Article
Multidisciplinary Sciences
Artem N. Abramov, Igor Y. Chestnov, Ekaterina S. Alimova, Tatiana Ivanova, Ivan S. Mukhin, Dmitry N. Krizhanovskii, Ivan A. Shelykh, Ivan V. Iorsh, Vasily Kravtsov
Summary: By using local deformation of monolayer WSe2, we have successfully created high-purity single-photon emitters. Through nanoindentation and atomic force microscopy, we have identified the single-photon emitting sites and reconstructed the details of the surrounding local strain potential. The experimental results suggest that the single-photon emission is likely due to strain-induced spectral shift of dark excitonic states and their hybridization with localized states of individual defects.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Qixing Wang, Julian Maisch, Fangdong Tang, Dong Zhao, Sheng Yang, Raphael Joos, Simone Luca Portalupi, Peter Michler, Jurgen H. Smet
Summary: Deformation strain is used to induce quasi-one-dimensional localized excitons in WSe2 monolayers, leading to emission with 95% linear polarization purity and conversion to high-purity circular polarization in a strong magnetic field. The deterministic control over polarization purity and orientation is a valuable asset in the context of integrated quantum photonics.
Article
Physics, Multidisciplinary
Koloman Wagner, Jonas Zipfel, Roberto Rosati, Edith Wietek, Jonas D. Ziegler, Samuel Brem, Raul Perea-Causin, Takashi Taniguchi, Kenji Watanabe, Mikhail M. Glazov, Ermin Malic, Alexey Chernikov
Summary: Experimental results show a highly unusual exciton diffusion behavior in monolayer semiconductors, where the diffusion coefficient decreases significantly with increasing temperature, challenging traditional descriptions of mobile excitons. The origin of this behavior is discussed in the context of nonclassical propagation and microscopic numerical models.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Physical
Trond Andersen, Giovanni Scuri, Andrey Sushko, Kristiaan De Greve, Jiho Sung, You Zhou, Dominik S. Wild, Ryan J. Gelly, Hoseok Heo, Damien Berube, Andrew Y. Joe, Luis A. Jauregui, Kenji Watanabe, Takashi Taniguchi, Philip Kim, Hongkun Park, Mikhail D. Lukin
Summary: Recent advancements have allowed for direct imaging of stacking domains in van der Waals heterostructures, enabling a better understanding of the correlation between moire structures and electronic/optical properties. Through this technique, researchers were able to investigate reconstructed moire patterns in twisted WSe2/WSe2 bilayers and identify the emergence of distinct exciton species in photoluminescence measurements, with the ability to tune these states individually through electrostatic gating.
Article
Physics, Multidisciplinary
Grace H. Chen, David Z. Li, Amy Butcher, Alexander A. High, Darrick E. Chang
Summary: This article investigates the emission properties of excitons in TMDCs near metal interfaces and explores the dependence of exciton emission behavior on temperature, momentum distribution, and transition dipole orientation. The findings reveal the differences between excitons and point dipoles, which can be amplified by considering excitons with a Bose Einstein distribution at high phase space densities. These insights are crucial for optimizing the performance of optoelectronic devices incorporating 2D semiconductors near metal electrodes and for future studies of exciton radiative dynamics at low temperatures.
NEW JOURNAL OF PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Xi Wang, Jiayi Zhu, Kyle L. Seyler, Pasqual Rivera, Huiyuan Zheng, Yingqi Wang, Minhao He, Takashi Taniguchi, Kenji Watanabe, Jiaqiang Yan, David G. Mandrus, Daniel R. Gamelin, Wang Yao, Xiaodong Xu
Summary: Researchers observed moire trions and their doping-dependent photoluminescence polarization in H-stacked MoSe2/WSe2 heterobilayers. As moire traps are filled with either electrons or holes, new sets of interlayer exciton photoluminescence peaks emerge with specific narrow linewidths. Circularly polarized photoluminescence reveals a switching polarization pattern as moire excitons transition from negatively charged to positively charged, driven by energy relaxation pathways during interlayer trion formation.
NATURE NANOTECHNOLOGY
(2021)
Article
Physics, Multidisciplinary
Yongzhi Xie, Yuchen Gao, Fengyu Chen, Yunkun Wang, Jun Mao, Qinyun Liu, Saisai Chu, Hong Yang, Yu Ye, Qihuang Gong, Ji Feng, Yunan Gao
Summary: This Letter presents theoretical and experimental investigations on the emission properties of quadrupolar excitons (QXs) in a WSe2/MoSe2/WSe2 heterotrilayer device. The optical brightness or darkness of QXs is determined by horizontal mirror symmetry, valley and spin selection rules. The emission intensity and energy of QXs can be adjusted by applying an out-of-plane electric field, due to changes in hole distribution and the Stark effect. The results provide experimental evidence for the existence of QXs in heterotrilayers and uncover their novel properties.
