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4. Negative differential capacitance in ultrathin ferroelectric hafnia

Author

Jo, Sanghyun, Lee, Hyangsook, Choe, Duk-Hyun, Kim, Jung-Hwa, Lee, Yun Seong, Kwon, Owoong, Nam, Seunggeol, Park, Yoonsang, Kim, Kihong, Chae, Byeong Gyu, Kim, Sangwook, Kang, Seunghun, Moon, Taehwan, Bae, Hagyoul, Won, Jung Yeon, Yun, Dong-Jin, Jeong, Myoungho, Lee, Hyun Hwi, Cho, Yeonchoo, Lee, Kwang-Hee, Lee, Hyun Jae, Lee, Sangjun, Nam, Kab-Jin, Jung, Dongjin, Kuh, Bong Jin, Ha, Daewon, Kim, Yongsung, Park, Seongjun, Kim, Yunseok, Lee, Eunha, and Heo, Jinseong

Published
2023
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5. Physical Parameter and Loss Determination of Piezoceramics Using Partial Electrode: k31 and k33 Mode Cases

Author

Park, Yoonsang, Daneshpajooh, Hossein, Scholehwar, Timo, Hennig, Eberhard, and Uchino, Kenji

Subjects
Condensed Matter - Materials Science
Abstract

The standard method to determine physical parameters of piezoceramics, established by IEEE, has been utilized for decades by the number of researchers, yet it omits presence of important loss factors and possesses serious deficits that restricts accurate parameter determination. In order to resolve these issues, the partial electrode (PE) method (mechanical excitation method) was previously proposed. In this study, we aim to propose a modified PE method to enhance the efficiency of parameter determination process, along with a simplified analytical admittance equation for better understanding of the PE configuration. To prove that the PE method is reliable, possible causes of errors were listed, and it was shown that they were either negligibly small or resolved with proper calibration methods. Throughout the paper, it was validated that the PE method not only reduces the errors of several physical parameters by avoiding error propagation, but also enables measurement compatibility with commercially available impedance analyzers., Comment: 29 pages with supplementary materials included

Published
2020

7. Improvement of the Standard Characterization Method on k33 Mode Piezoelectric Specimens

Author

Park, Yoonsang, Zhang, Yuxuan, Majzoubi, Maryam, Scholehwar, Timo, Hennig, Eberhard, and Uchino, Kenji

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Even though standard method to determine physical parameters of piezoelectric materials has been set up for several decades, bare attention has been made on loss determination method. Furthermore, several deficits have been recognized in the standard method for k33 mode. In this study, detailed discussion on deficits of IEEE Standard k33 is investigated and the method to resolve such deficits will be introduced. The standard k33 specimen suffers from small capacitance, which causes huge experimental error, intrinsic electrical energy leakage, specimen setup issue and inability to directly determine intensive elastic properties. In order to resolve these issues, partial electrode method was introduced, and curve fitting was demonstrated to determine physical parameters and losses., Comment: Total 33 pages including reference, figure captions and tables. 6 figures, 3 tables. Reason for the replacement: Corrected typos and minor grammatical errors, Change in Reference

Published
2019
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8. Analytical Modeling of k33 Mode Partial Electrode Configuration for Loss Characterization

Author

Park, Yoonsang, Majzoubi, Maryam, Zhang, Yuxuan, Scholehwar, Timo, Hennig, Eberhard, and Uchino, Kenji

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Accurate determination of three types of losses (dielectric, elastic and piezoelectric) in piezoelectric materials is critical, since they are closely related to the performance of high-power piezoelectric devices. The Standard k33 mode has a number of serious deficits that hinders researchers from determining accurate physical parameters and losses. In order to overcome such deficits, partial electrode has been devised and proposed. This study provides analytical derivation process and proposes parameter determination method by utilizing analytical solutions. Compared to finite element analysis, analytical solutions show 0.1 % difference in resonance frequencies and 2 % difference in mechanical quality factors, proving them as valid modeling. The analytical solutions are fitted to experimental data to determine physical parameters and losses. The k33 (electromechanical coupling factor) values were calculated with determined values from curve fitting in two different ways and show good agreement to each other., Comment: 24 pages, 5 figures and 3 tables. Reason for the replacement: Corrected typos and minor grammatical errors, Change in Reference

Published
2019
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10. Linear and nonlinear optical probe of the ferroelectric-like phase transition in a polar metal, LiOsO3

