Article
Nanoscience & Nanotechnology
Feng-Hui Gong, Yu-Ting Chen, Yin-Lian Zhu, Yun-Long Tang, Heng Zhang, Yu-Jia Wang, Bo Wu, Jia-Qi Liu, Tong-Tong Shi, Li-Xin Yang, Chang-Ji Li, Yan-Peng Feng, Xiu-Liang Ma
Summary: This work investigates the domain evolution and topological properties of ultrathin PbTiO3 (PTO) films using Cs-corrected scanning transmission electron microscopy (STEM), reciprocal space mapping (RSM), and piezoresponse force microscopy (PFM). It is found that when the thickness of PTO films is less than 6 nm, there is a coexistence of a/c domains and bowl-like topological structures, identified as convergent and divergent types of meron. Abundant 90 degrees charged domain walls are also identified. PFM studies confirm the ferroelectric properties of these ultrathin PTO films.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Multidisciplinary
Shuai Yuan, Zuhuang Chen, Sergei Prokhorenko, Yousra Nahas, Laurent Bellaiche, Chenhan Liu, Bin Xu, Lang Chen, Sujit Das, Lane W. Martin
Summary: Using phase-field simulations, the evolution of polar topology and the emergence of a hexagonal close-packed skyrmion lattice in ultrathin ferroelectric PbTiO3 films is explored. The lattice can be stabilized under an external electric field and the lattice constants increase with film thickness. These studies pave the way for the development of novel ordered condensed matter phases in nanoscale ferroelectrics.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Physical
Yoonho Ahn, Jong Yeog Son
Summary: Epitaxial BTO/PTO multilayer thin films exhibit ferroelectric polarization switching characteristics with an imprint phenomenon, which can be utilized for developing high-density ferroelectric-based storage media.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Physics, Multidisciplinary
Zhizhong Zhu, Wenhui Ma
Summary: The stress-depolarization field phase stability map for ultrathin [111]-PbTiO3 epitaxial films on SrTiO3 reveals that inducing low-symmetry states can be remarkably lowered by the presence of the depolarization field, restricting the polarization vector in a symmetry plane. Investigation of the competition of phase stability and evolution of monoclinic states shows significant enhancement in dielectric and piezoelectric responses under certain boundary conditions.
Article
Nanoscience & Nanotechnology
Yoonho Ahn, Jong Yeog Son
Summary: The ferroelectric domain switching kinetics of PbTiO3 nanostructures were investigated, showing faster domain switching behavior and lower activation energy compared to PbTiO3 thin film. This insight could be applied to highly integrated and fast ferroelectric random access memory applications.
SCRIPTA MATERIALIA
(2021)
Article
Materials Science, Multidisciplinary
Fernando Gomez-Ortiz, Pablo Garcia-Fernandez, Juan M. Lopez, Javier Junquera
Summary: We investigated the emergence of Berezinskii-Kosterlitz-Thouless (BKT) phases in (PbTiO3)3/(SrTiO3)3 superlattices using second-principles simulations. Under a tensile epitaxial strain of e = 0.25-1%, the local dipole moments within the superlattices are confined to the film-plane, leading to two-dimensional polarization. Our analysis of dipole-dipole correlation decay, density of defects, and temperature dependence supports the existence of a BKT phase, characterized by quasi-long-range order and the presence of tightly bound vortex-antivortex pairs. This proposed superlattice model can be experimentally verified due to its feasibility in fabrication and the imposed mechanical boundary conditions.
