Cluster reactions in C60 films induced by electron injection from a scanning tunneling microscope tip

Polymerization and decomposition of C60 clusters induced by electron injection from a scanning tunneling microscope (STM) tip have been studied experimentally. The tunneling current dependence of polymerization rate and decomposition rate was found to be both linear, indicating that each reaction is caused by injection of a single electron from the STM tip. We propose a model that an electron injected from an STM tip into a C60 crystal propagates in the electronic band of the C60 crystal until it becomes localized at a specific sites where it causes an ionically enhanced [2+2] cyclo-addition reaction. The positional variation of polymerization efficiency and peculiar patterns of polymerized areas are interpreted in terms of the strain field built-in or built-up in the crystal.