Author

Padmanabhan, Haricharan, Park, Yoonsang, Puggioni, Danilo, Yuan, Yakun, Cao, Yanwei, Gasparov, Lev, Shi, Youguo, Chakhalian, Jak, Rondinelli, James M., and Gopalan, Venkatraman

Subjects
Condensed Matter - Materials Science
Abstract

LiOsO3 is one of the first materials identified in a recent literature as a 'polar metal', a class of materials that are simultaneously noncentrosymmetric and metallic. In this work, the linear and nonlinear optical susceptibility of LiOsO3 is studied by means of ellipsometry and optical second harmonic generation (SHG). Strong optical birefringence is observed using spectroscopic ellipsometry. The nonlinear optical susceptibility extracted from SHG polarimetry reveals that the tensor components are of the same magnitude as in isostructural insulator LiNbO3, except the component along the polar axis d33, which is suppressed by an order of magnitude. Temperature-dependent SHG measurements in combination with Raman spectroscopy indicate a continuous order-disorder type polar phase transition at 140 K. Linear and nonlinear optical microscopy techniques reveal 109 deg/71 deg ferroelastic domain walls, like in other trigonal ferroelectrics. No 180 deg polar domain walls are observed to emerge across the phase transition., Comment: Supplementary material in ancillary files

Published
2018
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12. Theory‐Guided Synthesis of a Metastable Lead‐Free Piezoelectric Polymorph

Author

Garten, Lauren M, Dwaraknath, Shyam, Walker, Julian, Mangum, John S, Ndione, Paul F, Park, Yoonsang, Beaton, Daniel A, Gopalan, Venkatraman, Gorman, Brian P, Schelhas, Laura T, Toney, Michael F, Trolier‐McKinstry, Susan, Persson, Kristin A, and Ginley, David S

Subjects
Engineering, Materials Engineering, Chemical Sciences, Physical Sciences, lead-free piezoelectrics, metastability, theory-guided synthesis, Nanoscience & Nanotechnology, Chemical sciences, Physical sciences
Abstract

Many technologically critical materials are metastable under ambient conditions, yet the understanding of how to rationally design and guide the synthesis of these materials is limited. This work presents an integrated approach that targets a metastable lead-free piezoelectric polymorph of SrHfO3 . First-principles calculations predict that the previous experimentally unrealized, metastable P4mm phase of SrHfO3 should exhibit a direct piezoelectric response (d33 ) of 36.9 pC N-1 (compared to d33 = 0 for the ground state). Combining computationally optimized substrate selection and synthesis conditions lead to the epitaxial stabilization of the polar P4mm phase of SrHfO3 on SrTiO3 . The films are structurally consistent with the theory predictions. A ferroelectric-induced large signal effective converse piezoelectric response of 5.2 pm V-1 for a 35 nm film is observed, indicating the ability to predict and target multifunctionality. This illustrates a coupled theory-experimental approach to the discovery and realization of new multifunctional polymorphs.

Published
2018

17. Distinct solubility and cytotoxicity regimes of paclitaxel-loaded cationic liposomes at low and high drug content revealed by kinetic phase behavior and cancer cell viability studies.

Author

Steffes, Victoria, Murali, Meena, Park, Yoonsang, Fletcher, Bretton, Safinya, Cyrus, and Ewert, Kai

Subjects
Cancer chemotherapy, Drug delivery, Hydrophobic drug, Liposome, Nanoparticle, Paclitaxel, Cations, Cell Death, Cell Line, Tumor, Cell Survival, Crystallization, DNA, Humans, Kinetics, Liposomes, Neoplasms, Paclitaxel, Scattering, Small Angle, Solubility, Synchrotrons, X-Ray Diffraction
Abstract

