Article
Materials Science, Multidisciplinary
Rafael N. Gontijo, Tianyi Zhang, Kazunori Fujisawa, Ana Laura Elias, Marcos A. Pimenta, Ariete Righi, Mauricio Terrones, Cristiano Fantini
Summary: In this study, Raman spectroscopy was used to investigate low-frequency defect-induced Raman bands in MoS2, revealing the influence of excitation energy and temperature on defect-induced Raman processes. Additionally, it was observed that the ratio of intensities of the DI longitudinal and transversal acoustic modes with respect to the first-order E' mode was similar for two different samples when corrected by defect density. The largest intensity of the DI peaks was found to occur for laser energies in resonance with excitonic transitions, highlighting the importance of laser excitation energy in studying defects in MoS2 samples.
Article
Chemistry, Physical
Finn L. Sebastian, Nicolas F. Zorn, Simon Settele, Sebastian Lindenthal, Felix J. Berger, Christoph Bendel, Han Li, Benjamin S. Flavel, Jana Zaumseil
Summary: Researchers have proposed a direct quantification protocol based on a linear correlation that can accurately assess the defect density on the lattice of single-wall carbon nanotubes (SWCNTs) and determine the oscillator strengths of different defect types.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Physical
Philip Harder, Andreas Nielsen, Ann-Katrin Sassnau, Dennis Bonatz, Markus Perbandt, Tobias Kipp, Alf Mews
Summary: The study investigates the structural properties of CdS, CdSe, and CdTe semiconductor nanowires grown by the SLS method through a detailed experimental and simulation approach. The different samples show varying fractions of Wurtzite and Zincblende, as determined by high-resolution TEM and p-XRD analysis of selected wires and a large amount of NWs.
CHEMISTRY OF MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Megan O. Hill, Paul Schmiedeke, Chunyi Huang, Siddharth Maddali, Xiaobing Hu, Stephan O. Hruszkewycz, Jonathan J. Finley, Gregor Koblmueller, Lincoln J. Lauhon
Summary: This study successfully correlates the morphology, strain, defects, and emission characteristics of quantum wells in nanowires under specific geometries using 3D Bragg coherent diffraction imaging technique, revealing the limits of elastic strain accommodation.
Article
Chemistry, Multidisciplinary
Sandra Cortijo-Campos, Carlos Prieto, Alicia De Andres
Summary: A large set of single-layer and few-layer MoS2 flakes with sizes ranging from 10 nm to 20 μm were successfully obtained on sapphire substrate. The flakes were found to relax and experience hole doping as their size decreases. Additionally, the PL intensity was found to be independent of the size but correlated with the presence of defects.
Article
Chemistry, Multidisciplinary
Min-Ken Li, Adnan Riaz, Martina Wederhake, Karin Fink, Avishek Saha, Simone Dehm, Xiaowei He, Friedrich Schoeppler, Manfred M. Kappes, Han Htoon, Valentin N. Popov, Stephen K. Doom, Tobias Hertel, Frank Hennrich, Ralph Krupke
Summary: This work demonstrates that electroluminescence excitation is selective towards neutral defect-state configurations with the lowest transition energy, which, combined with gate control, leads to high spectral purity.
Article
Engineering, Electrical & Electronic
Mitesh Chakraborty, Dhritiman Banerjee, Sujeet Singh, Joydip Dutta
Summary: The zinc oxide (ZnO) phosphors co-doped with Gd3+/Yb3+ were synthesized using the solid-state reaction method. The compound ZGYO {Zn(1 1.5x- 1.5y)GdxYbyO} was prepared for different molar concentrations of Yb (y) = 0.00, 0.01, 0.03, 0.05 and Gd (x) fixed at 0.01. XRD analysis confirmed the hexagonal phase of the ZnO wurtzite structure, while EDX and XPS spectra confirmed the successful incorporation of Gd3+ and Yb3+ in the ZnO lattice.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Chemistry, Physical
Janusz Andrzejewski, Mieczyslaw Antoni Pietrzyk, Dawid Jarosz, Adrian Kozanecki
Summary: This paper investigates the photoluminescence spectra of excitons in ZnO/ZnMgO/ZnO double asymmetric quantum wells. The presence of an internal electric-field band structure lowers the energy of quantum states and allows for the spatial separation of electrons and holes in wide quantum wells, forming indirect excitons. The study uses single particle states in the wurtzite structure and a self-consistent model to calculate excitons with 2D hydrogenic 1s-like wave functions.
