Hamaguchi Laboratory

Our recent focus in research is on plasma-material interactions in general, including their industrial applications. The aim of research is to understand fundamental mechanics of plasma-material interactions under various conditions. To achieve this, we combine plasma/beam experiments with numerical simulation/modeling. More specifically our current research topics include 1) etching, deposition, and surface modification processes for micro/nano electronics device manufacturing, 2) surface modification and functionalization of biomaterials by plasmas, 3) processing of water and biological systems by atmospheric-pressure plasmas mainly for applications in plasma medicine and plasma agriculture, and 4) dynamics and chemical reactions in plasmas under various conditions, including atmospheric-pressure plasmas.

If you are interested in our research, please feel free to contact me.

Satoshi Hamaguchi
Professor, Center for Atomic and Molecular Technologies, Osaka University.


Events & News

JVST A cover art
A figure in a paper by Dr. Nicolas Mauchamp and Prof. Satoshi Hamaguchi was adopted as a cover art of JVST A.
See here.
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The 2nd Workshop on Artificial Intelligence in Plasma Science (WAIPS-2) will be held in France (on-site and online).: website
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Japan-RUB workshop was held (weekly seminars).
Lab Hiking: Mt. Katsuragi (Osaka & Nara)
We went to Mt. Katsuragi on the border between Osaka and Nara prefectures.
Graduation Ceremony
Erin-san, Hirata-san, and Nina-san successfully passed their graduation exams.
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The 1st Workshop on Artificial Intelligence in Plasma Science (WAIPS-1) was held in France (on-site and online).: website

CAMT Seminars

If you are interested in attending the seminars, please contact us.

"Multi-Ion Species Plasmas and the Bohm Criterion"
Prof. Dr. Uwe Czarnetzki
Ruhr-Universität Bochum, Institut für Experimentalphysik V: Plasma- und Atomphysik, Bochum, Germany
Date: (Fri) 16:00-17:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Plasmas containing a single ion species are rather well understood. A convenient description can be provided in the frame of fluid dynamics under the additional assumption of quasi-neutrality. The latter assumption eliminates access to the natural boundary conditions at the wall. However, an effective new boundary condition is included in the fluid equations since all derivatives diverge when the ions reach their sound speed. This divergence marks the breakdown of the quasi-neutrality assumption. Conditions in plasmas containing multiple ion species are less obvious. As was shown by Benilov, also here a divergence exists. However, this divergence provides only one condition while N>1 conditions for the ions are required. These conditions will be derived. A fully-self consistent calculation requires in addition also calculation of the N ionization rates. Further, the relative plasma densities are calculated. The concept introduced here is quite recent and still in progress. Comments are very welcome.

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"Machine learning plasma-surface interactions: from low to high fidelity surrogate models"
Prof. Dr.-Ing. Jan Trieschmann
Christian-Albrechts-Universität zu Kiel, Kiel, Germany
Date: (Wed) 16:00-17:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Many technological applications of low-temperature plasmas (LTPs) rely on the interaction of the plasma with the surrounding walls. Whereas plasma-surface interactions (PSIs) may be described by surface coefficients (e.g., emission), these are often effective, averaged over various physical processes. Detailed knowledge on the surface kinetics may be obtained by sophisticated diagnostics, modeling, or a combination. These are often limited due to acquisition or computational requirements. Moreover, a comprehensive understanding of LTPs and related PSIs must be inherently multi-scale. This holds specifically for plasma modeling, where a consistent description requires sub-models on individual levels. In this work, the applicability of machine learning surrogate models to depict PSIs is discussed in the context of metallic thin film sputter deposition. Different surface models are assessed in terms of quality and abundance of data, as well as reliable physical descriptors. Lower physical fidelity data based on the transport and range of ions in matter simulations provide insight into the steady surface state; higher physical fidelity reactive molecular dynamics data capture also the dependence of a changing surface state. Both data sets are exploited for the training of corresponding machine learning models. The applied model architectures – based on artificial neural networks – are reviewed and the resulting prediction metrics are assessed. It is concluded that the obtained data-driven surrogate models entail the fidelity of the original physical models. They allow for a reliable and consistent multi-scale model coupling at significantly reduced computational costs. Envisioned applications of this modeling procedure include different plasma processes, materials, and phenomena (e.g., plasma catalysis).

Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 138690629 (TRR 87) and Project-ID 434434223 (SFB 1461).

