Superconductivity in Langmuir-Blodgett multilayers of fullerene (C60) doped with potassium

Abstract

We report here on the first observation of superconductivity at and below 8.1 K, as evidenced by a low magnetic field microwave absorption signal, or low-field signal (LFS), in a potassium-doped Langmuir-Blodgett (LB) 50-layer film of buckminster-fullerence, C[sub 60] on a poly(ethylene terephthalate) substrate. We address the obvious issue, which is whether LB multilayers can be made to be superconducting, in line with the result from doping of bulk C[sub 60] with potassium, rubidium, or cesium. This is of interest, because, although conducting Langmuir-Blodgett films of partially ionic salts of amphiphilic molecules have been known for some time, no superconductivity has been reported as yet in LB films. Since the C[sub 60] LB films are not perfect, and the films must have many defects, it is not surprising that we observed a lower T[sub c] than in the bulk K[sub 3]C[sub 60]. To approach the bulk T[sub c] value in LB films, there is need for further processing improvements in the compression of the Pockels-Langmuir film, the transfer mode, the aging of the undoped films, and the K-doping temperatures and times. At present we have no estimate of the superconducting fraction of the sample. Nevertheless, this is to our knowledgemore » the first time that a superconducting Langmuir-Blodgett film has been observed. 20 refs., 2 figs.« less