Observation of an organic superconductor [bis(ethylenedithio)tetrathiafulvalene]2[Cu(NCS)2] by scanning tunneling microscopy

The surface of an organic high‐Tc superconductor, (BEDT‐TTF)2[Cu(NCS)2] [BEDT‐TTF: bis(ethylenedithio)tetrathiafulvalene, Tc=10.4 K under ambient pressure], was observed with a scanning tunneling microscope in air and at room temperature. The step height observed on its surface was 13.2 A and was very close to the one layer thickness of the (BEDT‐TTF)2[Cu(NCS)2] crystal (15.22 A, determined by x‐ray diffraction). Periodic zig‐zag structures were observed along the diagonal line of the surface unit cell and agreed well with the two‐dimensional BEDT–TFF molecular structure projected onto its crystal b‐c plane.