[7/19] The 8th “AIMR Seminar”
Speaker
Dr. Shuai Wei (Aarhus University, Denmark)
Title
Amorphous phase-change materials: linking local structures to thermodynamics and relaxation behaviors
Date
July 19 (Fri), 2024, 14:00–14:55 on Japan Time
Venue
Seminar Room, 2nd floor, AIMR Main Building
Abstract
Amorphous phase-change materials (PCMs) (e.g. Ge-Sb-Te) belong to a family of functional materials for novel electronic and photonic applications. PCMs can be rapidly and reversibly switched between amorphous and crystalline phases. With large optical and electric property contrast between the two phases, they can be used to encode data for non-volatile memory, photonic, and neuromorphic computing devices. However, due to their disordered structures and poor glass forming ability, the amorphous phases are not well characterized, and a better understanding of structure-property relations is an urgency for the relevance of applications.
In this work, we demonstrate structure, thermodynamics, and relaxation behaviors of amorphous PCMs over 14 orders magnitude in timescale and a thousand degree of temperature. In amorphous solid, we show how thermal annealing and pressure may induce and diminish local distortions of defective octahedral structures (Peierls-like distortion), which drastically alter materials properties (e.g. stability, crystallization, compressibility, electronic density of states). Above the glass transition temperature, materials enter a metastable supercooled liquid state, where thermodynamic anomalies are uncovered and associated with dynamic crossovers and switching behaviors. We show the evidence of a liquid-liquid transition in the metastable state with femtosecond diffractions using X-ray free electron lasers (XFEL). At higher temperature above the melting point, the density fluctuations of liquid state exhibit ultrafast structural relaxations. We demonstrate an experimental strategy to directly observe atomic-scale relaxations using femtosecond X-ray photon correlation spectroscopy by harnessing the coherent X-rays of XFEL. The fast atomistic dynamics is underlying the low viscosity and high fragility behaviour of PCM liquids. We will also briefly discuss the Boson peak in low-temperature heat capacity and development of new PCM alloys. A better understanding of amorphous PCMs may lead to the tailoring of materials properties for novel applications in photonic, and neuromorphic computing devices.
- [1] S. Wei, P. Lucas, and C. A. Angell, Phase-Change Materials: The View from the Liquid Phase and the Metallicity Parameter, MRS Bulletin 44, 691 (2019).
- [2] T. Fujita et al., Pressure-Induced Reversal of Peierls-like Distortions Elicits the Polyamorphic Transition in GeTe and GeSe, Nat Commun 14, 1 (2023).
- [3] Y. Cheng et al., Highly Tunable β-Relaxation Enables the Tailoring of Crystallization in Phase-Change Materials, Nature Communications 13, 7352 (2022).
- [4] P. Zalden et al., Femtosecond X-Ray Diffraction Reveals a Liquid–Liquid Phase Transition in Phase-Change Materials, Science 364, 1062 (2019).
- [5] S. Wei, P. Lucas, and C. A. Angell, Phase Change Alloy Viscosities down to Tg Using Adam-Gibbs-Equation Fittings to Excess Entropy Data: A Fragile-to-Strong Transition, J. Appl. Phys. 118, 034903 (2015).
- [6] S. Wei, Anomalous Liquids on a New Landscape: From Water to Phase-Change Materials, Journal of Non-Crystalline Solids: X 14, 100094 (2022).
AIMR Seminars and Tea Time
We hold AIMR Seminars and Friday Tea Time as part of the initiative to promote fusion research.
Seminars are presented by AIMR researchers and visiting scientists who provide a wide range of hot topics from materials science to mathematics. The aims of the AIMR Seminar are to build up mutual understanding, communication, and discussions of each other’s research fields.
Weekly held Friday Tea Time is where AIMR researchers and staff members can relax and talk freely while drinking coffee. Expectations of stimulating conversation may arise among the researchers and leading to new research.
From 2024, active fusion research through synergistic effects from AIMR Seminars and Friday Tea Time will be promoted.
