Maciej Koperski

@article{ISI:001620530800035,
title = {Electric field-tunable ferromagnetism in a van der Waals semiconductor up to room temperature},
author = {Deyi Fu and Jiawei Liu and Fuchen Hou and Xiao Chang and Tingyu Qu and Johan Felisaz and Gunasheel Kauwtilyaa Krishnaswamy and Sergey Grebenchuk and Yuang Jie and Kenji Watanabe and Takashi Taniguchi and Vitor M Pereira and Kostya S Novoselov and Maciej Koperski and Nikolai L Yakovlev and Anjan Soumyanarayanan and Ahmet Avsar and Oleg V Yazyev and Junhao Lin and Barbaros Ozyilmaz},
doi = {10.1038/s41467-025-59961-2},
times_cited = {0},
year = {2025},
date = {2025-11-20},
journal = {NATURE COMMUNICATIONS},
volume = {16},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Ferromagnetic semiconductors, coupling charge transport and magnetism via electrical means, show great promise for spin-based logic devices. Despite decades of efforts to achieve such co-functionality, maintaining ferromagnetic order at room temperature remains elusive. Here, we address this long-standing challenge by implanting dilute Co atoms into few-layer black phosphorus through atomically-thin boron nitride diffusion barrier. Our Co-doped black phosphorus-based devices exhibit ferromagnetism up to room temperature while preserving its high mobility (similar to 1000cm(2)V(-1)s(-1)) and semiconducting characteristics. By incorporating ferromagnetic Co-doped black phosphorus into magnetic tunnel junction devices, we demonstrate a large tunnelling magnetoresistance that extends up to room temperature. This study presents a new approach to engineering ferromagnetic ordering in otherwise nonmagnetic materials, thereby expanding the repertoire and applications of magnetic semiconductors envisioned thus far.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001523451200028,
title = {Van der Waals photonic integrated circuit with coherent light generation},
author = {Tianhua Ren and Andres Granados del aguila and Zhaolong Chen and Qianhui Xu and Xuehong Zhou and Rui Duan and Magdalena Grzeszczyk and Xiao Gong and Kenji Watanabe and Takashi Taniguchi and Kostya S Novoselov and Maciej Koperski and Handong Sun},
doi = {10.1038/s41467-025-60778-2},
times_cited = {1},
year = {2025},
date = {2025-07-01},
journal = {NATURE COMMUNICATIONS},
volume = {16},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Two-dimensional semiconductors hold great potential as coherent light sources for photonic integrated circuits. However, the conventional integration of two-dimensional materials onto silicon photonics introduces significant structural and optoelectronic drawbacks, hindering the practical realization of coherent photonic circuits. Here, we introduce the concept of a van der Waals photonic integrated circuit, which is a complete on-chip optical system fabricated entirely from a van der Waals heterostructure. By combining multifunctional two-dimensional materials into a single heterostructure, we realize a fully functional photonic circuitry capable of benchtop coherent light generation, propagation, transmission, and modulation via a silicon back gate. The monolithic approach to heterostructure circuitry supports the effective integration of various photonic components based on two-dimensional materials with stable electro-optic interconnections. The coherence of light emission is systematically verified by second-order correlation experiments at room temperature, showing a clear power-dependent transition to a Poissonian regime. Our work establishes a pathway for coherent van der Waals photonics incorporated with standard silicon manufacturing processes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001498039100001,
title = {Superior Adhesion of Monolayer Amorphous Carbon to Copper},
author = {Hongji Zhang and Artem K Grebenko and Konstantin V Iakoubovskii and Hanning Zhang and Ruslan Yamaletdinov and Anna Makarova and Alexander Fedorov and S K Rejaul and Ranjith Shivajirao and Zheng Jue Tong and Sergey Grebenchuk and Ugur Karadeniz and Lu Shi and Denis V Vyalikh and Ya He and Andrei Starkov and Alena A Alekseeva and Chuan Chu Tee and Carlo Mendoza Orofeo and Junhao Lin and Kazutomo Suenaga and Michel Bosman and Maciej Koperski and Bent Weber and Kostya S Novoselov and Oleg V Yazyev and Chee-Tat Toh and Barbaros Ozyilmaz},
doi = {10.1002/adma.202419112},
times_cited = {2},
issn = {0935-9648},
year = {2025},
date = {2025-05-29},
journal = {ADVANCED MATERIALS},
volume = {37},
number = {32},
publisher = {WILEY-V C H VERLAG GMBH},
address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
abstract = {The single-atom thickness of graphene holds great potential for device scaling, but its effectiveness as a thin metal-ion diffusion barrier in microelectronics and a corrosion barrier for plasmonic devices is compromised by weak van der Waals interactions with copper (Cu), leading to delamination issues. In contrast, monolayer amorphous carbon (MAC), a recently reported single-atom-thick carbon film with a disordered sp2 hybridized structure, demonstrates superior adhesion properties. This study reveals that MAC exhibits an adhesion energy of 85 J m-2 on Cu, which is 13 times greater than that of graphene. This exceptional adhesion is attributed to the formation of covalent-like Cu & horbar;C bonds while preserving its sp2 structure, as evidenced by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Density functional theory (DFT) calculations further elucidate that the corrugated structure of MAC facilitates the hybridization of C 2pz orbitals with Cu 4s and 3dz2 orbitals, promoting strong bonding. These insights indicate that the amorphous structure of MAC significantly enhances adhesion while preserving its elemental composition, providing a pathway to improve the mechanical reliability and performance of two-dimensional (2D) materials on metal substrates in various technological applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001465855100001,
