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3. Energy-resolved Photoconductivity Mapping in a Monolayer-bilayer WSe2 Lateral Heterostructure

Author

Chu, Zhaodong, Han, Ali, Lei, Chao, Lopatin, Sergei, Li, Peng, Wannlund, David, Wu, Di, Herrera, Kevin, Zhang, Xixiang, MacDonald, Allan H., Li, Xiaoqin, Li, Lain-Jong, and Lai, Keji

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe2 lateral heterostructure under multiple excitation lasers. As the photon energy increases, the light-induced conductivity detected by microwave impedance microscopy first appears along the hetero-interface and bilayer edge, then along the monolayer edge, inside the bilayer area, and finally in the interior of the monolayer region. The sequential emergence of mobile carriers in different sections of the sample is consistent with the theoretical calculation of local energy gaps. Quantitative analysis of the microscopy and transport data also reveals the linear dependence of photoconductivity on the laser intensity and the influence of interlayer coupling on carrier recombination. Combining theoretical modeling, atomic scale imaging, mesoscale impedance microscopy, and device-level characterization, our work suggests an exciting perspective to control the intrinsic band-gap variation in 2D heterostructures down to the few-nanometer regime., Comment: 18 pages, 5 figures; Nano Lett., Just Accepted Manuscript

Published
2018
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4. Current Controlled Magnetization Switching in Cylindrical Nanowires for High-Density 3D Memory Applications

Author

Mohammed, Hanan, Corte-León, Hector, Ivanov, Yurii P., Lopatin, Sergei, Moreno, Julian A., Chuvilin, Andrey, Salimath, Akshaykumar, Manchon, Aurelien, Kazakova, Olga, and Kosel, Jurgen

Subjects
Physics - Applied Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

A next-generation memory device utilizing a three-dimensional nanowire system requires the reliable control of domain wall motion. In this letter, domain walls are studied in cylindrical nanowires consisting of alternating segments of cobalt and nickel. The material interfaces acting as domain wall pinning sites, are utilized in combination with current pulses, to control the position of the domain wall, which is monitored using magnetoresistance measurements. Magnetic force microscopy results further confirm the occurrence of current assisted domain wall depinning. Data bits are therefore shifted along the nanowire by sequentially pinning and depinning a domain wall between successive interfaces, a requirement necessary for race-track type memory devices. We demonstrate that the direction, amplitude and duration of the applied current pulses determine the propagation of the domain wall across pinning sites. These results demonstrate a multi-bit cylindrical nanowire device, utilizing current assisted data manipulation. The prospect of sequential pinning and depinning in these nanowires allows the bit density to increase by several Tbs, depending on the number of segments within these nanowires.

Published
2018

6. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

Author

Govyadinov, Alexander A., Konečná, Andrea, Chuvilin, Andrey, Vélez, Saül, Dolado, Irene, Nikitin, Alexey Y., Lopatin, Sergei, Casanova, Fèlix, Hueso, Luis E., Aizpurua, Javier, and Hillenbrand, Rainer

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Van der Waals (vdW) materials exhibit intriguing structural, electronic and photonic properties. Electron Energy Loss Spectroscopy (EELS) within Scanning Transmission Electron Microscope (STEM) allows for nanoscale mapping of such properties. However, typical STEM-EELS detection is limited to energy losses in the eV range, which are too large for probing important low-energy excitation such as phonons or mid-IR plasmons. Here we adapt a conventional STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in h-BN, a representative van der Waals (vdW) material. The h-BN EELS spectra, surprisingly, depend on the h-BN thickness and the distance of the electron beam to h-BN flake edges. To explain this observation, we developed a classical response theory describing the interaction of fast electrons with (anisotropic) slabs of vdW materials. Theoretical and numerical calculations perfectly match the experimental h-BN spectra, and reveal that the electron loss is dominated by the excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, STEM-EELS offers the possibility to probe low-energy polaritons in vdW materials, with our theory being of fundamental importance for interpreting future experiments.

