Interface modifications with atomic monolayer

We present the results of our investigations on surface and interface properties of zinc oxide and nickel-graphene interfaces. We have used different surface science techniques to study these interfaces. First part of the abstract discusses ZnO research and the second part nickel graphene interface.;We discuss the surface effects in the core-level photoemission spectra of ZnO and use this information to understand the stabilization mechanism of the polar surfaces of ZnO. The ZnO(000--1)-O surface is very reactive toward hydrogen adsorption and only above 650 K a hydrogen free surface was observed. Coadsorption of sulfur lowered the desorption temperature for hydrogen indicating the possibility to tune the chemical properties of these polar surfaces by dopants. We also discuss the effect of functionalizing the ZnO polar surface with of ZnS on the band structure at the interface. We observe an effective surface band gap narrowing to 2.8 eV when ZnO is modified by submonolayer film of ZnS. Furthermore, the characterization of the space charge region and work function of ZnS modified ZnO indicate improved surface properties for enhancing photocatalytic activity.;The Ni-graphene interface has been studied by AES, TPD of CO-probe molecules and STM. In the first part we discuss the growth and stability of graphene on Ni(111) substrate. We found that graphene grows on pure Ni(111) surface between 480 °C and 650 °C. Below 480 °C graphene growth competes with formation of surface carbide. We also show that the carbide phase lies in the same surface layer with graphene and the two phases match perfectly at their boundary forming a coincidence structure. We also studied the interaction between graphene and Ni by depositing Ni clusters on graphene/Ni substrate. We find that a single layer of graphene supported on Ni(111) is stable up to ~ 950 K, but if it is sandwiched between two Ni-layers it becomes unstable and decomposes into a Ni-carbide at low temperatures (500K) already. Finally we discuss our observation of novel extended line defect on graphene/Ni(111) using STM. These 1D structures are the consequence of domain boundaries between graphene-sheets occupying different registry relative to the nickel substrate.