Dielectric and IR spectroscopy
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THz science and technology
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Light and neutron scattering
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Theory and simulations |
Solid-state materials science
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Liquid crystals |
About us
Main activities of Department of Dielectrics cover experimental and theoretical investigations of high-permittivity insulators like liquid crystals, ferroelectrics, multiferroics, piezoelectrics, semiconductor nanostructures, and low-loss materials.
- Dielectric and IR spectroscopy
- THz science and technology
- Light and neutron scattering
- Theory and simulations
- Solid-state materials science
- Liquid crystals
The most significant fresh scientific results of our deparment are listed in the section Highlights.
Karel Tesař received the Stanislav Hanzl award
Karel Tesař, a PhD student at the Department of Dielectrics and at the Faculty of Nuclear Sciences and Physical Engineering, won the Stanislav Hanzl award which is presented to best students of the Czech Technical University in Prague on the occasion of the International Student Day (on November 17, 2022).
The aim of the Stanislav Hanzl award is to reward students for their excellent results in studies and scientific, professional and other important student activities. The award was presented to nine students in the Bethlehem Chapel by the rector of the Czech Technical University (CTU) in Prague, doc. RNDr. Vojtěch Petráček, CSc., and doc. Antonín Pokorný, Chairman of the Board of Trustees of the Stanislav Hanzel Foundation.
The Stanislav Hanzl Foundation was founded in 1997 in honor of the first rector of the Czech Technical University (CTU) in Prague after November 1989, prof. Ing. Stanislav Hanzl, CSc. Professor Hanzl served as rector until his death in June 1996. The aim of the endowment fund is to support studies and students of study programs accredited at the faculties and university institutes of CTU in Prague. The fund receives financial resources in the form of subsidies, donations and contributions from collaborating organizations, businesses, and professional associations as well as individuals, especially former students - graduates of the faculties of CTU in Prague.
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Best three places in the FZU Photo Competition 2022 taken by our department
Alexey Bubnov won the
FZU Photo Competition 2022.
by his beautiful image of liquid crystal texture.
Manas Ranjan Parida received the 2nd place for his SEM image of V2O5 nanoflower,
Fedir Borodavka & Vladimir Pushkarev got the 3rd place for their artistic picture of a superlattice roll.
Best photos from Department of Dielectrics placed in top ten of the FZU Photo Competition 2022:
1st place, Alexey Bubnov: Observing liquid crystal textures in polarized light microscope.
2nd place, Manas Ranjan Parida: Scanning electron microscope image of V2O5 nanoflower.
3rd place, Fedir Borodavka & Vladimir Pushkarev: Artistic picture of a PbTiO3/SrTiO3 superlattice roll under a laser beam combining various experimental data (Raman, GPA, SXOM, and PFM maps).
4th place, Alexey Bubnov: Observing liquid crystal textures in polarized light microscope.
7th place, Vladimíra Novotná: When an organic material is crystalizing.
New Research Professor in Department of Dielectrics
We are happy to announce that Stanislav Kamba has received the Research Professor degree for his outstanding and o riginal scientific work in condensed matter physics, presented in his dissertation: Soft-mode spectroscopy of ferroelectrics and multiferroics.
Stanislav Kamba is a world-wide known expert in the field of high-frequency dielectric spectroscopy, especially in studies of soft phonons in ferroelectric and multiferroic materials. He made a fundamental contribution to understanding of the properties of hydrogen-bonded ferroelectrics, lead-based relaxor materials, and the mechanism of phase transitions in multiferroic materials. His dissertation, titled: Soft-mode spectroscopy of ferroelectrics and multiferroics, presents results which are outcomes of his research done and/or led by him in the Department of Dielectrics for the last 25 years.
(photo after the Czech Academy of Sciences).
About the degree Research Professor:
The scientific degree "Research Professor" (abbreviated as Res. Prof. or DSc.) was established by a resolution of the twenty-first session of
the Academy Assembly convened on December 18, 2002. The Academy awards the scientific degree of Research Professor to scientists
in recognition of their outstanding and original scientific work, contributing to the advancement of research in a specific scientific field and
characterizing the awardee as a scientist of recognizing stature.
