Article
Materials Science, Multidisciplinary
Ankit Arora, Pramoda K. Nayak, Swastibrata Bhattacharyya, Nikhilesh Maity, Abhishek K. Singh, Ananth Krishnan, M. S. Ramachandra Rao
Summary: This study reports different interlayer excitonic states in an aligned MoSe2/MoS2 incommensurate van der Waals heterostructure. Photoluminescence measurements and first-principles simulations were used to reveal the orbital resolved electronic band structure and the presence of interlayer excitons. The emergence of two low-energy peaks in the PL spectrum suggests energy band hybridization in the heterostructure.
Article
Chemistry, Multidisciplinary
Golam Haider, Krishna Sampathkumar, Tim Verhagen, Lukas Nadvornik, Farjana J. Sonia, Vaclav Vales, Jan Sykora, Peter Kapusta, Petr Nemec, Martin Hof, Otakar Frank, Yang-Fang Chen, Jana Vejpravova, Martin Kalbac
Summary: The recent study demonstrates the coherent oscillation of excitonic dipoles in van der Waals heterostructures composed of monolayer transition-metal dichalcogenides and few-layer hBN, achieved through strong suppression of phonon population at low temperatures. This results in robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Multidisciplinary Sciences
Philipp Merkl, Chaw-Keong Yong, Marlene Liebich, Isabella Hofmeister, Gunnar Berghaeuser, Ermin Malic, Rupert Huber
Summary: The authors demonstrate proximity-controlled strong-coupling between Coulomb correlations and lattice dynamics in neighboring van der Waals materials (WSe2 and a gypsum layer), creating electrically neutral hybrid exciton-phonon eigenmodes called excitonic Lyman polarons. This approach provides a promising new strategy to engineer novel ground states of two-dimensional systems by controlling the spatial wavefunction overlap of excitons and phonons.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Physical
X. R. Hou, S. D. Wang
Summary: In this study, the quasiparticle band structures and excitonic optical properties of SiC/MoSSe heterostructures were investigated using the GW + Bethe-Salpeter equation approach. The results show that all four stable structures of SiC/MoSSe heterostructures are favorable for producing high binding energy interlayer excitons. The modulation of optical dipole oscillator strength and radiative lifetimes is significant due to the different intrinsic dipole moments of MoSSe.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Multidisciplinary
Changxiu Li, Alexey V. V. Scherbakov, Pedro Soubelet, Anton K. K. Samusev, Claudia Ruppert, Nilanthy Balakrishnan, Vitalyi E. E. Gusev, Andreas V. V. Stier, Jonathan J. J. Finley, Manfred Bayer, Andrey V. V. Akimov
Summary: The development of new techniques for ultrafast control of physical properties in 2D van der Waals nanolayers is necessary due to the increasing role of 2D devices. Heterobilayers assembled from van der Waals monolayers have the special feature of femtosecond separation of photoexcited electrons and holes between neighboring layers, resulting in the formation of Coulomb force. Coherent phonons generated in MoSe2/WSe2 heterobilayers through laser pulses can modulate the thickness of the heterobilayer and the photogenerated electric field in the van der Waals gap. Additionally, the modulation of the van der Waals gap by coherent phonons enables the generation of THz radiation in 2D nanodevices with van der Waals heterobilayers.
Article
Chemistry, Multidisciplinary
Huan Liu, Jiangcai Wang, Yuanshuang Liu, Yong Wang, Lujie Xu, Li Huang, Dameng Liu, Jianbin Luo
Summary: A new defect-induced ultrafast interlayer electron-phonon coupling pathway is identified in a WS2/graphene heterostructure. This interaction significantly reduces defect-related Raman resonant activity and accelerates the electron-phonon scattering time. Furthermore, the ultrafast interlayer coupling process is directly imaged.
ADVANCED MATERIALS
(2022)
Review
Chemistry, Multidisciplinary
Xin Wu, Xiyue Chen, Ruxue Yang, Jianbin Zhan, Yingzhi Ren, Kun Li
Summary: 2D vdW heterostructures have attracted research attention for their theoretical properties and application potentials. However, the synthesized heterostructures generally underperform due to weak interlayer coupling. This paper provides a state-of-the-art review of different techniques for performance modulation of vdW heterostructures, summarizing general synthesis methods and discussing mechanical-based, external fields-assisted, and particle beam irradiation-based methods. The applications and future prospects of tailored properties in vdW heterostructures are also reviewed.
