei Liang, Xiaodong Zhuang
A Novel Heterostructure Based on RuMo Nanoalloys and N‐doped Carbon as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

A novel heterostructure based on uniform RuMo nanoalloys and hexagonal N‐doped carbon nanosheets is prepared through a combination of hard template and anion‐exchange methods. The obtained material exhibits excellent electrocatalytic activity for the hydrogen evolution reaction. Theoretical calculation confirms that the heterosurfaces play a crucial role in accelerating the hydrogen evolution activity.


Abstract

Heterostructures exhibit considerable potential in the field of energy conversion due to their excellent interfacial charge states in tuning the electronic properties of different components to promote catalytic activity. However, the rational preparation of heterostructures with highly active heterosurfaces remains a challenge because of the difficulty in component tuning, morphology control, and active site determination. Herein, a novel heterostructure based on a combination of RuMo nanoalloys and hexagonal N‐doped carbon nanosheets is designed and synthesized. In this protocol, metal‐containing anions and layered double hydroxides are employed to control the components and morphology of heterostructures, respectively. Accordingly, the as‐made RuMo‐nanoalloys‐embedded hexagonal porous carbon nanosheets are promising for the hydrogen evolution reaction (HER), resulting in an extremely small overpotential (18 mV), an ultralow Tafel slope (25 mV dec−1), and a high turnover frequency (3.57 H2 s−1) in alkaline media, outperforming current Ru‐based electrocatalysts. First‐principle calculations based on typical 2D N‐doped carbon/RuMo nanoalloys heterostructures demonstrate that introducing N and Mo atoms into C and Ru lattices, respectively, triggers electron accumulation/depletion regions at the heterosurface and consequently reduces the energy barrier for the HER. This work presents a convenient method for rational fabrication of carbon–metal heterostructures for highly efficient electrocatalysis.

01 Dec 02:39

Fully Light‐Controlled Memory and Neuromorphic Computation in Layered Black Phosphorus

by Taimur Ahmed, Muhammad Tahir, Mei Xian Low, Yanyun Ren, Sherif Abdulkader Tawfik, Edwin L. H. Mayes, Sruthi Kuriakose, Shahid Nawaz, Michelle J. S. Spencer, Hua Chen, Madhu Bhaskaran, Sharath Sriram, Sumeet Walia
Fully Light‐Controlled Memory and Neuromorphic Computation in Layered Black Phosphorus

An all‐optically tunable neuromorphic imaging element based on black phosphorus (BP) is demonstrated. Unusual wavelength‐dependent photocurrent in BP is harnessed to optically program and erase visual memory elements. Concurrently, the same elements are capable of in‐pixel image pre‐processing in an array and optoelectronic machine learning for image recognition through artificial neural networks.


Abstract

Imprinting vision as memory is a core attribute of human cognitive learning. Fundamental to artificial intelligence systems are bioinspired neuromorphic vision components for the visible and invisible segments of the electromagnetic spectrum. Realization of a single imaging unit with a combination of in‐built memory and signal processing capability is imperative to deploy efficient brain‐like vision systems. However, the lack of a platform that can be fully controlled by light without the need to apply alternating polarity electric signals has hampered this technological advance. Here, a neuromorphic imaging element based on a fully light‐modulated 2D semiconductor in a simple reconfigurable phototransistor structure is presented. This standalone device exhibits inherent characteristics that enable neuromorphic image pre‐processing and recognition. Fundamentally, the unique photoresponse induced by oxidation‐related defects in 2D black phosphorus (BP) is exploited to achieve visual memory, wavelength‐selective multibit programming, and erasing functions, which allow in‐pixel image pre‐processing. Furthermore, all‐optically driven neuromorphic computation is demonstrated by machine learning to classify numbers and recognize images with an accuracy of over 90%. The devices provide a promising approach toward neurorobotics, human–machine interaction technologies, and scalable bionic systems with visual data storage/buffering and processing.

