Article
Physics, Applied
Yu-Chen Chang, Bipul Das, Yu-Fan Chiang, Wen-Hao Chang, Yen-Chun Chen, Rahul Kesarwani, Wen-Cheng Ke, Yann-Wen Lan, Ting-Hua Lu
Summary: Displacement in conventional Raman spectroscopy can be caused by an increase in material layers or strain variation. Polarization-resolved Raman spectroscopy provides a method to distinguish between them. This study uses polarization-resolved Raman spectroscopy and numerical analysis to investigate strained graphene induced by different substrates. The research shows that the polarization properties of scattered light in strained graphene are different from unstrained graphene due to phonon polarization deformation caused by different strengths of substrate coupling. This research provides an efficient quantitative method to explore strain anisotropy in two-dimensional materials, which is important for the development of straintronics in the future.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Yu Zhang, Ying Su, Lin He
Summary: Vortices in graphene induced by single carbon defects can be considered as atomic-scale vortices mediated by pseudospin, with angular momenta of +2 and -2. Quantum interference measurements show that these vortices cancel each other, resulting in zero total angular momentum or aggregate chirality similar to a single vortex of the majority.
Article
Chemistry, Multidisciplinary
Zafer Mutlu, Juan Pablo Llinas, Peter H. Jacobse, Ilya Piskun, Raymond Blackwell, Michael F. Crommie, Felix R. Fischer, Jeffrey Bokor
Summary: The rational bottom-up synthesis of graphene nanoribbons (GNRs) provides precise control of widths and edges for a wide range of electronic properties, showing promise for electronic devices. A method for transfer-free placement of GNRs on insulators has been demonstrated, allowing for high-density and structurally-intact GNR growth on gold films deposited on SiO2/Si substrates. The scalability of this method to 12-inch wafers represents an important advancement towards large-scale integration of GNRs into electronic devices.
Article
Materials Science, Multidisciplinary
D. Ivekovic, P. Dubcek, A. Gajovic, T. Cizmar, B. Radatovic, A. L. Brkic, M. Kralj, M. Karlusic
Summary: In this study, we used atomic force microscopy, scanning tunnelling microscopy, and Raman spectroscopy to investigate the response of graphite to high-energy heavy ions irradiation. Ion tracks were observed on the surface after grazing incidence ion irradiation by 23 MeV I, indicating the susceptibility of the graphite surface to this type of irradiation. No tracks were found within the bulk after normal incidence irradiation. However, we demonstrate that electronic energy loss contributes to defect recovery, thus enhancing the stability of graphite below the surface to high-energy heavy ion irradiation.
JOURNAL OF NUCLEAR MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Heping Wu, Gang Niu, Wei Ren, Zhugen Yang, Qihang Xu, Liyan Dai, Luyue Jiang, Shijie Zhai, Jinyan Zhao, Nan Zhang, Libo Zhao, Zhuangde Jiang, Gang Zhao
Summary: This study demonstrates an improved double layer of PMMA/paraffin for the large-area transfer of graphene onto gold nanopyramid substrates. The properties of graphene on AuNPs, including Raman spectra and surface-enhanced Raman scattering effect, are examined in detail. These findings provide a new pathway for the applications of transferred graphene on raised nanostructures in various fields.
ACS APPLIED NANO MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Ya-Ning Ren, Zhen Zhan, Yi-Wen Liu, Chao Yan, Shengjun Yuan, Lin He
Summary: In two-dimensional small-angle twisted bilayers, the atomic-scale reconstruction caused by van der Waals interlayer interaction can be mapped by introducing a topmost small-period graphene moire pattern. This pattern magnifies sub-Angstrom lattice distortions in the small-angle twisted bilayer graphene by about 2 orders of magnitude, enabling real-space mapping of the networks of subdegree lattice rotations. This method provides a facile way to study subdegree lattice rotation in van der Waals systems.
