Materials Science Research Lecture

Wednesday November 20, 2019 4:00 PM

"Exploring and manipulating different quantum degrees of freedom in two-dimensional van der Waals materials and nano-metamaterials”

Speaker: Nai-Chang Yeh, Caltech
Location: Spalding Laboratory 106 (Hartley Memorial Seminar Room)

Abstract:

Recent advances in the development of two-dimensional (2D) atomic crystalsfrom various van der Waals (vdW) materialshave simulated intense research efforts and demonstrated great promises for a wide range of technological applications. Some of the representative vdW materials with honeycomb lattice structures include graphene, hexagonal boron nitride (h-BN), and transition metal dichalcogenides (TMDs) MX2(where M = transition metals and X = S, Se and Te) that exhibit novel properties such as strong spin-valley coupling, superconductivity, and nontrivial topology. In this talk I will first review the unique physical properties of graphene, h-BN and TMDs that are of particular interest to nanoscale electronic, optoelectronic/valleytronic/spintronic applications, and then describe our scalable fabrication of high-quality 2D materials by means of a single-step PECVD method for monolayer graphene and bilayer graphene with controlled twist angles as well as quasi-one-dimensional graphene nanostripes,1,2,3,4and CVD method for h-BN and TMDCs.5,6I will also describe our ongoing research progress in the exploration and manipulation of different quantume degrees of freedom in these 2D materials by using light and architected nano-metastructures,6,7,8and discuss our ultimate objective to advance the control and functionality of 2D materials and their heterostructures by tuning the composition, symmetry, topology, dimensionality, Fermi level, interface and spin-orbit-coupling of light, and by architected nano-metamaterials.

References:

  • “Single-step deposition of high-mobility graphene at reduced temperatures”, D. A. Boyd et al., Nature Communications6, 6620 (2015).
  • “High-yield single-step catalytic growth of graphene nano-strips by plasma enhanced chemical vapor deposition”, Chen-Chih Hsuet al., Carbon129, 527 –536 (2018).
  • “Recent advances in single-step plasma enhanced chemical vapor deposition of graphene and related nanostructures”, N.-C. Yehet al., invited review, Nanotechnology30, 162001 (2019).
  • “Direct growth of mm-size twisted bilayer graphene by plasma enhanced chemical vapor deposition”, Yen-Chun Chenet al., Carbon156, 212-224 (2020).
  • “Atomic-scale structural and chemical characterization of hexagonal boron nitride layers synthesized at the wafer-scale with monolayer thickness control”, W.-H. Linet al., Chemistry of Materials29, 4700−4707 (2017).
  • “Nearly 90% circularly polarized emission in monolayer WS2single crystals by chemical vapor deposition (CVD)”, Wei-Hsiang Linet al., ACS Nano(2019). [DOI: 10.1021/acsnano.9b05550]
  • “Nanoscale strain engineering of graphene and graphene-based devices”, N.-C. Yehet al.,Acta Mechanica Sinica32, 497 – 509 (2016). [DOI: 10.1007/s10409-015-0548-9]
  • “Nanoscale engineering of giant pseudo-magnetic fields, valley polarization and topological channels in strained graphene”, Chen-Chih Hsuet al.,manuscript under review (2019).
  • More about the Speaker:

    Nai-Chang Yeh is currently Professor of Physics at the California Institute of Technology (Caltech). Her principal research field is experimental condensed matter physics, and her research group focuses on scientific and technological topics of correlated electrons (e.g., high-temperature superconductors; colossal magnetic perovskites), topological materials (e.g., topological insulators and superconductors; topological states for quantum information), low-dimensional systems (e.g., van der Waals materials including graphene, h-BN and two-dimensional transition-metal dichalcogenides; graphene nanostripes; carbon nanotubes; nanoparticles; quantum dots), valleytronics, spintronics (based on spin-orbit-coupled materials, half-metallic ferromagnets), nanoscience and nanotechnology (e.g., instrumentation of scanning probe microscopy for nanoscale characterization; nanofabrication of electronic, optoelectronic, valleytronic and spintronic devices; nanoscale strain engineering of graphene and transition-metal dichalcogenides), energy research (e.g., energy conversion in photovoltaic and fuel cells; supercapacitors and lithium ion batteries for energy storage), and precise measurements using superconducting technology. To date she has published over 145 papers in refereed journals and one book chapter (printed by both Peking University Pressand World Scientific Publishing Company), edited one conference proceedings, and authored a book of autobiography (in Chinese) that was published by Business Weeklyin Taiwan.