Article
Chemistry, Multidisciplinary
Xilong Liang, Chengbing Qin, Yan Gao, Shuangping Han, Guofeng Zhang, Ruiyun Chen, Jianyong Hu, Liantuan Xiao, Suotang Jia
Summary: The study found that the spin-orbit coupling of monolayer MoS2 can be reversibly engineered by laser irradiation under controlled gas environments, where the spin-orbit splitting has been effectively regulated within 140 meV to 200 meV, and the photoluminescence intensity of the B exciton can be reversibly manipulated over 2 orders of magnitude.
Article
Materials Science, Multidisciplinary
Shraddha M. Rao, Alexander Kiligaridis, Aymen Yangui, Qingzhi An, Yana Vaynzof, Ivan G. Scheblykin
Summary: Defects in metal halide perovskites (MHP) exhibit photosensitivity, causing the observer effect in laser spectroscopy. The creation and healing of defects lead to transient phenomena such as photoluminescence (PL) bleaching and enhancement. The use of the dependence of PL quantum yield (PLQY) on laser pulse repetition rate and pulse fluence as a unique fingerprint of charge carrier dynamics and defect evolution is demonstrated. Automatic PLQY mapping can be used as a universal method for assessing the quality of perovskite samples.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Chemistry, Physical
Soungmin Bae, Tae Young Jeong, Hannes Raebiger, Ki-Ju Yee, Yong-Hoon Kim
Summary: We present spectroscopic evidence for the ultrafast trapping of band edge excitons at defects and the subsequent generation of defect-localized coherent phonons (CPs) in monolayer MoSe2. Our time-resolved pump-probe spectroscopy on the sub-picosecond time scale detects localized CPs only from the ultrafast exciton trapping at shallow traps. Based on density functional calculations, we identify the origins of deep and shallow traps as Se vacancy and oxygen molecule adsorbed on a Se vacancy, respectively. Our work establishes the correlations between defect-induced ultrafast exciton trapping and the generation of defect-localized CPs, providing new opportunities for engineering photoexcited carriers in two-dimensional materials through lattice defects.
NANOSCALE HORIZONS
(2023)
Article
Chemistry, Multidisciplinary
Simon Kahmann, Herman Duim, Hong-Hua Fang, Mateusz Dyksik, Sampson Adjokatse, Martha Rivera Medina, Matteo Pitaro, Paulina Plochocka, Maria A. Loi
Summary: 2D perovskites offer a rich field to explore exciton physics and have great potential for opto-electronic applications. This study investigates PEA(2)PbBr(4), PEA(2)PbI(4), and PEA(2)SnI(4) through optical spectroscopy, revealing complex excitonic transitions at low temperature. The study deepens insights into the photophysics of 2D perovskites through compositional substitution.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Zhenping Wang, Qing Cao, Kai Sotthewes, Yalei Hu, Hyeon S. Shin, Siegfried Eigler
Summary: This research focuses on modulating the optoelectronic properties of monolayer MoS2 on different graphene monolayers, showing that oxygen-functionalized graphene and reduced-oxo graphene can significantly enhance the photoluminescence intensity of MoS2, while pristine graphene leads to photoluminescence quenching. Additionally, the increase in photoluminescence intensity is higher in reduced-oxo graphene/MoS2 compared to oxygen-functionalized graphene/MoS2.
Article
Chemistry, Multidisciplinary
Natalia Zawadzka, Lucja Kipczak, Tomasz Wozniak, Katarzyna Olkowska-Pucko, Magdalena Grzeszczyk, Adam Babinski, Maciej R. Molas
Summary: The optical response of bulk germanium sulfide (GeS) is systematically investigated using different polarization-resolved experimental techniques, showing that the low-temperature optical band-gap absorption is governed by a single resonance related to the neutral exciton, while the emission is dominated by the disorder/impurity- and/or phonon-assisted recombination processes. Furthermore, the Raman scattering spectra consist of six Raman peaks identified with the help of Density Functional Theory (DFT) calculations, allowing for the determination of GeS crystallographic directions.
