UNUSUALLY BROAD AND INTENSE PHOTOLUMINESCENCE FROM MORPHOLOGICALLY MODIFIED C-60 FILMS

As an attempt to develop novel optically functional materials, C-60/Si layered composite was prepared by the alternate repetition of the the rmal evaporation of C-60 and the sputtering of Si. For the Si content higher than 0.5wt%, we found that under Ar ion laser excitation (514.5 nm) the composite demonstrated strong white photoluminescence that cou ld be seen by the naked eye. Its emission spectrum, after the correcti on for the detection system, was shown to increase monotonically from the visible to near infrared (up to 1.5 mu m) without any specific spe ctral features. For the lower Si content, the photoluminescence was we ak and peaked around 750nm resembling that of pristine C-60 films. The spectral shape analysis of the white luminescence based on the Planck distribution gave good fit and yielded surprisingly high black-body t emperatures of 1400-1600K. The fact that the replacement of the Si lay er with other sputtered materials gave essentially the same results su ggests that factors essential to this phenomenon are the C-60 layer an d its modification induced during the process of sputtering, but not t he Si layer. We discuss the present results in terms of similarities a nd differences with the previously reported white luminescence from C- 60 powder or crystallites and their implications are considered.