Weakly bound and strained C60 monolayer on the Si(111) √3 x √R30°-Ag substrate surface

Using scanning tunneling microscopy, we observed the growth and structure of a C-60 monolayer on a Si(111) root 3 x root 3R30 degrees-Ag substrate at room temperature, and found various C-60 arrangements with different strain fields in a molecularly flat C-60 monolayer. The results are understood by two kinds of molecule-substrate interactions, a weak interaction on the terrace and a strong interaction at the step of the substrate. The weak interaction may not be a pure van der Waals interaction, and the binding energy of a single C-60 molecule on the Si(111) root 3 x root 3R30 degrees - Ag surface is surmised to be 0.8-0.9 eV. The probability of defect appearance in the C-60 monolayer increases when the strain energy increases, and a highly ordered defect arrangement is realized probably due to the effective release of strain energy. [S0163-1829(99)11119-6].