Lu Jiong

@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 = {0},
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:001416560700001,
title = {Electron Ptychography for Atom-by-Atom Quantification of 1D Defect Complexes in Monolayer MoS_{2}},
author = {Leyi Loh and Shoucong Ning and Daria Kieczka and Yuan Chen and Jianmin Yang and Zhe Wang and Stephen J Pennycook and Goki Eda and Alexander L Shluger and Michel Bosman},
doi = {10.1021/acsnano.4c14988},
times_cited = {1},
issn = {1936-0851},
year = {2025},
date = {2025-02-07},
journal = {ACS NANO},
volume = {19},
number = {6},
pages = {6195-6208},
publisher = {AMER CHEMICAL SOC},
address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA},
abstract = {Defect complexes can induce beneficial functionalities in two-dimensional (2D) semiconductors. However, understanding their formation mechanism with single-atom sensitivity has proven to be challenging for light elements using conventional transmission electron microscopy (TEM) techniques. Here, we demonstrate the atom-resolved formation of various one-dimensional (1D) defect complexes-consisting of rhenium dopants, sulfur interstitials, and sulfur vacancies-in monolayer MoS2 by applying electron ptychography to our four-dimensional scanning transmission electron microscopy (4D-STEM) data sets. Our image resolution of 0.35 angstrom and a spatial precision of 2 pm allow us to achieve accurate matching between experimental structures and density functional theory (DFT) simulations at the atomic level. Additionally, we utilize out-of-focus ptychography to observe defect formation processes at dose rates comparable to those used in conventional TEM imaging, while maintaining a large field of view. This study demonstrates the systematic application of electron ptychography to extensive 4D-STEM data sets for quantitative defect imaging in 2D materials. We provide direct, atomically precise evidence that critical defect densities govern the formation of extended 1D defect complexes. For instance, we show that sulfur single-vacancy lines form when the vacancy density reaches 5 x 1013 cm-2 and transform into double-vacancy lines beyond 8 x 1013 cm-2. Rhenium-dopant lines emerge at a dopant concentration higher than 3 x 1013 cm-2, where metastable sulfur interstitial-vacancy lines also form as the cumulative electron dose reaches 3 x 105 e/angstrom 2, initiating a local nucleation of the 1T ' phase. Our results highlight the potential of electron ptychography for high-precision defect characterization and engineering in ultrathin 2D materials.},
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 = {2},
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}
}