Article
Chemistry, Physical
Amandine Bellec, Massine Kelai, Arthur Tauzin, Anastasia Railean, Vincent Repain, Jerome Lagoute, Yann Girard, Sylvie Rousset, Edwige Otero, Talal Mallah, Marie-Laure Boillot, Cristian Enachescu
Summary: In this study, the photoexcitation of ultrathin films of [FeII((3, 5-(CH3)2Pz)3BH)2] (Pz = pyrazolyl) adsorbed on a special substrate was investigated. The anomalous light-induced spin-state switching was observed for sub-monolayer coverage, while the well-known light-induced excited spin-state trapping effect was recovered for higher coverages. The combination of continuous light excitation and thermal cycling revealed light-induced thermal hysteresis for thicker films and extended thermal conversion over a large temperature range for sub-monolayer coverage. Mechanoelastic simulations showed opposite behaviors in different layers of the films due to intermolecular interactions.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Surajit Sarkar, Hritinava Banik, Sudip Suklabaidya, Barnali Deb, Swapan Majumdar, Pabitra Kumar Paul, Debajyoti Bhattacharjee, Syed Arshad Hussain
Summary: The study presents bipolar resistive switching devices based on the organic material Indole1 and characterizes their structure and performance using various methods. Experimental results demonstrate that the device made of Indole1 exhibits excellent storage characteristics and device performance, showing potential for future applications.
Article
Materials Science, Ceramics
Yoonho Ahn, Jong Yeog Son
Summary: This study reports on the control of ferroelectric domain structure switching in PbTiO3 (PTO) thin films using the flexoelectric effect. By applying external forces in different directions, predictable switching of vertically and horizontally oriented domains can be achieved.
JOURNAL OF THE KOREAN CERAMIC SOCIETY
(2023)
Article
Materials Science, Multidisciplinary
Linxing Zhang, Darui Sun, Maosheng Chai, Xianran Xing, Jun Chen, Bingbing Zhang, Jianjun Tian
Summary: The positive and negative thermal expansion effects in composite ferroelectric epitaxial films are investigated, showing the coupling of different thermal effects and piezoelectric/photovoltaic effects in ultrafast strain. Different lattice responses due to different thermal effects of samples with different axial ratios are observed, with a maximum UPS of up to 0.24%, comparable to that of conventional ferroelectric materials.
SCIENCE CHINA-MATERIALS
(2021)
Article
Mechanics
Satya Sekhar, V. Shankar
Summary: This study investigates the linear stability of freestanding thin films under the influence of attractive van der Waals forces, comparing three rheological models and finding that thin freestanding viscous films are unconditionally unstable, while elasticity plays different roles in the stability of solid and liquid films. The linear stability of Jeffreys viscoelastic freestanding films is compared with supported films in the inertialess limit, showing that the instability is unaffected by relaxation time but enhanced with a decrease in viscosity ratio.
Article
Materials Science, Multidisciplinary
E. A. C. Astrath, E. A. Volnistem, R. C. Oliveira, R. R. Barbosa, A. J. Santana, A. C. Ferreira, D. M. Silva, G. S. Dias, L. F. Cotica, I. A. Santos, L. C. Dias, T. G. M. Bonadio, V. F. Freitas
Summary: This study investigates the electrical, structural, and microstructural properties of high-quality BFPT thin films. It reveals that only electrode-limited mechanisms are present in BFPT thin films below 100 nm, with the Fowler-Nordheim mechanism being the predominant mechanism for fields above 240 kV/cm. Additionally, dielectric spectroscopy investigations show that the real dielectric constants of the BFPT thin films vary in the range of 10 kHz and 1 MHz, with low tangent loss.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Chemistry, Multidisciplinary
Mario Gies, Sebastian. L. L. Benz, Mark. M. M. Pradja, Derck Schlettwein, Sangam Chatterjee, Martin Becker, Angelika Polity
Summary: This study investigates the stabilization of the electrochromic switching performance of tungsten oxide by using an ultrathin optimized Al2O3 protective coating. The results show that the additional thin Al2O3 protective layer can effectively prevent degradation and aging of tungsten oxide and achieve a coloration efficiency of 50.4 cm(2) C-1 at 630 nm.
ADVANCED MATERIALS INTERFACES
(2023)
Article
Polymer Science
Lili Zhang, Norman A. Fleck
Summary: Molecular dynamics simulations are used to study the thickness dependence of uniaxial and equi-biaxial tensile responses of ultrathin PMMA films, revealing that tensile failure strain decreases with decreasing film thickness, temperature, and molecular weight, while side-branching plays a secondary role.