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"Current research at the Institute of Plasma and Atomic Physics at Ruhr University Bochum"
Prof. Dr. Uwe Czarnetzki
Ruhr-Universität Bochum, Institut für Experimentalphysik V: Plasma- und Atomphysik, Bochum, Germany
Date: (Thu) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Recent research at the Institute for Plasma and Atomic Physics at Ruhr University Bochum (RUB) is introduced. Particularly, four research topics are discussed in more detail. These topics range from plasmas at low pressure (p < 1Pa) to atmospheric pressures and include experimental as well as theoretical aspects: 1) The inductively coupled array (INCA) discharge, 2) Describing local and non-local electron heating described by the Fokker-Planck equation, 3) Enhanced dynamic range for ion retarding field energy analyzers (RFEA), 4) ns-pulsed atmospheric pressure discharges (jets) in nitrogen and CO2 - the latter topic includes also a wide range of different diagnostics (EFISH, CARS, QCLAS, OES, V/I), PIC/MCC simulation, and modelling. The intention is to provide an overview and not an in-depth discussion of these topics. However, questions and comments are be welcome at any time during my present stay at Osaka University.

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"The role of reactive oxygen and nitrogen species on the conversion of volatile organic compounds in a twin surface dielectric barrier discharge"
Dr. Lars Schücke
Ruhr University Bochum, Bochum, Germany
Date: (Tue) 16:00-17:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
A twin surface dielectric barrier discharge (SDBD), specially designed for the conversion of VOCs in synthetic air, has been previously studied regarding its fundamental plasma parameters, power efficiency, gas phase chemistry, gas dynamics, and conversion of frequently used hydrocarbons with and without catalyst [1-3]. However, the complex interaction of the different media and the underlying conversion mechanism is not yet fully understood.
Here, techniques such as flame ionization detectors and gas chromatography-mass spectrometry are used to gain insight into the occurring gas-phase chemistry, possible reaction pathways, and advantages of the presented discharge over comparable techniques. Optical absorption spectroscopy is used to measure absolute densities of selected reactive oxygen and nitrogen species to further elucidate the conversion mechanism based on these radicals. A mode-transition effect, also known from literature [4], can be observed for different volumetric flow rates and be replicated in both, the experiment and a complementary zero dimensional chemistry model. Finally, flow analysis by schlieren imaging is performed to illustrate the comparably high performance of the system, despite the low plasma to surrounding gas ratio.

  • [1] B. Offerhaus et al., Plasma Processes and Polymers 14 (2019).
  • [2] L. Schücke et al., Plasma Sources Science and Technology 29 (2020).
  • [3] N. Peters et al., Plasma Processes and Polymers 18 (2021).
  • [4] T. Shimizu et al., New Journal of Physics 14 (2012).

*This study was funded by the German Research Foundation (DFG) with the CRC 1316 project A7.
*Co-authors: Arisa Bodnar, Niklas Friedrichs, Alexander Böddecker, Niklas Peters, Andrew R. Gibson, Martin Muhler and Peter Awakowicz

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"Introduction to Convolutional Neural Network (CNN)"
Dr. Nathaniel Saura
CNRS-Aix Marseille University, Marseille, France
Date: (Fri) 14:00-15:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
During the last decade, Convolutional neural networks (CNN) have revolutionized the already prolific Artificial Intelligence field, surpassing classical neural networks in most applications including face recognition, classification, clustering, and so on. Properties like parameter sharing ensure this great accuracy while decreasing the needed number of parameters and computation time. In this introductory talk, we'll try to give a comprehensive view of the CNN basis as well as principal blocks, connections, and components. From there, the most known architectures will be presented. This talk will end with examples of how modern blocks can improve the aforementioned architectures. From mathematics background to recent CNN's components, efforts have been made to give interpretations and intuitive explanations.

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"Multifunctional Amine Plasma Polymers as Bioactive Surfaces"
Prof. Lenka Zajíčková
Department of Physical Electronics, Faculty of Science, CEITEC, Masaryk University, Brno, Czech Republic
Date: (Wed) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
In PECVD (plasma polymerization being a part of it), we have many knobs: reactants (gas feed) and discharge characteristics (type of discharge, substrate potential, pressure, power, pulsing). Comparison of the film properties for one of the usual varied parameters such as discharge power can be difficult. Considering the most used discharge, the low-pressure RF CCP, the questions remain about the role of ions, their energy, density, and chemistry in the particular experiment. The comparison among the experimental set-ups is hindered by the varied substrate potential and the pressure (collisional / collisionless regimes) or not well-defined transitions between the discharge modes (CCP/ICP or α/γ of CCP). In my talk, I will present our results on plasma polymerization of cyclopropylamine (CPA) mixed with Ar in three different CCP reactor set-ups and compare them with other experiments to prepare amine plasma polymers. I will show the variations of the film chemistry (nitrogen percentage, NH2 groups, nitriles etc.) and discuss the question of different observed trends with increasing discharge power. Based on a usual film characterization (e. g., XPS, FTIR), without testing a specific function, it is hard to say what films are the best for the intended application. Thus, I will try to answer the question if we optimize the film properties to the right values.

