Article
Nanoscience & Nanotechnology
Chiara Trovatello, Giulia Piccinini, Stiven Forti, Filippo Fabbri, Antonio Rossi, Sandro De Silvestri, Camilla Coletti, Giulio Cerullo, Stefano Dal Conte
Summary: Charge transfer processes in 2D van der Waals heterostructures enable upconversion of low energy photons and efficient extraction of charge carriers. In this study, the dynamics of charge transfer in large-area 2D heterostructures made of epitaxial WS2 grown on graphene were investigated using ultrafast optical spectroscopy. The results showed that selective carrier photoexcitation in graphene resulted in an almost instantaneous bleaching of the WS2 excitonic peaks in the visible range, indicating interlayer charge transfer. The transfer of hot carriers generated in graphene to the semiconducting layer was found to occur within a sub-20-fs timescale. The findings have both fundamental and technological importance for the development of novel 2D photodetectors.
NPJ 2D MATERIALS AND APPLICATIONS
(2022)
Article
Chemistry, Physical
Simin Wu, Zixuan Lu, Anqi Hu, Xianchong Miao, Fanjie Wang, Zhengzong Sun, Hugen Yan, Hao Zhang, Minbiao Ji
Summary: In this study, polarization-resolved femtosecond transient absorption microscopy was used to investigate the anisotropic coherent phonon responses of black phosphorus. Multiorder phonon harmonics with thickness dependence were observed. Additionally, exotic coherent phonon oscillations occurred with a pi-phase jump between armchair and zigzag polarizations, revealing opposite signs of photoelasticity under longitudinal strain.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Zhongguo Li, Zhendong Wu, Xiaolong Wang, Hongtao Cao, Lingyan Liang, Junyi Yang, Yinglin Song
Summary: The study demonstrates the fabrication of amorphous zinc tin oxide thin films with strong visible light absorption using rf magnetron sputtering and rapid postannealing. The ultrafast carrier dynamics of the ternary films were investigated using femtosecond transient absorption spectroscopy, revealing that visible light absorption is induced by band gap reduction rather than defect states in the ZTO film. These findings shed light on the photophysical mechanism of amorphous ZTO films and suggest their potential use in solar cell and photodetector devices.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Engineering, Electrical & Electronic
Luca Vancini, Michele Mengoni, Gabriele Rizzoli, Giacomo Sala, Luca Zarri, Angelo Tani
Summary: This article investigates the extension of overmodulation strategies from three-phase inverters to five-phase systems, with experimental tests conducted on a five-phase induction motor drive to verify the feasibility of the developed techniques, the quality of the current waveforms, and the improvement in the dynamic performance of the drive.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2021)
Article
Chemistry, Multidisciplinary
Mazhar Chebl, Xing He, Ding-Shyue Yang
Summary: This study reveals that black phosphorus undergoes interlayer lattice contraction and internal vibrations after photo injection and carrier relaxation, showing unique atomic motions that have important implications for single and few-layer black phosphorus and other vdW materials with strong electronic-lattice correlations.
Article
Chemistry, Physical
Nina Girotto, Fabio Caruso, Dino Novko
Summary: This study combines ab initio time-dependent Boltzmann equations and many-body phonon self-energy calculations to investigate the nonadiabatic phonon renormalization process in the MoS2 monolayer under nonequilibrium conditions. The results show that the nonequilibrium state of photoexcited MoS2 is influenced by the multi-valley topology of valence and conduction bands, leading to anisotropic electron-phonon thermalization paths and phonon renormalization around high-symmetry points. This work provides potential guidelines for controlling electron-phonon relaxation channels and phonon dynamics under extreme photoexcited conditions.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Nanoscience & Nanotechnology
Dipendranath Mandal, Megha Shrivastava, Sudarshan Sharma, Ajay K. Poonia, Sourav Marik, Ravi Prakash Singh, K. V. Adarsh
Summary: This study experimentally demonstrates the carrier-induced sign reversal of the ultrafast third-order nonlinear optical response in few-layer ReS2 nanoflakes. By controlling the thermalization time of the carriers, the transition from saturable absorption to reverse saturable absorption is achieved. The results suggest that few-layer ReS2 can be used as a high-performance optical limiter material.
