Nitride semiconductors have enabled transformative technologies that have changed the way people live their lives. They are pivotal components of a plethora of optical, electronic, and photonic devices, and their share in the expanding global semiconductor market is growing. Specific technological examples include use as light emitting diodes (LEDs) in solid state lighting, displays and cell phones, and blue to ultraviolet lasers. They also find use in radio-frequency (RF) filters and in bulk and surface acoustic wave resonators and transistor amplifiers in the form of high electron mobility transistors (HEMTs).
The ability to expand the chemistry and functionality of nitride semiconductors opens up new technological platforms. In this talk, I will discuss avenues to enhance the functionality and utilization of the nitride materials family by alloying with novel transition metals to generate novel properties. New technology spaces enabled by magnetic, thermoelectric, and superconducting properties from novel nitride materials will be introduced. A specific focus will be on the aspects of electronic response and implications on polarizability of novel nitrides such as aluminum scandium nitride (Al,ScN) and aluminum boron nitride (Al,BN). Highlights of this work include enhanced piezoelectric response and dielectric permittivity in epitaxial layers, ferroelectric HEMT performance, and ferroelectric behavior below 10 nm thickness at back end of line (BEOL) compatible growth temperatures. This emerging research area capitalizes on significant opportunities for materials discovery, heterostructure design, and device simulation and fabrication.
The Warsaw Doctoral School in Natural and Biomedical Sciences and the Institute of Organic Chemistry PAS cordially invites you to a Advanced Lecture Series.
The talk is given by Prof. Tomáš Šolomek (Van‘t Hoff Institute for Molecular Sciences, University of Amsterdam, The Netherlands).
When and where?
LECTURE SERIES: October 17, 2024 (Thursday) – conference room IOC PAS, Warsaw, Kasprzaka 44/52 2:30 – 4:00 pm, The basics of the electronic structure of organic diradicaloids 4:15 – 5:45 pm, Selected examples of their reactivity accessed by using light or heat Registration at aleksandra.butkiewicz@icho.edu.pl
OPEN LECTURE:October 18, 2024 (Friday) – 10 am – aula IOC/ICP PAS, Warsaw, Kasprzaka 44/52 “Topography and Topology: Unusual Playground for Chromophores”Prof. Tomáš Šolomek
About the lecturer
Tomáš Šolomek was born in Slovakia and chose chemistry as a career due to a passionate chemistry teacher that he had in the high-school. He obtained his Bachelor and Master’s degrees in organic photochemistry at the Masaryk University, Czechia. In 2014, he completed his PhD degree in chemistry under co-tutorship at the Masaryk University (Prof. Petr Klán) and the University of Fribourg (Prof. Thomas Bally), Switzerland, combining experiments and theory to understand the nature of reactive intermediates generated by light or heat. He then became an Experientia Foundation postdoctoral fellow at the University of Basel with Prof. Michal Juríček. From 2015-2017, he was a Swiss National Science Foundation postdoctoral fellow at Northwestern University (USA) in the group of Prof. Michael Wasielewski. Dr. Šolomek founded his independent research group at the University of Basel as a fellow of the Ambizione program of the Swiss National Science Foundation (2018), exploring porous covalent organic cages with built-in photo- and redox-active units. After receiving an ERC Starting grant TOPOCLIP (2021), he became a non-tenure track assistant professor at the University of Bern, where his team worked on the stable molecular representations of topologically complex carbon nanostructures. From January 2023, Dr Šolomek became a tenure-track assistant professor at Van ‘t Hoff Institute for Molecular Sciences in Amsterdam. In his research, Tomáš Šolomek aims to improve the design of more efficient and sustainable organic optoelectronic materials and organic photocages. To accomplish this, he blends the synthesis of organic molecules with the use of spectroscopy and computational chemistry.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001
The continued development of semiconductor lasers in the UV-B (280-320 nm) and UV-C (<280 nm) faces many challenges compared to visible lasers, including high defect densities, low electrical and thermal conductivity, low electrical injection efficiency, low reflectivity mirrors, and higher sensitivity to surface roughness. Despite this, there is a global effort working to tackle these problems and to devise innovative solutions to circumvent the more fundamental material limitations. Thanks to progress in many of these areas we have now seen, in both UV-B and UV-C, the first electrically driven edge-emitting lasers, optically pumped vertical-cavity surface-emitting lasers (VCSELs) and, more recently, optically pumped photonic crystal surface emitting lasers (PCSELs). UV lasers are now on the move.
