Studies of structural changes in C-60/C-70:NI layers annealed under oxidative conditions

The structural changes in C-60/C-70:Ni layers annealed at a temperature of 620 K were observed by Raman spectroscopy, electron diffraction, AFM and HRTEM methods. The 'as grown' C60C/(70):Ni layers exhibit the features of the amorphous structure, which is confirmed by broadened Raman bands of H-g(1) fullerene mode, diffused rings in the electron diffraction pattern (with 4.8 and 8.7 nm(-1) radius) and HRTEM pictures. The AFM topographies depict grains of 100-200 nm in size, rounded hillocks agglomerated in bigger 'zigzag' objects. The annealed layer contains two phases: amorphous and crystalline fcc C-60 with enlarged lattice parameter (a = 1.44 nm). The changes toward crystalline structure are observed in Raman spectra (sharp H-g(1)mode) and in the electron diffraction pattern (reflexes (111), (220), (311), (420) and (422) of pure C-60 fee structure). The AFM topographies show two kinds of objects with different lateral sizes 300 and 100-200 nm and different base to top height 100-150 and 35 nm, respectively. (C) 1997 Published by Elsevier Science Ltd.