ACS APPLIED NANO MATERIALS
(2022)
Article
Energy & Fuels
Jun-Hyuk Im, Yeol-Kyeong Lee, Jun-Kyu Park, Jin Hur
Summary: This paper proposes a method to reduce CMV and shaft voltage using carrier wave phase shift in SVPWM. The impact of CMV, shaft voltage, and bearing current is analyzed through a simulation model, while the output torque behavior with different input currents is studied.
Article
Chemistry, Multidisciplinary
Tobias Schreitmueller, Hyowon W. Jeong, Hamidreza Esmaielpour, Christopher E. Mead, Manfred Ramsteiner, Paul Schmiedeke, Andreas Thurn, Akhil Ajay, Sonja Matich, Markus Doeblinger, Lincoln J. Lauhon, Jonathan J. Finley, Gregor Koblmueller
Summary: This study evaluates the impact of impurity-induced point defects on the lasing performance of GaAs-AlGaAs based nanowire lasers. The findings demonstrate that these lasers have remarkably low lasing thresholds under Si doping and are highly tolerant to impurity defects. This discovery is significant for the application of nanowire lasers.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Optics
Tien-Tien Yeh, Te Lo, Hao-Hsiang Jia, Yu-Chan Tai, Ping-Hui Lin, Chih-Wei Luo
Summary: The ultrafast pump-probe microscope was used to investigate the ultrafast dynamics of photoexcited carriers and phonons in InSb, revealing the delocalized electron-phonon coupling and localized recombination of electrons and holes. The study also demonstrated the manipulation of phonon properties through an applied electric field, leading to the first observation of spatial breadth of phonons in InSb with large carrier concentrations.
Article
Materials Science, Multidisciplinary
Animesh Pandey, Alka Sharma, Nikita Vashistha, Sumit Kumar, Reena Yadav, Mandeep Kaur, Mahesh Kumar, Sudhir Husale
Summary: In this paper, the electron-phonon interactions of topological insulator (TI) thin films on a flexible substrate were studied using the ultrafast pump-probe method. The dynamics of hot carrier relaxation and coherent phonon behavior in Bi2Te3 thin films were investigated. Thickness-dependent low-frequency coherent acoustic phonon oscillations were observed, and the film's terahertz frequency response was calculated. These findings suggest potential applications of flexible topological insulator thin films in future terahertz devices.
Article
Materials Science, Multidisciplinary
K. Gurukrishna, Ashok Rao, K. Shyam Prasad, Yu-Chun Wang, Yung-Kang Kuo
Summary: To investigate the effect of cation disorders on the thermoelectric performance of the Cu3SbSe4 system, copper content in Cu3+xSbSe4 (x = -0.06, -0.04, 0, 0.04, 0.06, and 0.08) system was adjusted via solid-state reaction route. The intentional deviations from stoichiometry successfully enhanced electrical transport and reduced phonon transport simultaneously. The self-doping effect induced by non-stoichiometry provided acceptor levels, thereby increasing electrical conductivity. Modulating the Fermi level within the valence band allowed for the realization of a high power factor and considerable reduction in thermal conductivity, ultimately enhancing the figure of merit of the Cu3SbSe4 system.
MATERIALS RESEARCH BULLETIN
(2023)
Article
Physics, Applied
I. Makhfudz, N. Cavassilas, Y. Hajati, H. Esmaielpour, F. Michelini
Summary: This study theoretically investigates carrier thermalization in a superlattice solar cell made of polar semiconductors, focusing on the effect of phonon coherence on carrier energy loss. The results show that coherent longitudinal optical (LO) phonons weaken the electron-phonon coupling, leading to a lower carrier-energy-loss rate in the solar cell. This coherent phonon-driven phenomenon enhances the hot-carrier effect, especially in thin well layers with strong carrier confinement. The practical implications of phonon coherence in semiconductors for improving superlattice solar-cell performance are demonstrated.
