Surface interactions of molecular C60 and impact on Ni(100) and Co(0001) film growth: A scanning tunneling microscopy study

Here, the interactions of C60 at the surface of pseudomorphic Ni/Cu(100) and Co/Ru(0001) thin films and its effect on film growth and morphology were determined using in-situ scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). The novel development of C60-metallic based nanosystems, such as C60 molecular junction transistors, hinges on our ability to understand the factors governing structural stability in these nanosystems and the nature of the bond interactions at the C60-metal interface. In this study, C60 deposited onto the Ni(100) film surface is observed to be fairly immobile and uniformly distributed across the Ni surface. On the Co(0001) film surface however, C60 mobility is observed to be severely limited in some regions and highly mobile in others dependent upon Co film surface reconstruction, resulting in a non-uniform distribution of C60 across the Co film surface. Despite the presence of C60 on the Ni surface, there is no obvious influence of the C60 on further Ni film growth. In contrast, during Co film growth, islands only nucleate and grow from step edges or locally around C60 molecules. The strength of the Co-C60 bond interaction appears stronger than the Co-Co bond on Co film terrace. Generally, the Ni and Co films both continue epitaxial film growth in the presence of molecular C60. AES results indicate the C60 molecules maintain their chemical integrity during growth.