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"Atmospheric pressure plasma for bio-coating and fundamental introduction of plasma medicine"
Prof. Yun-Chien Cheng
Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Taiwan
Date: (Fri) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
This talk includes a basic introduction to the plasma-related medical applications that are currently in use, including argon plasma coagulation (APC), sterilization, and surface modification. My work about plasma polymerized coating for biosensor fabrication will also be reported. The aerosol-assisted dielectric-barrier-discharge atmospheric-pressure plasma deposition (AAAPPD) involves depositing plasma-polymerized ethylene (ppE) with grafted hydroxyl functional groups and embedding the protein in the ppE in one step, making the protein entrapment faster than conventional methods and without using reagents. The immunostaining result of AAAPPD protein was close to that of covalent-bonded protein. This method is a rapid and reagent-free method to entrap proteins on different substrates for biosensor fabrication.

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"Atmospheric pressure plasma for cancer therapy, plasma equivalent circuit, and plasma current classification II"
Prof. Yun-Chien Cheng
Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Taiwan
Date: (Fri) 15:00-16:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
This is the sequel to the seminar presented last week. that we started last week will continue in this seminar. As we discussed last week, we compared the effects of plasma with thermal therapy on lung cancer with malignant pleural effusion. This study finds out that the plasma can selectively kill lung cancer cells and the benign cells remain its viability. Besides, thermal therapy kills both cancer cells and benign cells. To investigate what is the plasma factor that inhibits cancer cells, we investigated the effects of plasma-generated short-lived species, long-lived species, and electric fields on skin melanoma and basal cell carcinoma cells (A2058 cells, BCC cells) and normal cells (BJ cells, Detroit 551 cells) and found that the short-lived species do make selective inhibition to the benign and malignant cells. The second part of my study is that we mix water aerosol with plasma jet at downstream region makes the plasma jet generate more • OH. We designed different mixing chambers and adjusted the water aerosol flow rate to maximize the • OH generated by plasma jet for biological applications. We also constructed an impedance matching circuit for a partial-discharge calibrated (PDC) atmospheric-pressure plane-to-plane DBD equivalent circuit. The last part of my work is that we used machine learning to distinguish the discharge current of different plasma. The plasma discharge can be different depending on the conditions, and the resulting discharge current has quite different electrical features. Hence, a real-time and cost-effective diagnosis of atmospheric-pressure plasma discharge can be possibly provided via the current classification with deep learning models.

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"Atmospheric pressure plasma for cancer therapy, plasma equivalent circuit, and plasma current classification"
Prof. Yun-Chien Cheng
Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Taiwan
Date: (Fri) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
We compared the effects of plasma with thermal therapy on lung cancer with malignant pleural effusion. This study find out that the plasma can selectively kill lung cancer cells and the benign cells remain its viability. Besides, the thermal therapy kills both cancer cell and benign cells. To investigate what is the plasma factor that inhibits cancer cells, we investigated the effects of plasma-generated short-lived species, long-lived species, and electric fields on skin melanoma and basal cell carcinoma cells (A2058 cells, BCC cells) and normal cells (BJ cells, Detroit 551 cells) and found that the short-lived species do make selective inhibition to the benign and malignant cells. The second part of my study is that we mix water aerosol with plasma jet at downstream region makes the plasma jet generate more • OH. We designed different mixing chambers and adjusting the water aerosol flow rate maximize the • OH generated by plasma jet for biological applications. We also constructed an impedance matching circuit for a partial-discharge calibrated (PDC) atmospheric-pressure plane-to-plane DBD equivalent circuit. The last part of my work is that we used machine learning to distinguish the discharge current of different plasma. The plasma discharge can be different depending on the conditions, and the resulting discharge current has quite different electrical features. Hence, a real-time and cost-effective diagnosis of atmospheric-pressure plasma discharge can be possibly provided via current classification with deep learning model.

