Schottky junctions based on vacuum evaporated films of thiophene oligomers

α-sexithienyl (α-6T) was synthesized and deposited as thin films onto platinized glass slides by the technique of vacuum evaporation. Metal-semiconductor (MS) junctions were then realized by evaporating small dots of Ag and Au. On the asformed film, Au gives an ohmic contact, and Ag a rectifying barrier. It is then concluded that α-6T behaves as a p-type semiconductor. After annealing at 150°C, rectifying barriers are obtained on both Au and Ag contacts, and α-6T turns to an n-type semiconductor. Changes in the respective UV-visible absorption may help in understanding the change from p- to n-type doping. A rough estimate of the band position of α-6T was obtained from the current-voltage and capacitance-voltage measurements on the MS diodes.