Article
Chemistry, Physical
Xiucai Sun, Xiaoting Liu, Zhongti Sun, Xintong Zhang, Yuzhu Wu, Yeshu Zhu, Yuqing Song, Kaicheng Jia, Jincan Zhang, Luzhao Sun, Wan-Jian Yin, Zhongfan Liu
Summary: This study reveals the importance of vapor catalysis in superclean graphene growth through density functional theory calculations, an ideal gas model, and a designed experiment. The study finds that the vapor mainly consists of Cui clusters, which have a significant impact on graphene growth. DFT calculations show that Cu clusters exhibit strong capabilities for adsorption, dehydrogenation, and decomposition, providing a sufficient supply of active carbon atoms for rapid graphene growth. Experimental validation confirms that increasing the amount of Cu vapor improves the growth rate and surface cleanliness of graphene.
Article
Multidisciplinary Sciences
Luzhao Sun, Zihao Wang, Yuechen Wang, Liang Zhao, Yanglizhi Li, Buhang Chen, Shenghong Huang, Shishu Zhang, Wendong Wang, Ding Pei, Hongwei Fang, Shan Zhong, Haiyang Liu, Jincan Zhang, Lianming Tong, Yulin Chen, Zhenyu Li, Mark H. Rummeli, Kostya S. Novoselov, Hailin Peng, Li Lin, Zhongfan Liu
Summary: The authors developed a chemical vapor deposition method for synthesizing twisted bilayer graphene with controllable angles. By employing a hetero-site nucleation strategy, they successfully prepared bilayer graphene with twist angles ranging from 0 degrees to 30 degrees, demonstrating high-quality and improved performance for potential applications in fundamental research and practical use.
NATURE COMMUNICATIONS
(2021)
Review
Chemistry, Multidisciplinary
Wenqian Yao, Hongtao Liu, Jianzhe Sun, Bin Wu, Yunqi Liu
Summary: This review provides a comprehensive overview of current challenges and opportunities for chemical vapor deposition (CVD) growth, characterization, and electrical properties of graphene depending on the layer number and twist angles. Various state-of-the-art innovations using the CVD method are presented, and the underlying growth mechanisms and characterization methods are discussed.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Physical
Chamseddine Bouhafs, Sergio Pezzini, Fabian R. Geisenhof, Neeraj Mishra, Vaidotas Miseikis, Yuran Niu, Claudia Struzzi, R. Thomas Weitz, Alexei A. Zakharov, Stiven Forti, Camilla Coletti
Summary: The study successfully synthesized rhombohedral graphene with a thickness of up to 9 layers, with alternating crystal domains identified in Raman spectroscopy. Microscopic and spectroscopic analyses suggest that rhombohedral-stacking formation is correlated to underlying copper step-bunching.
Article
Materials Science, Multidisciplinary
Jie Wang, Tengfei Fan, Jianchen Lu, Xiaoming Cai, Lei Gao, Jinming Cai
Summary: Graphene with different morphologies, such as dendrites, rectangle, and hexagon, has been grown on polycrystalline copper substrates using low-pressure chemical vapor deposition. The evolution of fractal graphene grown on the copper substrate has also been observed. The study investigates the changes in graphene morphology as a function of the methane to hydrogen volume ratio. Additionally, phenomena of stitching snow-like graphene and stacking graphene with different angles have been observed.
INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Minghao Liang, Ling-Xuan Qian, Yuting Hou, Jun Li, Changqing Shen, Fangzhu Qing, Xuesong Li
Summary: Both batch-to-batch (B2B) and roll-to-roll (R2R) processes can be used for mass production of graphene films. R2R process is more industrially preferred due to automation and compatibility with transfer process, but a deeper understanding of growth kinetics is needed.
SCIENCE CHINA-MATERIALS
(2022)
Review
Chemistry, Multidisciplinary
Jinhong Du, Bo Tong, Shuangdeng Yuan, Nian Dai, Rui Liu, Dingdong Zhang, Hui-Ming Cheng, Wencai Ren
Summary: This article reviews the recent advances and significant development of CVD-grown graphene towards flexible optoelectronics. The challenges of improving optoelectronic properties, tuning work functions, and controlling interfaces are discussed, and the importance of fabricating large-area devices on flexible substrates is emphasized.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Multidisciplinary Sciences
Sergey G. Menabde, In-Ho Lee, Sanghyub Lee, Heonhak Ha, Jacob T. Heiden, Daehan Yoo, Teun-Teun Kim, Tony Low, Young Hee Lee, Sang-Hyun Oh, Min Seok Jang
Summary: The acoustic plasmon mode in a graphene-dielectric-metal structure shows strong light-matter interaction with relatively small propagation loss, allowing for real-space mapping under ambient conditions.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Sandra Rodriguez-Villanueva, Frank Mendoza, Brad R. Weiner, Gerardo Morell
Summary: This study presents a method to grow graphene on a 6H-SiC substrate using the hot filament chemical vapor deposition technique. The graphene films were analyzed using various techniques, such as Raman spectroscopy and scanning electron microscopy, and it was found that few-layer and multilayer graphene were deposited. Compositional analysis confirmed the deposition of graphene on SiC substrates without any metal involvement.