Article
Materials Science, Composites
Sijia Hao, Zheling Li, Cheng Yang, Alexander J. Marsden, Ian A. Kinloch, Robert J. Young
Summary: Bio-inspired nanocomposites were fabricated using GO-based fillers and their interfacial energy dissipation during cyclic deformation was studied. It was found that the presence of functional groups reduced the interfacial energy dissipation in the elastic regime, but increased it with strain. This study provides new insights for the fabrication and evaluation of bio-inspired nanocomposites.
COMPOSITES SCIENCE AND TECHNOLOGY
(2022)
Article
Nanoscience & Nanotechnology
Jinglan Liu, Chunhua Zhu, Zilong Zhang, Qiancheng Ren, Xuewei Zhang, Yang Zhang, Yanhan Jin, Wei Qiu, Hongtao Wang, Junhua Zhao, Pei Zhao
Summary: This study investigates the interfacial shear coupling (ISC) of layered 2D van der Waals (vdW) materials using bilayer graphene (BLG) and isotope-labeled Raman spectroscopy. The results reveal an inverse proportionality between the interfacial shear strength and the sample size, with the ISC undergoing bonding, sliding, and debonding processes under uniaxial tensile strain. Molecular dynamics simulations attribute this inverse proportionality to the stronger interlayer vdW interaction induced by the edge lattices and atoms of BLG. These findings provide fundamental insights into the macroscopic interfacial shear properties of 2D vdW stacks and have potential applications in guiding the design of graphene-based composite materials and flexible 2D electronics.
NPJ 2D MATERIALS AND APPLICATIONS
(2022)
Article
Chemistry, Physical
Mingming Yang, Longlong Wang, Guofeng Hu, Xue Chen, Peng Lai Gong, Xin Cong, Yi Liu, Yuanbo Yang, Xiaoli Li, Xiaohui Zhao, Xuelu Liu
Summary: The study investigates the interlayer coupling in graphene/MoS2 vdW heterostructures through spectroscopy analysis, revealing the electron transfer and coupling mechanism between graphene and MoS2.
Article
Chemistry, Physical
Jinglan Liu, Xuewei Zhang, Yang Zhang, Qiancheng Ren, Yanhan Jin, Pei Zhao
Summary: The electrical properties of bilayer graphene are strongly influenced by external forces. Raman spectroscopy and molecular dynamics simulations were used to study the strain states of bilayer graphene synthesized by chemical vapor deposition, revealing that twisted BLG is under compression with the bottom layer experiencing larger compressive strain, while AB-stacked BLG has its top layer compressed and bottom layer tensile.
Article
Chemistry, Physical
Zied Othmen, Riadh Othmen, Kais Daoudi, Michel Boudard, Antonella Cavanna, Ali Madouri, Pascale Gemeiner, Doru C. Lupascu, Meherzi Oueslati, Brahim Dkhil
Summary: The successful synthesis and transfer of graphene monolayers onto epitaxial mixed valence La0.7Sr0.3CoO3 (LSCO) thin films revealed the activation of Jahn-Teller modes in the LSCO films. The presence of graphene was found to affect the magnetic properties of LSCO, leading to a phase transition at around 135 K as compared to the bare LSCO films which exhibit a ferromagnetic transition at around 200 K. Raman spectroscopy measurements confirmed the magnetic phase transition as a function of temperature, indicating a vibrational transition around the same temperature.
SURFACES AND INTERFACES
(2021)
Article
Chemistry, Physical
Hyungsub Lim, Hyo Chan Lee, Kilwon Cho
Summary: Graphene/Cu composites show promise as future electrode materials due to their mechanical, electrical, and thermal stability. However, the presence of graphene accelerates oxidation of the underlying Cu surface, which affects the properties of the composites. Therefore, it is critical to investigate the effects of Cu oxidation on the interfacial properties of graphene/Cu composites.