01 Dec 02:38

Compositional Fluctuations Locked by Athermal Transformation Yielding High Thermoelectric Performance in GeTe

by Yi‐Fen Tsai, Pai‐Chun Wei, Liuwen Chang, Kuang‐Kuo Wang, Chun‐Chuen Yang, Yen‐Chung Lai, Cheng‐Rong Hsing, Ching‐Ming Wei, Jian He, G. Jeffrey Snyder, Hsin‐Jay Wu
Compositional Fluctuations Locked by Athermal Transformation Yielding High Thermoelectric Performance in GeTe

The interplay between phase decomposition and athermal phase transition is leveraged in a Ge–Sb–Te ternary system to enable exquisite microstructure features by strong composition fluctuations and coexistence of rhombohedral and cubic GeTe. Specifically, alloying GeTe with Sb2Te3 significantly suppresses thermal conductivity while retaining eligible carrier concentration over a wide composition range, resulting in high zT values of >2.6.


Abstract

Phase transition in thermoelectric (TE) material is a double‐edged sword—it is undesired for device operation in applications, but the fluctuations near an electronic instability are favorable. Here, Sb doping is used to elicit a spontaneous composition fluctuation showing uphill diffusion in GeTe that is otherwise suspended by diffusionless athermal cubic‐to‐rhombohedral phase transition at around 700 K. The interplay between these two phase transitions yields exquisite composition fluctuations and a coexistence of cubic and rhombohedral phases in favor of exceptional figures‐of‐merit zT. Specifically, alloying GeTe by Sb2Te3 significantly suppresses the thermal conductivity while retaining eligible carrier concentration over a wide composition range, resulting in high zT values of >2.6. These results not only attest to the efficacy of using phase transition in manipulating the microstructures of GeTe‐based materials but also open up a new thermodynamic route to develop higher performance TE materials in general.

01 Dec 02:37

Liquid‐Flowing Graphene Chip‐Based High‐Resolution Electron Microscopy

by Kunmo Koo, Jungjae Park, Sanghyeon Ji, Saltanat Toleukhanova, Jong Min Yuk
Liquid‐Flowing Graphene Chip‐Based High‐Resolution Electron Microscopy

The liquid‐flowing graphene chip (LFGC) is a novel imaging platform enabling the atomic‐scale observation of liquid‐phase reactions during in operando circumstances. Graphene viewing windows and anti‐bulging SiN x supports provide a controllable liquid thickness and structural integrity under harsh experimental conditions. Using LFGC, both atomic‐resolution imaging and molecular‐level information for inorganic and biological samples can be acquired under liquid circulation.


Abstract

The recent advances in liquid‐phase transmission electron microscopy represent tremendous potential in many different fields and exciting new opportunities. However, achieving both high‐resolution imaging and operando capabilities remain a significant challenge. This work suggests a novel in situ imaging platform of liquid‐flowing graphene chip TEM (LFGC‐TEM) equipped with graphene viewing windows and a liquid exchange system. The LFGCs are robust under high‐pressure gradients and rapid liquid circulation in ranges covering the experimental conditions accessible with conventional thick SiN x chips. LFGC‐TEM provides atomic resolution for colloidal nanoparticles and molecular‐level information limits for unstained wet biomolecules and cells that are comparable to the resolutions achievable with solid‐phase and cryogenic TEM, respectively. This imaging platform can provide an opportunity for live imaging of biological phenomena that is not yet achieved using any current methods.

01 Dec 02:37

Tailored Graphene Micropatterns by Wafer‐Scale Direct Transfer for Flexible Chemical Sensor Platform

by Yeonhoo Kim, Taehoon Kim, Jinwoo Lee, Yong Seok Choi, Joonhee Moon, Seo Yun Park, Tae Hyung Lee, Hoon Kee Park, Sol A Lee, Min Sang Kwon, Hyung‐Gi Byun, Jong‐Heun Lee, Myoung‐Gyu Lee, Byung Hee Hong, Ho Won Jang
Tailored Graphene Micropatterns by Wafer‐Scale Direct Transfer for Flexible Chemical Sensor Platform

A strategy to micropattern 2D materials on large‐scale flexible substrates using a direct polymer curing transfer method is demonstrated. Graphene microchannels on polymer substrates exhibit ultrahigh effective self‐heating under an applied bias voltage of less than 10 V. An entirely flexible and transparent chemical sensor array based on graphene micropatterns successfully discriminates gas species under the self‐activated state without external heating.


