Scanning Tunneling Microscopy Study For Detecting And Manipulating Molecular Adsorbate Systems On Metal Surfaces

Study of molecular adsorbate systems on metal surfaces is both very important in research of natural phenomena and constructing artificial structures and functional devices in the"bottom-up"scheme. Scanning tunneling microscope (STM) allows us to directly detect and manipulate single atoms, molecules and clusters and has shown powerful ability in study of molecular adsorbate systems on metal surfaces.In Chapter 1, we briefly introduced the fundamental principles and methods of STM and the STM system with theoretical method used in this dissertation. We also reviewed the recent progress in study of molecular adsorbate systems on metal surfaces with STM as well as the STM techniques employed.In Chapter 2, we demonstrate how one can alter electron transport behavior of a single melamine molecule adsorbed on Cu(100) surface by performing a sequence of specifically designed and well controlled single molecular chemical processes. It is found that with a dehydrogenation reaction the melamine molecule becomes firmly bonded on the Cu surface and acts as a normal conductor controlled by elastic electron tunneling process. A current-induced hydrogen tautomerization leads to an asymmetric melamine tautomer, resulting in a significant rectifying effect. By turning on inelastic multi-electron scattering processes, a mechanical oscillation of an N-H bond between two configurations of the asymmetric tautomer is trigged with tuneable frequency.In Chapter 3, we studied the adsorption properties of H2O on Ni(110) surface by STM. H2O adsorption on Ni(110) surface at 80 ~ 90 K with coverage of 0.1 ~ 0.2 monolayer leads to 2D islands with slightly distorted hexagonal ring. After annealing to 120 K, the 2D islands change to 1D zigzag chains, and the chains arrange nearly regular intervals after annealing to 150 K. Both structures are proposed based on the high resolution STM images.