Water assisted CO intercalation underneath Ir(111) supported graphene studied with scanning tunneling microscopy

Sammanfattning: Graphene have attracted attention recently due to its unique properties and opportunities for development of high performance carbon based devices. The intercalation, absorption and reactions processes of small molecules above and below the graphene islands hold the key for new perspectives in catalysis, molecular sensors and other technologies. The present master thesis is focused on the investigation of the process for the intercalation of small molecules, such as Carbon Monoxide (CO), below graphene islands under Ultra High Vacuum conditions using Scanning Tunneling Microscopy (STM). It has been proven that the intercalation is facilitated with the presence of water under graphene islands. The water is formed underneath graphene by sequentially dosing of oxygen and hydrogen molecules. The formed water is visible with STM and preferentially located in the graphene edges and across the graphene islands grown on Ir(111) step edges. This phase raised the height of graphene by approximately 100 pm leading the graphene areas to be elevated from the Ir substrate. Furthermore, different amount of CO were dosed and STM was used to study the intercalation process. On saturating the surface with CO, digital CO intercalation was achieved below water phased graphene islands at room temperature and low pressures (in the range of 10-5mbar). Digital intercalation means graphene areas where fully intercalated by CO molecules or not at all. The graphene corrugation (ripples) was also decreased by one order of magnitude, as compared to pristine graphene. Finally the intercalation at 1 × 10-8 mbar CO exposure was also studied using STM. Irregular shaped CO channels were formed under graphene islands crossing over Ir(111) step edge suggested a possible mechanism for the CO intercalation. The STM studies gained from this intercalation method and the proposed edge mechanism can give an insight on the design of new graphene interfaces.