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Research on Semiconductors Light Weakens Magic Nanoclusters
[21.01.2021] They are known as "magic sized nano clusters" because they have special properties: The particles consist of only a few atoms, but since they are arranged in a special crystal structure, they are extremely stable. Unless you expose them to light. Scientists from the Center for Nanointegration (CENIDE) at the University of Duisburg-Essen (UDE) have discovered that such materials undergo fundamental changes as soon as they are merely analysed using optical methods. "Nature Communications" reports on the issue.
Junior professor Dr. Franziska Muckel is head of the working group "Electroenergetic Functional Materials" at the chair "Materials of Electrical Engineering”. Her team investigates cadmium selenide particles, which consist of no more than 26 atoms. Yet these atoms are arranged in a crystal structure, i.e. in a regular lattice similar to the symmetrical climbing frames made of ropes and metal on children's playgrounds. This structure renders the particles extremely stable.
In collaboration with the Seoul National University (South Korea) and the Max-Planck-Institut für Eisenforschung in Düsseldorf, UDE's researchers demonstrated that light above a certain wavelength weakens the bonds within these semiconductor nano clusters significantly – a hundred times more than in the same material with much larger dimensions.
Optical analysis methods as standard techniques in semiconductor research thus reach their limits in these dimensions: Instead of merely elucidating material properties, they change the investigated material itself. Since magic nano clusters are an important intermediate step on the way to larger functional particles, this is a decisive discovery.
Muckel, who conducts her research at the NanoEnergieTechnikZentrum (NETZ) on the Duisburg campus, now wants to put the results to practical use: "In the long term, we plan to develop components from similar materials that convert light into charge carriers and could therefore serve as optical sensors."
F. Muckel, S. Lorenz, J. Yang, T. A. Nugraha, E. Scalise, T. Hyeon, S. Wippermann, G. Bacher „Exciton-driven change of phonon modes causes strong temperature dependent bandgap shift in nanoclusters“ Nat Commun 11, 4127 (2020)
Master thesis sponsored by the Stiftung Industrieforschung
[24.09.2020] Every year, the Stiftung Industrieforschung supports students from technical and scientific studying programs throughout Germany whose master's thesis promises relevance to medium-sized industrial companies with a scholarship. B.Sc. Henrik Myja receives one of these coveted scholarships for his thesis on "Transparent and flexible light emitting devices based on nanometer-thin 2D semiconductors" at the Chair of Electronic Materials and Nanostructures (Prof. Dr. Gerd Bacher). The active material used for the devices are large-area tungsten disulfide monolayers, which originate from a cooperation with Prof. Dr. Andrei Vescan from the RWTH Aachen University. These are investigated with respect to internal quantum efficiency and embedded in to a transparent and flexible device environment. The analysis of the devices will be used to estimate the application potential, e.g. in the field of flexible lighting or display elements for weight-reduced mobile solutions.
Creating magnetism from light!
[02.04.2020] Generating magnetism on demand without the use of electrical currents – in the field of doped nanocrystals no science fiction anymore, but close to reality. A major breakthrough in this area was recently achieved by the group of Prof. Gerd Bacher in collaboration with the Gamelin Group at the University of Washington, Seattle. Using spectroscopy on individual nanocrystals in a rotatable magnetic field it was shown how light induced magnetism can be purposefully directed.
In future, this work will be continued and extended with funding of the Deutsche Forschungsgemeinschaft, which has just granted a full 3 year project on this topic.