title = {Site-Selective Creation of Blue Emitters in Hexagonal Boron Nitride},
author = {Haidong Liang and Yuan Chen and Leyi Loh and Nicholas Lin Quan Cheng and Dmitrii Litvinov and Chengyuan Yang and Yifeng Chen and Zhepeng Zhang and Kenji Watanabe and Takashi Taniguchi and Maciej Koperski and Su Ying Quek and Michel Bosman and Goki Eda and Andrew Anthony Bettiol},
doi = {10.1021/acsnano.5c03423},
times_cited = {5},
issn = {1936-0851},
year = {2025},
date = {2025-04-12},
journal = {ACS NANO},
volume = {19},
number = {15},
pages = {15130-15138},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Hexagonal boron nitride (hBN) has been of great interest due to its ability to host several bright quantum emitters at room temperature. However, the identification of the observed emitters remains challenging due to spectral variability, as well as the lack of atomic defect structure information. In this work, we demonstrate the site-selective creation of blue emitters in exfoliated hBN flakes with high-energy ion irradiation. With the correlation analysis of cryogenic and temperature-dependent photoluminescence (PL) spectroscopy, we observe two zero phonon lines (ZPLs) at similar to 432.8 and 454.3 nm. Photoluminescence excitation (PLE) measurements further confirm the emission origins of the two prominent lines. Scanning transmission electron microscopy (STEM) reveals that the dominant defect structures present in ion-irradiated samples are vacancy-type (V x ) and adatom(intercalant)-type (A x ). Together with first-principles GW-BSE (Bethe-Salpeter equation) calculations, we deduce that the observed blue emissions are likely related to boron intercalants (Bint). Our results not only discover a group of blue emissions in hBN but also provide insights into the physical origin of the emissions with local atomic structures in hBN.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001453704200001,
title = {Imaging the Neel Vector in Few-Layer CrPS_{4} with Second-Harmonic Generation},
author = {Yi Wei Ho and Mingjun Chen and Cheng Quan Wong and Magdalena Grzeszczyk and Adam K Budniak and Jose C Viana-Gomes and Xinwei Li and Maciej Koperski and Goki Eda},
doi = {10.1021/acs.nanolett.4c06237},
times_cited = {1},
issn = {1530-6984},
year = {2025},
date = {2025-03-26},
journal = {NANO LETTERS},
volume = {25},
number = {14},
pages = {5624-5630},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Second-harmonic generation (SHG) is a powerful technique for probing the crystallographic symmetry. Recently, SHG has also been shown to exhibit sensitivity to time-reversal symmetry, allowing studies of magnetic order in layered antiferromagnetic (AFM) materials. Here, we report SHG investigation of chromium thiophosphate (CrPS4), a layered A-type AFM material with a finite/zero net magnetization for odd/even-layer-number crystals, respectively. The SHG intensity of bulk CrPS4 across its Neel temperature reveals that both crystallographic and magnetic symmetry breaking contribute to SHG at low temperatures. From the polarization analysis, we identify the tensor element linked to the magnetic order. Interestingly, the polarization response is sensitive to the history of the magnetic field applied to the even-number-layer crystals, suggesting that the SHG is sensitive to the Neel vector direction. Polarized SHG microscopy of a terraced CrPS4 shows that the AFM order of even-number-layer regions is determined by the ferromagnetic order of the neighboring odd-number-layer regions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001360396900001,
title = {Nb impurity-bound excitons as quantum emitters in monolayer WS_{2}},
author = {Leyi Loh and Yi Wei Ho and Fengyuan Xuan and Andres Granados del Aguila and Yuan Chen and See Yoong Wong and Jingda Zhang and Zhe Wang and Kenji Watanabe and Takashi Taniguchi and Paul J Pigram and Michel Bosman and Su Ying Quek and Maciej Koperski and Goki Eda},
doi = {10.1038/s41467-024-54360-5},
times_cited = {10},
year = {2024},
date = {2024-11-20},
journal = {NATURE COMMUNICATIONS},
volume = {15},
number = {1},
publisher = {NATURE PORTFOLIO},
address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY},
abstract = {Point defects in crystalline solids behave as optically addressable individual quantum systems when present in sufficiently low concentrations. In two-dimensional (2D) semiconductors, such quantum defects hold potential as versatile single photon sources. Here, we report the synthesis and optical properties of Nb-doped monolayer WS2 in the dilute limit where the average spacing between individual dopants exceeds the optical diffraction limit, allowing the emission spectrum to be studied at the single-dopant level. We show that these individual dopants exhibit common features of quantum emitters, including narrow emission lines (with linewidths <1 meV), strong spatial confinement, and photon antibunching. These emitters consistently occur within a narrow spectral range across multiple samples, distinct from common quantum emitters in van der Waals (vdW) materials that show large ensemble broadening. Analysis of the Zeeman splitting reveals that they can be attributed to bound exciton complexes comprising dark excitons and negatively charged Nb.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}