Strongly correlated electron materials and functional materials with reduced dimensions
Research on correlated electron materials enriches our understanding of solid state physics and offers a route toward novel useful devices. Many unique properties of strongly correlated electron materials originate from the competition of different degrees of freedom, which usually results in complex phase diagrams and stabilizes multiple phase coexistence at the sub-micron scale. Integration of multiple functionalities of these materials thus requires controlling and understanding their properties on the single or few domain level. Specifically, this project involves synthesis of transition metal chalcogenide and oxide nanostructures, fabrication and characterization of nanodevices, and examining various types of phase transitions at the nanoscale using scanning probe, optical and in situ tools.
Energy applications of electronic materials
We examine photon-carrier and phonon-carrier interactions in electronic materials thin films and nanostructures, targeting fundamental problems in their photovoltaic, infrared and thermal/thermoelectric applications. Specifically, we study group III-nitride alloys and highly mismatched semiconductor alloys for broad-spectrum photovoltaics, and phase transition materials for infrared, photonic and thermal/thermoelectric technologies. Our work also heavily involves numerical modeling of charge behavior and device performance of various device structures. We are also officially part of the Electronic Materials Program in LBNL.
Materials Interfaces, membranes and Composites
We have strong research interest and efforts in electronically and mechanically dynamic phenomena ocurring at the interface between dissimilar materials. These phenomena involve some of the most fundamental processes in materials physics, such as atomic diffusion, phase segragation, charge transfer and scattering, and electron-phonon interactions. Using a number of advanced in situ microscopic and spectroscopic techniques, we seek to understand these processes, and look for ways to engineer them for synergistic materials properties that cannot be found in any of the constituents alone.
A poster (PDF) describing our recent research activities (2018-2019).
Research Collaborations (partial list)
Prof. Jeffrey C. Grossman, MIT Dr. Wladek Walukiewicz, LBNL
Dr. Joel W. Ager III, LBNL Prof. Daryl C. Chrzan, U. C. Berkeley
Prof. Ali Javey, U. C. Berkeley Prof. Peidong Yang, U. C. Berkeley
Prof. Jie Yao, U. C. Berkeley
Dr. Jingbo Li, Chinese Academy of Sciences Prof. Costas P. Grigoropoulos, U. C. Berkeley Prof. Long-Qing Chen, Penn State University
Prof. Dapeng Yu, Peking University and South University of Science and Tech
Prof. Kaili Jiang, Tsinghua University
Prof. Feiyu Kang, Tsinghua University
Prof. Volker Eyert, Augsburg University
Prof. Olivier Delaire, Duke Univ
Prof. Sefaattin Tongay, Arizona State University
Prof. Sungwng Kim, SKKU Korea
Dr. Bin Chen, HPSTAR Shanghai China
Prof. Jeong Y. Park, KAIST Korea
Prof. Chris Dames, U. C. Berkeley
Prof. Jiawang Hong, Beijing Institute of Technology
Prof. Peter Fan Yang, Stevens Institute of Technology
Research Highlights and Gallery
Reconfiguring crystal and electronic structures of MoS2 by substitutional doping, Nature Communications, 9, 199 (2018).
A fabrication-free and field-programmable photonic meta-canvas, Advanced Materials, 30, 1703878 (2018).
Enhancing thermoelectric power factor with highly mismatched isoelectronic doping; Phys. Rev. Lett., 104, 016602 (2010).
Determining surface Fermi level pinning position of InN nanowires using electrolyte gating; Appl. Phys. Lett., 95, 173114 (2009).
Thermoelectric Effect across the Metal-Insulator Domain Walls in VO2 Microbeams. Nano. Lett., 9, 4001 (2009)
Sublimation of GeTe nanowires and evidence of its size effect studied by in situ TEM. J. Am. Chem. Soc., 131, 14526 (2009).
Strain engineering and one-dimensional organization of metal-insulator domains in single-crystal VO2 beams. Nature Nanotech., 4, 732 (2009). (cover highlight)
When Group III - Nitrides Go Infrared: New Properties and Perspectives. J. Appl. Phys., 106, 011101 (2009).
Modulating Surface Electron Accumulation in InN by the Electrolyte Gated Hall Effect. Appl. Phys. Lett.; 93, 262105 (2008)
Effects of Surface States on Electrical Characteristics of InN and InGaN. Phys. Rev. B, Rapid Commun.; 76, 041303(R) (2007).
Gate Coupling and Charge Distribution in Nanowire Field Effect Transistors. Nano Lett., 7, 2778 (2007).