Article
Chemistry, Physical
Hyo Won Kim, Insu Jeon, Wonhee Ko, Seong Heon Kim
Summary: The anisotropic twofold symmetry of Ge(110) makes it unique for single-crystalline graphene growth. Growth of graphene on Ge(110) surface initiates unidirectionally from carbon cluster seeds, forming graphene nanoribbons (GNRs) that eventually transform into graphene nanoislands (GNIs) and coalesce into single crystalline monolayer graphene. STS measurements reveal GNRs with small bandgaps, induced by graphene confinement effect, providing insights into growth mechanism of graphene on Ge(110) surface under various synthesis conditions.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
Amogh Kinikar, Xiushang Xu, Marco Di Giovannantonio, Oliver Groening, Kristjan Eimre, Carlo A. Pignedoli, Klaus Muellen, Akimitsu Narita, Pascal Ruffieux, Roman Fasel
Summary: In this study, a new design motif is introduced to synthesize edge-extended zigzag graphene nanoribbons (ZGNRs). Using scanning probe techniques and density functional theory, the chemical structure and electronic characteristics of a 3-zigzag-row ZGNR instance are confirmed. This approach expands the range of possible ZGNRs, contributing to further understanding of structure-dependent electronic properties in GNRs.
ADVANCED MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Giuliana Faggio, Rossella Grillo, Antonino Foti, Simonpietro Agnello, Fabrizio Messina, Giacomo Messina
Summary: Carbon-based nanomaterials such as carbon dots (CDs) and graphene (Gr) exhibit excellent optical and electronic properties. Integrating CDs and Gr into a nanocomposite material, CDs/Gr, can enhance their optoelectronic properties and pave the way for advanced carbon nanotechnology. Research on the structural and emission properties of CDs deposited on single-layer and bilayer graphene reveals insights into their interaction and potential for further optimization.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Mengyang Xu, Yang Li, Muhammad Ihsan-Ul-Haq, Nauman Mubarak, Zhenjing Liu, Junxiong Wu, Zhengtang Luo, Jang Kyo Kim
Summary: A strategy of in situ forming a protective layer to suppress dendrite growth on sodium metal has been developed, leading to enhanced cyclic stability of sodium metal batteries. The design of a NaF-rich solid electrolyte interface prevents continuous electrolyte depletion during charge/discharge cycles and contributes to the high performance of the batteries.
ENERGY STORAGE MATERIALS
(2022)
Article
Engineering, Environmental
Xue Li, Ya Huang, Wen Fang Wei, Wan Lin Guo, Zhengtang Luo, Jiangtao Xu, Tao Cai
Summary: Two-dimensional (2D) metal-organic framework (MOF) nanosheets have great potential due to their highly exposed active sites and high aspect ratio. In this study, PCN-134(Zn)-2D nanosheets were found to be effective catalysts for enhancing the photocatalytic performance of metalloporphyrins. The polymerization kinetics could be orthogonally regulated by solution pH and light stimuli.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Eric Y. Ma, Jenny Hu, Lutz Waldecker, Kenji Watanabe, Takashi Taniguchi, Fang Liu, Tony F. Heinz
Summary: In this study, we experimentally and theoretically describe the Reststrahlen response in hexagonal boron nitride across a wide range of thicknesses. As the material becomes optically thin, the high reflectivity plateau of the Reststrahlen band evolves into a single peak and two distinct regimes emerge.
Article
Optics
Christian Heide, Yuki Kobayashi, Denitsa R. Baykusheva, Deepti Jain, Jonathan A. Sobota, Makoto Hashimoto, Patrick S. Kirchmann, Seongshik Oh, Tony F. Heinz, David A. Reis, Shambhu Ghimire
Summary: Researchers have found that circularly polarized laser-field-driven high-harmonic generation is highly sensitive to the non-trivial and trivial topological phases in topological insulators. By chemically reducing the spin-orbit interaction strength, the phase transition between non-trivial and trivial topological states can be achieved. This purely optical method offers sensitivity to the electronic structure of the material and is compatible with a wide range of samples and sample environments.