Article
Chemistry, Physical
Kaihao Zhang, A. John Hart
Summary: The transfer-free synthesis route allows highly-uniform bilayer graphene to grow directly on dielectric substrates, addressing the issue of wrinkles and folds that occur in traditional methods. The graphene produced through this technique has a smooth surface, free of wrinkles, and exhibits low twist angles, making it promising for various applications.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Physical
Yue Li, Yong Liu, Yunbiao Zhao, Yifan Zhang, Yi Chen, Qining Wang, Ziqiang Zhao
Summary: A new fabrication method for graphene on quartz was developed in this study, which utilizes high-quality graphene films as catalysts for methane decomposition, avoiding the contamination of other elements and significantly increasing the growth rate of graphene films compared to conventional CVD methods. The study confirmed the excellent quality of graphene glass through experimental characterization and the fabrication of a transparent heating device without any transfer process.
Article
Chemistry, Physical
Xue Zhang, Xing Guo, Xiucai Sun, Zhen Su, Li Sun, Peng Wang, Yanlu Li, Fapeng Yu, Xian Zhao
Summary: This study investigated the role of oxygen in graphene growth and found that CuO and Cu2O are beneficial in promoting graphene nucleation and growth. The research provides new data for the preparation of high-quality monolayer graphene on copper substrate.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Multidisciplinary
Sandra Rodriguez-Villanueva, Frank Mendoza, Alvaro A. Instan, Ram S. Katiyar, Brad R. Weiner, Gerardo Morell
Summary: This study reports the direct synthesis of graphene on SiO2/Si using hot-filament chemical vapor deposition. The results show the growth of few-layers of graphene over the entire SiO2/Si substrate, far beyond the catalytic copper-strip.
Review
Chemistry, Multidisciplinary
Jingyuan Shan, Jingyu Sun, Zhongfan Liu
Summary: Growing graphene on sapphire substrates using CVD allows for fewer grain boundaries, larger grain sizes, and transfer-free properties. Sapphire has emerged as an ideal substrate for graphene growth due to its low cost, good mechanical strength, and stability under CVD conditions. Applications of graphene/sapphire hybrid materials are diverse and the synthesis of graphene over sapphire shows promise.
Review
Chemistry, Physical
Yi Cheng, Kun Wang, Yue Qi, Zhongfan Liu
Summary: This article reviews the application of chemical vapor deposition (CVD) method in the fabrication of graphene fiber materials. The CVD method allows for effective control of graphene quality and adhesion in both graphene fiber and graphene-coated hybrid fiber preparation. Graphene fiber materials have broad application prospects in flexible energy storage devices, electromagnetic shielding, and wearable electronics.
ACTA PHYSICO-CHIMICA SINICA
(2022)
Article
Chemistry, Multidisciplinary
Filippo Pizzocchero, Bjarke S. Jessen, Lene Gammelgaard, Andrei Andryieuski, Patrick R. Whelan, Abhay Shivayogimath, Jose M. Caridad, Jens Kling, Nicholas Petrone, Peter T. Tang, Radu Malureanu, James Hone, Timothy J. Booth, Andrei Lavrinenko, Peter Boggild
Summary: The purity and morphology of the copper surface play an important role in synthesizing high-quality graphene using chemical vapor deposition. Smooth copper foils fabricated through physical vapor deposition and subsequent electroplating exhibit lower surface roughness after annealing, leading to lower nucleation and defect density in the graphene film. These ultraflat foils facilitate the easier dry pickup and encapsulation of graphene by hexagonal boron nitride, likely due to the conformal interface and stronger van der Waals adhesion between them.