PHYSICAL REVIEW LETTERS
(2023)
Article
Optics
Haihong Zheng, Biao Wu, Shaofei Li, Jun He, Zongwen Liu, Chang-Tian Wang, Jian-Tao Wang, Ji-An Duan, Yanping Liu
Summary: We demonstrate the generation and detection of strained localized excitons in monolayer WSe2 by fabricating strained structures using nanoindentation technique. Enhanced emission of strain-localized excitons is observed with two sharp photoluminescence peaks. The valley polarization of strained localized excitons is increased, reaching a high value of approximately 79.6%, by modulating a magnetic field. These findings highlight the potential of tunable valley polarization and localized excitons in WSe2 monolayers for valleytronic applications.
Article
Multidisciplinary Sciences
Michael Foerg, Anvar S. Baimuratov, Stanislav Yu Kruchinin, Ilia A. Vovk, Johannes Scherzer, Jonathan Foerste, Victor Funk, Kenji Watanabe, Takashi Taniguchi, Alexander Hoegele
Summary: The authors studied excitons in twisted heterobilayers and heterotrilayers of transition metal dichalcogenides, finding different optical signatures. In heterobilayers, the photoluminescence is dominated by valley-direct excitons, while in heterotrilayers, interlayer hybridization transforms momentum-indirect interlayer excitons into energetically lowest states with phonon-assisted emission.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Parviz Saeidi, Bernhard Jakoby, Gerald Puhringer, Andreas Tortschanoff, Gerald Stocker, Jasmin Spettel, Florian Dubois, Thomas Grille, Reyhaneh Jannesari
Summary: This work investigates the optimization of a plasmonic slot waveguide (PSWG) in the mid-IR region, with a focus on a representative wavelength of 4.26 μm, which is the absorption line of CO2. The study analyzes the mode features of different structures and optimizes the PSWG based on a figure of merit (FOM) that considers confinement factor and propagation length. Attractive wavelengths and geometries that maximize the FOM are also identified for other wavelengths.
Article
Multidisciplinary Sciences
Richen Xiong, Jacob H. Nie, Samuel L. Brantly, Patrick Hays, Renee Sailus, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Chenhao Jin
Summary: We observe a bosonic correlated insulator composed of excitons in tungsten diselenide/tungsten disulfide (WSe2/WS2) moire superlattices. The insulator transitions continuously into an electron correlated insulator with varying charge density, suggesting a mixed correlated insulating state between the two limits.
Article
Multidisciplinary Sciences
Erfu Liu, Elyse Barre, Jeremiah van Baren, Matthew Wilson, Takashi Taniguchi, Kenji Watanabe, Yong-Tao Cui, Nathaniel M. Gabor, Tony F. Heinz, Yia-Chung Chang, Chun Hung Lui
Summary: Moire superlattices formed by van der Waals materials can support a wide range of electronic phases including Mott insulators, superconductors, and generalized Wigner crystals. The coupling of moire trions to charge carriers in tungsten diselenide/molybdenum diselenide heterobilayers leads to the emergence of new excitonic crystals with distinct properties and behaviors, motivating further theoretical and experimental studies of higher-order electron correlation effects in moire superlattices.
Article
Multidisciplinary Sciences
Kamyar Parto, Shaimaa Azzam, Kaustav Banerjee, Galan Moody
Summary: Quantum-dot-like single-photon emitters in atomically thin van der Waals materials show promise as future chip-scalable quantum light sources, but the challenge lies in extending their working temperatures while maintaining high yield and purity.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
Mauro Brotons-Gisbert, Hyeonjun Baek, Aidan Campbell, Kenji Watanabe, Takashi Taniguchi, Brian D. Gerardot
Summary: In gate-tunable 2H-MoSe2/WSe2 heterobilayers, researchers observed a continuous evolution from a few trapped interlayer excitons (IXs) to an ensemble of IXs with both triplet- and singlet-spin configurations. Electron doping led to the formation of three different species of localized negative trions with contrasting spin-valley configurations. The study highlights the important role of exciton-exciton interactions and Fermi-level control in highly tunable quantum materials.