Article
Nanoscience & Nanotechnology
Aditya Sood, Jonah B. Haber, Johan Carlstrom, Elizabeth A. Peterson, Elyse Barre, Johnathan D. Georgaras, Alexander H. M. Reid, Xiaozhe Shen, Marc E. Zajac, Emma C. Regan, Jie Yang, Takashi Taniguchi, Kenji Watanabe, Feng Wang, Xijie Wang, Jeffrey B. Neaton, Tony F. Heinz, Aaron M. Lindenberg, Felipe H. da Jornada, Archana Raja
Summary: In this study, lattice dynamics in photoexcited WSe2/WS2 heterostructures were directly visualized using femtosecond electron diffraction. It was found that both WSe2 and WS2 were heated simultaneously on a picosecond timescale, which cannot be explained by phonon transport across the interface. First-principles calculations revealed a fast channel involving layer-hybridized electronic states, enabling phonon-assisted interlayer transfer of photoexcited electrons. Phonons were emitted in both layers on the femtosecond timescale via this channel, consistent with the simultaneous lattice heating observed experimentally. Strong electron-phonon coupling via layer-hybridized electronic states was identified as a novel route for controlling energy transport across atomic junctions.
NATURE NANOTECHNOLOGY
(2023)
Article
Physics, Multidisciplinary
Yuki Kobayashi, Christian Heide, Amalya C. Johnson, Vishal Tiwari, Fang Liu, David A. Reis, Tony F. Heinz, Shambhu Ghimire
Summary: Interactions between quantum materials and strong laser fields can result in non-equilibrium electronic states. Monolayer transition metal dichalcogenides, as direct-gap semiconductors with quantum confinement, offer opportunities for controlling excitons. However, characterizing strong-field driven exciton dynamics has been challenging.
Article
Chemistry, Multidisciplinary
Yin Liu, Sze Cheung Lau, Wen-Hui Cheng, Amalya Johnson, Qitong Li, Emma Simmerman, Ouri Karni, Jack Hu, Fang Liu, Mark L. Brongersma, Tony F. Heinz, Jennifer A. Dionne
Summary: In this study, integration of MoS2 monolayers with a chiral silicon disk array metasurface is used to enhance and control the absorption and emission of excitons in two-dimensional transition metal dichalcogenides. The metasurface coupling enhances the intensity and shortens the lifetime of excitons, trions, and defect bound excitons, and also modifies their spectral shape. Furthermore, the degree of polarization of exciton and trion emission from the valley is symmetrically enhanced at 100 K, resulting from the metasurface-enhanced chiral absorption and the metasurface-enhanced exciton emission from the Purcell effect. The combination of Si-compatible photonic design and large-scale integration of 2D materials in this work is a crucial step towards on-chip valleytronic applications at room temperature.
Article
Materials Science, Multidisciplinary
Hirohito Ogasawara, Han Wang, Jorgen Gladh, Alessandro Gallo, Ralph Page, Johannes Voss, Alan Luntz, Elias Diesen, Frank Abild-Pedersen, Anders Nilsson, Markus Soldemo, Marc Zajac, Andrew Attar, Michelle E. Chen, Sang Wan Cho, Abhishek Katoch, Ki-Jeong Kim, Kyung Hwan Kim, Minseok Kim, Soonnam Kwon, Sang Han Park, Henrique Ribeiro, Sami Sainio, Hsin-Yi Wang, Cheolhee Yang, Tony Heinz
Summary: We conducted optical pumping and x-ray absorption spectroscopy experiments on a graphene monolayer adsorbed on copper using a free electron laser. Our analysis suggests that the excitation of graphene is primarily due to indirect excitation from hot electron-hole pairs created in the copper. However, once the excitation occurs in graphene, its decay follows a similar path as in previous studies of graphene adsorbed on semiconductors, involving rapid excitation of strongly coupled optical phonons and eventual thermalization. The lifetime of the hot electron-hole pairs in copper likely influences the lifetime of the electronic excitation in graphene.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Sergio L. L. M. Ramos, Bruno R. Carvalho, Raphael Longuinhos Monteiro Lobato, Jenaina Ribeiro-Soares, Cristiano Fantini, Henrique B. Ribeiro, Laurent Molino, Ryan Plumadore, Tony Heinz, Adina Luican-Mayer, Marcos A. Pimenta
Summary: Using multiple excitation and polarized Raman spectroscopy, it has been discovered that a dimerized double-layer stacking configuration exists in 1T-TaS2, which is related to the formation and interaction of charge density waves. This finding sheds light on the role of electron-phonon coupling in the CDW formation of 1T-TaS2.