Lipid-based particles are used worldwide in clinical trials as carriers of hydrophobic paclitaxel (PTXL) for cancer chemotherapy, albeit with little improvement over the standard-of-care. Improving efficacy requires an understanding of intramembrane interactions between PTXL and lipids to enhance PTXL solubilization and suppress PTXL phase separation into crystals. We studied the solubility of PTXL in cationic liposomes (CLs) composed of positively charged 2,3-dioleyloxypropyltrimethylammonium chloride (DOTAP) and neutral 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) as a function of PTXL membrane content and its relation to efficacy. Time-dependent kinetic phase diagrams were generated from observations of PTXL crystal formation by differential-interference-contrast microscopy. Furthermore, a new synchrotron small-angle x-ray scattering in situ methodology applied to DOTAP/DOPC/PTXL membranes condensed with DNA enabled us to detect the incorporation and time-dependent depletion of PTXL from membranes by measurements of variations in the membrane interlayer and DNA interaxial spacings. Our results revealed three regimes with distinct time scales for PTXL membrane solubility: hours for >3 mol% PTXL (low), days for ≈ 3 mol% PTXL (moderate), and ≥20 days for

Published
2017

18. Distinct solubility and cytotoxicity regimes of paclitaxel-loaded cationic liposomes at low and high drug content revealed by kinetic phase behavior and cancer cell viability studies

Author

Steffes, Victoria M, Murali, Meena M, Park, Yoonsang, Fletcher, Bretton J, Ewert, Kai K, and Safinya, Cyrus R

Subjects
Medical Biotechnology, Biomedical and Clinical Sciences, Bioengineering, Cancer, Cations, Cell Death, Cell Line, Tumor, Cell Survival, Crystallization, DNA, Humans, Kinetics, Liposomes, Neoplasms, Paclitaxel, Scattering, Small Angle, Solubility, Synchrotrons, X-Ray Diffraction, Liposome, Nanoparticle, Hydrophobic drug, Drug delivery, Cancer chemotherapy
Abstract

Lipid-based particles are used worldwide in clinical trials as carriers of hydrophobic paclitaxel (PTXL) for cancer chemotherapy, albeit with little improvement over the standard-of-care. Improving efficacy requires an understanding of intramembrane interactions between PTXL and lipids to enhance PTXL solubilization and suppress PTXL phase separation into crystals. We studied the solubility of PTXL in cationic liposomes (CLs) composed of positively charged 2,3-dioleyloxypropyltrimethylammonium chloride (DOTAP) and neutral 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) as a function of PTXL membrane content and its relation to efficacy. Time-dependent kinetic phase diagrams were generated from observations of PTXL crystal formation by differential-interference-contrast microscopy. Furthermore, a new synchrotron small-angle x-ray scattering in situ methodology applied to DOTAP/DOPC/PTXL membranes condensed with DNA enabled us to detect the incorporation and time-dependent depletion of PTXL from membranes by measurements of variations in the membrane interlayer and DNA interaxial spacings. Our results revealed three regimes with distinct time scales for PTXL membrane solubility: hours for >3 mol% PTXL (low), days for ≈ 3 mol% PTXL (moderate), and ≥20 days for

Published
2017

30. Analytical modeling of k33 mode partial electrode configuration for loss characterization.

Author

Park, Yoonsang, Majzoubi, Maryam, Zhang, Yuxuan, Scholehwar, Timo, Hennig, Eberhard, and Uchino, Kenji

Subjects
PIEZOELECTRIC devices, PIEZOELECTRIC materials, CURVE fitting, FINITE element method, QUALITY factor, ELECTRODES, ANALYTICAL solutions
Abstract

Accurate determination of three types of losses (dielectric, elastic, and piezoelectric) in piezoelectric materials is critical, since they are closely related to the performance of high-power piezoelectric devices. The standard k 33 mode has a number of serious deficits that hinder researchers from determining accurate physical parameters and losses. In order to overcome such deficits, "partial electrode" has been devised and proposed. This study provides an analytical derivation process and proposes a parameter determination method by utilizing analytical solutions. Compared to finite element analysis, analytical solutions show a 0.1% difference in resonance frequencies and a 2% difference in mechanical quality factors, proving themselves as valid modeling. The analytical solutions are fitted to experimental data to determine physical parameters and losses. The k 33 (electromechanical coupling factor) values were calculated with determined values from curve fitting in two different ways and show good agreement to each other. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Laminated Ferroelectric FET With Large Memory Window and High Reliability

Author

Lee, Hyun Jae, Nam, Seunggeol, Lee, Yunseong, Kim, Kihong, Choe, Duk-Hyun, Yoo, Sijung, Park, Yoonsang, Jo, Sanghyun, Kim, Donghoon, and Heo, Jinseong