Article
Chemistry, Physical
Matthew Gabel, Patrick Z. El-Khoury, Yi Gu
Summary: The study visualized excitons in WSe2/MoSe2 heterobilayers using tip-enhanced photoluminescence, revealing strong confinement of charged excitons in individual nanoscopic bubbles. The localized trion emission spectra show sub-10-nm spatial variations, originating from atomic-scale potential energy fluctuations. These findings demonstrate the potential for confining charged exciton complexes in electrically tunable locations, opening up new opportunities for probing many-body exciton physics and exploring sites for strong exciton localization leading to quantum emission.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Multidisciplinary Sciences
Arne Quellmalz, Xiaojing Wang, Simon Sawallich, Burkay Uzlu, Martin Otto, Stefan Wagner, Zhenxing Wang, Maximilian Prechtl, Oliver Hartwig, Siwei Luo, Georg S. Duesberg, Max C. Lemme, Kristinn B. Gylfason, Niclas Roxhed, Goran Stemme, Frank Niklaus
Summary: The study presents a generic methodology for large-area integration of 2D materials through adhesive wafer bonding, utilizing equipment, processes, and materials readily available in large-scale semiconductor manufacturing lines. This approach is suitable for back end of the line integration of 2D materials on top of integrated circuits, with the potential to accelerate progress in electronics, photonics, and sensing. Existing integration approaches for 2D materials often degrade material properties and are not compatible with industrial processing, highlighting the need for new strategies like adhesive wafer bonding.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Maximilian Prechtl, Shayan Parhizkar, Oliver Hartwig, Kangho Lee, Josef Biba, Tanja Stimpel-Lindner, Farzan Gity, Andreas Schels, Jens Bolten, Stephan Suckow, Anna Lena Giesecke, Max C. Lemme, Georg S. Duesberg
Summary: This paper introduces a low-temperature growth method for layered platinum diselenide and discusses its application in the integration of silicon photonics devices. The new growth method provides a new design route for synthesizing 2D materials with more complex structures.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Sebastian Lukas, Oliver Hartwig, Maximilian Prechtl, Giovanna Capraro, Jens Bolten, Alexander Meledin, Joachim Mayer, Daniel Neumaier, Satender Kataria, Georg S. Duesberg, Max C. Lemme
Summary: Platinum diselenide (PtSe2) is a 2D material known for its exceptional electronic and piezoresistive properties, and can be grown at low temperatures in a scalable manner. The nanocrystalline structure of PtSe2 thin films grown using thermally assisted conversion (TAC) was investigated for its correlation with electronic and piezoresistive properties. The findings suggest that variations in crystallite size and orientation have a strong impact on the electronic and piezoresistive properties of the films, offering potential for tuning and optimizing PtSe2 properties for various applications.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Nanoscience & Nanotechnology
Shayan Parhizkar, Maximilian Prechtl, Anna Lena Giesecke, Stephan Suckow, Sophia Wahl, Sebastian Lukas, Oliver Hartwig, Nour Negm, Arne Quellmalz, Kristinn Gylfason, Daniel Schall, Matthias Wuttig, Georg S. Duesberg, Max C. Lemme
Summary: This article describes the study of low-cost, easily integrable photodetectors based on the two-dimensional material PtSe2, which can operate in a higher wavelength range and has high responsivity and low response time. The PtSe2 photodetectors integrated by direct growth outperform those manufactured by the standard 2D layer transfer method. PtSe2 shows promising potential for optoelectronics and photonic-integrated circuits due to its infrared responsivity, chemical stability, selective and conformal growth at low temperatures, and high carrier mobility.
Article
Chemistry, Multidisciplinary
Roman Kempt, Sebastian Lukas, Oliver Hartwig, Maximilian Prechtl, Agnieszka Kuc, Thomas Brumme, Sha Li, Daniel Neumaier, Max C. Lemme, Georg S. Duesberg, Thomas Heine
Summary: The study focuses on PtSe2 and reveals the existence of stacking phases other than the 1T phase at elevated temperatures. These phases significantly affect the synthesis and performance of polycrystalline thin films.