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Open Science internships at the Institute of Physics open doors to universities worldwide
In 2018, a secondary school student, Nela Sedláčková has undertaken a one-year Open Science internship under supervision of Alexej Bubnov. At present, she is enjoying the studies of Physics at University of St Andrews supported by The Kellner Family Foundation and says: “I am convinced that the Open Science played the key role in my admittance to university in abroad”.
English translation of the full article from the Open Science website:
Nela Sedláčková dreamed to devote herself to science already at high school. She was therefore interested in the possibility of attending Open Science internships at the Czech Academy of Sciences. At that time, she wanted to extend the knowledge and prepare herself for entering a foreign university. Nela successfully entered and completed a highly competitive internship under supervision of Alexej Bubnov in 2018, in the Liquid Crystal group of the Department of Dielectrics, where she studied novel liquid crystalline materials used most frequently in the LCD displays.
How do you remember the Open Science internship?
Thanks to Open Science internship, I had the opportunity to work in a research laboratory,
meet international scientists and present the gained results at the Open Science conference.
High school students do not usually have access to real scientific environment, and
I also referred to my Open Science experience while applying to St Andrews (Note: University of St Andrews in Scotland).
I believe that the Open Science internship played a key role in my acceptance to St Andrews as well as to gain
the scholarship from
The Kellner Family Foundation which financially supports my studies in the UK.
The aim of the Open Science is to provide an access to scientific work for talented students already during their high school studies. Researchers from the Czech Academy of Sciences anually announce internships within the framework of the Open Science.
https://www.fzu.cz/en/popularization/events/open-science.
How did you actually find out about internships and what made you try out how science is done?
I saw an advertisement of the Open Science project on the Internet and searched through the database of internships. At that time I was in the second year of high school and I was considering to study science at some university abroad. Until then, I had the impression that "real" science was inaccessible to someone who had not yet graduated from college, and the project attracted my attention because it was aimed specifically for the high school students.
How was the internship and cooperation with the supervisor?
The objective of the internship "Study of phase transitions of novel liquid crystals" was to investigate the properties of new liquid crystalline materials, which are nowadays most often used in LCD displays. The supervisor of the internship, Alexej Bubnov, was always willing to answer any of my questions, and our cooperation continues even after the end of the internship. Thanks to him, the results of the internship were published as a regular research article, and I even became a co-author, which does not happen very often for a high school student.
Did the internship help you in choosing your next field of study?
The internship confirmed that I want to study physics with a focus on experiments rather than theory. In the laboratory, I met scientists from abroad and was able to practice and improve my communication skills in English, which, in turn, strengthened my decision to study abroad.
Your dream has come true. So where are you studying now and in which field?
Currently, I study Physics at the
University of St Andrews with the support of The Kellner Family Foundation.
The studies are very fulfilling for me and living abroad has broadened my horizons.
The main difference in the teaching system is in the greater emphasis on independent work and tutorials,
which are classes where a small group of students meets with a professor and the students’ task is asking questions to the professor. The study at St Andrews has met and exceeded my expectations, even though the last year was greatly affected by covid-related limitations.
Do you think about future career in science?
My curiosity continues to draw me into science and I am most interested in plasma physics. At the moment,
I am applying for summer scientific internships and I use my experience from Open Science in my applications.
Scientist and supervisor A. Bubnov about the cooperation with Nela Sedláčková:
Nela Sedláčková is a very hardworking and talented student who did excellent work during and after the Open Science internship.
In 2018, she was chosen for a highly competitive internship "Study of phase transitions of new liquid crystalline materials".
The internship was carried out in the
Liquid Crystal group of the Dielectrics Department
at the Institute of Physics of the Czech Academy of Sciences.
The results we gained by Nela during the internship were presented at an international conference
(XXIII Czech-Polish seminar - Structural and ferroelectric phase transitions),
in the form of a contribution entitled "Self-assembling behavior of new photosensitive cinnamoyl-based monomers aimed for
design of smart macromolecular materials", and received a positive feedback from conference participants.