Article
Chemistry, Physical
Mohamed A. Helal, H. M. El-Sayed, Ahmed A. Maarouf, Mohamed M. Fadlallah
Summary: The study investigated the impact of different pore structures on 2D-TMD using density functional theory, revealing higher stability for smaller pores, lattice deformation and decreased Young's modulus with increasing pore size. Certain systems exhibited magnetism due to missing metal atoms, while the emergence of metal states at pore edges resulted in some systems being half-metallic. Oxygen passivation restored metallic behavior in the systems.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Ho Kwang Choi, Aram Lee, Mina Park, Dong Su Lee, Sukang Bae, Seoung-Ki Lee, Sang Hyun Lee, Takhee Lee, Tae-Wook Kim
Summary: Research has shown that hierarchical porous Cu foils assembled from Cu nanosheets exhibit outstanding EMI shielding performance, suggesting that Cu nanosheets and their layer-by-layer assembly are a promising technology for practical electronic applications.
Article
Chemistry, Physical
Jeongjae Lee, Woocheol Lee, Keehoon Kang, Takhee Lee, Sung Keun Lee
Summary: In this study, H-1 and Pb-207 solid-state nuclear magnetic resonance (NMR) spectroscopy was successfully used to probe the local structural features of 2D halide perovskites, providing important insights for a better understanding of the properties of multidimensional halide perovskites.
CHEMISTRY OF MATERIALS
(2021)
Article
Nanoscience & Nanotechnology
Junwoo Kim, Woocheol Lee, Kyungjune Cho, Heebeom Ahn, Jonghoon Lee, Kyeong-Yoon Baek, Jae-Keun Kim, Keehoon Kang, Takhee Lee
Summary: The study investigates the impact of crystallinity on photodetector performance in n = 4 two-dimensional RP perovskite polycrystalline films by tuning film orientation through solvent evaporation rate control. It explores how grain boundary and low energy edge state effects in n = 4 RP perovskites are reflected in the variation of photodetector performance, emphasizing the importance of understanding the interplay between different factors for designing high-performance optoelectronic devices based on RP perovskites.
Article
Materials Science, Multidisciplinary
Jonghoon Lee, Woocheol Lee, Jeongjae Lee, Kyeong-Yoon Baek, Jiwon Shin, Jae-Keun Kim, Junwoo Kim, Heebeom Ahn, Keehoon Kang, Takhee Lee
Summary: This study successfully optimized the responsivity of OHP photodetector devices through the design-of-experiment process, achieving an enhanced responsivity of 112.2 mA W-1, which is up to an order of magnitude higher than that of the unoptimized devices. The experimental results using the DoE method not only provide the conditions required for enhancing the device performance, but also offer guidelines for improving the overall film quality through exploring the variable space of the flash evaporation technique.
ADVANCED MATERIALS TECHNOLOGIES
(2021)
Correction
Multidisciplinary Sciences
Woocheol Lee, Jonghoon Lee, Hyeon-Dong Lee, Junwoo Kim, Heebeom Ahn, Youngrok Kim, Daekyoung Yoo, Jeongjae Lee, Tae-Woo Lee, Keehoon Kang, Takhee Lee
SCIENTIFIC REPORTS
(2021)
Article
Nanoscience & Nanotechnology
Lifa Ni, Xiaojin Li, Zhibin Zhao, Jongwoo Nam, Pengfei Wu, Qingling Wang, Takhee Lee, Hongliang Liu, Dong Xiang
Summary: This study investigated the interface between microscale ferroelectric crystals (KTN) and liquid metal electrodes (EGaIn), revealing that the contact geometry plays a crucial role in determining the electrical properties. The microscale KTN junctions exhibit electrical rectifying characteristics under light illumination, with the rectification direction being reversible by increasing the ambient temperature. The quasi-negative differential resistance observed in half-enclosed KTN by EGaIn electrodes highlights the importance of carrier trapping/detrapping affected by crystal size and temperature.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Nanoscience & Nanotechnology
Jiwon Shin, Kyeong-Yoon Baek, Jonghoon Lee, Woocheol Lee, Jaeyoung Kim, Juntae Jang, Jaehyoung Park, Keehoon Kang, Kyungjune Cho, Takhee Lee
Summary: In this study, we synthesized MAPbI(3) perovskites via two methods and irradiated them with proton beams. Our results showed that the proton irradiation had different effects on the physical properties of the perovskites synthesized through different methods, possibly due to differences in bonding strength.