Article
Chemistry, Physical
Liangguang Jia, Fei Gao, Yu Zhang, Yaoyao Chen, Baofei Hou, Zeping Huang, Quanzhen Zhang, Xu Wu, Liwei Liu, Shiwu Gao, Mads Brandbyge, Hong-Jun Gao, Yeliang Wang
Summary: This study reports the influence of defects in vdW crystals on the local atomic configurations and interlayer coupling. The findings show that Se vacancies in few-layer NbSe2 can cause atomic distortions and generate in-gap states in single-layer NbSe2. Moreover, these vacancies lead to a significant suppression of interlayer coupling in the bilayer system.
Article
Chemistry, Physical
Shuai Yang, Chao Wang, Jing Wu, Hong Yan, Gang Wang, Jianmin Feng, Bo Zhang, Dejun Li, Timonthy J. Booth, Peter Boggild, Gui Yu, Birong Luo
Summary: Engineering interfacial interactions is crucial for manipulating the properties and applications of two-dimensional (2D) materials. In this study, a self-relaxation vapor-liquid-solid (SRVLS) growth method for 2D transition metal dichalcogenides (TMDs) was proposed and investigated. The growth process involves coordination between the precipitation of metal oxides and the capture of chalcogens, resulting in loose interface adhesion and strain relaxation in the as-grown TMD layers. The SRVLS-grown TMDs exhibit significantly reduced adhesion energy compared to traditional vapor-solid (VS) growth, and the growth features allow for curl-free delamination and reverse transfer of TMD layers onto target substrates through water-dissolving the solidified droplets.
APPLIED SURFACE SCIENCE
(2023)
Article
Physics, Condensed Matter
Sofia Sanz, Nick Papior, Geza Giedke, Daniel Sanchez-Portal, Mads Brandbyge, Thomas Frederiksen
Summary: We theoretically study electron interference in a Mach-Zehnder-like geometry formed by four parallel pairs of zigzag graphene nanoribbons. By adjusting the interribbon separation, each intersection can function as an electron beam splitter or mirror, allowing for tuneable circuitry with interfering pathways. We evaluate the electron transport properties of these eight-terminal devices and identify pairs of terminals subject to self-interference. The proposed devices have potential applications as magnetic field sensors, detectors of phase shifts induced by local scatterers, and for the study of quantum entanglement.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Chemistry, Multidisciplinary
Cesar Moreno, Xabier Diaz de Cerio, Manuel Vilas-Varela, Maria Tenorio, Ane Sarasola, Mads Brandbyge, Diego Pena, Aran Garcia-Lekue, Aitor Mugarza
Summary: Recent advances in surface-assisted synthesis have demonstrated the ability to create highly anisotropic nanoporous graphene structures by laterally coupling arrays of nanometer wide graphene nanoribbons. In this study, a new nanoporous graphene structure was synthesized in which the interribbon electronic coupling can be controlled by phenylene bridges. The versatility of this structure arises from the multiple configurations of phenylene cross-coupling and the twist angle, which can be altered by interaction with the substrate and other external stimuli.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Physics, Multidisciplinary
Xiaocui Wu, Nicolas Neel, Mads Brandbyge, Joerg Kroeger
Summary: The abstraction of pyrrolic hydrogen from a single phthalocyanine on graphene turns the molecule into a sensitive probe for graphene phonons. The inelastic electron transport measured with a scanning tunneling microscope across the molecular adsorbate and graphene becomes strongly enhanced for a graphene out-of-plane acoustic phonon mode. Supporting density functional and transport calculations elucidate the underlying physical mechanism.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Analytical
Binbin Zhou, Mattias Rasmussen, Patrick Rebsdorf Whelan, Jie Ji, Abhay Shivayogimath, Peter Boggild, Peter Uhd Jepsen
Summary: We accurately determine the conductivity of graphene on thin-film polymer substrates using reflection-mode air-plasma-based THz time-domain spectroscopy (THz-TDS). The phase uncertainty issue associated with reflection measurements is discussed and our implementation is validated through convincing agreement with graphene electrical properties extracted from more conventional transmission-mode measurements. Both reflection and transmission THz-TDS measurements reveal a strong non-linear and instantaneous conductivity depletion across an ultra-broad bandwidth (1-9 THz) under relatively high incident THz electrical field strengths (up to 1050 kV/cm).
