Organic semiconductor evaporated films

The other films were produced to study the influence of the interface between the metal top contact and the organic semiconductor. Here, silicon wafers with a native oxide were used as substrates. The samples were provided by the group of Pflaum at the University of Stuttgart. To minimise impurities, like in the case of DIP, Pc (purchased from Fluka) is purified twice by gradient sublimation before being used as starting material. The films were prepared in UHV at a base pressure of about 7 x 10 mbar from a graphite effusion cell. The evaporation rate was about 3 A/s it was controlled by a quartz microbalance located next to the sample [8]. 

The basic structure of an OTFT gas sensor is shown in Fig. 5.4. Typically, a conductive mechanical support is used as the gate electrode, upon which an insulating dielectric coating is deposited. Next, a thermally evaporated or spun-coated thin film of active organic semiconductor is added. Finally, the source and drain electrodes are deposited over the semiconductor and are patterned to allow exposure of the active region to the environment. The organic... 

The synthetic chemistry of thiophene-based organic semiconductors develops essentially along two main lines namely (1) processible materials that are mostly based on polymeric structures and (2) short-chain oligomers used either as single crystals or as polycrystalline films prepared by thermal evaporation under vacuum. Although this latter class of materials has given rise to much development during the last two decades, only polymeric materials will be considered here. 

---