After completing the internship, the results were also published in the important international scientific journal Liquid Crystals
with a high impact factor (3.6 in 2020 according to Journal Citation Reports):
A. Bubnov, M. Cigl, N. Sedláčková, D. Pociecha, Z. Böhmová, V Hamplová,
Self-assembling behavior of new functional photosensitive cinnamoyl-based reactive mesogens,
Liquid Crystals 47, 2276 (2020). Although the article was published a year ago, it already has 10 citations, which is above the average for this specific field.
I know that Nela Sedláčková is currently a student at the School of Physics and Astronomy, at the University of St Andrews in Great Britain, and that she received a quite prestigious scholarship from the Kellner Family Foundation in 2021. I wish Nela the best of luck. I really hope that one day she will return to the Czech Republic and will work at the Czech Academy of Sciences, which would be of great benefit for us.
authors: Michaela Marková (Open Science) in collaboration with Nela Sedláčková and Alexej Bubnov (Department of Dielectrics)
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Silver medal for young scientists
Team of secondary school students (nicknamed NAFTA), consisting of M. Švanda (captain), T. Čajan, B. Růžičková, P. Štencl and M. Yurchenko, representing the Czech Republic in the 35th International Young Physicists Tournament was awarded a silver medal!
This year the tournament (sometimes referred to as the “Physics World Cup”) took place in Timisoara, Romania from 15th to 25th July 2022. The NAFTA team finished at the 7th place among 25 teams from all over the world. This ranking thus builds on the previous success of the Czech teams in this challenging competition. During the year-lasting preparation for this international competition the team was also strongly supported by feedback from Hynek Němec, Dalibor Repček, and Martin Kempa from the Departments of Dielectrics who were also involved as jury members in the national round at the Faculty of Nuclear Sciences and Physical Engineering at CTU, Prague.
The key to the success in this tournament is a teamwork. The success of the Czech team has to be particularly appreciated in the context of the epidemy circumstances which severely limited cooperation possibilities and which reduced the number of participants in the Czech Republic. In the next year there are planned accompanying events (introductory workshop, training course VYDRA, final symposium with the possibility to present achieved results, discussions with experts, etc.) which all aim to support new participants. We believe that the success acknowledged by the silver medal will motivate to participate the next generation of young physicists in this competition!
About the tournament:
The preparation of the Young Physicists Tournament participants takes almost a year during
which the students have to solve 17 open-ended inquiry problems. Similarly as in the real-world scientific research,
they have to inspect problems from different points of view, to look for relevant information in literature,
to analyze data, to defend results obtained, etc. The competition itself consists in a model scientific discussion
about the achieved results, in which the teams alternate in three different roles:
presenting their solution of the problem, acting as an opponent, and evaluating solutions of the other teams.
The performance of the team in each role is evaluated by a jury which consists of real experts.
The tournament is thus a demanding competition not only for students but also for their teachers.
It exceeds common knowledge competitions – the aim is not only solving problems,
but especially the ability of critical thinking, presentation, and discussion of the results.
These are exactly the skills in the knowledge-based economics of the 21th century.
For this reason, it is strongly recommended in the outcomes of the project DIBALI
(Development of Inquiry Based Learning via IYPT) to support the competitions according to
their benefits rather than by the number of participants, and
to acknowledge the work of teachers preparing students for such demanding competitions with high added value.
(website of the competition: https://tmf.fzu.cz/)
text: H. Němec
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Application of HfO2 thin films in non-volatile memories – a review
We review main factors in preparation of HfO2 thin films and their physical properties which are important for applications in high-density resistive random access memories and ferroelectric memories [Small 18, 2107575 (2022)].
Ultrathin films of HfO2 become ferroelectric although bulk crystals are paraelectric. In this review we describe how grain size, thermal stress, dopants, oxygen vacancies, film thickness, annealing process and electrodes influence dielectric properties of HfO2, which are important for applications in high-density resistive random access memories and ferroelectric memories. We also discuss how to achieve superlative performance with high-speed reliable switching, excellent endurance and retention.