Article
Multidisciplinary Sciences
Peter Boggild
Summary: More than a decade after large-scale graphene synthesis was demonstrated, the commercialization of graphene products is hindered by price and consistency issues. The author addresses the reproducibility problems in the field and proposes solutions to improve the reliability of published results.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Saskia Fiedler, Sergii Morozov, Leonid Iliushyn, Sergejs Boroviks, Martin Thomaschewski, Jianfang Wang, Timothy J. Booth, Nicolas Stenger, Christian Wolff, N. Asger Mortensen
Summary: Cathodoluminescence spectroscopy combined with second-order auto-correlation measurements of g(2)(tau) allows for extensive study of the synchronization of photon emitters in low-dimensional structures. Co-existing excitons in two-dimensional transition metal dichalcogenide monolayers serve as a great source of identical photon emitters that can be simultaneously excited by an electron. In this study, we demonstrate large photon bunching with g(2)(0) up to 156 +/- 16 in a tungsten disulfide monolayer (WS2), showing a strong dependence on the electron-beam current. By carefully selecting a simple and compact geometry, such as a thin monocrystalline gold nanodisk, we achieve a record-high bunching g(2)(0) of up to 2152 +/- 236, improving the excitation synchronization and electron-emitter interaction. This approach of controlling electron excitation of excitons in a WS2 monolayer enables the synchronization of photon emitters in an ensemble, which is crucial for advancing light information and computing technologies.
Article
Physics, Multidisciplinary
Fei Gao, Rodrigo E. E. Menchon, Aran Garcia-Lekue, Mads Brandbyge
Summary: Recently, researchers have combined porphyrin units with graphene nanoribbons (Por-GNR) to create various structures. In this study, the authors use first-principles calculations to investigate the properties of two experimentally feasible Por-GNR hybrids. They find that one of the hybrids has a small band gap and can be used as electrodes in devices. By embedding a Fe atom in the porphyrin, a spin-polarized ground state is achieved. The authors examine the spin transport properties of a 2-terminal setup involving a Fe-Por-GNR between Por-GNR electrodes and observe a Fano anti-resonance feature. They also demonstrate how mechanical strain or chemical adsorption can induce spin-crossover, leading to different spin states. These findings provide valuable insights for the development of carbon-based spintronics and chemical sensing applications.
COMMUNICATIONS PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Jie Ji, Yingqiu Zhou, Binbin Zhou, Eva Desgue, Pierre Legagneux, Peter Uhd Jepsen, Peter Boggild
Summary: In this study, the electronic properties and light-induced carrier transport of large-scale PtSe2 films were investigated using terahertz spectroscopy techniques. The results demonstrate that PtSe2 films have a tunable electronic structure and high carrier mobility, and the terahertz methods provide information about the spatial and temporal properties of the films.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Physics, Applied
Manh-Ha Doan, Shrawan Roy, Yingqiu Zhou, Peter Boggild
Summary: The research suggests that correlated electron-hole pair tunneling can occur at room temperature in a monolithic multilayer WSe2 device with bottom Au contacts. This finding opens up the opportunity for realizing room-temperature superfluidity in vdW materials.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Aleksander Bach Lorentzen, Mehdi Bouatou, Cyril Chacon, Yannick J. Dappe, Jerome Lagoute, Mads Brandbyge
Summary: Recent studies have shown the spatial control of nitrogen dopant concentration in graphene using a molecular mask. This technique enables the creation of ballistic electron optics-like structures and has implications for current focusing and quantized conductance.
Article
Materials Science, Multidisciplinary
Victor Rosendal, Walber H. Brito, Milan Radovic, Alla Chikina, Mads Brandbyge, Nini Pryds, Dirch H. Petersen
Summary: This study maps the energy landscape of octahedral tilting in Strontium niobate using density functional theory calculations, and finds that compressive strain induces tilting around the out-of-plane axis, while tensile strain induces tilting around the in-plane axes. The competition between in-phase and out-of-phase tilting in SrNbO3 allows for tuning the thermoelectric and optical properties. The study also shows how the tilt angle and mode affect the Seebeck coefficient and the plasma frequency due to changes in the band structure.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Cesar Moreno, Xabier Diaz de Cerio, Manuel Vilas-Varela, Maria Tenorio, Ane Sarasola, Mads Brandbyge, Diego Pena, Aran Garcia-Lekue, Aitor Mugarza
Summary: Recent advances in surface-assisted synthesis have shown that graphene nanoribbons can be coupled laterally to form nanoporous graphene structures. This graphene nanoarchitecture consists of weakly coupled semiconducting nanochannels with electron propagation characterized by interchannel quantum interferences. By utilizing phenylene bridges, the electronic coupling between the nanoribbons in the nanoporous graphene structure can be controlled, providing versatility through different phenylene cross-coupling configurations and twist angles. Simulation results demonstrate the ability to switch on/off or modulate the interribbon coupling using the chemical or conformational knob. Molecular bridges offer efficient tools for engineering quantum transport and anisotropy in carbon-based 2D nanoarchitectures.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)