Abstract

2D materials, such as graphene, exhibit great potential as functional materials for numerous novel applications due to their excellent properties. The grafting of conventional micropatterning techniques on new types of electronic devices is required to fully utilize the unique nature of graphene. However, the conventional lithography and polymer‐supported transfer methods often induce the contamination and damage of the graphene surface due to polymer residues and harsh wet‐transfer conditions. Herein, a novel strategy to obtain micropatterned graphene on polymer substrates using a direct curing process is demonstrated. Employing this method, entirely flexible, transparent, well‐defined self‐activated graphene sensor arrays, capable of gas discrimination without external heating, are fabricated on 4 in. wafer‐scale substrates. Finite element method simulations show the potential of this patterning technique to maximize the performance of the sensor devices when the active channels of the 2D material are suspended and nanoscaled. This study contributes considerably to the development of flexible functional electronic devices based on 2D materials.

01 Dec 02:36

Indium Nitride at the 2D Limit

by Béla Pécz, Giuseppe Nicotra, Filippo Giannazzo, Rositsa Yakimova, Antal Koos, Anelia Kakanakova‐Georgieva
Indium Nitride at the 2D Limit

A bilayer of InN is formed between graphene and SiC by an intercalation process. The coverage of the SiC surface is very high, above 90%. Scanning tunneling spectroscopy (STS) measurements prove a bandgap value of 2 ± 0.1 eV for the 2D InN.


Abstract

The properties of 2D InN are predicted to substantially differ from the bulk crystal. The predicted appealing properties relate to strong in‐ and out‐of‐plane excitons, high electron mobility, efficient strain engineering of their electronic and optical properties, and strong application potential in gas sensing. Until now, the realization of 2D InN remained elusive. In this work, the formation of 2D InN and measurements of its bandgap are reported. Bilayer InN is formed between graphene and SiC by an intercalation process in metal–organic chemical vapor deposition (MOCVD). The thickness uniformity of the intercalated structure is investigated by conductive atomic force microscopy (C‐AFM) and the structural properties by atomic resolution transmission electron microscopy (TEM). The coverage of the SiC surface is very high, above 90%, and a major part of the intercalated structure is represented by two sub‐layers of indium (In) bonded to nitrogen (N). Scanning tunneling spectroscopy (STS) measurements give a bandgap value of 2 ± 0.1 eV for the 2D InN. The stabilization of 2D InN with a pragmatic wide bandgap and high lateral uniformity of intercalation is demonstrated.

01 Dec 02:36

Layered PtSe2 for Sensing, Photonic, and (Opto‐)Electronic Applications

by Gaozhong Wang, Zhongzheng Wang, Niall McEvoy, Ping Fan, Werner J. Blau
Layered PtSe2 for Sensing, Photonic, and (Opto‐)Electronic Applications

Layered PtSe2 holds great promise for industries, benefiting from its exciting physical and chemical properties, high air‐stability, and semiconductor‐technology‐compatible fabrication methods. An overview of the use of PtSe2 for applications in photonics, (opto‐)electronics, and sensors is provided. Challenges associated with the synthesis and integration of PtSe2, and the outlook for industry adoption of this material, are discussed.


Abstract

Since the first experimental discovery of graphene 16 years ago, many other 2D layered nanomaterials have been reported. However, the majority of 2D nanostructures suffer from relatively complicated fabrication processes that have bottlenecked their development and their uptake by industry for practical applications. Here, the recent progress in sensing, photonic, and (opto‐)electronic applications of PtSe2, a 2D layered material that is likely to be used in industries benefiting from its high air‐stability and semiconductor‐technology‐compatible fabrication methods, is reviewed. The advantages and disadvantages of a range of synthesis methods for PtSe2 are initially compared, followed by a discussion of its outstanding properties, and industrial and commercial advantages. Research focused on the broadband nonlinear photonic properties of PtSe2, as well as reports of its use as a saturable absorber in ultrafast lasers, are then reviewed. Additionally, the advances that have been achieved in a range of PtSe2‐based field‐effect transistors, photodetectors, and sensors are summarized. Finally, a conclusion on these results along with the outlook for the future is presented.