Figure: Dependence of crystal structure of HfO2 on the thin film thickness, strain and electrodes.
[1] W. Banerjee, A. Kashir, and S. Kamba, Hafnium Oxide (HfO2) – A Multifunctional Oxide: A Review on the Prospect and Challenges of Hafnium Oxide in Resistive Switching and Ferroelectric Memories, Small 18, 2107575 (2022).
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Multidomain ordered metal–ferroelectric superlattices
By combination of advanced experimental techniques and phase-field simulations, we found that electric dipoles in superlattices, composed of layers of a ferroelectric material separated by thin metallic spacers, form an unusual pattern of nanoscale domains that order in three dimensions. These ferroelectric multidomain ordered superlattices exhibit an outstanding dielectric response and their engineered modulated structural and electronic properties can be controlled using electric field [Nat. Mater. 20, 495 (2021)].
Figure:
Two-dimensional base motif of the ferroelectrically ordered PbTiO3–SrRuO3 superlattices as seen by
(a-d) phase-field simulations and (e,f) transmission electron microscopy:
(a) electric polarization showing ferroelectric domain structure in two PbTiO3 layers separated by SrRuO3 spacers
(b) gradient energy density coming from domain walls and boundaries between layers,
(c-f) in-plane (exx) and out-of-plane (ezz) strain components demonstrating correlations between ferroelectric PbTiO3 layers.
The arrows in (a,b) panels show direction of electric polarization forming characteristic flux-closure patterns.
[1] M. Hadjimichael, Y. Li, E. Zatterin, G. A. Chahine, M. Conroy, K. Moore, E. N. O’ Connell, P. Ondrejkovic, P. Marton, J. Hlinka, U. Bangert, S. Leake, and P. Zubko, Metal–ferroelectric supercrystals with periodically curved metallic layers, Nat. Mater. 20, 495 (2021).
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Ferroelectric and antiferroelectric phases in liquid crystalline compounds with terphenyl in the molecular coere
We designed a new type of antiferroelectric liquid crystalline structure with terphenyl in the molecular core and two lactate units attached to the chiral chain [J. Mol. Liq. 336, 116267 (2021)].
For the series of compounds, we studied the mesomorphic properties by various experimental techniques and confirmed the phase identification by x-ray measurements. For selected homologues we proved the antiferroelectric phase with orthoconic properties existing in a wide temperature interval including the room temperatures. Valuable optical properties with the tilt angle about 45 degrees promised a big potential for applications.
Figure: Texture of the liquid crystalline compound with a terphenyl in the molecular core in antiferroelectric phase without field (left picture) and under applied electric field (right picture). The scale, orientation of polariser (P) and analyser (A) are presented. In the centre, there is a model of the studied molecule in the optimised conformation.
[1] N. Podoliak, M. Cigl, V. Hamplová, D. Pociecha, and V. Novotná, Multichiral liquid crystals based on terphenyl core laterally substituted by chlorine atom, J. Mol. Liq. 336, 116267 (2021).
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New material for 5G mobile networks
Epitaxial strained thin films of (SrTiO3)n-1(BaTiO3)1SrO were found to be a promising new material for mobile network of the 5th generation [Nature Mater. 19, 176 (2020)].
Epitaxial strained thin films of (SrTiO3)n-1(BaTiO3)1SrO were grown on DyScO3 substrates using molecular beam epitaxy [1]. The best microwave dielectric properties were discovered in samples with n= 6. Permittivity exhibits huge tuning using electric field and microwave dielectric loss is anomalously low. Unique properties were confirmed using first-principles calculations and by experimental observation of the soft mode behavior in THz region. These films are ideal for components in 5G networks.
Collaborating institutions: Prof. D.G. Schlom from the Cornell University and other American and German institutions.
Figure: Schema of crystal structures of investigated (SrTiO3)n-1(BaTiO3)1SrO films and their view in scanning transmission electron microscope. Yellow octahedra depict TiO6 layers, green and red points mark atoms of Sr and Ba.