Article
Materials Science, Multidisciplinary
Kangho Lee, Beata M. Szydlowska, Oliver Hartwig, Kevin Synnatschke, Bartlomiej Tywoniuk, Tomas Hartman, Tijana Tomasevic-Ilic, Cian P. Gabbett, Jonathan N. Coleman, Zdenek Sofer, Marko Spasenovic, Claudia Backes, Georg S. Duesberg
Summary: Liquid-phase exfoliation (LPE) is a versatile and scalable method for producing two-dimensional (2D) materials. In this study, highly conductive films made of platinum diselenide (PtSe2) flakes were successfully fabricated using LPE. These films showed uniform morphology and electrical behavior, and were used to create a chemiresistive sensor structure capable of detecting ammonia gas at sub-0.1 parts per million (ppm) levels. Remarkably, the PtSe2-based devices remained fully functional even after 15 months, demonstrating their high stability.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Chemistry, Multidisciplinary
Rita Tilmann, Cian Bartlam, Oliver Hartwig, Bartlomiej Tywoniuk, Nikolas Dominik, Conor P. Cullen, Lisanne Peters, Tanja Stimpel-Lindner, Niall McEvoy, Georg S. Duesberg
Summary: The interest in 2D materials is increasing due to the discovery of compounds with unique electrical, optical, chemical, and thermal characteristics. We report the presence of polymeric adlayers on layered transition metal dichalcogenides (TMDs), which are not easily identifiable using common analytic methods. These atomically thin layers consist of hydrocarbons, which preferentially adsorb to the hydrophobic surfaces of TMDs. The presence of polymeric films on 2D materials has implications for their investigation, processing, and applications.
Article
Chemistry, Multidisciplinary
Alessandro Enrico, Oliver Hartwig, Nikolas Dominik, Arne Quellmalz, Kristinn B. Gylfason, Georg S. Duesberg, Frank Niklaus, Goran Stemme
Summary: The performance of 2D materials makes them promising for electronic, photonic, and sensing devices. However, current lithography methods for patterning these materials are limited in efficiency and can degrade performance. In this study, we demonstrate a noncontact and resist-free patterning method using a two-photon 3D printer, enabling fast and precise fabrication of patterns in 2D materials. This method has the potential to accelerate device prototyping in various research areas.
Article
Multidisciplinary Sciences
Po-Han Huang, Miku Laakso, Pierre Edinger, Oliver Hartwig, Georg S. Duesberg, Lee-Lun Lai, Joachim Mayer, Johan Nyman, Carlos Errando-Herranz, Goeran Stemme, Kristinn B. Gylfason, Frank Niklaus
Summary: This study demonstrates a method for 3D printing solid silica glass with sub-micrometer resolution without the need for a sintering step. By locally crosslinking hydrogen silsesquioxane using nonlinear absorption of sub-picosecond laser pulses, silica glass can be formed. This approach allows for the fabrication of optical microtoroid resonators, luminescence sources, and suspended plates on optical-fiber tips.
NATURE COMMUNICATIONS
(2023)
Proceedings Paper
Engineering, Electrical & Electronic
Arne Quellmalz, Simon Sawallich, Maximilian Prechtl, Oliver Hartwig, Georg S. Duesberg, Max C. Lemme, Frank Niklaus, Kristinn B. Gylfason
Summary: In this paper, a generic methodology for the large-area transfer of 2D materials and their heterostructures is presented. The approach utilizes adhesive wafer bonding and processes readily available in most large-scale semiconductor manufacturing lines. Experimental results demonstrate successful transfer and formation of different composite structures, indicating an important step towards the commercial use of 2D materials in optics and photonics.
2D PHOTONIC MATERIALS AND DEVICES V
(2022)
Article
Chemistry, Multidisciplinary
Conor P. Cullen, Cormac O. Coileain, John B. McManus, Oliver Hartwig, David McCloskey, Georg S. Duesberg, Niall McEvoy
Summary: This study explores the differences in characteristics and synthesis methods between PtS2 and non-layered PtS within Group-10 transition metal dichalcogenides (TMDs), providing a systematic characterization of these materials.
Article
Materials Science, Multidisciplinary
Filiberto Ricciardella, Sten Vollebregt, Rita Tilmann, Oliver Hartwig, Cian Bartlam, Pasqualina M. Sarro, Hermann Sachdev, Georg S. Duesberg
Summary: Chemical vapor deposition (CVD) is a highly promising technique for large-scale production of graphene with tunability of defects. This study investigates the correlation between defect density and the interaction kinetics of multi-layered graphene (MLG) with nitrogen dioxide (NO2) at different growth temperatures. Results show that higher growth temperatures lead to lower defect density and higher quality MLG, with more defective MLG exhibiting stronger interaction with NO2 molecules during chemi-resistor testing.
