Yuegang Zhang
Staff Scientist, Inorganic Nanostructures Facility
yzhang5@lbl.gov
510.486.5282
Research Interests
- Synthesis and characterization of carbon nanomaterials, including graphene and carbon nanotubes.
- Nanoelectronic devices and non-volatile memory technologies.
- Nanostructured materials for electrochemical energy storages.
Current projects
- Graphene Synthesis
- Advancing the fabrication of graphene films
Direct deposition of graphene on various dielectric substrates is demonstrated using a single-step chemical vapor deposition process. Single-layer graphene is formed through surface catalytic decomposition of hydrocarbon precursors on thin copper films predeposited on dielectric substrates. The copper films dewet and evaporate during or immediately after graphene growth, resulting in graphene deposition directly on the bare dielectric substrates. Scanning Raman mapping and spectroscopy, scanning electron microscopy, and atomic force microscopy confirm the presence of continuous graphene layers on tens of micrometer square metal free areas. The revealed growth mechanism opens new opportunities for deposition of higher quality graphene films on dielectric materials. Learn more
- Ariel Ismach, Clara Druzgalski, Samuel Penwell, Adam Schwartzberg, Maxwell Zheng, Ali Javey, Jeffrey Bokor, and Yuegang Zhang
- Advancing the fabrication of graphene films
- Electronic transport in graphene and nanoribbons
- Studying the low frequency noise in graphene nanoribbon devices
Conductance fluctuation is usually unavoidable in graphene nanoribbons (GNR) due to the presence of disorder along its edges. By measuring the low-frequency noise in GNR devices, we find that the conductance fluctuation is strongly correlated with the density-of-states of GNR. In single-layer GNR, the gate-dependence of noise shows peaks whose positions quantitatively match the subband positions in the band structures of GNR. This correlation provides a robust mechanism to electrically probe the band structure of GNR, especially when the subband structures are smeared out in conductance measurement. Learn more
- Guangyu X, Carlos M. Torres, Jr., Emil B. Song, Jianshi Tang, Jingwei Bai, Xiangfeng Duan, Yuegang Zhang, and Kang L. Wang
- Studying the low frequency noise in graphene nanoribbon devices
- Ultra-high density data storage
- Fully Inverted Single-Digit Nanometer Domains in Ferroelectric Films
Achieving stable single-digit nanometer inverted domains in ferroelectric thin films is a fundamental issue that has remained a bottleneck for the development of ultrahigh density (> 1 Tbit/ in.2) probe-based memory devices using ferroelectric media. Here, we demonstrate that such domains remain stable only if they are fully inverted through the entire ferroelectric film thickness, which is dependent on a critical ratio of electrode size to the film thickness. This understanding enables the formation of stable domains as small as 4 nm in diameter, corresponding to 10 unit cells in size. Such domain size corresponds to 40 Tbit/ in.2 data storage densities. Read the full research paper.
- Noureddine Tayebi, Yoshie Narui, Nathan Franklin, C. Patrick Collier, Konstantinos P. Giapis, Yoshio Nishi, and Yuegang Zhang
- Fully Inverted Single-Digit Nanometer Domains in Ferroelectric Films
- Electrochemical energy storage
- Carbon Nanofiber Supercapacitors with Large Areal Capacitances
We develop supercapacitor (SC) devices with large per-area capacitances by utilizing three dimensional (3D) porous substrates. Carbon nanofibers (CNFs) functioning as active SC electrodes are grown on 3D nickel foam. The 3D porous substrates facilitate a mass loading of active electrodes and per-area capacitance as large as 60 mg/cm2 and 1.2 F/cm2, respectively. We optimize SC performance by developing an annealing-free CNF growth process that minimizes undesirable nickel carbide formation. Superior per-area capacitances described here suggest that 3D porous substrates are useful in various energy storage devices in which per-area performance is critical. Read the full research paper.- James R. McDonough, Jang Wook Choi, Yuan Yang, Fabio La Mantia, Yuegang Zhang, and Yi Cui
- Carbon Nanofiber Supercapacitors with Large Areal Capacitances
Selected publications
- G. Xu, C. M. Torres, Jr., E. B. Song, J. Tang, J. Bai, X. Duan, Y. Zhang, and K. Wang, “Enhanced Conductance Fluctuation by Quantum Confinement Effect in Graphene Nanoribbons,” Nano Letters, Publication Date (Web): October 12, 2010 (ASAP Article).
- N. Tayebi, Y. Zhang, R. J. Chen, Q. Tran, R. Chen, Y. Nishi, Q. Ma, and V. Rao, “An UltracleanTip-Wear Reduction Scheme for Ultrahigh Density Scanning Probe-Based Data Storage,” ACS Nano, Publication Date (Web): October 7, 2010 (ASAP Article).
- G. Xu, C. M. Torres Jr., Y. Zhang, F. Liu, E. B. Song, M. Wang, Y. Zhou, C. Zeng, and K. L. Wang, “Effect of Spatial Charge Inhomogeneity on 1/f Noise Behavior in Graphene,” Nano Letters 10, 3312-3317 (2010).
- A. Ismach, C. Druzgalski, S. Penwell, Adam Schwartzberg, M. Zheng, A. Javey, J. Bokor, Y. Zhang, “Direct Chemical Vapor Deposition of Graphene on Dielectric Surfaces,” Nano Letters 10, 1542-1548 (2010).
- N. Tayebi, Y. Narui, N. Franklin, C. P. Collier, K. P. Giapis, Y. Nishi, and Y. Zhang, “Fully Inverted Single-Digit Nanometer Domains in Ferroelectric Films,” Applied Physics Letters 96, 023103 (2010).
Book Chapters
- Y. Zhang, "Composite Nanowires," in Nanowires and Nanobelts, ed. Zhong Lin Wang, Kluwer Academic Publishers, Boston, 2003, Vol. 2, pp. 257-268.
- Y. Zhang, W. Han, G. Gu, "Nanocables and Nanojunctions," in Encyclopedia of Nanoscience and Nanotechnology, ed. H. S. Nalwa, American Scientific Publishers, 2004, Vol. 6, pp. 61-76.
- Y. Zhang, "Carbon nanotube based nonvolatile memory devices," in Nanotubes and Nanowires, ed. P. J. Burke, World Scientific Publishing Co., Singapore, 2007, pp.77-93.
Education
Ph.D. Materials Science & Engineering, University of Tokyo Supervisor: Yoichi Ishida
“High-resolution electron microscopy & electron energy loss spectroscopy of grain boundaries in diamond thin films”
M.S. Physics, Tsinghua University
B.S. Physics, Tsinghua University
Past Professional Positions
July 2002 – August 2008
Senior Researcher, Intel Corporation (Santa Clara, CA, USA)
Chair, Memory Strategic Research Sector (05 - 08)
Project leader, Nanotube Strategic Research Project, Intel Research (02 - 05)
January 2000 – July 2002
Research Associate, Department of Chemistry, Stanford University (Stanford, CA, USA)
Mentor: Prof. Hongjie Dai
(also affiliated with Molecular Nanosystems Inc. during Sept. 2001 – July 2002)
October 1996 – January 2000
Researcher, Fundamental Research Laboratories, NEC Corporation (Tsukuba, Japan)
Mentor: Dr. Sumio Iijima
August 1989 – September 1993
Lecturer/Assistant Professor, Department of Physics, Tsinghua University (Beijing, China)