PHYSICAL REVIEW APPLIED
(2023)
Article
Physics, Applied
Wentao Qiu, Weizheng Liang, Jia Guo, Limei Fang, Ning Li, Qingguo Feng, S. N. Luo
Summary: The study reveals that the hot carrier dynamics of PtSe2 are significantly dependent on its thickness, with different processes contributing to carrier decay in semiconducting and metallic PtSe2 films. In semiconducting films, electron-phonon coupling, interlayer charge transfer, and nonradiative recombination are involved, while in metallic films, electron-phonon coupling dominates the carrier decay.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Engineering, Electrical & Electronic
Fazal Akbar, Ahmad Elkhateb, Hafiz Furqan Ahmed, Ashraf Ali Khan, Honnyong Cha, Jung-Wook Park
Summary: This article introduces a new family of transformerless buck-boost voltage-source inverter topologies for photovoltaic systems. These topologies effectively mitigate the common-mode voltage issue and achieve low leakage current. Various inverter designs based on the proposed concept are capable of achieving wide gain range and high boost voltage gain.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2023)
Article
Chemistry, Physical
Shiva Choupanian, Wolfhard Moller, Martin Seyring, Carsten Ronning
Summary: This study experimentally demonstrates channeling of low-energy ions in crystalline nanoparticles, which differs from conventional high-energy ion irradiation. Channeling has a significant impact on ion transport in crystals and is relevant for focused ion beam (FIB) applications. Therefore, it is recommended not to solely rely on standard Monte-Carlo algorithms for predicting ion distribution depths in amorphous materials.
Article
Materials Science, Multidisciplinary
Lukas Peters, Christoph Margenfeld, Jan Krugener, Carsten Ronning, Andreas Waag
Summary: The presence of carbon impurities in AlN was believed to be the main cause of the absorption at 265 nm. However, this study revealed that the intrinsic nitrogen-vacancy defect V-N plays a crucial role in the absorption. This finding is significant for further improvement of UV-LEDs.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Optics
Daniel Repp, Angela Barreda, Francesco Vitale, Isabelle Staude, Ulf Peschel, Carsten Ronning, Thomas Pertsch
Summary: Semiconductor nanowire lasers can have their lasing threshold modified by their environment, and using metallic substrates can access low-volume Surface-Plasmon-Polariton (SPP) modes and describe mode competition in nanowire lasers. The study found that an aluminum substrate decreases the lasing threshold for ZnO nanowire lasers, while a silver substrate increases the threshold compared to a dielectric substrate. These findings allow for predictions about the interaction between planar metals and semiconductor nanowires, guiding future improvements in highly-integrated laser sources.
Article
Nanoscience & Nanotechnology
Kirill Gubanov, Manuel Johnson, Melda Akay, Benedikt C. C. Wolz, Dan Shen, Xing Cheng, Silke Christiansen, Rainer H. H. Fink
Summary: Advances in organic materials manufacturing have enabled the creation of electronic devices using solution-processing techniques. This study demonstrates the use of micro-contact for high-quality structured electrodes in top-contact organic field-effect transistors (OFETs) by depositing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer ink. The optimized solution-processing fabrication of OFETs shows promising potential for simple and cost-effective roll-to-roll manufacturing processes, with comparable electrical performance to transistors with gold electrodes and lower contact resistance (R-c) due to carbon-based organic electrodes.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Christian T. Plass, Valentina Bonino, Maurizio Ritzer, Lukas R. Jager, Vicente Rey-Bakaikoa, Martin Hafermann, Jaime Segura-Ruiz, Gema Martinez-Criado, Carsten Ronning
Summary: The dynamics of color centers in quantum technology are influenced by the local environment, and a combined approach of X-ray fluorescence analysis and X-ray excited optical luminescence (XEOL) was used to study this relationship. The simultaneous acquisition of data revealed compositional and functional variations at the nanoscale, demonstrating the extraordinary capabilities of these techniques. The findings on cobalt doped zinc oxide nanowires showed an anticorrelation between the band edge emission of the zinc oxide host and the intra-3d cobalt luminescence, indicating two competing recombination paths. Time-resolved XEOL measurements also revealed two exponential decays of the cobalt luminescence, with the fast decay attributed to a recombination cascade within the cobalt atom.