[1] N.M. Dawley, E.J.Marksz, A.M. Hagerstrom, G.H. Olsen, M.E. Holtz, V. Goian, C. Kadlec, J. Zhang, X. Lu, J.A. Drisko, R. Uecker, S. Ganschow, C.J. Long, J.C. Booth, S. Kamba, C.J. Fennie, D.A. Muller, N.D. Orloff, D.G. Schlomk, Targeted chemical pressure yields tuneable millimetre-wave dielectric, Nature Mater. 19, 176 (2020).
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Ferroelectric phase transition in water molecules localized in mineral cordierite
We discovered that hydrogen bonds are eliminated and the Coulombic interactions dominate in water molecules localized in nano-channels of mineral cordierite. Their dipole moment is perpendicular to the channel axis c and our dielectric spectroscopy study have revealed their ordering at ~3 K. The critical relaxation tending to this ordering is polarized along the a-axis direction and lies in the radiofrequency range. Spontaneous polarization measurements yield the saturated value of ~3 nC/cm2 at 0.3 K [Nat. Commun. 11, 3927 (2020)].
Water molecules localized in structural crystal nano-channels give a possibility to eliminate hydrogen bonds, dominating among water molecules at short distances up to ~2 Å which prevent ordering of their dipole moments. On larger distances 1-10 nm the Coulombic interactions dominate, which can lead to their ordering. We continued in our previous studies on beryl, where we, on cooling, have detected tendency to ferroelectric ordering, so called incipient ferroelectric behaviour. Mineral cordierite (Mg,Fe)2Al4Si5O18 also comprise structural channels similar to those in beryl, in which the chains of water molecules are ideally suited for the ordering study (Fig. 1).
Figure 1: Cordierite crystal structure. Investigated water was localized in the free channels along the c-axis.
Crystal structure is orthorhombic, the channels in the c-axis direction are in the distance of 9.9 Å and the water molecules in the channels are by 4.7 Å from each other. Their dipole moment is perpendicular to the channel axis and our dielectric spectroscopy study have revealed their ordering at ~3 K. The critical relaxation tending to this ordering is polarized along the a-axis direction and lies in the radiofrequency range (Fig. 2). Spontaneous polarization measurements yield the saturated value of ~3 nC/cm2 at 0.3 K. Molecular dynamics calculations show the ferroelectric ordering in the plane perpendicular to the channels and antiferroelectric ordering along them.
Figure 2: Ferroelectric phase transition of water in cordierite is induced by a critical slowing down of dielectric relaxation. νp denotes frequency of the maxima in the dielectric loss spectra and τ denotes the relaxation time of the relaxation.
[1] M. A. Belyanchikov, M. Savinov Z. V. Bedran, P. Bednyakov, P. Proschek, J. Prokleska, V. A. Abalmasov, J. Petzelt, E. S. Zhukova, V. G. Thomas, A. Dudka, A. Zhugayevych, A. S. Prokhorov, V. B. Anzin, R. K. Kremer, J. K. H. Fishcer, P. Lunkenheimer, A. Loidl, E. Uykur, M. Dressel, and B. Gorshunov Targeted chemical pressure yields tuneable millimetre-wave dielectric,
Nat. Commun. 11, 3927 (2020)
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Tiling the Silicon for Added Functionality: PLD Growth of Highly Crystalline STO and PZT on Graphene Oxide-Buffered Silicon Surface
ACS Applied Materials and Interfaces 15, 6058 (2023).
Texture, elastic anisotropy and thermal stability of commercially pure titanium prepared by room temperature ECAP
Mater. Des. 226, 111678 (2023).
Effect of oxygen defects on microstructure, optical and vibrational properties of ScN films deposited on MgO substrate from experiment and first principles
Appl. Surf. Sci. 615, 156203 (2023).
The comparison of self-assembling behaviour of phenyl biphenylate and biphenylyl benzoate compounds with the different length and shape of chiral terminal chain
J. Mol. Liq. 369, 120882 (2023).