In this talk I will focus primarily on surface-emitting UV lasers: VCSELs and PCSELs. VCSELs, because of their small active areas (<10 µm diameter), have the potential to deliver optical output powers in the mW range with beam divergence ranging from a few up to 10°, with a low threshold current below 1 mA. PCSELs, on the other hand, are large area devices (>100 µm), resulting in high potential output powers in the Watt range and beam divergence of less than 1°, but with consequently large threshold currents in the range of 1 A. VCSELs and PCSELs have many similarities, notably that they both rely on photonic crystals; a one-dimensional photonic crystal form the distributed Bragg reflector in a VCSEL, while a two-dimensional photonic crystal is employed in a PCSEL. Additionally, both devices require very precise spectral control over the resonance since modal gain strongly depends on the overlap between the gain peak and the sparsely placed modes of low loss. In a VCSEL, this resonance is set by the distance between the DBRs, and in a PCSEL by the photonic crystal parameters.
Here we will show that for VCSELs, using a special lift-off technique based on photo-assisted electrochemical etching, we obtain excellent cavity length control with deviations between devices of <1%. Moreover, in PCSELs, we will demonstrate how we can select the desired lasing mode by controlling the photonic crystal parameters, thereby obtaining high-quality far-fields with beam divergence of <1°. Looking towards electrically driven UV VCSELs, a first step towards overcoming the problem of poor hole conduction and current spreading has been taken in the form of a tunnel-junction based resonant-cavity light-emitting diode, in which a tunnel junction enables the use of an n-doped layer for current spreading on the p-side of the device. Thus, while UV surface-emitting lasers still face significant challenges, they are nonetheless inching closer and closer to becoming technologically and societally useful devices.
About the lecturer
Åsa Haglund’s research interests encompasses III-nitride lasers and light-emitting diodes in the visible and ultraviolet wavelength regions. The focus is on nanostructuring for new optical functionality and thin-film devices realized by electrochemical etching which enables vertical-cavity surface-emitting lasers (VCSELs) and photonic crystal surface-emitting lasers (PCSELs). Åsa has a Master’s Degree in Physics from Gothenburg University and received a PhD degree in Electrical Engineering in 2005 from Chalmers University of Technology. She has been a visiting researcher at Ulm University in Germany and Lund University in Sweden and is since 2018 a Professor at Chalmers University of Technology. She is a recipient of for example the European Research Council’s consolidator grant (2020), the Swedish Research Council’s consolidator grant (2019), and the Swedish Foundation for Strategic Research’s young research leader award (2014).
Studies on the photochemical reactivity and characterization of the primary photoproducts permit a deeper understanding of reaction mechanisms. In this talk, the experimental technique of low temperature matrix isolation allowing to experimentally test the incipient steps of photochemical reactions, and to characterize novel species with unusual functionalities, properties and behavior will be addressed.
We shall start with the fundamentals of the method and show its possibilities in the studies of structure and reactivity at cryogenic temperatures (~10 K). Typically, the molecules are embedded in solid inert matrices (Ar, Xe, N2) and excited in situ either by a broadband light source, such as Hg/Xe lamp, or by narrowband light generated in an optical parametric oscillator or in a diode laser. The structures of reactants and photoproducts are characterized experimentally by infrared spectroscopy and theoretically by computation of vibrational spectra.
The potential of the method will be demonstrated using several conformational studies. Narrowband near-infrared irradiations, tuned at the frequencies of the OH or NH first overtone modes, result in conformational switching. Hereby, it becomes possible to characterize high-energy conformers, not accessible experimentally otherwise, and study processes of intramolecular vibrational energy transfer. The examples will include carboxylic acids, amino acids, nucleobase cytosine, among others. Besides, the isomerizations occurring in matrix-isolated molecules in dark (H-atom and heavy-atom tunneling) and those induced by the light source of the spectrometer will be discussed.
Further examples concern the reactivity induced by frequency-tunable UV light. Here, H-atom transfer reactions, resulting in oxo-hydroxy, amine-imino, thiol-thione isomerism, for phenol, cytosines, thiophenol, and some heterocycles will be described.