01 Dec 02:33

Electrochemical Delamination of Ultralarge Few‐Layer Black Phosphorus with a Hydrogen‐Free Intercalation Mechanism

by Ning Wang, Nannan Mao, Zhien Wang, Xue Yang, Xi Zhou, Haining Liu, Shanlin Qiao, Xingfeng Lei, Junru Wang, Hua Xu, Xi Ling, Qiuyu Zhang, Qingliang Feng, Jing Kong
Electrochemical Delamination of Ultralarge Few‐Layer Black Phosphorus with a Hydrogen‐Free Intercalation Mechanism

Ultralarge few‐layer black‐phosphorus single crystals are obtained with a hydrogen‐free electrochemical exfoliation mechanism using CH3COOTBA intercalation. The largest size is up to 119 µm with an average around at 77.6 ± 15.0 µm. A high hole mobility of 76 cm2 V–1 s–1, and a broadband photoresponse from 532 to 1850 nm with ultrahigh responsivity are achieved at 298 K.


Abstract

Due to strong interlayer interaction and ease of oxidation issues of black phosphorus (BP), the domain size of artificial synthesized few‐layer black phosphorus (FL‐BP) crystals is often below 10 µm, which extremely limits its further applications in large‐area thin‐film devices and integrated circuits. Herein, a hydrogen‐free electrochemical delamination strategy through weak Lewis acid intercalation enabled exfoliation is developed to produce ultralarge FL‐BP single‐crystalline domains with high quality. The interaction between the weak Lewis acid tetra‐n‐butylammonium acetate (CH3COOTBA) and P atoms promotes the average domain size of FL‐BP crystal up to 77.6 ± 15.0 µm and the largest domain size is found to be as large as 119 µm. The presence of H+ and H2O is found to sharply decrease the size of as‐exfoliated FL‐BP flakes. The electronic transport measurements show that the delaminated FL‐BP crystals exhibit a high hole mobility of 76 cm2 V–1 s–1 and an on/off ratio of 103 at 298 K. A broadband photoresponse from 532 to 1850 nm with ultrahigh responsivity is achieved. This work provides a scalable, simple, and low‐cost approach for large‐area BP films that meet industrial requirements for nanodevices applications.

01 Dec 02:33

The Art of Constructing Black Phosphorus Nanosheet Based Heterostructures: From 2D to 3D

by Shameel Thurakkal, David Feldstein, Raül Perea‐Causín, Ermin Malic, Xiaoyan Zhang
The Art of Constructing Black Phosphorus Nanosheet Based Heterostructures: From 2D to 3D

Black phosphorus nanosheet (BPNS)‐based heterostructures are an emerging material with numerous potential applications in many appealing fields. Recent advancements in the construction of BPNS‐based heterostructures ranging from 2D hybrid structures to 3D networks, including preparation and characterization methods, optical and electronic properties, applications, challenges, and future directions, are discussed.


Abstract

Assembling different kinds of 2D nanosheets into heterostructures presents a promising way of designing novel artificial materials with new and improved functionalities by combining the unique properties of each component. In the past few years, black phosphorus nanosheets (BPNSs) have been recognized as a highly feasible 2D material with outstanding electronic properties, a tunable bandgap, and strong in‐plane anisotropy, highlighting their suitability as a material for constructing heterostructures. In this study, recent progress in the construction of BPNS‐based heterostructures ranging from 2D hybrid structures to 3D networks is discussed, emphasizing the different types of interactions (covalent or noncovalent) between individual layers. The preparation methods, optical and electronic properties, and various applications of these heterostructures—including electronic and optoelectronic devices, energy storage devices, photocatalysis and electrocatalysis, and biological applications—are discussed. Finally, critical challenges and prospective research aspects in BPNS‐based heterostructures are also highlighted.

