Electronic structure studies of graphene grown on SiC (0001), Ni(111) and a topological insulator Bi2Se3 using angle resolved photoemission spectroscopy

In recent years, topological insulators and graphene have attracted considerable attention of the scientific community due to their potential applications and underlying fundamental physics. This talk is focused on recent research work done on graphene and topological insulators. In graphene research, I will discuss the electronic structure of graphene grown on SiC(0001) andalkali metal (Na and Cs) adsorption on epitaxial graphene grown on Ni(111) substrate. In the graphene grown on SiC(0001), I will discuss a band gap induced by symmetry breaking using angle-resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). The STM topography reveals that the six fold symmetry breaks into the three fold due to sub-lattice symmetry breaking. The (√3×√3)R30 superstructure and quantum interference (QI) pattern observed on the terrace in the neighborhood of steps is attributed to the symmetry breaking. The QI pattern observed around the steps indicates that the terrace behaves like graphene nanoribbons (GNR) and surrounding steps like edge of GNR. Our findings show a400 meV band gap in graphene grown on SiC(0001)due to symmetry breaking.
In graphene grown on Ni(111), I will Decoupling of graphene layer from the Ni(111) substrate via alkali metals (Na and Cs) was adsorption. The graphene monolayer was grown on Ni(111) substrate under ultrahigh vacuum chamber using in an ambient C2H2 atmosphere and studied using high resolution photoelectron spectroscopy (HR-PES) angle-resolved photoemission spectroscopy (ARPES) at 10D and 4A2 beam lines of PAL. The ARPES data measured near K point for Graphene/Ni(111)shows strong interaction between graphene π and Ni 3d bands. The alkali metals (Na and Cs) were deposited at low temperature (120K) and the ARPES data was measured with increasing temperature. It has been observed that the Cs partials intercalation starts ~125K and intercalated completely at ~175K. The ARPES data of Na intercalation shows that Na intercalated at ~175K. In the last, I will discuss some of the result of Bi2S3 films grown on different substrate and studied using HRPES and ARPES. The Bi-4f and Se 3d core level spectrum show successful growth of Bi2Se3 topological insulators.