Article
Physics, Applied
F. Vitale, D. Repp, T. Siefke, U. Zeitner, U. Peschel, T. Pertsch, C. Ronning
Summary: In this study, a mode selection scheme based on distributed feedback was proposed to achieve quasi-single mode lasing action in plasmonic nanowires. The orientation of the nanowire on the grating was found to affect the emission spectrum, with an additional peak emerging when the nano-cavity was perpendicular to the ridge direction. This peak was attributed to a hybrid mode dominating the mode competition and supported by localized plasmon polaritons on the metal grating ridges.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
M. Popovic, M. Novakovic, D. Vana, C. Ronning, D. Jugovic, V. Rajic, P. Noga
Summary: In this study, sequential implantation of gold and silver ions with varying ion fluence, as well as subsequent annealing, were used to modify the optical and plasmonic properties of TiN thin films and correlate them with their structural properties. The implanted films showed reduced metallicity and lower losses compared to the as-deposited film, while subsequent annealing partially recovered the destroyed structure and improved the metallic properties. By optimizing the implantation fluence of silver ions, TiN films with desirable optical performances were obtained.
Article
Materials Science, Multidisciplinary
Lukas Peters, Hendrik Spende, Stefan Wolter, Christoph Margenfeld, Carsten Ronning, Tobias Voss, Andreas Waag
Summary: In this study, carbon-implanted and high-temperature annealed AlN layers were analyzed using cathodoluminescence spectroscopy. Donor-acceptor pair transitions between carbon and oxygen impurities were identified. The presence of oxygen led to absorption in the deep UV range, while carbon was responsible for an absorption band at around 265 nm. The findings were supported by temperature- and power-dependent emission energy shifts and luminescence transients.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Multidisciplinary Sciences
Nicholas A. Gusken, Ming Fu, Maximilian Zapf, Michael P. Nielsen, Paul Dichtl, Robert Roeder, Alex S. Clark, Stefan A. Maier, Carsten Ronning, Rupert F. Oulton
Summary: Since Purcell's seminal report 75 years ago, electromagnetic resonators have been used to control light-matter interactions to make brighter radiation sources and unleash unprecedented control over quantum states of light and matter. In this letter, the authors report a strong radiative emission rate enhancement of Er3+-ions across the telecommunications C-band in a single plasmonic waveguide based on the Purcell effect. The waveguide uses a reverse nanofocusing approach to efficiently enhance, extract, and guide emission from the nanoscale to a photonic waveguide, while keeping losses at a minimum.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Lamborghini Sotelo, Tommaso Fontanot, Sanjana Vig, Patrick Herre, Peyman Yousefi, Maria Helena Fernandes, George Sarau, Gerd Leuchs, Silke Christiansen
Summary: This study investigates the effect of the initial surface roughness of TiAl6V4 samples on laser-induced periodic surface structures (LIPSS), surface wettability, and chemistry. Different polishing grain sizes were used to adjust the surface roughness of the samples. Laser irradiation was performed with varying laser power and distance. The resulting structures were characterized by SEM, AFM, Raman spectroscopy, and contact angle measurements. The study also explores the bone implant viability of the generated structures. The results demonstrate that initial surface roughness affects the wettability and orientation of the resulting LIPSS, and structures with higher integrated fluence enhance cell differentiation and reduce bacterial activity, making them promising for bone implant compatibility and durability.