Published
2016
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7. Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

Author

Karuthedath, Safakath, Gorenflot, Julien, Firdaus, Yuliar, Chaturvedi, Neha, De Castro, Catherine S. P., Harrison, George T., Khan, Jafar I., Markina, Anastasia, Balawi, Ahmed H., Peña, Top Archie Dela, Liu, Wenlan, Liang, Ru-Ze, Sharma, Anirudh, Paleti, Sri H. K., Zhang, Weimin, Lin, Yuanbao, Alarousu, Erkki, Lopatin, Sergei, Anjum, Dalaver H., Beaujuge, Pierre M., De Wolf, Stefaan, McCulloch, Iain, Anthopoulos, Thomas D., Baran, Derya, Andrienko, Denis, and Laquai, Frédéric

Published
2021
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9. Ledge-directed epitaxy of continuously self-aligned single-crystalline nanoribbons of transition metal dichalcogenides

Author

Aljarb, Areej, Fu, Jui-Han, Hsu, Chih-Chan, Chuu, Chih-Piao, Wan, Yi, Hakami, Mariam, Naphade, Dipti R., Yengel, Emre, Lee, Chien-Ju, Brems, Steven, Chen, Tse-An, Li, Ming-Yang, Bae, Sang-Hoon, Hsu, Wei-Ting, Cao, Zhen, Albaridy, Rehab, Lopatin, Sergei, Chang, Wen-Hao, Anthopoulos, Thomas D., Kim, Jeehwan, Li, Lain-Jong, and Tung, Vincent

Published
2020
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12. Author Correction: Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

Author

Karuthedath, Safakath, Gorenflot, Julien, Firdaus, Yuliar, Chaturvedi, Neha, De Castro, Catherine S. P., Harrison, George T., Khan, Jafar I., Markina, Anastasia, Balawi, Ahmed H., Peña, Top Archie Dela, Liu, Wenlan, Liang, Ru-Ze, Sharma, Anirudh, Paleti, Sri H. K., Zhang, Weimin, Lin, Yuanbao, Alarousu, Erkki, Lopatin, Sergei, Anjum, Dalaver H., Beaujuge, Pierre M., De Wolf, Stefaan, McCulloch, Iain, Anthopoulos, Thomas D., Baran, Derya, Andrienko, Denis, and Laquai, Frédéric

Published
2022
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14. Towards super-clean graphene

Author

Lin, Li, Zhang, Jincan, Su, Haisheng, Li, Jiayu, Sun, Luzhao, Wang, Zihao, Xu, Fan, Liu, Chang, Lopatin, Sergei, Zhu, Yihan, Jia, Kaicheng, Chen, Shulin, Rui, Dingran, Sun, Jingyu, Xue, Ruiwen, Gao, Peng, Kang, Ning, Han, Yu, Xu, H. Q., Cao, Yang, Novoselov, K. S., Tian, Zhongqun, Ren, Bin, Peng, Hailin, and Liu, Zhongfan

Published
2019
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18. Direct Visualization and Identification of Membrane Voltage‐Gated Sodium Channels from Human iPSC‐Derived Neurons by Multiple Imaging and Light Enhanced Spectroscopy (Small Methods 7/2022)

Author

Moretti, Manola, primary, Limongi, Tania, additional, Testi, Claudia, additional, Milanetti, Edoardo, additional, De Angelis, Maria Teresa, additional, Parrotta, Elvira I., additional, Scalise, Stefania, additional, Santamaria, Gianluca, additional, Allione, Marco, additional, Lopatin, Sergei, additional, Torre, Bruno, additional, Zhang, Peng, additional, Marini, Monica, additional, Perozziello, Gerardo, additional, Candeloro, Patrizio, additional, Pirri, Candido Fabrizio, additional, Ruocco, Giancarlo, additional, Cuda, Giovanni, additional, and Di Fabrizio, Enzo, additional

Published
2022
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19. Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors

Author

Liang, Jian-Wei, primary, Firdaus, Yuliar, additional, Kang, Chun Hong, additional, Min, Jung-Wook, additional, Min, Jung-Hong, additional, Al Ibrahim, Redha H., additional, Wehbe, Nimer, additional, Hedhili, Mohamed Nejib, additional, Kaltsas, Dimitrios, additional, Tsetseris, Leonidas, additional, Lopatin, Sergei, additional, Zheng, Shuiqin, additional, Ng, Tien Khee, additional, Anthopoulos, Thomas D., additional, and Ooi, Boon S., additional

Published
2022
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22. Charge Transfer Control of Emergent Magnetism at SrMnO3/LaMnO3 Interfaces.