01 Dec 02:29

Ternary Ta2PdS6 Atomic Layers for an Ultrahigh Broadband Photoresponsive Phototransistor

by Peng Yu, Qingsheng Zeng, Chao Zhu, Liujiang Zhou, Weina Zhao, Jinchao Tong, Zheng Liu, Guowei Yang
Ternary Ta2PdS6 Atomic Layers for an Ultrahigh Broadband Photoresponsive Phototransistor

A new 2D material, atomic layer Ta2PdS6, is introduced to the 2D family, and exhibits excellent optoelectronic and electronic performances including an ultrahigh photoresponsivity of 1.42 × 106 A W−1, photoconductive gain of 2.7 × 106, electron mobility of 25 cm2 V–1 s–1, I on/I off ratio of 106, and one‐year air stability, making it a promising 2D material for nanoelectronic and nano‐optoelectronic applications.


Abstract

2D noble‐transition‐metal chalcogenides (NTMCs) are emerging as a promising class of optoelectronic materials due to ultrahigh air stability, large bandgap tunability, and high photoresponse. Here, a new set of 2D NTMC: Ta2PdS6 atomic layers is developed, displaying the excellent comprehensive optoelectronic performance with an ultrahigh photoresponsivity of 1.42 × 106 A W−1, detectivity of 7.1 × 1010 Jones and a high photoconductive gain of 2.7 × 106 under laser illumination at a wavelength of 633 nm with a power of 0.025 W m−2, which is ascribed to a photogating effect via study of the device band profiles. Especially, few‐layer Ta2PdS6 exhibits a good broadband photoresponse, ranging from 450 nm in the ultraviolet region to 1450 nm in the shortwave infrared (SIR) region. Moreover, this material also delivers an impressive electronic performance with electron mobility of ≈25 cm2V–1s–1, I on/I off ratio of 106, and a one‐year air stability, which is better than those of most reported 2D materials. Our studies underscore Ta2PdS6 as a promising 2D material for nano‐electronic and nano‐optoelectronic applications.

01 Dec 02:28

Solution‐Processed Ti3C2Tx MXene Antennas for Radio‐Frequency Communication

by Meikang Han, Yuqiao Liu, Roman Rakhmanov, Christopher Israel, Md Abu Saleh Tajin, Gary Friedman, Vladimir Volman, Ahmad Hoorfar, Kapil R. Dandekar, Yury Gogotsi
Solution‐Processed Ti3C2Tx MXene Antennas for Radio‐Frequency Communication

MXene microstrip patch antennas with ultrahigh‐power radiation in a wide frequency range are fabricated by spray‐coating. The radiation efficiency of a 5.5 µm thick MXene patch antenna reaches 99% at 16.4 GHz, which is about the same as that of a 35 µm thick copper patch antenna. MXene outperforms all other materials evaluated for patch antennas to date.


Abstract

Highly integrated, flexible, and ultrathin wireless communication components are in significant demand due to the explosive growth of portable and wearable electronic devices in the fifth‐generation (5G) network era, but only conventional metals meet the requirements for emerging radio‐frequency (RF) devices so far. Here, it is reported on Ti3C2T x MXene microstrip transmission lines with low‐energy attenuation and patch antennas with high‐power radiation at frequencies from 5.6 to 16.4 GHz. The radiation efficiency of a 5.5 µm thick MXene patch antenna manufactured by spray‐coating from aqueous solution reaches 99% at 16.4 GHz, which is about the same as that of a standard 35 µm thick copper patch antenna at about 15% of its thickness and 7% of the copper weight. MXene outperforms all other materials evaluated for patch antennas to date. Moreover, it is demonstrated that an MXene patch antenna array with integrated feeding circuits on a conformal surface has comparable performance with that of a copper antenna array at 28 GHz, which is a target frequency in practical 5G applications. The versatility of MXene antennas in wide frequency ranges coupled with the flexibility, scalability, and ease of solution processing makes MXene promising for integrated RF components in various flexible electronic devices.