Construction of C₆₀ monolayer based on structural relaxation on the water surface

A C₆₀ monolayer was constructed by a multi-step creep method for the first time. In the case that a dilute C₆₀ benzene solution of 1 x 10^-5 M (1 M = 1 mol dm^-3) was spread on the water surface, C₆₀ molecules formed into highly organized 2-dimensional crystalline domains. On the other hand, in the case of the conventional continuous compression method up to a low surface pressure below 15 mN m^-1, the C₆₀ monolayer-like aggregates were formed with a lot of vacancies. Each monolayer-like C₆₀ aggregate was easily collapsed into small fragments and changed into 3-dimensional aggregates at a high surface pressure above 20 mN m^-1. The C₆₀ film could not full up the vacancies during continuous compression, since the C₆₀ molecules formed rigid aggregates. These results clearly indicate that structural relaxation at a low surface pressure was required to construct the defect-diminished C₆₀ monolayer. The occupied area of a C₆₀ molecule in the monolayer prepared by the multi-step creep method was in good agreement with that of a 2-dimensional C₆₀ crystal calculated from lattice constants of a 3-dimensional C₆₀ crystal. The surface morphology of the C₆₀ monolayer prepared by the multi-step creep method was homogeneous, and C₆₀ molecules in the monolayer were closely and regularly packed in a hexagonal array. The hexagonal packing of the C₆₀ molecules was confirmed on the basis of atomic force microscopic and electron diffraction observations.