Author

Bange, Jan Philipp, Roddatis, Vladimir, Schüler, Leonard, Lyzwa, Fryderyk, Keunecke, Marius, Lopatin, Sergei, Bruchmann‐Bamberg, Vitaly, and Moshnyaga, Vasily

Subjects
CHARGE transfer, MAGNETISM, FERROMAGNETISM, SUPERLATTICES, ELLIPSOMETRY
Abstract

Emergent phases at the interfaces in strongly correlated oxide heterostructures display novel properties not akin to those of constituting materials. The interfacial ferromagnetism in (LaMnO3)m/(SrMnO3)n (LMO)m/(SMO)n superlattices (SLs) with antiferromagnetic bulk LMO and SMO layers is believed to be a result of the interfacial charge transfer (CT). By using in situ optical ellipsometry, it is demonstrated directly that CT and emergent magnetism in (LMO)m/(SMO)n SLs are controlled by the LMO/SMO thickness ratio, chosen as m/n = 1 and 2. The enhanced CT in SLs with m/n = 2 favors the high‐TC emergent ferromagnetism with TC = 350–360 K, whereas the reduced CT in m/n = 1 SLs suppresses it yielding TC = 300 K. A complex dependence of the saturation magnetization as a function of interface density Λ = (m + n)−1 with minima at Λ = 0.11 (m/n = 2) and Λ = 0.25 (m/n = 1) was observed and rationalized by the competition of ferromagnetic and antiferromagnetic contributions, originating from the volume of LMO and SMO layers as well as from the LMO/SMO interfaces. The role of epitaxy stress and MnO6 octahedral tilts in the emergent magnetic behavior is discussed. [ABSTRACT FROM AUTHOR]

Published
2022
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23. Author Correction: Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

Author

Karuthedath, Safakath, primary, Gorenflot, Julien, additional, Firdaus, Yuliar, additional, Chaturvedi, Neha, additional, De Castro, Catherine S. P., additional, Harrison, George T., additional, Khan, Jafar I., additional, Markina, Anastasia, additional, Balawi, Ahmed H., additional, Peña, Top Archie Dela, additional, Liu, Wenlan, additional, Liang, Ru-Ze, additional, Sharma, Anirudh, additional, Paleti, Sri H. K., additional, Zhang, Weimin, additional, Lin, Yuanbao, additional, Alarousu, Erkki, additional, Lopatin, Sergei, additional, Anjum, Dalaver H., additional, Beaujuge, Pierre M., additional, De Wolf, Stefaan, additional, McCulloch, Iain, additional, Anthopoulos, Thomas D., additional, Baran, Derya, additional, Andrienko, Denis, additional, and Laquai, Frédéric, additional

Published
2021
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26. Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells

Author

Karuthedath, Safakath, primary, Gorenflot, Julien, additional, Firdaus, Yuliar, additional, Chaturvedi, Neha, additional, De Castro, Catherine S. P., additional, Harrison, George T., additional, Khan, Jafar I., additional, Markina, Anastasia, additional, Balawi, Ahmed H., additional, Peña, Top Archie Dela, additional, Liu, Wenlan, additional, Liang, Ru-Ze, additional, Sharma, Anirudh, additional, Paleti, Sri H. K., additional, Zhang, Weimin, additional, Lin, Yuanbao, additional, Alarousu, Erkki, additional, Lopatin, Sergei, additional, Anjum, Dalaver H., additional, Beaujuge, Pierre M., additional, De Wolf, Stefaan, additional, McCulloch, Iain, additional, Anthopoulos, Thomas D., additional, Baran, Derya, additional, Andrienko, Denis, additional, and Laquai, Frédéric, additional

Published
2020
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34. MXene Derived Metal–Organic Frameworks

Author

Wu, Hao, primary, Almalki, Maram, additional, Xu, Xiangming, additional, Lei, Yongjiu, additional, Ming, Fangwang, additional, Mallick, Arijit, additional, Roddatis, Vladimir, additional, Lopatin, Sergei, additional, Shekhah, Osama, additional, Eddaoudi, Mohamed, additional, and Alshareef, Husam N., additional

