Electrical properties of a two-dimensionally hexagonal C60 photopolymer

We investigated the electrical properties of a two-dimensionally (2D) hexagonal C-60 photopolymer, using four-probe measurements in air at room temperature. The current-voltage curve shows that the photopolymer exhibits nondoped semiconducting behavior. This behavior is consistent with the theoretical prediction that a 2D hexagonal C-60 polymer with a crosslinkage of a [2+2] cycloadditional four-member ring between adjacent C-60 molecules is semiconducting [S. Okada and S. Saito, Phys. Rev. B 59, 1930 (1999)]. The origin of these semiconducting properties is discussed on the basis of density-functional calculations for the valence molecular orbitals of the dumbbell C-120, which is regarded as a basic unit of the [2+2] crosslinkage of the 2D photopolymer. (C) 2004 American Institute of Physics.