Article
Biochemistry & Molecular Biology
Gianfranco Cordella, Antonio Tripodo, Francesco Puosi, Dario Pisignano, Dino Leporini
Summary: This paper examines the nanoscale surface instability of ultrathin molecular films deposited on a substrate under uniaxial compression using molecular dynamics simulations. The study reveals the development of one-dimensional wrinkling structures and the scaling relationship between wavelength and film length. It is found that small compressions can be well described, while large compressions lead to increased wrinkling amplitudes with nearly constant cross sections, offering a novel interpretation of instability. These findings may be crucial for designing effective wrinkling and buckling patterns in flexible platforms for electronics and photonics.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2021)
Article
Chemistry, Applied
Shingo Maruyama, Kana Ouchi, Tomoyuki Koganezawa, Yuji Matsumoto
ACS COMBINATORIAL SCIENCE
(2020)
Article
Chemistry, Physical
Rio Konno, Shingo Maruyama, Takumu Kosaka, Ryuzi Katoh, Ryota Takahashi, Hiroshi Kumigashira, Nobuyuki Ichikuni, Hiroshi Onishi, Yuji Matsumoto
Summary: In this study, Sr-doped NaTaO3 (NTO) single-crystalline films with different Sr compositions were successfully fabricated, showing changes in lattice constants and optical absorption edge energies as the Sr doping level increased. The doped Sr atoms were found to substitute for both A and B sites in the crystal structure. Furthermore, compositionally graded Sr-doped NTO films were successfully prepared with different Sr composition gradients, and the lifetime of photoexcited carriers in these films was longer compared to NTO and homogeneous Sr-doped NTO films.
CHEMISTRY OF MATERIALS
(2021)
Article
Engineering, Electrical & Electronic
Runar Plunnecke Dahl-Hansen, Frode Tyholdt, Jo Gjessing, Andreas Vogl, Paul Wittendorp, Jon Vedum, Thomas Tybell
Summary: The study evaluated the lifetime and reliability of PZT-based micromirrors operated under different humidity conditions, revealing the impact of humidity on the devices. The use of an Al2O3 humidity barrier increased the failure time of the devices, but also decreased their initial performance.
JOURNAL OF MICROELECTROMECHANICAL SYSTEMS
(2021)
Article
Materials Science, Multidisciplinary
Mikk Lippmaa, Seiji Kawasaki, Ryota Takahashi, Takahisa Yamamoto
Summary: Spontaneous noble metal dopant segregation in an oxide lattice can lead to the formation of metallic clusters and extended acicular inclusions. In a thin-film process, the shape and orientation of such noble metal inclusions are governed by the crystal growth direction, resulting in a composite material with lattice-matched metal nanopillars embedded vertically in an insulating or semiconducting oxide matrix. These vertically aligned metal-oxide nanopillar composites have interesting applications in photoelectrochemical water-splitting cells for direct solar-powered hydrogen generation, where the metallic nanopillars serve multiple roles such as forming a Schottky junction and creating an efficient electrocatalytic active site on the electrode surface.
Article
Chemistry, Multidisciplinary
Ryota Takahashi, Takahisa Yamamoto, Mikk Lippmaa
Summary: The study investigated the moderation of kinetic energy in PLD growth of SrTiO3 thin films using helium buffer gas. By reducing the kinetic energy of the plume, crystal defects were minimized, leading to improved film quality. Helium pressure was found to be crucial in tuning the functional properties of oxide films.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Materials Science, Multidisciplinary
Suraj Singh, Nanhe Kumar Gupta, Soumyarup Hait, Sujeet Chaudhary, Thomas Tybell, Erik Wahlstrom
Summary: The investigation focused on the spin wave propagation in ion beam sputtered Co2FeAl Heusler alloy thin film on Si(100) substrate, with the estimation of technologically relevant parameters such as group velocity, attenuation length, and Gilbert damping parameter. The frequency dependency of these parameters was observed, showing variations with increasing frequency. The propagation parameters were independently verified using time-resolved propagating spin wave spectroscopy.