In general, this contribution will provide a selection of experimental and computational results, co-authored by the presenter, providing insight into the observed reactivity.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
About the speaker
Igor Reva graduated in Biophysics, with honors, from the Kharkiv State University. Upon graduation, worked for several years as engineer, at the Institute for Low Temperature Physics & Engineering (ILTPE), a major research centre of the National Academy of Sciences of Ukraine (in Kharkiv), where he mastered diverse technical aspects of cryogenic applications.
In 1995, completed a PhD degree in Molecular Physics & Biophysics, at ILTPE.
In July 1997 – September 1999, Igor Reva was awarded a post-doctoral fellowship of the Alexander von Humboldt Foundation at Max-Planck-Institute (MPI) for Radiation Chemistry (Mülheim-an-der-Ruhr, Germany) and MPI for Nuclear Physics (Heidelberg, Germany).
Since October 1999 and until 2020, moved to the University of Coimbra (UC), Portugal, where he worked as: (i) post-doctoral fellow of the Portuguese “Fundação para a Ciência e a Tecnologia” (FCT), (ii) Researcher (FCT program “Science-2007”), (iii) Principal Researcher (program “Investigador FCT”), all above positions at the Centre of Chemistry of Coimbra, Department of Chemistry (DQ) at UC. Since 2021 (till present), Igor Reva works at the Research Centre hosted at the Department of Chemical Engineering (DEQ) at UC. Since 2024, this research centre at DEQ/UC is named CERES (from Portuguese: “Chemical Engineering and Renewable Resources for Sustainability”).
In 2010, the degree of Habilitation in Chemistry was conferred on Igor Reva by UC, with specialization in Molecular Spectroscopy.
The engineering skills and qualification, acquired by Igor Reva at ILTPE, allowed him subsequently to design and construct in Portugal (at DQ/UC) a home-made fully operational experimental setup for matrix-isolation spectroscopy and photochemistry at cryogenic temperatures. This setup is now an integrated part of Coimbra Laser Lab (CLL), hosted at DQ/UC. CLL is a Research Infrastructure of FCT established at UC and is a part of LaserLab Europe – Consortium of European Laser Research Infrastructures (35 organizations from 18 countries). At CLL, Igor Reva provided scientific supervision and technical training for users from +20 countries.
Main specializations of Igor Reva are infrared spectroscopy, photochemistry, photochromic molecules, molecular switches, reactive intermediates, systems with open electronic shells, quantum mechanical tunneling, including their experimental and computational studies.
He participated in +30 competitively funded FCT projects (in 8 as principal investigator). As of September 2024, published +170 articles in peer-reviewed journals, in 1/3 of these Igor Reva is the corresponding author. H-index: 42 (Publons) / 43 (Scopus), with +5 K citations.
Considering the present STER application to NAWA, it should be noted that Igor Reva participated in two bilateral projects with IF PAN, acting as coordinator for the Portuguese side. Each of these two projects lasted two years. Collaborations with researchers from IF PAN resulted in 42 joint peer-reviewed publications.
In recent years, membrane external-cavity surface-emitting lasers (MECSELs) have made rapid progress. A historical introduction will be given. The developments in this field are summarized and discussed, and an overview of the state of the art is given. Key advances, such as radical design simplification, double-side pumping and the ability to scale performance, play a major role. It also discusses the most important aspects of active region membrane design in terms of flexible pumping capabilities enabled by the absence of an integrated DBR and substrate. Specifically, optical pumping of a relative thick membrane will be discussed and the latest results from newly designed broadband structures optimized for a very wide tuning range by employing two different kinds of quantum wells, will be given. The talk will be summarized by a short glimpse into the future about extending this technology to other material systems.
About the lecturer
Dr. Hermann Kahle received his PhD in Physics at the University of Stuttgart, Germany, in 2016. The thesis was performed at the Institute for Semiconductor Optics and Functional Interfaces on the detailed investigation and optimization of red emitting semiconductor disk laser structures. He developed a novel concept – the membrane external-cavity surface-emitting laser (MECSEL) with first double-side diamond cooling implementation. After PhD graduation he moved to Tampere, Finland, where he joined the Optoelectronics Research Centre (ORC) at the Tampere University in 2017. He was granted an Academy of Finland Postdoctoral Researcher position in 2018 and was leading a research team further developing and investigating this novel category of heat spreader sandwiched membrane structures as laser gain elements with optimized cooling and broad tuning until 2022. After a short research stay in 2022 at Kassel University, Germany, he was with the Paderborn University, Institute for Photonic Quantum Systems (PhoQS) in 2023. Since April 2024 he is a Postdoctoral Research Fellow at University of New Mexico in the Department of Physics and Astronomy.
