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@article{WOS:001701838600001,
title = {Surface defects in carbon-doped hexagonal boron nitride for
negative-contrast direct laser writing},
author = {Dmitrii Litvinov and Virgil Gavriliuc and Magdalena Grzeszczyk and Kristina Vaklinova and Kenji Watanabe and Takashi Taniguchi and Kostya S Novoselov and Maciej Koperski},
doi = {10.1088/2053-1583/ae463c},
times_cited = {0},
issn = {2053-1583},
year = {2026},
date = {2026-06-01},
journal = {2D MATERIALS},
volume = {13},
number = {2},
publisher = {IOP Publishing Ltd},
address = {No.2 The Distillery, Glassfields, Avon Street, Bristol, ENGLAND},
abstract = {Radiative defects in hexagonal boron nitride (hBN) are active in a broad
spectral range from deep ultraviolet to near-infrared wavelengths.
Representatives of these defects act as bright single photon sources,
spin-1 systems, and multiproperty atomic-scale sensors. They are
predominantly investigated in bulk hBN films, where defects are
decoupled from surface and interfacial effects. Here, we demonstrate a
novel class of surface defects optically active in the green/yellow
visible spectral range, which exhibit photophysical properties distinct
from their bulk counterparts. High-power resonant laser illumination
quenched the emission from the ensemble of such defects, which was
attributed to a light-driven structural reconfiguration. The quenched
defects were found to recover their emissive capabilities via a thermal
cycling process, revealing an activation energy of 24.5 meV for the
structural transition. Alternatively, permanent quenching of the defects
was triggered by surface chemistry, involving lithiation-enabled
attachment of functional groups. These mechanisms were utilized to
realize negative-contrast direct laser writing, designing arbitrary
geometric emissive patterns on demand in a microscopic configuration.
The surface-active radiative centers in hBN appear particularly
attractive for exploring environmental sensitivity, surface science, and
coupling to photonic structures or electronic devices by taking unique
advantage of the two-dimensional characteristics of the host lattice.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001634241900001,
title = {Electrically modulated light-emitting device driven by resonant and
antiresonant tunneling between
Cr2Ge2Te6 electrodes},
author = {Natalia Zawadzka and Kristina Vaklinova and Tomasz Wozniak and Mihai Sturza I and Holger Kohlmann and Kenji Watanabe and Takashi Taniguchi and Adam Babinski and Maciej Koperski and Maciej R Molas},
doi = {10.1088/2053-1583/ae2520},
times_cited = {0},
issn = {2053-1583},
year = {2026},
date = {2026-03-01},
journal = {2D MATERIALS},
volume = {13},
number = {1},
publisher = {IOP Publishing Ltd},
address = {No.2 The Distillery, Glassfields, Avon Street, Bristol, ENGLAND},
abstract = {Exploring the electron tunneling mechanisms in diverse materials systems
constitutes a versatile strategy for tailoring the properties of
optoelectronic devices. In this domain, bipolar vertical tunneling
junctions composed of van der Waals materials with vastly different
electronic band structures enable simultaneous injection of electrons
and holes into an optically active material, providing a universal
blueprint for light-emitting devices. Efficient modulation of the
injection efficiency has previously been demonstrated by creating
resonant states within the energy barrier formed by the luminescent
material. Here, we present an alternative approach towards resonant
tunneling conditions by fabricating tunneling junctions composed
entirely from gapped materials: Cr2Ge2Te6 as electrodes, hBN as a
tunneling barrier, and monolayer WSe2 as a luminescent medium. The
characterization of such light-emitting tunneling structure revealed a
nonmonotonous evolution of the electroluminescence intensity with the
tunneling bias. The dominant role driving the characteristics of the
electron tunneling was associated with the relative alignment of the
density of states in Cr2Ge2Te6 electrodes. The unique device
architecture introduced here presents a universal pathway towards
electroluminescent devices operating at room temperature with
electrically modulated emission intensity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001541286100001,
title = {Interplay between charge transfer and magnetic proximity effects in
WSe2/CrCl3 heterostructures},
author = {Lucja Kipczak and Zhaolong Chen and Magdalena Grzeszczyk and Sergey Grebenchuk and Pengru Huang and Kristina Vaklinova and Kenji Watanabe and Takashi Taniguchi and Adam Babinski and Maciej Koperski and Maciej R Molas},
doi = {10.1039/d5nh00198f},
times_cited = {2},
issn = {2055-6756},
year = {2025},
date = {2025-09-01},
journal = {NANOSCALE HORIZONS},
volume = {10},
number = {10},
pages = {2465-2474},
publisher = {ROYAL SOC CHEMISTRY},
address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
ENGLAND},
abstract = {Ferromagnetism in van der Waals systems with diverse spin arrangements
opened a pathway to use proximity magnetic fields to activate the
properties of materials that would otherwise require external stimuli.