ADVANCED MATERIALS TECHNOLOGIES
(2023)
Article
Nanoscience & Nanotechnology
Lucia H. Prado, David Boehringer, Anca Mazare, Lamborghini Sotelo, George Sarau, Silke Christiansen, Ben Fabry, Patrik Schmuki, Sannakaisa Virtanen, Wolfgang H. Goldmann, Alexander B. Tesler
Summary: Researchers have developed a convenient UV-grafting technique to covalently attach silicone-based coatings to solid substrates. The short-time exposure to UV light results in the formation of lubricant-infused slippery surfaces (LISS), while longer exposure leads to the formation of semi-rigid cross-linked polydimethylsiloxane (PDMS) coatings. These coatings exhibit excellent resistance to corrosion and biofouling in aquatic environments. Due to its simple fabrication, low cost, rapid binding kinetics, eco-friendliness, non-toxicity to aquatic life, and excellent wetting-repellent characteristics, this technology has great potential for implementation in aquatic environments.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Materials Science, Multidisciplinary
Robert Wonneberger, Gloria Kirste, Martin Seyring, Martin Hafermann, Carsten Ronning, Maximilian Schaal, Felix Otto, Torsten Fritz, Andreas Undisz
Summary: Understanding the growth mechanism of oxide layer on 316 L requires knowledge of reaction front position, oxide phase formation, and elements diffusion paths. By using Mn as a tracer in a new experimental approach, essential information of the early stages of oxidation up to 600 °C is obtained. The study suggests a previously undocumented role of Cr valence state during oxide growth, as Cr6+ is detected at 600 °C.
Article
Instruments & Instrumentation
Martin Borchert, Julia Braenzel, Richard Gnewkow, Leonid Lunin, Themistoklis Sidiropoulos, Johannes Tuemmler, Ingo Will, Tino Noll, Oliver Reichel, Dirk Rohloff, Alexei Erko, Thomas Krist, Clemens von Korff Schmising, Bastian Pfau, Stefan Eisebitt, Holger Stiel, Daniel Schick
Summary: We present a laser-driven soft-x-ray plasma source with short pulse duration and wide spectral range. This source is used in two laboratory-scale beamlines for time-resolved magnetic resonant scattering, spectroscopy, and NEXAFS spectroscopy. Dedicated reflection zone plates are utilized as optical elements to capture, disperse, and focus the soft x rays, achieving high resolving powers and efficient data acquisition. Our setup enables soft-x-ray experiments that were not previously possible on a laboratory scale, making it a viable alternative to large-scale facilities.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Materials Science, Multidisciplinary
Alexander Koch, Hongyan Mei, Jura Rensberg, Martin Hafermann, Jad Salman, Chenghao Wan, Raymond Wambold, Daniel Blaschke, Heidemarie Schmidt, Jurgen Salfeld, Sebastian Geburt, Mikhail A. A. Kats, Carsten Ronning
Summary: This study demonstrates the heavy and hyper doping of ZnO with gallium (Ga) ions using a focused ion beam (FIB) system combined with post-implantation laser annealing. The ion implantation allows for the incorporation of impurities with high concentrations, while the laser annealing process activates the dopants close to or beyond the solid-solubility limit of Ga in ZnO. Heavy doped ZnO:Ga with a free-carrier concentration of approximately 10^(21) cm^(-3) and a plasma wavelength of 1.02 μm is achieved, making it a promising plasmonic material for applications in the near infrared regime.
ADVANCED PHOTONICS RESEARCH
(2023)
Article
Chemistry, Multidisciplinary
Edwin Eobaldt, Francesco Vitale, Maximilian Zapf, Margarita Lapteva, Tarlan Hamzayev, Ziyang Gan, Emad Najafidehaghani, Christof Neumann, Antony George, Andrey Turchanin, Giancarlo Soavi, Carsten Ronning
Summary: Mixed-dimensional hybrid structures are promising building blocks for controlling and modulating lasers at the nanoscale. Hybridization of ZnO nanowires with MoS2 monolayers allows for tuning the lasing wavelength at the nanoscale.