Abstract

In this work, we report a planar Si-based ferroelectric field-effect transistor (FEFET) characterized by a high memory window (MW) of 4.79 V, ten-year retention, and pass disturb-free characteristics. This achievement is realized through the use of a 20-nm-thick laminated Hf $_{{0}.{5}}$ Zr0.5O2 (L-HZO) film with Al2O3 (AO)-insertion layers (ILs). The 2.4-Å-thick AO-ILs effectively severed the bulk-HZO film and scaled down each FE-thickness ( ${t}_{\text {FE}}$ ) in the L-HZO. This resulted in suppression of non-FE monoclinic phase formation to less than 10%, and more notably, an increase in the coercive field ( ${E}_{C}$ ) within the FE stack. With an increase in the number of HZO-lamination ( ${N}_{\text {HZO}}$ ), the ${E}_{C}$ was enhanced by 76% in L-HZO ( ${N}_{\text {HZO}}$ = 4) compared to single-HZO (S-HZO). This led to an increase in effective polarization ( ${P}_{\text {eff}}$ ), representing the portion of remnant polarization ( ${P}_{\text {r}}$ ) uncompensated by channel-injected charge, thereby validly influencing the threshold voltage ( ${V}_{\text {T}}$ ) shift of FEFET. The augmented ${P}_{\text {eff}}$ in L-HZO (350% increase compared to S-HZO) was directly confirmed through a more pronounced ${V}_{\text {T}}$ shift by the change of ${P}_{\text {r}}$ , which was 230% steeper in L-HZO compared to S-HZO. The revealed mechanism behind the enhanced MW and reliability in laminated-FE, stemming from the increased ${P}_{\text {eff}}$ rooted in enlarged ${E}_{C}$ , paves the way for designing the FE-stack for high-density memory or neuromorphic applications.

Published
2024
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33. Clinical big-data-based design of GLUT2-targeted carbon nanodots for accurate diagnosis of hepatocellular carcinoma

Author

Heo, Hye Jin, primary, Park, Yoonsang, additional, Lee, Jung Hee, additional, Kim, Yujin, additional, Kim, Eun Kyoung, additional, Kim, Ga Hyun, additional, Yu, Yeuni, additional, Park, So Youn, additional, Seo, Hie Bum, additional, Pak, Kyoungjune, additional, Goh, Tae Sik, additional, Park, Sehyeon, additional, Oh, Sae-Ock, additional, Kwon, Woosung, additional, and Kim, Yun Hak, additional

Published
2022
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35. Nanoengineering room temperature ferroelectricity into orthorhombic SmMnO 3 films

Author

Choi, Eun-Mi, Maity, Tuhin, Kursumovic, Ahmed, Lu, Ping, Bi, Zenxhing, Yu, Shukai, Park, Yoonsang, Zhu, Bonan, Wu, Rui, Gopalan, Venkatraman, Wang, Haiyan, MacManus-Driscoll, Judith L., Choi, Eun-Mi [0000-0003-0287-1080], Maity, Tuhin [0000-0003-4386-1006], Lu, Ping [0000-0002-9369-7462], Zhu, Bonan [0000-0001-5601-6130], Wang, Haiyan [0000-0002-7397-1209], and Apollo - University of Cambridge Repository

Subjects
639/301/119/996, 120, 639/301, 132, 145, 147/3, 147/137, 639/301/119, article, 128, 147/143
Abstract

Orthorhombic RMnO3 (R = rare-earth cation) compounds are type-II multiferroics induced by inversion-symmetry-breaking of spin order. They hold promise for magneto-electric devices. However, no spontaneous room-temperature ferroic property has been observed to date in orthorhombic RMnO3. Here, using 3D straining in nanocomposite films of (SmMnO3)0.5((Bi,Sm)2O3)0.5, we demonstrate room temperature ferroelectricity and ferromagnetism with TC,FM ~ 90 K, matching exactly with theoretical predictions for the induced strain levels. Large in-plane compressive and out-of-plane tensile strains (−3.6% and +4.9%, respectively) were induced by the stiff (Bi,Sm)2O3 nanopillars embedded. The room temperature electric polarization is comparable to other spin-driven ferroelectric RMnO3 films. Also, while bulk SmMnO3 is antiferromagnetic, ferromagnetism was induced in the composite films. The Mn-O bond angles and lengths determined from density functional theory explain the origin of the ferroelectricity, i.e. modification of the exchange coupling. Our structural tuning method gives a route to designing multiferroics.

Published
2021
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