RUBIDIUM-DOPED EPITAXIAL C-60 THIN-FILMS - SYNTHESIS AND ELECTRONIC TRANSPORT

Epitaxial thin films of C60 have been synthesized and doped with rubid ium. Above 80 K, the sample resistivity shows classic metallic tempera ture dependence just like that of K3C60 single crystals. However, the temperature coefficient changes sign at about 80 K, and the resistivit y increases by 5% before the superconducting state near 30 K is reache d. As for different samples, the zero-resistance temperature varies sh arply with the sample lowest resistivity and can be fitted to a functi onal form of T(c0) = a + brho-5. The critical current density J(c) is 10(3)-10(4) A cm-2 at congruent-to 5 K, 0 T and it is found that J(c) is proportional to (1 - T/T(c))alpha, where alpha is in the range 1.3- 2.0. Furthermore, the voltage-current characteristic of the films is v ery similar to that of high-T(c) superconductors and remains a problem for further research on this new kind of material.