Recently novel topological states are predicted to exist in two-dimensional (2D) metal-organic networks containing heavy metals. To investigate this phenomenon, in this thesis, we first study the self-assembled trimesic acid (TMA) molecule networks functionalized by lead (Pb) and bismuth (Bi) on a Au(111) surface by scanning tunneling microscopy (STM). Kagome and stripe structures are formed out of TMA molecules and Pb atoms. In the Kagome structure, Pb atoms attach to the TMA molecules without destructing TMA molecular networks. Multiple Pb-O and Pb-H bonds are involved in the formation of the stripe structure. These two structures are the first 2D metal-organic networks containing Pb atoms formed on surface. Uniform-size Bi cluster triangular superlattices are self-assembled in TMA po...[ Read more ]

Recently novel topological states are predicted to exist in two-dimensional (2D) metal-organic networks containing heavy metals. To investigate this phenomenon, in this thesis, we first study the self-assembled trimesic acid (TMA) molecule networks functionalized by lead (Pb) and bismuth (Bi) on a Au(111) surface by scanning tunneling microscopy (STM). Kagome and stripe structures are formed out of TMA molecules and Pb atoms. In the Kagome structure, Pb atoms attach to the TMA molecules without destructing TMA molecular networks. Multiple Pb-O and Pb-H bonds are involved in the formation of the stripe structure. These two structures are the first 2D metal-organic networks containing Pb atoms formed on surface. Uniform-size Bi cluster triangular superlattices are self-assembled in TMA porous network templates, by nucleation of Bi atoms in the pores of the TMA networks. The lattice constant of the Bi cluster superlattices is tuned by controlling the density of TMA molecules deposited on the surface. The Bi cluster superlattices provide potentials to form artificial honeycomb lattice of 2D electron gas, which may exhibit properties of 2D topological insulators. To investigate the unique spin property of 2D topological insulators in molecular level, we prepare a spin-polarized STM with chromium-coated tungsten tip. The tip is etched by electrochemical method, cleaned by annealing and coated with Cr films. An antiferromagnetic Cr(001) sample with terraces separated by monoatomic steps is prepared by sputtering and annealing cycles. Our findings represent first attempt of experimental realization of 2D organic-based topological insulators. The successful preparation of spin-polarized STM offers many opportunities for molecular level characterization of the novel 2D topological states.