Solitons show up in many fields of physics from the monopoles and models of nucleons in strong interactions, to conducting plastics and novel memory storage devices. However, solitons are largely understood using classical physics. It is widely believed that quantum mechanics qualitatively changes some of their properties, for example causing some to quickly decay. We will describe a new method which allows for an efficient, reliable and complete treatment of solitons in quantum physics.
In the second lecture, we will describe some recent progress in constructing quantum kinks. We will describe how states, decay rates and scattering amplitudes may be found. Also we will introduce oscillons, which are thought to be the dominant degrees of freedom after violent events including some first order phase transitions and inflationary paradigms. We will describe how these new methods may be used to understand whether quantum corrections cause oscillons to decay so quickly that they are phenomenologically irrelevant.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
About the speaker
Jarah Evslin got his Bachelor of Science degree in Math and Bachelor of Science degree in Physics from Caltech in 1997, he got his PhD degree in Physics from the University of California Berkeley in 2001. After that he did his postdocs in Pisa, Trieste and Brussels. Later he became an adjunct professor at the University of Pisa.
Since 2014, he is a professor at the Institute of Modern Physics, Chinese Academy of Sciences. He is the coordinator of the International Science Development Team for Fundamental Physics at the Thirty Meter Telescope. He published 112 papers in refereed journals, plus 1 book chapter and 7 proceedings. In the past, he has studied dark matter, dark energy, string theory, black holes and neutrino physics. For the past 5 years, his research has worked towards understanding why gluons and quarks are always confined in nuclei.
Solitons show up in many fields of physics from the monopoles and models of nucleons in strong interactions, to conducting plastics and novel memory storage devices. However, solitons are largely understood using classical physics. It is widely believed that quantum mechanics qualitatively changes some of their properties, for example causing some to quickly decay. We will describe a new method which allows for an efficient, reliable and complete treatment of solitons in quantum physics.
In the first lecture, classical solitons will be introduced. We will give a brief introduction to different kinds of solitons: kinks, vortices, monopoles and domain walls. We will describe them using classical field theory and note some of their applications in classical and quantum physics.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
About the speaker
Jarah Evslin got his Bachelor of Science degree in Math and Bachelor of Science degree in Physics from Caltech in 1997, he got his PhD degree in Physics from the University of California Berkeley in 2001. After that he did his postdocs in Pisa, Trieste and Brussels. Later he became an adjunct professor at the University of Pisa.
Since 2014, he is a professor at the Institute of Modern Physics, Chinese Academy of Sciences. He is the coordinator of the International Science Development Team for Fundamental Physics at the Thirty Meter Telescope. He published 112 papers in refereed journals, plus 1 book chapter and 7 proceedings. In the past, he has studied dark matter, dark energy, string theory, black holes and neutrino physics. For the past 5 years, his research has worked towards understanding why gluons and quarks are always confined in nuclei.
These days, mankind has been starting to face many difficult issues: energy problems, environmental problems, water problems and so on. It is a common feeling that new advanced materials will play an important role in the current challenge to develop alternative and sustainable energy technologies to reduce our dependence on nuclear and fossil fuels and eliminate greenhouse gas emissions. In particular, superconducting and thermoelectric materials seem fitted to solve the energy puzzle since they can provide efficient energy transport and conversion, respectively.
This presentation will highlight the recent development of highly oriented nanostructured films of superconducting and thermoelectric materials with strongly enhanced properties for sustainable energy applications.