Article
Chemistry, Multidisciplinary
Tae Gwan Park, Hong Ryeol Na, Seung-Hyun Chun, Won Bae Cho, Sunghun Lee, Fabian Rotermund
Summary: An all-optical method for precise control of interlayer vibrations in layered structures using Bi2Se3 as a promising material is proposed in this study. Fast interlayer breathing modes and slow interfacial modes induced by the substrate are observed, with their behavior explained by a modified linear chain model including coupling effect with the substrate. The results of coherent control experiments are in agreement with simulation results based on the interference of interlayer vibrations, providing insight into interlayer vibration-related dynamics and potential applications for novel devices on an ultrafast timescale.
Article
Materials Science, Multidisciplinary
F. Michael Bartram, Yu-Chen Leng, Yongchao Wang, Liangyang Liu, Xue Chen, Huining Peng, Hao Li, Pu Yu, Yang Wu, Miao-Ling Lin, Jinsong Zhang, Ping-Heng Tan, Luyi Yang
Summary: In this study, we investigated the ultrafast carrier dynamics and coherent interlayer phonons in few-layer MnBi2Te4 using time-resolved pump-probe reflectivity spectroscopy. We observed pronounced coherent phonon oscillations from the interlayer breathing mode in the time domain. The frequency of the coherent oscillation, as well as the decay rates of photocarriers and coherent phonons, were found to be sensitive to the sample thickness.
NPJ QUANTUM MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Paulina Ewa Majchrzak, Yuntian Liu, Klara Volckaert, Deepnarayan Biswas, Chakradhar Sahoo, Denny Puntel, Wibke Bronsch, Manuel Tuniz, Federico Cilento, Xing-Chen Pan, Qihang Liu, Yong P. Chen, Soren Ulstrup
Summary: We investigated the hybrid structures composed of the intrinsic magnetic topological insulator MnBi2Te4 and its nonmagnetic counterpart Bi2Te3 using time-and angle-resolved photoemission spectroscopy and density functional theory calculations. The results showed that the surface electronic band structures of these hybrid structures depend on the stacking order and exposed termination.
Review
Chemistry, Multidisciplinary
Waqas Ahmad, Liang Pan, Karim Khan, Lingpu Jia, Qiandong Zhuang, Zhiming Wang
Summary: Van der Waals (vdWs) heterostructures enable bandgap engineering of different 2D materials to broaden the spectrum beyond individual 2D materials' cut-off wavelength. Interlayer transition plays a significant role in the optoelectronic performance of vdWs heterostructure devices, and strong interlayer transition is always desirable for charge transfer and speed response. This review summarizes recent progress on interlayer transition in vdWs heterostructures for near-infrared (NIR) photodetectors, including synthesis techniques, band alignments, mechanism, and applications.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Victor Zatko, Simon Mutien-Marie Dubois, Florian Godel, Cecile Carretero, Anke Sander, Sophie Collin, Marta Galbiati, Julian Peiro, Federico Panciera, Gilles Patriarche, Pierre Brus, Bernard Servet, Jean-Christophe Charlier, Marie-Blandine Martin, Bruno Dlubak, Pierre Seneor
Summary: This study presents a growth process utilizing pulsed laser deposition to create large-scale complex van der Waals heterostructures at a high temperature, demonstrating the successful construction of multilayer stacks in a single run with high homogeneity. The structural preservation achieved through continuous in situ growth allows even the most fragile 2D layers to remain intact when encapsulated in van der Waals heterostructures.
Article
Chemistry, Multidisciplinary
Duan Luo, Jian Tang, Xiaozhe Shen, Fuhao Ji, Jie Yang, Stephen Weathersby, Michael E. Kozina, Zhijiang Chen, Jun Xiao, Yusen Ye, Ting Cao, Guangyu Zhang, Xijie Wang, Aaron M. Lindenberg
Summary: The study utilized ultrafast electron diffraction to simultaneously visualize charge transfer and electron-phonon coupling in MoS2-graphene heterostructures. It was found that the timescale of charge transfer and relaxation varies significantly with twist angle, indicating that twist angle can serve as an additional tuning knob for interlayer charge transfer in heterobilayers. The research deepened the understanding of fundamental photophysical processes in heterostructures, which is important for future applications in optoelectronics and light harvesting.
Article
Chemistry, Multidisciplinary
Hao Wang, Lihong Bao, Roger Guzman, Kang Wu, Aiwei Wang, Li Liu, Liangmei Wu, Jiancui Chen, Qing Huan, Wu Zhou, Sokrates T. Pantelides, Hong-Jun Gao
Summary: The development of electrically ultrafast-programmable semiconductor homojunctions can lead to transformative multifunctional electronic devices. Here, 2D, multi-functional, lateral homojunctions made of van der Waals heterostructures with a semi-floating-gate configuration on a p(++) Si substrate are introduced. These homojunctions can be electrostatically programmed in nanoseconds, and have rectification ratio up to & AP;10(5), enabling them to function as logic rectifiers, memories, and multi-valued logic inverters. The devices are also compatible with Si technology.
