2-DIMENSIONAL SELF-ASSEMBLY OF URACIL MOLECULES ON CU(111) SURFACES -A LOW-TEMPERATURE STM STUDY

Novel superstructures of self-assembled uracil molecules, one of the R NA bases, have been observed using scanning tunneling microscopy on cl ean Cu(111) single crystal surfaces in ultra-high vacuum at approximat e to 70 K. Isolated uracil trimers are formed at low coverage, and two -dimensional islands with a hexagonal superstructure are built up at i ncreased coverage. The dominant force responsible for the formation of the trimers and the islands is electrostatic interaction through anis otropic hydrogen bonding between uracil molecules on the surface.