Past AIMR Seminar
| 7th | July 5, 2024 | Prof. Henning Schomerus (Lancaster University, U.K.) |
|---|---|---|
| 6th | May 10, 2024 | Prof. Hidekazu Kurebayashi (University College London, U.K.) |
| 5th | May 1, 2024 | Prof. Michael Hirscher (Max-Planck-Institute for Intelligent Systems, Germany) |
| 4th | Apr. 26, 2024 | Prof. Konstantinos Danas (ELyTMax, CNRS-Tohoku University) |
| 3rd | Mar. 13, 2024 | Prof. Ryoko Tomiyasu (Institute of Mathematics for Industry, Kyushu University) |
| 2nd | Jan. 26, 2024 | Prof. Michael I. Ojovan (Imperial College London, U.K.) |
| 1st | Jan. 12, 2024 | Dr. William Chuck Witt (University of Cambridge, U.K.) |
About Tea Time Talk
As part of an event during Friday Tea Time, AIMR has been hosting lectures by famed researchers and the archives up to 2023 are listed below:
| 43rd | July 21, 2023 | Prof. Feral Temelli (University of Alberta, Canada) |
|---|---|---|
| 42nd | June 30, 2023 | Dr. Douglas Brumley (The University of Melbourne, Australia) |
| 41st | Mar. 28, 2023 | Prof. Motomu Tanaka (Physical Chemistry of Biosystems, Institute of Physical Chemistry, Heidelberg University, Germany) |
| 40th | Nov. 10, 2022 | Prof. Masahiro Yoshimura (National Cheng Kung University, Taiwan) |
| 39th | June 17, 2022 | Prof. Rana Mohtadi (Toyota Research Institute of North America) |
| 38th | June 17, 2022 | Prof. Michael Hirscher (Max-Planck-Institute for Intelligent Systems, Germany) |
| 37th | June 3, 2022 | Prof. Reiko Oda (French National Centre for Scientific Research) |
| 36th | May 28, 2021 | Prof. Magda Titirici (Imperial College London, U.K.) |
| 35th | Mar. 26, 2021 | Prof. Yaroslav Blanter (Kavli Institute of Nanoscience, Delft University of Technology) |
| 34th | Oct. 23, 2020 | Dr. Kazuhito Tsukagoshi (PI:WPI-MANA, NIMS & AIMR) |
| 33rd | July 17, 2020 | Prof. Kaoru Tamada (IMCE, Kyushu University & AIMR) |
| 32nd | Jan. 17, 2020 | Prof. Miho Yamauchi (I2CNER / Kyushu University & AIMR) |
| 31st | Jan. 17, 2020 | Prof. Mickaël Lallart (INSA Lyon, Université de Lyon) |
| 30th | Oct. 25, 2019 | Assoc. Prof. Frédéric Gillot (Department of Solid Mechanics, Mechanical Eng. and Civil Eng., École Centrale de Lyon) |
| 29th | July 12, 2019 | Prof. Qian Niu (Department of Physics, The University of Texas at Austin) |
| 28th | May 17, 2019 | Prof. Damien Fabrègue (INSA Lyon, France / ELyT MaX Lab at Tohoku University) |
| 27th | Dec. 14, 2018 | Prof. Yukitoshi Motome (Department of Applied Physics, The University of Tokyo, Japan) |
| 26th | July 13, 2018 | Dr. Shimpei Ono (Central Research Institute of Electric Power Industry, Japan) |
| 25th | May 11, 2018 | Dr. Pierre-Antoine Geslin (Mateis lab, INSA Lyon/CNRS / ELyTMaX Lab at Tohoku University / Institute for Materials Research, Tohoku University) |
| 24th | Apr. 27, 2018 | Prof. Masaru Tsukada (AIMR, Tohoku University) |
| 23rd | Dec. 8, 2017 | Prof. Jean-Yves Cavaillé (INSA Lyon, France / ELyT MaX Lab at Tohoku University) |
| 22nd | July 28, 2017 | Prof. Nicolas Mary (INSA Lyon, France / ELyT MaX Lab at Tohoku University) |
| 21st | July 21, 2017 | Prof. Gael Sebald (INSA Lyon, France / ELyT MaX at Tohoku University) |
| 20th | July 7, 2017 | Prof. Arun Bansil (Northeastern University) |
| 19th | June 30, 2017 | Dr. Takeshi Nakanishi (AIST-Tohoku U Mathematics for Advanced Materials Open Innovation Laboratory (MathAM-OIL)) |
| 18th | June 23, 2017 | Prof. Denis Arčon (Jožef Stefan Institute, Slovenia) |
| 17th | Apr. 28, 2017 | Prof. Ayumi Hirano (AIMR, Tohoku University) |
| 16th | Nov. 29, 2016 | Dr. David Guy Austing (National Research Council Canada, Canada) |
| 15th | Sept. 30, 2016 | Prof. C. Suryanarayana (University of Central Florida, U.S.A.) |
| 14th | June 17, 2016 | Prof. Tomoteru Fukumura (AIMR, Tohoku University) |
| 13th | May 13, 2016 | Prof. Jean-Yves Cavaillé (ELyT MaX (Joint Lab at Tohoku University), University of Lyon, France) |
| 12th | June 26, 2015 | Dr. B. Muralidharan (Indian Institute of Technology Bombay, India) |
| 11th | June 27, 2014 | Prof. Michael B. Santos (The University of Oklahoma, U.S.A.) |
| 10th | Nov. 19, 2013 | Dr. Pawel Hawrylak (National Research Council Canada, Canada) |
| 9th | Oct. 1, 2013 | Dr. Yuan T. Lee (Nobel laureate in Chemistry, Academia Sinica of Taiwan) |
| 8th | June 28, 2013 | Dr. Bjorn Mysen (Geophysical Laboratory, Carnegie Institution for Science, U.S.A.) |
| 7th | Apr. 12, 2013 | Prof. Yiming Li (National Chiao Tung University, Taiwan) |
| 6th | Jan. 18, 2013 | Prof. Tomasz Dietl (Polish Academy of Sciences, Poland) |
| 5th | Aug. 31, 2012 | Prof. John H. Perepezko (University of Wisconsin-Madison, U.S.A.) |
| 4th | Aug. 17,2012 | Prof. Alain Reza Yavari (Grenoble Institute of Technology, France) |
| 3rd | Aug. 10, 2012 | Prof. Alan Lindsay Greer (University of Cambridge, U.K.) |
| 2nd | July 6, 2012 | Prof. Winfried Teizer (Texas A&M University, U.S.A.) |
| 1st | May 25, 2012 | Prof. Thomas P. Russell (The University of Massachusetts Amherst, U.S.A.) |
Contact
Kazuto Akagi
Deputy Director, Research Support Division, AIMR
| E-mail: | kazuto.akagi.b5@tohoku.ac.jp |
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