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"Graphene multiscale temporal evolution investigated with an Innovative setup for fundamental studies of plasma-surface interactions"
Dr. Pierre Vinchon
Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Japan
Date: (Tue) 14:00-15:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
During deposition, modification, and etching of thin films and nanomaterials in reactive plasmas, a large number of active species can interact with the sample simultaneously. This includes reactive neutrals created by fragmentation of the feed gas, positive ions and electrons created by electron-impact ionization of the feed gas and fragments, excited states (in particular the long-lived metastable species), and UV photons due to the spontaneous de-excitation of excited atoms and molecules. In order to provide insights into the dominant role of each active species in specific plasma-based processes of advanced materials, a unique system has been established combining beams of neutral atoms, positive ions, UV photons and a magnetron plasma. Furthermore, this setup is equipped with a unique ensemble of in plasma surface characterization tools. The reactor chamber is attached to an ion beam line of a 1.7 MV Tandetron accelerator generating a beam at grazing incidence that allows Rutherford Backscattering Spectrometry (RBS) to be carried out at high resolution near the surface. Elastic recoil detection (ERD) can also be used for standard ERD detection of H, but high resolution of surface H is available through nuclear reaction analysis. It In parallel, an optical port facing the substrate allows to perform Raman spectroscopy of the samples during plasma modification of the substrate. This system enables fast monitoring of a given Raman peak over nine points scattered on a surface of 2 mm2 without inter­ference from the light emitted by the plasma. An example of a possible experiment involving monolayer graphene will be presented. Raman measurements in real-time shed light on the influence of low-energy ions on monolayer CVD graphene and how self-healing takes place immediately after irradiation. The mechanism responsible will be also be detailed to show that carbons adatoms resulting from vacancy creation are essential for graphene self-healing.

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"Fundamental study of plasma-graphene interactions in Argon/B2H6 plasmas"
Dr. Pierre Vinchon
Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Japan
Date: (Wed) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Raman spectroscopy is an efficient method to characterize the graphene structure. The technique gives distinctive features for pristine, damaged, and even doped graphene. Nonetheless, especially when graphene is grown on a polycrystalline substrate, strong discrepancies may appear on the macroscopic scale. Moreover, in the case of plasma irradiation of graphene, it is essential to understand the impact of the small heterogeneities in pristine graphene (local defects, grain boundaries, etc.) on the resulting graphene structure after treatment. Hyperspectral Raman Imaging (RIMA for Raman Imaging) is a powerful method enabling the capture of qualitative as well as quantitative data on a macroscopic scale. Grain Boundaries (GBs) reveal themselves being more resistant to plasma treatment than pristine graphene domains. After careful consideration of Raman parameters, it appears clearly that preferential self-healing of GBs and its surrounding is taking place, a phenomenon observed in 3D materials, yet to be observed in graphene. This mechanism is governed by carbon adatoms generated from impacts of low-energy argon ions with graphene film. Under constant irradiation from exited species (ions, metastable, VUV photons), carbon adatoms can easily migrate on graphene surface and, in particular, alongside GBs. Hence, defects created at GBs or present nearby might be healed by the adatoms influx. Furthermore, another plasma conditions shown that energy fluence from Argon metastable deexcitation can be linked to an enhanced defect migration and self-healing at GBs [4]. Finally, the previous study in Argon plasma enables the determination of ideal operating conditions for Argon plasma with B2H6 trace. The exposition of graphene to such plasma reveals boron in-plane substitution combined with low-level hydrogenation and defect generation.

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"Prosumer Coalitions With Energy Management Using Cooperative Game Theory"
Prof. Sadruddin. Benkadda
CNRS-Aix Marseille University, Marseille, France
Date: (Mon) 11:00-12:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Integration of distributed renewable generation technologies is an important issue in power networks. Distributed energy storage (ES) systems, although seen as a tool to mitigate the stress on local networks, tend to be operated only to minimize the energy cost of their direct owner. In this talk, cooperative game theory together with Artificial Intelligence tools is used to construct an energy grand coalition, in which ES system operations are optimized to minimize the coalitional energy cost.