Published
2019
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39. MXenes for Plasmonic Photodetection

Author

Velusamy, Dhinesh Babu, primary, El‐Demellawi, Jehad K., additional, El‐Zohry, Ahmed M., additional, Giugni, Andrea, additional, Lopatin, Sergei, additional, Hedhili, Mohamed N., additional, Mansour, Ahmed E., additional, Fabrizio, Enzo Di, additional, Mohammed, Omar F., additional, and Alshareef, Husam N., additional

Published
2019
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41. Addressing vibrational excitations in Van der Waals materials and molecular layers within electron energy loss spectroscopy

Author

Thermo Fisher Scientific, Konečná, Andrea, Govyadinov, Alexander A., Neuman, Tomáš, Chuvilin, Andrey, Vélez, Saül, Dolado, Irene, Lopatin, Sergei, Nikitin, Alexey Y., Casanova, Félix, Hueso, Luis E., Hillenbrand, Rainer, Aizpurua, Javier, Thermo Fisher Scientific, Konečná, Andrea, Govyadinov, Alexander A., Neuman, Tomáš, Chuvilin, Andrey, Vélez, Saül, Dolado, Irene, Lopatin, Sergei, Nikitin, Alexey Y., Casanova, Félix, Hueso, Luis E., Hillenbrand, Rainer, and Aizpurua, Javier

Published
2018

42. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

Author

Konečná, Andrea, Govyadinov, Alexander A., Chuvilin, Andrey, Vélez, Saül, Dolado, Irene, Nikitin, Alexey Y., Lopatin, Sergei, Casanova, Félix, Hueso, Luis E., Aizpurua, Javier, Hillenbrand, Rainer, Konečná, Andrea, Govyadinov, Alexander A., Chuvilin, Andrey, Vélez, Saül, Dolado, Irene, Nikitin, Alexey Y., Lopatin, Sergei, Casanova, Félix, Hueso, Luis E., Aizpurua, Javier, and Hillenbrand, Rainer

Abstract

Only recently, specially designed instrumentation for spatially-resolved electron energy-loss spectroscopy (EELS) has been developed to substantially improve spectral resolution and operating spectral range. This progress has dramatically broadened application potential of EELS in probing low-loss vibrational excitations. Pioneering experiments demonstrated capability of probing vibrational signal in organic samples, ionic crystals, and also van der Waals materials. In our work, we theoretically and experimentally studied the very low-loss EELS of multilayer hexagonal boron nitride (h-BN), a representative van der Waals structure. The weak coupling between individual atomic layer results in extreme optical anisotropy, which gives rise to hyperbolic phonon polaritons (h-PhPs): coupled excitations of optical phonons and light with hyperbolic dispersion in the range of 90 – 200 meV. H-PhPs might be a key to many emerging photonic technologies relying on nanoscale light confinement and manipulation. Thus, efficient design and utilization of h-BN structures require spectroscopic studies with adequate spatial resolution, which can be provided by EELS utilizing electrons as localized electromagnetic probes. To that end, we performed spatially-resolved EELS on a simple h-BN flake structure with an optimized STEM-EELS tool, which revealed the peak energy dependence on the h-BN thickness and on the proximity of the electron beam to the h-BN edge. Such behavior is a consequence of the polaritonic nature of the induced excitations. Indeed, with help of the classical dielectric response theory for EELS, applied to anisotropic slabs and edges, we demonstrate that the electron energy loss in h-BN is dominated by h-PhP excitation and not directly by bulk phonons as in preliminary interpretations. This finding describes and quantitatively matches experimental observations. We thus suggest that EELS can be a technique complementary to scanning near-field optical microscopy for charac

Published
2018

45. Cover Feature: Single‐Site Ruthenium Pincer Complex Knitted into Porous Organic Polymers for Dehydrogenation of Formic Acid (ChemSusChem 20/2018)

Author

Wang, Xinbo, primary, Ling, Eleanor Ang Pei, additional, Guan, Chao, additional, Zhang, Qinggang, additional, Wu, Wenting, additional, Liu, Pengxin, additional, Zheng, Nanfeng, additional, Zhang, Daliang, additional, Lopatin, Sergei, additional, Lai, Zhiping, additional, and Huang, Kuo‐Wei, additional

Published
2018
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