Variable-temperature scanning tunneling microscopy and scanning tunneling spectroscopy study on copper phthalocyanine ultrathin films on a Au(111) surface

Variable-temperature high-resolution scanning tunneling microscopy (STM) images reveal that well-ordered copper phthalocyanine (CuPc) strips can be self-assembled by depositing CuPc molecules on a Au(111) surface. The self-assembled strips are supposed to result from the balance of the intermolecular interaction and the interaction between the molecules and substrate during annealing. The energy band (approximately 1.9-2.1 eV) of CuPc, measured by scanning tunneling spectroscopy (STS), is comparable to the optical band gap (approximately 1.7 eV). Spectroscopic measurements confirm that a dipole layer and/or an effect of image force exist at the CuPc/Au(111) interface.