Superconducting bulks and single crystals are quite important for the study of the basic physical properties, however for practical applications, like direct current transportation or winding of magnets, development of superconducting wires and tapes based on thin films technology is strongly required. In the past 20 years, introduction of nanosized Artificial Pinning Centers (APCs) was widely used to strongly enhance critical current (Jc) and global pinning force (Fp) of YBa2Cu3Ox (YBCO, Tc = 92 K) and related superconducting materials in magnetic field. Furthermore, nanoengineering approach to control microstructure, distribution, concentration and dimensionality of APCs represents a powerful tool to understand the pinning mechanisms. Nanosized defects of different dimensionality, called artificial pinning centers (APCs), have been introduced in YBCO films fabricated by pulsed laser deposition (PLD). At first, by ablation of mixed BaSnO3-YBCO targets with increasing BSO content (2~9 wt%), we obtained high quality YBCO thin films incorporating BSO in form of nanorods, which are classified as one-dimensional APCs (1D-APCs). YBCO films added with 4 wt% BSO have isotropic Jc = 0.3 MA/cm2 and FpMAX = 28.3 GN/m3 (77K, 3T, B//c) [1], twice of the performance of conventional Nb3Sn superconductor at 4.2K. Secondly, we tried the incorporation of Y2O3 nanoparticles (three-dimensional APCs, 3D-APCs) inside the YBCO film, using surface-modified YBCO targets. Randomly distributed Y2O3 particles, which density was proportional to the area of sector, were incorporated in YBCO films. Consistent with the microstructure, Jc was isotropic. The 5.44 A% Y2O3 added sample presented FpMAX =14.3 GN/m3 (77K, 3T, B//c)) The single vortex dynamics model was used to account for vortex pinning in the samples [2]. Ultimate approach was combination of advantages of 1D- and 3D-APCs pinning, with coexistence of BSO nanorods and Y2O3 nanoparticles. Best result was obtained with the combination [(90 nm YBCO+BSO)/(30 nm YBCO+Y2O3)]×3 presenting FpMAX =17.6 GN/m3 (77K, 2.2T, B//c). Co-existence of random and correlated pinning in the periodically structured 1D+3D APCs-added YBCO films can be discussed on the bases of the global pinning models [3].
Thermoelectrics can convert heat into electrical energy. Efficient, small and light thermoelectric modules are fundamental to recycle waste heat from industrial plant, cars, or even domestic stoves and human body heat.
The nanostructuration of thin films and the introduction of artificial nanodefects has just recently recognized as crucial for the improvement of the performance of thermoelectric thin films, leading to depressed thermal conductivity by enhanced phonon scattering and consequent improved figure of merit ZT. Highlights of the research are: insertion of hydroquinone nanolayers in Al-doped ZnO (AZO) films prepared by atomic layer deposition (ALD): kALD (300 K) = 3.56 W/m×K [4]; addition of polymethylmethacrylate (PMMA) particles to AZO films prepared by multi-beam multi-target matrix-assisted PLD (MBMT/MAPLE-PLD): kMAPLE (300 K) = 5.9 W/m×K and ZTMAPLE (600 K) = 0.07 [5]; formation of nanopores in AZO films prepared by Mist-Chemical Vapor Deposition (Mist-CVD): kporous (300 K) = 0.60 W/m×K and ZT porous (300 K) = 0.06 [6]; dispersion of Al2O3 nanoparticulate in AZO films prepared by surface-modified target PLD: knanoAl2O3 (300 K) = 3.98 W/m×K and ZTnanoAl2O3 (600 K) = 0.0007 [7]. Overall, 1/10 ~1/100 depression of k and 3~5 times ZT enhancement with respect to the typical bulk AZO values was achieved.
In conclusion, these results clarify the crucial role of nanosized artificial defects in the improvement of performance of superconducting and thermoelectric thin films and put in evidence the promise of nanostructured films for future wide-scale energy applications.
References
[1] P. Mele K. Matsumoto, T. Horide, A. Ichinose, Y. Yoshida, M. Mukaida, S. Horii, R. Kita, Supercond. Sci. and Technol.. 21 (2008) 032002; [2] P. Mele, R. Guzman, J. Gazquez, T. Puig, X. Obradors, S. Saini, Y. Yoshida, M. Mukaida, A. Ichinose, K. Matsumoto, M. I Adam. Supercond. Sci. and Technol., 28 (2015) 024006; [3] P. Mele, M. I. Adam, T. Suzuki, Y. Yoshida, S. Awaji, A. Ichinose, S. Saini, A. K. Jha, K. Matsumoto, Sci. Adv. Mat. 6 (2017) 1042; [4] Tynell, T., Giri, A., Gaskins, J., Hopkins, P. E., Mele, P., Miyazaki, K., & Karppinen, M. J. Mater Chem. A 2 (2014) 12150; [5] A.M. Darwish, A. Muhammad, S.S. Sarkisov, P. Mele, S. Saini, J. Liu, J. Shiomi, Composites Part B: Engineering 167 (2019) 406; [6] S. Saini; P. Mele; T. Oyake; J. Shiomi; J. Niemelä; M. Karppinen; K. Miyazaki; C. Li; T. Kawaharamura; A. Ichinose; L. Molina-Luna, Thin Solid Films 685 (2019) 180; [7] P. Mele et al., in preparation
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
The talk is given by Dr. Sérgio Nuno Canteiro de Magalhães (IPFN, Instituto de Plasmas e Fusão Nuclear, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal).
