Construction of C60 Monolayer Based on Structural Relaxation on the Water Surface

Abstract

Abstract 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 1×10-5 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.