MOBILITIES OF CHARGE-CARRIERS IN C-60 ORTHORHOMBIC SINGLE-CRYSTAL

Time-of-flight technique has been used to measure mobilities of electrons and holes in C60 orthorhombic single crystals at room temperature. Single crystals of C60 grown from the CS2 solution have been characterized as having about 10(14) cm-3 deep trapping sites for electrons and holes. The mobility for holes (mu(h)) at room temperature is 1.1 +/- 0.1 cm2 Vs and that for electrons is found within the same limits. Temperature dependence of mu(h) is revealed to be almost constant from 325 to 250 K. Mu(h) starts increasing and below 250 K may be approximated by the law mu(h) approximately exp (DELTAE/kT) with DELTAE = 0.053 eV. Coincidence of the point of the increase of hole mobility with the phase transition temperature is worthy to be noted.