Chemically Derived Graphene Nanoribbons and Large-scale High Quality Graphene Sheets: Synthesis, Assembly, N-doping and Applications
报告人:
李晓林
博士Postdoc Research Fellow, Stanford University
报告时间:
2009-11-12 14:30
报告地点:
清华-富士康纳米科技研究中心四楼报告厅
主办单位:
物理系
简介:
摘 要：
Emerging as a star material, graphene (single layer graphite) provides a rich lode of novel fundamental physics and practical applications. With its electronic mobility more than 100 times higher than silicon, graphene is desirable for high-performance nanoelectronics. Graphene nanoribbons with the width smaller than 10nm are believed to be all semiconductors suitable for field effect transistors.
We developed a chemical route to produce graphene nanoribbons (GNR) with width below 10 nanometers, as well as single ribbons with varying widths along their lengths or containing lattice-defined graphene junctions for potential molecular electronics. The GNRs are solution-phase derived, stably suspended in solvents with non-covalent polymer functionalization, and exhibit ultra-smooth edges with possibly well-defined zigzag or arm-chair edge structures. Electrical transport experiments show that unlike SWNTs, all of the sub-10 nanometer GNRs produced are semiconductors and afford graphene field effect transistors (FET) with on-off ratios ~105 at room temperature. Doping the graphene ribbons through electro-thermal reactions with ammonia, we obtain the first n-type graphene FET operating at room temperature.
We also developed a method of exfoliation-reintercalation-expansion of graphite to produce large-scale high quality single-layer graphene sheets (GS) stably suspended in organic solvents. The GS exhibit high electrical conductance at room and cryogenic temperatures. Large amounts of GS in organic solvents are made into large transparent conducting films by Langmuir-Blodgett (LB) assembly in a layer-by-layer manner. In addition to the LB method, a chemical self-assembly of these graphene sheets on patterned gold substrates were also discovered. Using graphene oxide sheets as the starting material, we synthesized large-scale N-doped reduced graphene through the reaction with NH3 at elevated temperature and systematically studied the N-doping with X-ray photoelectron spectroscopy (XPS). The chemically derived graphene sheets could lead to future clean energy applications like supercapacitors and oxygen reduction catalysts in fuel cells.
