Photochemical transformation of C 60 and C 70 films

• Published in: Thin solid films Vol. 257; no. 2; pp. 185 - 203
• Main Authors: Eklund, P.C., Rao, A.M., Zhou, Ping, Wang, Ying, Holden, J.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-1995
• Subjects: Fullerenes; Optical properties; Oxygen; Polymers; Fullerenes; Oxygen; Polymers; Optical properties
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(94)05704-4

Thin solid films of C
60 and C
70 have been found to be sensitive to UV-visible light. In the absence of oxygen, which acts as a triplet state quencher, C
60 and C
70 have been observed to phototransform from a toluene-soluble to a toluene-insoluble state. This phototransformation has been studied via Raman and FTIR spectroscopies, UV-visible transmission spectroscopy and laser desorption mass spectroscopy. The results of these experiments have been interpreted as evidence for a phototransformation from a van der Waals solid to one in which the fullerenes are linked by covalent bonds. For C
60, it is proposed that a transformation to a polymeric solid has occurred, whereas a similar flux of UV-visible light applied to C
70 is proposed to lead to a random dimerization of the lattice and a much smaller population of higher oligomers. For both phototransformed C
60 and C
70, the covalent bonds between fullerenes can be broken thermally and the phototransformed material returns to the pristine, toluene-soluble state. UV-visible light can also be used to photochemically assist the diffusion of dioxygen into the interstitial voids in the solid C
60 and C
70 lattices. For C
60, a photochemical enhancement of the O
2 diffusion rate by a factor of ~ 10 is observed by alpha particle backscattering, leading to a stoichiometry of ~ C
60O
2. Similar to C
60-polyfullerene, C
60(O
2)
x
is also toluene insoluble. As a result, these C
60-based films might find photolithographic applications.