Temperature-dependent Raman study on C 70 film. Observation of a rotational ordering transition

Abstract

An orientational ordering transition was observed near 260 K from a C 70 film in a temperature-dependent Raman study. The 1183 cm −1 Raman band shows a rather dramatic change in both frequency and bandwidth over the range of 220–280 K. The low-frequency Raman band at 260 cm −1 disappears, and at its expense, a new band emerges at 266 cm −1 as the temperature is decreased. The relatively smooth transition in temperature is attributed to the stacking disorder in molecular packing and the nonuniform orientational conformation of C 70 solid.