Article
Chemistry, Multidisciplinary
Inho Jeong, Kyungjune Cho, Seobin Yun, Jiwon Shin, Jaeyoung Kim, Gyu Tae Kim, Takhee Lee, Seungjun Chung
Summary: This study demonstrates the controllable surface charge transfer doping (SCTD) of molybdenum disulfide (MoS2) field-effect transistors using inkjet-printed benzyl viologen (BV). The BV-doped MoS2 FETs exhibit elaborately tailored electrical performance by adjusting the concentration and areal coverage of inkjet-printed BV dopants. The inkjet-printed SCTD method provides a feasible solution for modulating the electrical and optical performances of TMD-based devices.
Biographical-Item
Nanoscience & Nanotechnology
Laurie E. Calvet, Jia Chen, Takhee Lee, Alan Seabaugh
NATURE NANOTECHNOLOGY
(2022)
Article
Multidisciplinary Sciences
Sunbin Hwang, Minji Kang, Aram Lee, Sukang Bae, Seoung-Ki Lee, Sang Hyun Lee, Takhee Lee, Gunuk Wang, Tae-Wook Kim
Summary: In this study, an integrated electronic fibre platform was developed by fabricating and integrating multiple electronic components onto a one-dimensional microfibre substrate. The platform showed high performance potential for wearable electronic textile systems, as demonstrated by its switching, data processing, and sensing capabilities.
NATURE COMMUNICATIONS
(2022)
Review
Chemistry, Multidisciplinary
Zhibin Zhao, Saurabh Soni, Takhee Lee, Christian A. Nijhuis, Dong Xiang
Summary: Eutectic gallium-indium (EGaIn) is a liquid metal that has attracted significant attention due to its excellent properties. It can be adjusted and mixed with other materials to obtain composite materials with extended properties. This review provides an introduction to the unique properties of EGaIn, illustrates the working principles of EGaIn-based devices, and summarizes the developments in EGaIn-related techniques. Additionally, it reviews the applications of EGaIn in various fields and discusses the challenges and potential applications for the development of EGaIn-based techniques.
ADVANCED MATERIALS
(2023)
Review
Chemistry, Multidisciplinary
Maoning Wang, Tao Wang, Oluwafemi S. Ojambati, Thorin Jake Duffin, Keehoon Kang, Takhee Lee, Elke Scheer, Dong Xiang, Christian A. Nijhuis
Summary: This review presents the latest advancements in plasmonic resonances in molecular junctions, detailing the progress in plasmon excitation and coupling, and highlighting emerging experimental approaches to unravel the mechanisms of light-matter interactions at the molecular scale. The potential of these plasmonic-electronic hybrid systems in various future applications is also discussed.
NATURE REVIEWS CHEMISTRY
(2022)
Review
Nanoscience & Nanotechnology
Jia Chen, Takhee Lee, Chongwu Zhou
Summary: In memory of Professor Mark Reed, this article presents a summary of his groundbreaking developments in molecular electronic devices, including the measurement of electrical conductance in molecular junctions using the mechanically controlled break junction technique, the demonstration of negative differential resistance, and the observation of the orbital gating effect in molecular junctions. It also provides a brief outlook on the research field of molecular electronics.
Article
Engineering, Electrical & Electronic
Hayun Kim, Hyunuk Oh, Hyunjun Yoo, Kyungjune Cho, Takhee Lee, Seungjun Chung, Byeongmoon Lee, Yongtaek Hong
Summary: Single-walled carbon nanotube (SWCNT) random networks have been developed for next-generation electronics with exceptional mechanical, electrical, and optical properties. However, the presence of metallic nanotubes in the networks limits the performance of SWCNT-based devices. In this study, SWCNT thin-film transistors (TFTs) with varying purity profiles of semiconducting SWCNTs were introduced to exploit the superior mobility of metallic SWCNTs while maintaining high-purity semiconducting regions to block off-state leakage. This approach resulted in SWCNT TFTs with superior carrier mobility, channel width normalized on-current, and on/off ratio, making them suitable for high-performance electronics.
ACS APPLIED ELECTRONIC MATERIALS
(2023)
Review
Chemistry, Physical
Kyungjune Cho, Takhee Lee, Seungjun Chung
Summary: This review presents recent achievements and challenges in inkjet-printed device applications based on two-dimensional van der Waals materials (2D vdW materials). The review provides a brief introduction to 2D vdW materials and inkjet printing principles, discusses various ink formulation methods, and highlights the applications of inkjet-printed 2D vdW devices and their technical issues.
NANOSCALE HORIZONS
(2022)
