STRUCTURE AND FORMATION OF POLYTHIOPHENE FILMS STUDIED BY SCANNING TUNNELING MICROSCOPY

The local structure and general conformation of polythiophene (PT) perchlorate doped and dedoped have been studied by scanning tunneling microscopy (STM) both in solvent and in air. PT films with various thicknesses were prepared on PT foil using the conventional electrochemical method. The STM images of PT showed that a single chain of PT was formed on the substrate at the initial stage of film growth. Under properly chosen conditions, thiophene rings of PT have been mapped with atomic resolution for the first time. It is surprising that the bonds between two thiophene rings are almost perpendicular to the molecular plane, so that such rod-like conformation is in a zigzag corrugated structure. Some helical-like conformations were discovered in the vast majority of the rod-like conformations in either doped or dedoped PT films. The insight into the arrangement between neighbor chains is revealed. The effects of doping on the geometric structure and the conductivity are discussed.