Scanning Tunneling Microscopy Study of Molecular Adsorbate Systems on Metal and Metal Oxide Surfaces
|School||University of Science and Technology of China|
|Course||Condensed Matter Physics|
|Keywords||STM molecule adsorption chirality spiropyran titanium dioxide|
In this thesis we report STM investigations on molecular adsorbate systems on metal and metal oxide surfaces.In Chapter I, we briefly introduce the fundamental principles and theories of STM, and then present some recent progresses in STM studies on molecular adsorbate systems. In the end, we describe the structures of the UHV LT-STM and the details of other experiment techniques used in the work.In Chapter II, we studied the adsorption and chiral expression of 6-nitrospiropyran （SP6） molecules on Au（111）. By using STM in combination with density functional theory calculation, we found and interpret an unique chiral phenomenon - quasi chiral seperation in 2D orientationally disordered system - in the SP6 monolayers. On the basis of this finding, we further investigated the coverage dependent chiral phase transition of SP6 molecules on Au（111）.In Chapter III, we investigated the packing and chiral expression of 8-nitrospiropyran （SP8） molecules on Au（111）. The slight structural difference between SP8 and SP6 lead to two distinct 2D chiral structures. While SP6 underwent quasi chiral separation, SP8 formed two enantiomorphous phases with hierarchical chiral structures. The present result shows that the chiral expression of the low-symmetric nitrospiropyran molecules can be manipulated in a facile way.In Chapter IV, we concerned in the adsoption behavior of small molecules on TiO2（110）, a very important catalysis relevant metal oxide surface. By selectively desorb the H atoms of surface OH groups, we obtained and investigated the isolated O vacancy and OH group on the TiO2（110） surface. We also systematically investigated the adsorption of O2 on stoichiometric, defective and hydroxylated TiO2（110） surfaces. The specific adsorption sites of CO and the reactivity between CO and pre-adsorbed O atoms are also investigated and discussed.