New generation of organic-based thin-film transistors

Among the newly developed organic semiconductors, thiophene oligomers e.g., sexithiophene molecules are very stable under ambient conditions and they can be easily deposited as thin homogeneous films by the use of mild techniques such as vacuum evaporation at about 300/spl deg/ C. From X-ray diffraction, polarized light absorption spectroscopy and scanning electron microscopy studies, it has been shown that structural organization of molecules in the film is the determining factor which controls its electrical properties. By varying the experimental conditions for film deposition (substrate temperature) and by the development of self assembly properties in these oligomers (molecular engineering of semiconductors), highly structured film with long range order can be easily obtained as evidenced by the large anisotropy observed in conductivity, /spl sigma//sub 11///spl sigma//sub /spl perp//=150. The fabrication and mode of operation of thin film transistors based on these p-type organic semiconductors is described, in which substrate, insulator, and electrodes can be made from organic materials corresponding to an all organic device.