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"The Elucidation of Cu-Zn Surface Alloying on Cu(997) by Machine-Learning Molecular Dynamics"
Mr. Harry Handoko Halim
Department of Precision Engineering, Graduate School of Engineering, Osaka University, Japan
Date: (Tue) 14:00-15:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
The structure and the formation process of a Cu-Zn surface alloy formed on Cu(997) were investigated by machine-learning molecular dynamics (MLMD). The force-field required in the MD simulations is built by means of Gaussian Process (GP) regression aided with an on-the-fly active learning scheme. The simulation reveals a detailed atomistic picture of the long-time scale formation of Cu-Zn alloy on Cu(997) surface which was intractable in experiments. The surface alloying is initiated at the terrace near the step edge, highlighting the importance of step edges in the surface alloying. The rationalization of alloying behavior is performed based on statistics and activation energies of various elementary events that occur during the simulations. The dominant alloying mechanisms are found to be hopping descend and exchange descend near the step edge.

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"Nanoparticle scaffolds for multilayered Si-based Li-ion battery anodes"
Dr. Panagiotis Grammatikopoulos
Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Japan
Date: (Thu) 14:00-15:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
As mentioned in the Nobel Prize in Chemistry 2019 press release: “Lithium-ion batteries have revolutionised our lives… They have laid the foundation of a wireless, fossil fuel-free society, and are of the greatest benefit to humankind.” With this in mind, we (i) identified an optimised building block for our previously reported multi-layered Si-based Li-ion battery anodes [1], (ii) built it with a cheap, one-pot, green, and scalable cluster beam deposition method, and (iii) elucidated with large-scale atomistic computer simulations the underlying physical mechanism leading to its superior mechanical and electrochemical performance.
The Nano-Vault is a novel sculptured-thin-film nanostructure synthesised with the help of nanoparticles grown and deposited in the gas phase [2]. The name alludes to the civil engineering definition of a multi-arch structure sustained on columns, characterised by its high elastic modulus. As a result, Si anodes in Li-ion batteries with vaulted structures simultaneously show high mechanical stability and low lithium consumption during formation of solid electrolyte interface, addressing the two main challenges for Si anode commercialisation. This optimal electrochemical performance is associated with a distinct transition in mechanical behaviour at the exact moment when individual Si columns merge to form closed arches (but not beyond that point, with further growth of amorphous Si film on top).
The introduction of nano-vault and arch action brings many new possibilities in the design of new materials for batteries, but also, potentially, for other applications in which the surface is under variable and strong stress action.

References
  1. M. Haro, V. Singh, S. Steinhauer, E. Toulkeridou, P. Grammatikopoulos, M. Sowwan, Adv Sci 4 (2017) 1700180 (10pp)
  2. M. Haro, P. Kumar, J. Zhao, P. Koutsogiannis, A.J. Porkovich, Z. Ziadi, T. Bouloumis, V. Singh, E.J. Juarez-Perez, E. Toulkeridou, K. Nordlund, F. Djurabekova, M. Sowwan, P. Grammatikopoulos, Commun Mater 2 (2021) 16 (10pp)

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"Introduction to Nanoparticle Science"
Dr. Panagiotis Grammatikopoulos
Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Japan
Date: (Tue) 14:00-15:00 (JST)
Location: Main Conference Room (1st floor), Bldg. A12, Suita Campus, Osaka University
Webex Online Conference available

Abstract
Smoke from a fire; a stormy cloud: both naturally occurring phenomena due to aggregation of molecules from the gas phase. In this seminar we will focus on a special type of “cloud”, that of inorganic nanoparticles grown from some sort of physical vapour deposition (PVD) method. To design and fabricate sophisticated nanoparticles for specific (nano)technological applications, molecular dynamics simulations offer an invaluable tool, as they can probe various simultaneous processes during nucleation and growth in atomistic detail. Nanomatter can be dramatically different from bulk matter, as physical properties do not always scale down to the nano-regime. Why? Which fundamental properties showcase this difference? In this seminar we will also identify some cases where nanomatter behaves “weirdly” (i.e., differently from our every-day experience), and choose one as the most characteristic; we will also try to understand why.

Learning objectives
  1. In silico observation of nucleation & growth processes
  2. Understanding of physical mechanisms of gas aggregation (e.g., cloud formation)
  3. Examples of physical properties that differentiate nanoobjects from bulk, everyday objects.

Keywords: atomistic modelling, nanoparticles, cluster beam deposition, nucleation & growth, magnetron sputtering

[1] P. Grammatikopoulos, Current Opinion in Chemical Engineering, 2019, 23, 164.

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PiAI Seminars

Seminar Series on "Physics informed Artificial Intelligence in Plasma Science"
For more information, please see here .