题目：Defect generation on graphene through scanning probe lithography
The emergence of two dimensional (2D) materials since 2004 has drawn vast research activities and ignited high expectation on their potential in various applications. Graphene is the most thoroughly studied 2D material. Nevertheless, the lack of band gap in graphene restricts its applicability in many areas. Efforts in creating band gap in graphene through various methods including modification of sp3/sp2hybridization by functionalization or defect engineering have proven successful to certain degrees. The alternative paths for band gap engineering in graphene related materials is through controlled reduction of graphene oxide(GO).In general, the GO reduction processes involve breaking and reconstruction of C-O and C-C related bonds. Nevertheless, the exact pathways and dynamics for GO reduction has not been thoroughly investigated experimentally. Besides band gap engineering, defect introduction into the originally perfect 2D honey-comb lattice in a controlled manner may open up more dimensions for tuning of graphene properties such as surface reactivity. It is therefore important to study the dynamics of defect generation and its recovery in a controllable and systematic way in order to fully realizing the controllability of graphene related materials.
Scanning probe lithography (SPL) is a mask-less technique that enables nanometer scale patterning on metallic or semiconducting substrates. We have demonstrated the feasibility of applying the above technique to generate local strain in a graphene sheet by formation of surface bump through subsurface silicon oxide protrusion. Local anodic oxidation or vacancy formation through ion bombardment can be achieved by adequately adjust the SPL parameters. We have employed micro-Raman spectroscopy (?-RS)and scanning photoelectron spectroscopy (SPEM) to investigate the structural and chemical natures of the defect structures. In-situ monitoring of the local x-ray photoelectron spectra (XPS) are employed to study the reduction dynamics. The reduction dynamics can be described with a set of nonlinearly coupled differential equations. From data fitting, we have found three unambiguously identified characteristic time scales which correlate to dissociation/creation of respective carbon-oxygen related bonds during the reduction processes.
Wei-Yen Woon received the B. S., M. S., Ph. D. degrees in physics from National Central University (NCU), Jungli, Taiwan, in 1998, 2000, and 2005, respectively. He had worked on soft matter and complex plasma at NCU from 2001-2005. He became an invited speaker in European Physical Society (EPS) in 2004 for his work on defects turbulence in dusty plasma liquids. In 2005-2008, he worked on novel metrology and dopant annealing technologies at Taiwan Semiconductor Manufacturing Company (TSMC), Hsinchu, Taiwan. During the above period, he pioneered the works in establishing novel methodologies for precise strain measurement with micro-Raman spectroscopy, and dopant profiling with atomic force microscopy. In 2008, He became an assistant professor in department of physics in NCU, and was subsequently promoted to associate professor in 2013. His current research interests are in the physics of defects in bulk and two dimensional materials; and complex collective dynamics in bio-micro-fluidics systems. He has authored 21 journal papers and one U.S. Patent.