Structure and optical properties of C60 films on polymer substrates

Abstract

The results of investigations of the structure and optical properties of films of fullerene C60 are reported. The films were obtained by vacuum thermal evaporation on substrates from heat-resistant polymers (polyacrylonitrile and cyclized polyacrylonitrile in composition with polyimide). The structure of C60 films was determined by X-ray diffractometry. In all diffraction patterns of fullerene films, their structure manifests itself through reflections from the (111), (220), and (311) planes. Cubic C60 films were obtained by fullerene deposition at substrate temperatures as high as 200°C. Atomic force microscopy of the film surface revealed the existence of a laminated structure. The infrared (IR) transmission spectra are indicative of the presence and constancy of the position of characteristic bands of C60 (527, 576, 1183, and 1428 cm−1) for all fullerene films. The investigation of photoluminescence of fullerene films revealed bands whose energy position both exceeded typical values for molecular C60 or fell below these values. This circumstance is caused by the interaction between the electron π systems of C60 and the polymer substrate at the heterointerface, as well as by the photopolymerization reaction of fullerene under the effect of high-energy laser radiation and by the emergence of trap centers in the films.