    Yeh received her B.Sc. degree from National Taiwan University in June of 1983 and her Ph.D. degree in physics from the Massachusetts Institute of Technology in January of 1988. She was a visiting scientist at IBM Thomas J. Watson Research Center from 1988 to 1989, and joined the physics faculty of Caltech as an assistant professor in August of 1989. She was tenured as an associate professor in 1995, and promoted to full professorship in 1997. Some of her professional honors include: Distinguished Visiting Professor, Shanghai University, China (2019); Achievement Award, Tsien Excellence in Education Program, Tsinghua University, China (2019); Visiting Chair Professor, National Central University, Taiwan (2017-2018); Eminent Visiting Professor, Universiti Brunei Darussalam (UBD), Brunei (2014–2015); Visiting Chair Professor, Center for Nano and Micro Mechanics (CNMM), Tsinghua University, Beijing, China (2012–2014); Wu Chien-Shiung Distinguished Lectureship Award, National Central University, Taiwan (2012); Fellow, American Association for the Advancement of Science (2007); Fellow, American Physical Society (2004); Distinguished Alumni Award, Department of Physics, National Taiwan University (2003); Fellow, The Institute of Physics, UK (2001); Achievement Awards, Southern California Chinese-American Faculty Association (2001); Outstanding Young Researcher Award, International Organization of Chinese Physicists and Astronomers (OCPA) (1998); Packard Fellowship for Science and Engineering (1992–1997); and Sloan Research Fellowship (1990–1992). In 1991, TimeMagazine named her a scientific “rising star” in California. In 2016, BBC World Newsfeatured her research in one of the Horizonepisodes “Abundant World”.

    Professor Yeh has also served on many national and international committees and professional activities. Some of her recent roles include: Fletcher Jones Foundation Co-Director of the Kavli Nanoscience Institute (2013–2019); Member, Advisory Committee on International Science and Engineering, National Science Foundation, USA (2016–present); Member, Committee on Equal Opportunities in Science and Engineering, National Science Foundation, USA, (2016–present); Member, American Physical Society (APS) Development Committee & Task Force on International Collaborations (2016–2018); Handling Editor, Reviews in Physics, Elsevier, The Netherlands, (2015–2019); International Advisor, Physics Honor’s Program, Shanghai Jiao Tong University, Shanghai, China (2015–present); International Advisor, Tsien Excellence in Education Program, Tsinghua University, Beijing, China (2014–present); President, International Organization of Chinese Physicists and Astronomers (2013–2014); Member, International Advisory Committee, Chinese High Magnetic Field Laboratory (2009–present); Member at Large, Division of Condensed Matter Physics, APS (2011–2014); Member, Presidential Science Prize Selection Committee (Physical Sciences), Taiwan (2011, 2013, 2015); Member, Presidential Search Committee, National Taiwan University (2012–2013); Member, Scientific Advisory Board, Center of Electronic Correlations and Magnetism, University of Augsburg, Germany (2008–present); Member, External Advisory Committee, National High Magnetic Field Laboratory (NHMFL), USA, (2004– present); Member, Steering Committee, Keck Institute for Space Studies (KISS), USA (2008–2013).

    Series Materials Research Lecture Series

    Contact: Elizabeth Rodriguez at 626-395-3329 elizabeth@caltech.edu