Herein, we demonstrate this concept by creating heterostructures
comprising a bulk CrCl3 antiferromagnet with in-plane easy-axis
magnetization and a monolayer (ML) WSe2 semiconductor. Photoluminescence
and magnetic force microscopy techniques were performed to reveal the
interaction between the relevant layers in the WSe2/CrCl3
heterostructures (HSs). The quenching of the WSe2 emission is apparent
in the WSe2/CrCl3 HSs due to an efficient charge transfer process
enabled by the relative band alignment within the structures. Moreover,
we demonstrate that at specific spatial locations in the structures, the
magnetic proximity effect between the WSe2 ML and the CrCl3 bulk
activates dark exciton emission within the WSe2 ML. The dark exciton
emission in the WSe2 ML survives to a higher temperature than the
intraplane Curie temperature (TC) of the CrCl3 because of its elevated
TC in the strained regions of the CrCl3 layer. Our findings are relevant
to the development of spintronics and valleytronics with long-lived dark
states on technological timescales, as well as to sensing applications
of local magnetic fields realized simultaneously in multiple dimensions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001407856300001,
title = {Single photon sources and single electron transistors in two-dimensional
materials},
author = {D Litvinov and A Wu and M Barbosa and K Vaklinova and M Grzeszczyk and G Baldi and M Zhu and M Koperski},
doi = {10.1016/j.mser.2025.100928},
times_cited = {5},
issn = {0927-796X},
year = {2025},
date = {2025-04-01},
journal = {MATERIALS SCIENCE & ENGINEERING R-REPORTS},
volume = {163},
publisher = {ELSEVIER SCIENCE SA},
address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND},
abstract = {The future optoelectronic technologies may operate on the basis of
individual elementary particles, including photons and electrons.
Achieving control knobs at such a fundamental level necessitates
substantial progress in the domains of materials and device engineering.
Recently, two-dimensional (2D) materials have become an important
platform for such investigations, as their layered crystal structures
give rise to inherent in-plane confinement of electrons. Defect
engineering and/or van der Waals heterostructure device fabrication
provide multiple strategies to induce further lateral confinement,
leading to discrete electronic states required for both single photon
emission and single electron operation. Herewith, we review the
cutting-edge developments regarding single photon sources and single
electron transistors in 2D materials. We provide a perspective on the
convergence of these two separate fields into single electron-photon
device platforms enabled by the unique characteristics of 2D systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{WOS:001295117800001,
title = {Atomic and Electronic Structure of Defects in hBN: Enhancing
Single-Defect Functionalities},
author = {Zhizhan Qiu and Kristina Vaklinova and Pengru Huang and Magdalena Grzeszczyk and Kenji Watanabe and Takashi Taniguchi and Kostya S Novoselov and Jiong Lu and Maciej Koperski},
doi = {10.1021/acsnano.4c03640},
times_cited = {35},
issn = {1936-0851},
year = {2024},
date = {2024-08-01},
journal = {ACS NANO},
volume = {18},
number = {35},
pages = {24035-24043},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Defect centers in insulators play a critical role in creating important
functionalities in materials: prototype qubits, single-photon sources,
magnetic field probes, and pressure sensors. These functionalities are
highly dependent on their midgap electronic structure and orbital/spin
wave function contributions. However, in most cases, these fundamental
properties remain unknown or speculative due to the defects being deeply
embedded beneath the surface of highly resistive host crystals, thus
impeding access through surface probes. Here, we directly inspected the
atomic and electronic structures of defects in thin carbon-doped
hexagonal boron nitride (hBN:C) by using scanning tunneling microscopy
(STM) and scanning tunneling spectroscopy (STS). Such investigation adds
direct information about the electronic midgap states to the
well-established photoluminescence response (including single-photon
emission) of intentionally created carbon defects in the most commonly
investigated van der Waals insulator. Our joint atomic-scale
experimental and theoretical investigations reveal two main categories
of defects: (1) single-site defects manifesting as donor-like states
with atomically resolved structures observable via STM and (2) multisite
defect complexes exhibiting a ladder of empty and occupied midgap states
characterized by distinct spatial geometries. Combining direct probing
of midgap states through tunneling spectroscopy with the inspection of
the optical response of insulators hosting specific defect structures
holds promise for creating and enhancing functionalities realized with
individual defects in the quantum limit. These findings underscore not
only the versatility of hBN:C as a platform for quantum defect
engineering but also its potential to drive advancements in atomic-scale
optoelectronics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}