MATERIALS RESEARCH EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Haotong Liang, Valentin Stanev, Aaron Gilad Kusne, Yuto Tsukahara, Kaito Ito, Ryota Takahashi, Mikk Lippmaa, Ichiro Takeuchi
Summary: The article introduces a phase mapping method based on machine learning analysis of RHEED images, which allows for the extraction of quantitative structural information. The method can automatically identify different RHEED pattern types and is applicable to mapping the structural phase diagram of hematite-magnetite phase boundary.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Physical
Shizuka Suzuki, Takuro Dazai, Tomoharu Tokunaga, Takahisa Yamamoto, Ryuzi Katoh, Ryota Takahashi
Summary: This study investigates the effect of structural defect on the luminescence properties of TbxY2-xO3 composition-gradient films. The films were grown using pulsed laser deposition (PLD) on a SrTiO3 (001) substrate. The presence of structural defects in the films significantly weakens the luminescence intensity. Concentration quenching of the luminescence is observed at high Tb concentrations. The study provides insights into the material parameters and offers a pathway for enhancing the luminescence properties.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Physics, Applied
Shizuka Suzuki, Takuro Dazai, Yukio Yamamoto, Hideomi Koinuma, Ryota Takahashi
Summary: This study investigates the acceleration of the combinatorial optimization process for phosphor materials using a machine learning method based on Bayesian optimization. By applying Bayesian optimization to sequential measurements of photoluminescence properties, the researchers were able to significantly reduce the number of measurement points and accelerate material evaluation.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Yuta Sato, Kenichi Kaminaga, Ryota Takahashi, Shingo Maruyama, Yuji Matsumoto
Summary: The impact of band gap-graded structures on the photoelectrochemical properties was investigated, and it was found that the down-graded film exhibited better photoanodic current density and photooxidation ability. These differences are attributed to the graded band structures of the films.
CATALYSIS SCIENCE & TECHNOLOGY
(2022)
Article
Engineering, Electrical & Electronic
Shizuka Suzuki, Takuro Dazai, Kazuhiro Kawashima, Tomoharu Tokunaga, Takahisa Yamamoto, Ryota Takahashi
Summary: The feasibility of using a He buffer gas to moderate the kinetic energy of PLD plumes during the growth of EuxY2-xO3 phosphor films was investigated. It was found that the use of He buffer gas successfully reduced crystal defect generation and improved the film characteristics.
ACS APPLIED ELECTRONIC MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
K. Kjaernes, I Hallsteinsen, R. Chopdekar, M. Moreau, T. Bolstad, I-H Svenum, S. M. Selbach, T. Tybell
Summary: This study demonstrates the uniaxial control of the Ned vector in antiferromagnetic thin films through strain engineering, providing a viable tool for designing unique functional responses and enabling further application of AF materials in mesoscopic device technology.
Article
Education & Educational Research
Torstein Bolstad, Patric Wallin, Lars Lundheim, Bjorn B. Larsen, Thomas Tybell
Summary: This study found that combining project-based learning with other pedagogical scaffolding approaches has a positive influence on students' experiences during their transition into university, particularly in terms of student socialization, curriculum integration, and peer-learning. The relationships students establish with other students, teachers, and practicing engineers have significant impacts on their university start.
EUROPEAN JOURNAL OF ENGINEERING EDUCATION
(2021)
Article
Chemistry, Multidisciplinary
Naoki Sannodo, Asuka Osumi, Kenichi Kaminaga, Shingo Maruyama, Yuji Matsumoto
Summary: The heteroepitaxial growth of 3C-SiC thin films on alpha-Al2O3(0001) substrates was achieved through a VLS-like mechanism, using alternating deposition of SiC and NiSi2 flux. The process was facilitated by a pulsed laser deposition system with rapid beam deflection (RBD-PLD), resulting in uniform and high-quality SiC films with low carbon impurity inclusion.