When and where?
25th June 2024, 10:30 am at the IP PAS Auditorium, duration: 45 min + question time
Recent progress in the growth techniques makes it possible to fabricate low-dimensional structures, e.g., thin films (planar multilayers), mesoscopic structures and nanostructures (lateral surface and multilayer gratings, quantum wires and dots). The opto- and micro-electronics are among the fields where the resulting novel properties of homo(hetero)-epitaxial growth of semiconductors are more significant. The optimization of the fabrication process and the physical understanding of the samples requires non-destructive structural studies of the materials. Improving the properties of the as-grown quantum materials is also fundamental from the point of view of the Nanotechnology. An example of controlled process to change the properties of materials is the ex-situ incorporation of ion species. The possibility to control dopant concentrations, depth profiling and the high purity through mass selection turn ion implantation into a silicon industry ready-to-use tool. However, the stochastic nature of the process in which energetic ions collide and penetrate the semiconductor, results in lattice damage. Although the crystal degradation is partially reversed after thermal or pressure annealing’s, vacancies and point defects introduced and rearranged after annealing create a strain field which does not disappear completely. Complementary to the direct local probing methods (atomic force microscopy, transmission electron microscopy (TEM), high angle annular dark field (HAADF) or phase analysis to determine the strain in quantum materials), the X-ray elastic scattering methods probe locally the reciprocal space, thus providing relevant information about the statistical properties of the structural parameters averaged over a large volume of a sample. X-ray diffraction (XRD) and reflectivity (XRR) in the specular and non-specular geometries are relevant techniques for these structural studies of both crystalline and amorphous systems. They are highly sensitive to the distribution of the lattice parameters (diffraction) and refractive index (reflectivity). This presentation explores the synergy between ion beam implantation and X-ray scattering techniques to advance the understanding of implanted crystalline materials. Several examples of implanted single and polycrystalline crystals will be presented following by an overview of the required theoretical principles underlying both techniques. To predict the decrease of the crystalline induced by the ion implantation, a new approach to the interpretation of the diffraction data of implanted crystals will be presented. The novel methodology considers the effects of the variations of the atom’s positions in the lattice instead of employing the static Debye-Waller, strictly related to thermal vibrations. The new method, supported by preliminary molecular dynamics simulations, is tentatively applied to chromium implanted Ga2O3 and carbon implanted 4H-SiC bulk-crystals and to argon implanted GaN thick layers grown by MOCVD on sapphire-c substrates. Finally, a brief description of the MROX software, acronym for Multiple Reflection Optimization package for X-ray scattering used to simulate the XRD data, is highlighted.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
About the speaker
Sérgio Nuno Canteiro de Magalhães (ORCID number: 0000-0002-5858-549X; Web of Science ResearcherID: A-6709-2018) is a DL57 researcher under the 16/IPFN contract at Instituto Superior Técnico in Lisbon, Portugal. This contract was awarded for the development of models aimed at studying the effects of ion-implanted nano-materials using X-rays and ion beams.
Sérgio Magalhães’s journey into the realm of crystal growth began with the exploration of recent advancements in techniques, which have revolutionized the creation of low-dimensional structures. These structures, encompassing thin films, mesoscopic forms, and nanostructures, hold immense significance for Condensed Matter Physics, particularly in opto- and micro-electronics. Their uniqueness stems from the epitaxial growth of semiconductors, facilitated by cutting-edge crystal growth methods.