Original publication can be found under:
S. Lorenz et al., Nano Letters 20, 1896 (2020)
VDE Promotion Award 2019 for Dr. Franziska Muckel
[20.11.2019] This year's VDE Promotion Award, endowed with 3,000 Euro, was presented to Dr. Franziska Muckel for her dissertation "Magnetically doped semiconductor quantum dots from solvent-based production: from functionality to device" in a ceremony at the Gerhard Mercator House in Duisburg. During her doctorate, Ms. Muckel developed semiconductor nanocrystals that combine electrical, optical and magnetic functions in a very small space. With this basic research, many devices will soon be even more powerful. Since its foundation, VDE Nordrhein-Westfalen has donated an annual doctoral prize for special achievements in the fields of electrical engineering, electronics and information technology to female scientists at the universities of Aachen, Bochum, Duisburg, Dortmund, Hagen, Paderborn, Siegen and Wuppertal. In addition to the scientific originality and innovative value of the submitted work, the applicability and relevance of the results for the state of North Rhine-Westphalia are also examined and evaluated.
by Siegbert Kmetz
Innovation Prize of the Sparkasse am Niederrhein for Dr. Franziska Muckel
[13.11.2019] For her dissertation entitled "Transition Metal Doped Colloidal Semiconductor Nanocrystals: From Functionality to Device Development" Dr. Franziska Muckel was awarded the coveted innovation prize of the Sparkasse am Niederrhein. Ms. Muckel developed semiconductor nanocrystals that combine electrical, optical and magnetic functions in the smallest of spaces. With this basic research, many devices will soon be even more powerful". For more than 20 years, the Sparkasse, in cooperation with the in Moers-based development association for engineering sciences, has been honoring application-related and outstanding dissertations and master's theses written in the engineering sciences of the UDE.
Best PhD Student Oral Contribution Award for transparent graphene electrodes on GaN based LEDs
[29.6.2019] For the conference contribution „Direct growth of graphene on GaN under N2 atmosphere“ M.Sc Jan Mische was priced with the Best PhD Student Oral Contribution award at Graphene2019. In his talk he spoke about the direct growth of graphene via plasma enhanced chemical vapor deposition (PECVD) on GaN based LEDs. Goal of the work is to get graphene utilize as a transparent electrode for LEDs, which would increase the efficiency.
ACS Photonics Poster Award for Hybrid QD-LECs
[29.7.2018] M. Sc. Julia Frohleiks was honored with the ACS Photonics Poster Prize and a reward of 1000 US-Dollar for her poster entitled „Hybrid Quantum Dot – Light-Emitting Electrochemical Cells“ in context of QD2018 – the 10th Biannual Conference on Quantum Dots in Toronto (Canada).
Julia Frohleiks, a member of the junior research group Solid State Lighting (Dr. E. Nannen) and the department for electronic materials and nanostructures (Prof. G. Bacher), develops innovative light-emitting devices. These hybrid devices are a combination of light-emitting semiconducting nanocrystals (quantum dots, QDs) and light-emitting electrochemical cells (LEC). The poster shows the results on devices that use colloidal QDs to supplement the LEC emission color as well as on devices that replace the LEC emitter completely and show light emission solely of the light-emitting QDs.
Further details on the results can be found in ACS Applied Materials & Interfaces 8, 24692 (2016), LED Lighting Technologies – Smart Technologies for Lighting Innovations, Luger Research e.U., 206 (2017) and Advanced Materials Technologies 2, 1700154 (2017).
New special research field at UDE with involvement of Electronic Materials and Nanostructures
[17.05.2018] The German Research Foundation DFG is funding a new Collaborative Research Center "Heterogeneous Oxidation Catalysis in the Liquid Phase" under the umbrella of the University Alliance Ruhr with approximately € 10 million for the first four years. Spokesman is Prof. Malte Behrens from the Faculty of Chemistry. The WET is also on board. In the coming years we will investigate charge carrier dynamics in oxide photocells with spinel and perovskite crystal structures.
Successful Cooperation with Technical University Nanyang, Singapore
[9.05.2018] A scientific breakthrough in the area of doped nanocrystals has been achieved in a collaboration between the Chair of Electronic Materials and Nanostructures in Duisburg and colleagues from the Technical University Nanyang in Singapore: Semiconductor nanoplatelets with a thickness of only a few monolayers could be doped with transition metal ions quite precisely resulting in an extraordinary magneto-optical functionality. The unique architecture of the nanoplatelets allowed to adjust the coupling between magnetic and optical properties and to elucidate the electronic structure of these advanced nanomaterials with exceptional accuracy. These results have been published in the high impact journal Nano Letters.