ADVANCED MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Ryung Kim, Byoung Ki Choi, Kyeong Jun Lee, Hyuk Jin Kim, Hyun Hwi Lee, Tae Gyu Rhee, Yeong Gwang Khim, Young Jun Chang, Seo Hyoung Chang
Summary: This study used crystal truncation rod (CTR) analysis to investigate the atomic arrangement of bilayer VSe2 and bilayer graphene (BLG) heterostructures and its impact on the magnetic properties. The results showed that the interface can modulate the lattice parameters of VSe2. The atomic arrangement of the VSe2/BLG heterostructure provides deeper understanding of the magnetic properties of van der Waals heterostructures.
CURRENT APPLIED PHYSICS
(2023)
Article
Optics
Ji Eun Bae, Thomas Calmano, Christian Kraenkel, Fabian Rotermund
Summary: This study demonstrates the dynamic single- and dual-channel graphene Q-switching of a Yb:YAG waveguide by controlling the power-splitting ratio, enabling the selective excitation of individual channels and controlled splitting ratios of output powers. The beam-splitter-type waveguide laser developed in this study has potential advantages in various applications such as optical communication, metrology, and sensing.
LASER & PHOTONICS REVIEWS
(2022)
Article
Chemistry, Multidisciplinary
Nguyen Huu Lam, Phuong Lien Nguyen, Byoung Ki Choi, Trinh Thi Ly, Ganbat Duvjir, Tae Gyu Rhee, Yong Jin Jo, Tae Heon Kim, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Younghun Hwang, Young Jun Chang, Jaekwang Lee, Jungdae Kim
Summary: In this study, the strength of spin-orbit coupling in NiTe2 is shown to be tunable through Se substitution, resulting in shifts of the bulk Dirac point while maintaining the type-II Dirac band. This approach provides an effective means of controlling the type-II Dirac band in NiTe2 and can be applicable to other topological materials.
Article
Physics, Multidisciplinary
Tae Gwan Park, Jae Ho Jeon, Seung-Hyun Chun, Sunghun Lee, Fabian Rotermund
Summary: This study investigates the interface effects between VSe2 and topological insulator Bi2Se3 using ultrafast time-resolved spectroscopy. The results show that VSe2 as an electrode does not alter the surface state of Bi2Se3 and enables efficient electron transfer and current flow.
COMMUNICATIONS PHYSICS
(2022)
Article
Optics
Tae Gwan Park, Eon-Taek Oh, Sungwon Kim, Yunbo Ou, Jagadeesh Moodera, Hyunjung Kim, Fabian Rotermund
Summary: This study comprehensively investigated the coherent lattice dynamics in Bi(2)Se(3) using ultrafast optical pump-probe spectroscopy. The optical properties of Bi2Se3 were found to play a key role in the generation and detection of photoinduced strain waves, leading to coherent interlayer vibrations. The frequency and lifetime of these vibrations were quantitatively explained by considering elastic coupling at the sample-substrate interfaces. This work provides insights for analyzing and interpreting nanomechanical interactions in layered materials using ultrafast optical spectroscopy.
Article
Multidisciplinary Sciences
Ji-Ho Park, Won Tae Kim, Woonjae Won, Jun-Ho Kang, Soogil Lee, Byong-Guk Park, Byoung S. Ham, Younghun Jo, Fabian Rotermund, Kab-Jin Kim
Summary: In a ferrimagnet, the magnetic moments at deeper energy levels show spin-glass like characteristics and are more easily influenced by external magnetic fields compared to those near the Fermi level. Investigating the energy-level-selective magnetic moment configuration in rare earth-transition metal ferrimagnetic alloys provides insights into the understanding of ferrimagnets and spin-glass studies.
NATURE COMMUNICATIONS
(2022)
Article
Nanoscience & Nanotechnology
Ganbat Duvjir, Jee-Ahn Jung, Trinh Thi Ly, Nguyen Huu Lam, Young Jun Chang, Sunghun Lee, Hanchul Kim, Jungdae Kim
Summary: In this study, the fine structure and charge distribution of the charge density wave (CDW) phase in VTe2 were investigated using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The results provide valuable insights for further research on the electronic structure of VTe2.
