Dim C60 fullerenes on Si(111) 3×3-Ag surface

► Dark features in C60 arrays on Si(111)3×3-Ag are not vacancy defects but dim C60 molecules. ► Dim C60 molecules are more tightly bonded and reside ~ 1.6 Å lower than other C60 molecules. ► Dynamic switching between dim and normal C60 is a kinetically driven process. ► Deposition of 0.1 ML of Ag onto C60 array eliminates completely dim C60 molecules. ► Formation of dim C60 is suggested to be associated with disintegration of underlying Ag trimer.