Day 3 :
US Naval Research Laboratory
Time : 09:30AM
Dr. Tsoi received his PhD in Physics from Purdue University. He conducted his postdoctoral work at US Naval Research Laboratory (NRL), and later was hired as a research scientist at NRL. His research interests include monolayer materials, nanoplasmonics and nanophotonics, and solid oxide fuel cells.
Physical phenomena occurring at the nanoscale often have no analogues in the macroscopic world. In this regard, nanomaterials offer exciting opportunities to create unique physical devices and effects. This presentation focuses on monolayer materials, a class of crystalline 2D solids with a thickness of less than 1 nm, and their unprecedented capacity to modify surface interactions. Forces operating at solid surfaces, such as the van der Waals force and hydrogen bonding, determine outcomes of many common phenomena, from liquid spreading (wetting) to adhesion of particles to bioadhesion. Remarkably, these forces are confined within the nanoscale from the surface: van der Waals within 20 nm and the hydrogen bonding within 1 nm. A simplified picture of such short-range forces effectively attributes them to the surface and a few sub-surface atomic layers of the solid. In this context, the recent advent of the atomically thin monolayer materials offers an unprecendented opportunity to build surface interactions in a bottom-up approach, by sequentially applying different monolayers on top of existing surfaces. Our work focuses on fundamental understanding of how the monolayer materials modify surface van der Waals interactions and this presentation highlights novel physical phenomena, unique to the monolayer materials, such as van der Waal screening.
Kochi University of Technology, 782-8502, JAPAN
Chaoyang Li is currently a professor at Kochi University of Technology, Japan. She received the B.S degree in physics, the M.S degree in microelectronics and solid state electronics from Heilongjiang University, China. She received the Ph.D degree in Electrical Engineering at the Kochi University of Technology, Japan. She has worked on the semiconductor growth, physics, processing and devices for 20 years. She also contributed to the hundreds of scientific international journals and international conferences. Her current research interests include nanotechnology, sensor and photovoltaic devices.
Recently, more and more attention has been paid to the ZnO nanostructures for its potential applications such as gas sensor, UV laser, light emitting diode, dye-sensitized solar cell (DSSC), etc . Among these applications, ZnO based DSSC has been extensively investigated because ZnO exhibit similar bandgap with TiO2, however, ZnO is much easier to fabricate into nanostructures to enlarge the surface area and has much higher electron mobility. Many methods have been developed for synthesizing ZnO nanostructures including chemical vapor deposition, hydrothermal method, sol-gel method and chemical bath deposition, etc. We had succeeded in developing a novel multiple-annealing method,which includes both the reducing reaction and oxidazation reaction processes, to synthesize ZnO nanostructures on different transparent conductive oxide films at a low temperature. It was found that the substrates had significantly influence on vertical alignment of ZnO nanostructures. The lower mismatch of the lattice imperfection between ZnO film and substrates contributed to fabricating ZnO film with good crystallinity and well-aligned ZnO nanostructures. The annealing temperature contributed to the density and length of ZnO nanostructures. The surface morphology and the crystallinity of the ZnO nanostructures could be modified by a novel mistCVD method. In order to increase the convertion efficiency of DSSC, a designed photoanodes using vertically aligned ZnO nanostructures were applied to replace nanocrystalline porous TiO2 films. The pure anatase-structured- TiO2 thin film was successfully coated on ZnO nanostructures to improve the stablity by mist CVD method. As the result, the conversion efficiency of DSSC was significantly improved.
KISTEC, Ebina, Kanagawa 243-0435, Japan
Satoru Kaneko received B.S. at Tokyo Metropolitan Univ., M.S. at Univ. of Arizona, and ph.D. at Tokyo Institute of Technology. His study focuses on synthesis of functional materials of oxides, superconductor, and graphite related materials, and also interested in fabrication of nano structure, for example, self-organisation of periodic nanostructure by laser scanning. He has published more than 100 papers in reputed journals. He spends weekend with road bike and jogging, and enjoys making bacon and beer in back yard.
After the discovery of graphene prepared by peeling graphite off using scotch tape, many methods are proposed and actually have used to prepare graphene film such as thermal decomposition of silicon carbide (SiC), and chemical vapor deposition (CVD) method. However the CVD method requires metal catalyst (Cu, Ni), and films are required to transfer onto insulating substrates for device fabrications. Another interesting method employs pencils and paper. Paper sheet drawn using a lead pencil is irradiated by femtosecond laser, and graphitic materials remain on the paper sheet . In this presentation, yet another method using pulsed laser deposition (PLD) in carbon oxide will be proposed.
Carbon dioxide (CO2) is product after hydrocarbon combustion in oxygen atmosphere. However, interestingly, CO2 can be an oxidant in certain situations. We show direct growth of graphene on insulating substrates in 100% CO2 environment, and observed the layer by layer growth on stepped edge of insulating substrate. Oxidizing environment prepared by carbon oxides offers optimal environment for graphene growth, and AFM images was indicative of layer by layer growth of graphene on insulating substrate. We will show details of AFM and Raman spectra at our presentation.