This publication represents the starting point for an ongoing collaboration between the partners in this fascinating area of research, which will be supported by the Deutsche Forschungsgemeinschaft in the frame of a novel research project granted for 3 years just recently.
F. Muckel et al., Nano Letters 18, 2047 (2018)
Student of NanoEngineering is awarded VDI-Förderpreis
[22.03.2018] Alexander Schmitz was awarded the Förderpreis 2018 by the Ruhrbezirksverein of the Association of German Engineers (VDI) for his master thesis in the NanoEngineering study course. His thesis was written at the institute for Electronic Materials and Nanostructures under supervision of Prof. Gerd Bacher in corporation with the group of Prof. David S. Ginger at the University of Washington. Currently, Alexander Schmitz is working on his PhD thesis on novel optoelectronic materials at the institute for Electronic Materials and Nanostructures in the context of the International Max Planck Research School for Interface Controlled Materials for Energy Conversion (IMPRS-SurMat).
CENIDE Awards for WET Scientists
[16.11.2017] During the annual CENIDE-Meeting several scientists from the chair of Electronic Materials and Nanostructures were awarded with a Best Paper Award and Best Poster Awards. Out of 25 nominees Franziska Muckel and Alexander Schmitz were awarded with the Best Paper Award for their publication Current-Induced Magnetic Polarons in a Colloidal Quantum-Dot Device, a joint publication together with Daniel Gamelin’s group from the University of Washington, Seattle. Bilge Bekdüz and Dominik Andrzejewski were awarded with a Best Poster Award for their posters Graphene growth at low temperatures via chemical vapor deposition and Impact of MOCVD parameters on crystallinity and photoluminescence efficiency in MoS2 monolayers.
UDE researchers win LED Professional Science Award for their “Large-area white light-emission”
[28.09.2017] Dr. Ekaterina Nannen and Julia Frohleiks, who work in the junior research group “Solid State Lighting” at the “Electronic Materials and Nanostructures” group at the University of Duisburg-Essen, combined for the first time yellow LECs with blue light-emitting quantum dots. Quantum dots are colloidal nanostructures with a size of only 5 nanometers, which have exceptional physical and optical properties. The hybrid QD-LEC devices show stable white light emission while maintaining all benefits which are typical for LECs.
For this “remarkable degree of novelty”, the group was awarded with the “LED Professional Science Award” at the leading international lighting technologies event in Bregenz (Austria). The selection committee certifies the results to have a “significant impact on future research and development”.
Nanostructures for innovative lighting
[25.10.2016] Lighting-up a bag‘s interior or illuminating joggers from the darkness: Light-emitting electrochemical cells, LECs, provide significant benefits compared to the well-known LEDs, although appropriate light is still lacking. Up to now, only yellow light-emitting LECs are suitable for application, for white light at least one more color component is necessary. Researchers from the Center for Nanointegration (CENIDE) at University Duisburg-Essen (UDE) were for the first time able to modify specifically the emission color and improve the device performance of the LEC at the same time.
Julia Frohleiks, PHD student in the junior research group of Dr. Ekaterina Nannen, based her idea on semiconducting quantum dots, tiny structures which allow for quantum effects.
Digital Doping of tiny Nanocluster consisting of only 26 atoms
[24.08.2016] Doping of semiconductors (i.e. the intentional incorporation of impurity atoms) allows the precise tuning of the electrical and optical properties, representing the basis of the entire field of micro- and optoelectronics. Upon further reduction of the dimensions approaching the nanometer scale, doping becomes more and more challenging. Reaching the ultimate limit the question occurs, weather single dopants can generate new functionalities – the cutting-edge research area called “Solotronic”. Recently, scientists from the “Electronic Materials and Nanostructures”-group at the University of Duisburg-Essen together with Co-workers from the Soul National University have successfully proven that a single magnetic dopant in tiny nanoclusters – built up of only 26 atoms – generates a pronounced magneto- optical response.