Article
Nanoscience & Nanotechnology
Bong-Rim Shin, In Cheol Yu, Myeong-Hoon Shin, Mojca Jazbinsek, Fabian Rotermund, O-Pil Kwon
Summary: In this study, efficient organic THz wave generators, 2-(4-hydroxystyryl)-1-methylquinolinium 4-bromobenzenesulfonate (OHQ-BBS) single crystals, were reported. The OHQ-BBS crystals exhibit a wide molecular vibrational mode-free range in the THz frequency region with low absorption. By optical rectification, the OHQ-BBS crystals generate extremely broad, dimple-free THz waves and achieve a higher THz electric field compared to the widely used ZnTe inorganic crystal.
Article
Physics, Multidisciplinary
Yeong Gwang Khim, Beomjin Park, Jin Eun Heo, Young Hun Khim, Young Rok Khim, Minseon Gu, Tae Gyu Rhee, Seo Hyoung Chang, Moonsup Han, Young Jun Chang
Summary: The study finds that high-temperature growth of TiN thin films leads to significant enhancement of electrical conductivity, promising for durable and scalable electrode applications.
JOURNAL OF THE KOREAN PHYSICAL SOCIETY
(2023)
Article
Materials Science, Multidisciplinary
Klara Volckaert, Byoung Ki Choi, Hyuk Jin Kim, Deepnarayan Biswas, Denny Puntel, Simone Peli, Fulvio Parmigiani, Federico Cilento, Young Jun Chang, Soren Ulstrup
Summary: This study investigates the femtosecond dynamics of photoinduced excitations in single-layer ReSe2 grown on a bilayer graphene substrate. The optical gap of ReSe2 is measured to be (1.53 +/- 0.02) eV, and the exciton distribution can be tuned by the polarization of the pump pulse. The decay of the exciton distribution has two time constants, facilitated by interlayer charge transfer and recombination via an in-gap state at the Fermi level.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Hyuk Jin Kim, Minsu Chong, Tae Gyu Rhee, Yeong Gwang Khim, Min-Hyoung Jung, Young-Min Kim, Hu Young Jeong, Byoung Ki Choi, Young Jun Chang
Summary: In this study, machine learning-assisted analysis of RHEED videos was used to investigate the growth of 2D thin films of transition metal dichalcogenides (ReSe2) on graphene substrates. By utilizing principal component analysis (PCA) and K-means clustering, statistically important patterns can be separated and the trend of pattern evolution can be visualized without notable loss of information. The findings demonstrate the successful application of machine learning analysis in examining and understanding the film-growth dynamics of 2D materials, and have the potential to pave the way for advanced real-time monitoring and autonomous material synthesis techniques.
Article
Materials Science, Multidisciplinary
Minseon Gu, Moon Seop Hyun, Moonsup Han, Gyungtae Kim, Young Jun Chang
Summary: The increasing demands for multi-stacked memory devices require the urgent development of backside contact electrode technologies. Two inspection methods, voltage contrast (VC)-SEM and conducting AFM (C-AFM), were investigated in this study for testing samples with different contact hole states. VC-SEM showed contrast variation at the contact holes, allowing for discerning the contact status with an optimal voltage. C-AFM demonstrated a finite electrical current in connected contacts and negligible current in disconnected ones. The insights gained from these methods are valuable for analyzing high aspect ratio contact hole technologies.
CURRENT APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Kyungtaek Lee, In Hak Lee, Yeong Gwang Khim, Suh-young Kwon, Geunweon Lim, Junha Jung, Young Jun Chang, Ju Han Lee
Summary: The potential of two-dimensional nanomaterial Cr2Te3 in nonlinear photonics has been investigated. The Cr2Te3 film shows saturable absorption and self-defocusing properties at telecommunication wavelengths. The study suggests that Cr2Te3 has broad optical applications potential.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Materials Science, Multidisciplinary
Si-Hong Lee, Yun Chang Park, Jinwoong Chae, Gunn Kim, Hyuk Jin Kim, Byoung Ki Choi, In Hak Lee, Young Jun Chang, Seung-Hyun Chun, Minkyung Jung, Jungpil Seo, Sunghun Lee
Summary: The study reports the fabrication of a perfect 1T-phase VS2 single crystal using chemical vapor transport and annealing treatment, and reveals the formation of two clear CDW orders at low temperature with the absence of nesting vectors on the Fermi surface. This finding provides important insights for further research on the physical properties of VS2.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Nanoscience & Nanotechnology
Hyuk Jin Kim, Nguyen Van Quang, Thi Huong Nguyen, Sera Kim, Yangjin Lee, In Hak Lee, Sunglae Cho, Maeng-Je Seong, Kwanpyo Kim, Young Jun Chang
Summary: This study investigates the effect of helium ion irradiation on transition metal dichalcogenide thin films and finds that helium ion irradiation can significantly improve their thermoelectric properties.
NANOSCALE RESEARCH LETTERS
(2022)
