Structural, morphological and optical properties of C₆₀ cluster thin films produced by thermal evaporation under argon gas

C60 cluster thin films were obtained by thermal evaporation under argon atmosphere. The surface morphology, optical absorption characteristics and structure of these films have been investigated. The ultraviolet-visible optical absorption spectrum of this C₆₀ film is obviously different from that of the film obtained under vacuum conditions. The position and intensity of absorption peaks of the films grown in argon are modified compared with the film grown in vacuum. The bandgap energy changes from 2.02 eV to 2.24 eV. IR analyses show no evidence of chemical change. The x-ray diffraction pattern reveals the existence of a mixture of face-centred cubic and hexagonal close-packed phases. The collisions of C₆₀ molecules and buffer gas molecules are discussed. We also found the surface particles of these C₆₀ cluster films are larger and sharper than those of C₆₀ films prepared in vacuum by the observation of atomic force microscopy (AFM). This may be advantageous for using C₆₀ for electron field emission.