LOW-TEMPERATURE ANOMALIES IN PHOTOLUMINESCENCE OF (C-60)(1-X)-(C-70)(X) SOLID-SOLUTIONS

In this communication, is reported a detailed analysis of the temperat ure dependence of the photoluminescence measured on (C-60)(1-x)-(C-70) (x) thin films (x in the range: 0, <7%). We show that an additional em ission peak at 1.77 eV appears below 90 K in the (C-60)(1-x)-(C-70)(x) mixed compounds (x>0). The intensity of this peak is closely related to the amount of C-70 (the x value) in the (C-60)(1-x)-(C-70)(x) films (at least in the [0<x <7%] range). In the [10 K-90 K] temperature ran ge, its intensity significantly increases when the temperature decreas es. Nevertheless the origin of this peak is unclear and the assignment of the enhancement of the 1.77 eV emission peak intensity below 90 K to the photoluminescence signature of the ''glass phase transition'' i n the (C-60)(1-x)-(C-70)(x) mixed compounds is discussed.