BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Analytical Description of Size Effects\, Strains and Ferro-ionic C oupling in Si-Compatible Nanosized Ferroelectrics DTSTART;VALUE=DATE-TIME:20240926T070000Z DTEND;VALUE=DATE-TIME:20240926T072000Z DTSTAMP;VALUE=DATE-TIME:20260818T132306Z UID:indico-contribution-331@indico.bitp.kiev.ua DESCRIPTION:Speakers: Anna Morozovska (Institute of Physics\, National Aca demy of Sciences of Ukraine)\nThe analytical methods based on the Landau-G inzburg-Devonshire (LGD) approach and variational principle allow the anal ytical description of size effects\, strain and ferro-ionic coupling in lo w-dimensional ferroelectric materials\, such as thin films and small nanop articles. The validity of LGD approach is corroborated by experimental evi dence of the size- and strain-induced transitions as well as the related p henomena in the low-dimensional ferroelectric materials. For the correct d escription of these effects in ferroelectric thin films and small nanopart icles the LGD approach should be combined with the classical electrostatic s and elasticity theory\, and variational principle. It is important to de termine how the LGD expansion coefficients depend on various factors\, suc h as temperature\, size\, elastic stresses and/or strains\, and ionic-elec tronic charge density and distribution. For classical ferroelectric films with a pronounced temperature-dependent and strain-dependent soft mode\, t he first expansion coefficients have a linear dependence on the temperatur e and elastic strain.\nThe significant attention is devoted to the compari son with experimental results and finite element modelling\, as well as on the theoretical predictions of the size-\, strain- and ionic- control of polar and dielectric properties of nanosized ferroelectric materials.\nAs the first example\, we consider ultra-thin layers and nanoflakes of van de r Waals ferrielectric CuInP2S6 covered by an ionic surface charge and reve al the appearance of polar states with relatively high polarization and st ored free charge\, which can mimic “mid-gap” states related with a sur face field-induced transfer of Cu and/or In ions in the van der Waals gap [1]. The changes of the ionic screening degree and mismatch strains can in duce the transitions between paraelectric phase\, antiferroelectric\, ferr ielectric\, and ferroelectric-like states in CuInP2S6 nanoflakes. Due to t he emergence of manyfold-degenerated metastable states of spontaneous pola rization the ultra-thin layers of CuInP2S6 reveal features of the controll able negative capacitance effect [2]\, which make them attractive for adva nced electronic devices\, such as nano-capacitors and gate oxide nanomater ials with reduced heat dissipation.\nAs the second example\, we use the LG D model to quantify the strain-charge-polarization coupling in nanosized H fxZr1-xO2. A key factor ruling the observed polar properties of nanosized HfxZr1-xO2 is the presence of the polar orthorhombic phase. This phase is metastabile compared to the bulk monoclinic phase\, leading to problems wi th the ferroelectric phase stability in nanoscale. The electrophysical pro perties of the HfxZr1-xO2 thin films and nanoparticles are very sensitive to the elastic strain induced by the substrate\, annealing conditions\, de position method\, film thickness\, content x and dopants. Depending on the interplay of these factors\, the nanosized HfxZr1-xO2 exhibits dielectric \, ferroelectric\, or antiferroelectric behavior. \nThe used model [3] inc orporates parametrized Landau expansion coefficients for the polar and ant ipolar orderings. Obtained results agrees with the recent existing experim ental data for HfxZr1-xO2-y thin films and oxygen-deficient HfO2-y nanopar ticles [4]\, namely the X-ray diffraction confirmed the formation of a fer roelectric orthorhombic phase in the HfO2-y nanoparticles under special fa vorable annealing conditions. \nThe analytical LGD approach correctly pred icts the phase diagrams\, ground and metastable states\, alongside the dom ain structure morphology\, associated polar and structural properties of H fxZr1-xO2-y thin films and nanoparticles with different shapes and sizes. The successful application of the analytical LGD approach can be useful fo r the prediction of the silicon-compatible ferroelectric nanomaterials bas ed on HfxZr1-xO2-y. \nThe work is funded by the National Research Foundati on of Ukraine (projects “Manyfold-degenerated metastable states of spont aneous polarization in nanoferroics: theory\, experiment and perspectives for digital nanoelectronics”\, grant N 2023.03/0132 and “Silicon-compa tible ferroelectric nanocomposites for electronics and sensors”\, grant N 2023.03/0127).\n[1]. Anna N. Morozovska\, Sergei V. Kalinin\, Eugene A. Eliseev\, Svitlana Kopyl\, Yulian M. Vysochanskii\, and Dean R. Evans. Fer ri-ionic Coupling in CuInP2S6 Nanoflakes: Polarization States and Controll able Negative Capacitance (2024)\, https://doi.org/10.48550/arXiv.2405.143 68\n[2]. Anna N. Morozovska\, Eugene A. Eliseev\, Yulian M. Vysochanskii\, Sergei V. Kalinin\, and Maksym V. Strikha. Size Effect of Negative Capaci tance State and Subthreshold Swing in Van der Waals Ferrielectric Field-Ef fect Transistors\, https://doi.org/10.48550/arXiv.2406.13051\n[3]. Anna N. Morozovska\, Maksym V. Strikha\, Kyle P. Kelley\, Sergei V. Kalinin\, and Eugene A. Eliseev. Effective Landau-type model of a HfxZr1-xO2-graphene n anostructure\, Phys. Rev. Applied 20\, 054007 (2023) https://doi.org/10.11 03/PhysRevApplied.20.054007\n[4]. Eugene A. Eliseev\, Yuri O. Zagorodniy\, Victor N. Pavlikov\, Oksana V. Leshchenko\, Hanna V. Shevilakova\, Mirosl av V. Karpec\, Andrei D. Yaremkevych\, Olena M. Fesenko\, Sergei V. Kalini n\, and Anna N. Morozovska. Phase diagrams and polarization reversal in na nosized HfxZr1-xO2-y\, AIP Advances\, 14\, 055224 (2024)\, https://doi.org /10.1063/5.0209123\n\nhttps://indico.bitp.kiev.ua/event/13/contributions/3 31/ LOCATION:Bogolyubov Institute for Theoretical Physics (Section 1-4)\, Inst itute of Mathematics (Section 5) 322 URL:https://indico.bitp.kiev.ua/event/13/contributions/331/ END:VEVENT END:VCALENDAR