We have investigated the growth and structure of a C 60 monolayer film on Cu͑001͒ with scanning tunneling microscopy at room temperature and 100 K. We discovered that the equilibrium adsorption structure of annealed C 60 films depends sensitively on the initial deposition coverage; for a coverage of 0.5 monolayer C 60 orders in an one-bright-and-one-dim ͑1B1D͒ row sequence along the ͓110͔ direction whereas for a coverage close to one monolayer C 60 orders in a two-bright-and-one-dim ͑2B1D͒ sequence. At the transition region of the bright and dim row segments, C 60 often appears "frizzy" at room temperature. This indicates that a C 60 rotates and adopts molecular orientations with inequivalent symmetry. Upon annealing, the C 60 film exhibits a high thermal stability before C 60 fragmentation and desorption occur at ϳ880-960 K, depending on its adsorption superstructure. The duality of equilibrium superstructure in C 60 / Cu͑001͒ is unique among studied C 60 monolayers on metals. We argue that different boundary energy of the 1B1D and 2B1D phases offers a plausible explanation on the observed tunability of superstructure versus coverage.

We demonstrate a molecular approach of tuning the magnetic properties of ferromagnetic ͑FM͒ thin films by reversing the functional groups of the organic underlayer. For the CoFe/Langmuir-Blodgett ͑LB͒ film system, we find that the coercivity of CoFe thin films ͑from 4 to 10 nm͒ made on hydrophobic surfaces is significantly enhanced whereas that on hydrophilic surfaces remains unchanged, as compared with the films directly on glass substrates. These findings suggest an alternative way for tuning the magnetic properties of the FM layer by LB film in which the functional groups play an important role.

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