Title: Graphene; Broader Picture & Engineering it’s wave function via scanning probe techniques
Speaker: Dr. Asieh Kazemi (Bath University)
Date/Time: December 16, 2015 Wednesday at 13:40
Place: Sabancı University, FENS G029
Abstract: Graphene, a single, atomically-thin layer of graphite, is the most researched material today. Since 2004 - when it was isolated for the first time, ground breaking experiments of fundamental science were followed by a cascade of demonstrations of potential usages of graphene in day-to-day applications. This led to a Nobel Prize in Physics in 2010 and to graphene being named by industry as a potential “disruptive technology” that would bring profound changes to many existing technologies or enable some completely new. If the current focus is in using graphene to better the performance of existing technologies (in applications such as flexible displays, solar cells, chemical and biosensors, faster wireless networks, supercapacitors and graphene based inks, graphene based composites in aerospace and automotive technology, or DNA sequencing and biomedical devices), there is tremendous unlocked potential in using properties that only graphene itself possesses.
It was in this domain that my research lied. I studied the spatial modulation of the wave function in bilayer and trilayer graphene systems originating from two underlying mechanisms: quantum interference phenomena (QIP) and quantum confinement. I also took a bottom-up approach to tailoring surface potential distributions at the atomic scale to influence/control electron behaviour, by utilising the interaction between graphene layers and nanostructured, atomically flat insulating ionic surfaces. Quantum interference phenomena were explored at bilayer-trilayer armchair interfaces in multilayer graphene with various stacking orders by using scanning tunnelling microscopy and with support from theoretical simulations. Effects of various types of edges, which terminate the stacks abruptly or appear at lateral interfaces within the multistack, were revealed and correlated with scattering mechanisms, while a taxonomy of interference patterns was established based on stacking order. The effect of extra sources of scattering was also studied to understand the origin of the well-known superstructure in graphene systems, and a new explanation was proposed based on decomposing defects into armchair contours, able to provide multiple sources of scattering. The energy dependency of the superstructure and its motifs was quantitatively explored in bilayer graphene. Finally, bilayer and trilayer graphene were overlaid on atomically flat insulating surfaces decorated with nanostructures such as step edges and closed contours, and able to induce sizeable local electrostatic potential distribution within the graphene overlayers. A well-defined, rectangular subsurface potential distribution, akin to a nanoscale quantum box applied to a physically unconfined graphene overlayer, produced state localization in the local density of states of a trilayer, while resonances were also observed in bilayer graphene around irregular subsurface features within the ionic substrate.
Dr. Asieh Kazemi is a Research Associate in Center for Graphene Science, Department of Physics, University of Bath, Bath, United Kingdom, 2015-now. She has received her PhD at the same department 2011-2015. The central theme of her work, “engineering the wave function in graphene systems”, is to probe, engineer and harness the very special behaviour of electrons within the graphene sheet (the so-called “Dirac electrons”). Some of the results of her work are published and some are in the preparation process for submission. She is interested in other 2D materials such as TMDs and has experienced exploring their properties via SPM. Theoretical approach to approximation of the Van der Waals and Casimir effects on NEMS is her other field of interest.
She has received MSc degree in Solid State Physics at Damghan University, Damghan, Iran, 2006-2008 on Synthesis and Characterization of semiconducting ZnO nanoparticles and their application as gas sensors. She has also received BSc in Solid State Physics from Khajeh Nasir University of Technology, Tehran, Iran, 2001-2005. For a full list of publications and Conferences please visit http://people.bath.ac.uk/askss20/.