= 아 래 =
1. 일 시 : 2014. 7. 21 (월), 11:00 ~
2. 장 소 : KI 빌딩 Matrix Hall
3. 연 사 : Jamie Warner (University of Oxford)
4. 제 목 : Understanding the structure and dynamics of defects and dopants in graphene at the atomic level
Defects and dopants influence the chemical, electrical, magnetic, and mechanical properties of graphene. It is therefore very important to have a clear understanding of their precise atomic structure so that they can be accurately model in theoretical calculations of properties. Furthermore, understanding how defects and dopants migrate within the lattice of graphene is important as it reveals how plasticity evolves in 2D materials and the stability of doped graphene. In this talk I will summarize our recent work on atomic resolution imaging of graphene defects and dopants using low-voltage aberration-corrected transmission electron microscopy. I will show how we can map defect structures down to measuring single C-C bond length changes and correlate this to variations in the electronic charge density. A variety of dopant atoms are studied, including nitrogen, silicon, and iron. Using scanning TEM (ADF-STEM) combined with atomic resolution electron energy loss spectroscopy (EELS), I will demonstrate how the density of states can be mapped atom-by-atom at graphene edges, within defects such as pentagons and heptagons, and around dopant atoms. This provides important insights into the charge-transfer of dopant atoms to graphene and the perturbation to the sub-lattice structure of graphene from introducing 5 and 7 membered rings.