Article
Chemistry, Multidisciplinary
Jenny Hu, Leo Yu, Xueqi Chen, Wanhee Lee, C. Mathew Mate, Tony F. Heinz
Summary: This study investigates the transfer of strain in vertically stacked van-der-Waals heterostructures and finds that high strain transfer efficiency is observed in aligned heterostructures with small twist angles.
Article
Chemistry, Physical
Leo Yu, Kateryna Pistunova, Jenny Hu, Kenji Watanabe, Takashi Taniguchi, Tony F. Heinz
Summary: We demonstrate the emergence of quadrupolar excitons in angle-aligned WSe2/WS2/WSe2 heterotrilayers and confirm their nature. At high exciton density, we also observe signatures of a phase of oppositely aligned dipolar excitons.
Article
Multidisciplinary Sciences
Jiaojian Shi, Haowei Xu, Christian Heide, Changan HuangFu, Chenyi Xia, Felipe de Quesada, Hongzhi Shen, Tianyi Zhang, Leo Yu, Amalya Johnson, Fang Liu, Enzheng Shi, Liying Jiao, Tony Heinz, Shambhu Ghimire, Ju Li, Jing Kong, Yunfan Guo, Aaron M. Lindenberg
Summary: The authors report giant room-temperature nonlinearity enhancements in Janus transition metal dichalcogenides, which may be leveraged through electronic band topology. The giant nonlinear optical response is linked to topological band mixing and strong inversion symmetry breaking due to the Janus structure. This work defines general protocols for designing materials with large nonlinearities and heralds the applications of topological materials in optoelectronics.
NATURE COMMUNICATIONS
(2023)
Article
Nanoscience & Nanotechnology
Chenfang Lin, Faruk Krecinic, Hiroko Yoshino, Adnan Hammud, Anlian Pan, Martin Wolf, Melanie Mueller, Takashi Kumagai
Summary: In this study, we demonstrate the generation of multiphoton photocurrents in a plasmonic scanning tunneling microscope (STM) junction using continuous-wave excitation. The photocurrent shows a power-law dependence on the incident intensity, with the exponent varying between 3 and 1 depending on the photon energy and bias voltage. The bias-voltage dependence of the photocurrent exhibits characteristic steps that can be explained by the transmission of nonthermal carriers through the potential barrier of the tunnel junction.
Article
Nanoscience & Nanotechnology
Christian Heide, Yuki Kobayashi, Amalya C. Johnson, Tony F. Heinz, David A. Reis, Fang Liu, Shambhu Ghimire
Summary: We report the layer-by-layer build-up of high-order harmonic generation (HHG) in artificially stacked transition metal dichalcogenides (TMDC) crystals. High-order harmonics up to the 19th order are generated by the interaction with a mid-infrared (MIR) driving laser. The generation of harmonics is sensitive to the number of layers and their relative orientation, with different stacking configurations showing different harmonic intensities.
Article
Chemistry, Multidisciplinary
Shang-Jie Yu, Helen Yao, Guangwei Hu, Yue Jiang, Xiaolin Zheng, Shanhui Fan, Tony F. Heinz, Jonathan A. Fan
Summary: This study presents hyperbolic polaritonic rulers based on low-dimensional, strongly anisotropic nanomaterials, which exhibit near-field polaritonic characteristics that are highly sensitive to device geometry. Using scanning near-field optical microscopy, the researchers demonstrate the strongly confined image polariton modes supported by these rulers and describe and predict their behavior using a simple analytic model.
