Annealing effect for LaxC60 thin films

Numerous studies on metal-doped C-60 compounds had been done since the discovery of superconducting C-60 compounds. It is interesting to study physical properties of trivalent-meta-doped C-60. We examined La-doped C-60 thin films fabricated by layer-by-layer (LBL) deposition with a multi-source evaporation system. The physical properties of LaxC60 depend on the diffusion of La atoms in the film, so we studied the effect of annealing. The crystal structure and morphology of LaxC60 thin films were examined by X-ray diffraction and AFM and electronic structure was also examined by UPS. We found that annealing promotes orientation of the crystal. UPS spectra showed the change depends on the concentration of La atoms. Moreover, the spectrum of annealed thin film was quite different from that of as-deposited thin film. (C) 1998 Published by Elsevier Science S.A. All rights reserved.