Sérgio Magalhães’s fascination with enhancing the attributes of these materials led to delve into the realm of Nuclear Sciences. Here, Sérgio Magalhães discovered the pivotal role of controlled processes in modifying materials, particularly through ex-situ incorporation of ion species. This method allows for precise manipulation of dopant concentrations, depth-profiling, and ensuring high purity through mass selection, thereby positioning ion implantation as a key tool for integration into the silicon industry. However, the journey is not without its challenges. On the on hand, the stochastic nature of ion implantation brings forth lattice damage as energetic ions interact and penetrate the semiconductor lattice. While thermal or pressure annealing offers partial relief, the introduction of vacancies and point defects during this process leaves behind residual strain fields that persist beyond annealing. On the other hand, the advanced measurements acquired from X-ray scattering and ion beam techniques demand equally sophisticated computer software tools to simulate their data. In response to this need, the MROX (Multiple Reflection Optimization) package for X-ray diffraction/reflection software has been recently developed. It should be emphasized that program made by Sérgio Magalhães allows to simulate XRD data of advanced semiconductor structure systems (superlattices, nanowires, quantum-dots, thin layers, ion implanted structures) what is impossible in commercial available XRD software. Already, MROX program has been credited in 16 research manuscripts published in reputable international peer-reviewed journals. Driven by the quest to unravel these complexities and enhance material properties, Sérgio Magalhães embarked on a mission to conduct non-destructive structural investigations. Leveraging X-ray and ion beam techniques, Sérgio Magalhães’s goals are to gain deeper insights into the mechanisms of damage accumulation in crystals. The success has been bolstered by over 60 research publications, facilitated by numerous international collaborations, including partnerships with esteemed institutions such as the Institute of Physics at the Polish Academy of Sciences.
In the first part, the talk will focus on capillary rise mechanisms in heterogeneous porous material with different capillary sizes. Both theoretical and experimental work are performed to investigate the time evolution and the exchange at the interface of different porous media. It contains the homogeneous capillary (without layer exchange), which is presented to distinguish the different characteristic times and the liquid capillary rise regimes. Considering gravity effect, shear stress and inertia, three regimes are distinguished theoretically and experimentally based on these two dimensionless parameters (Bo and Ga). Theoretical analysis and simulation results show the capillary rise in tendency and the appearance of oscillatory phenomenon. The heterogeneous porous media are also investigated. A multilayer domain is adopted to model the multiple distribution in capillary sizes. The interaction between these layers (different equivalent capillary sizes) demonstrate how the cooperation appears in nature so as to fit with the optimal situation of fast filling the porous media or the equivalent in drying. Experimental results on both homogeneous and heterogenous cases have a favorable effect on the imbibition enhancement. In the second part, the talk will complete with the local and global evaporation in such complex porous media.
This event is supported by the Polish National Agency for Academic Exchange, grant no. BPI/STE/2021/1/00034/U/00001.
About the speaker
Prof. Dr. Ing. Rachid BENNACER: is an Engineer in Mechanical field (1989), and he got his PhD thesis at Pierre et Marie Curie University (Paris 6) in 1993. He worked as lecturer in the University Paris XI (1993/94), became an associate professor at Cergy Pontoise University in 1994 and full Professor in 2008. He moved as senior Professor to the prestigious school Ecole Normale Superieure (Paris-Saclay) since 2010. He becomes in 2017 an Exceptional National Class Professor. He is also adjunced professor at Tianjin Uni. Of comm. (China) and UMB Univ. He assumed several responsibilities, director of the LEEVAM research team (2003-2007), Licence degrees & Aggregation title (2008-2011), Master research degree (2011 2013), Transfer and Environmental Research Unit (CNRS LMT-Lab) (since July 2012), dean of Civil/Environmental department (Oct. 2012/Sep. 2016) and 2019/2023 Coordinate International Affairs Related to Ph.D Univ. Paris-Saclay; President of ENS Paris-Saclay Special Executive committee and vice Dean of the ISI Graduate school. His present research activity is within the LMPS laboratory. His Research field covers wide spectrum and several domains. It covers the building material for energy applications or on durability aspect, renewable and energy system. The expertise covers the direct numerical simulation including CFD coupling on multi-scales. The previous approach is consolidated by analytical or reduction approach in order to identify the instabilities and global behavior bifurcation and similarity controlling parameters in multiphysics situations. He published around 10 book chapters and more than 300 referenced international journals (Rank A).
