OFET on Foil Substrates

1000 pm channel width, using a 200 nm thick high-epsilon resist film as gate dielectric. 

Over periods of three months the device was measured again, up to nine months. During this time interval the drain current decreased from -61 pA directly after the deposition to a value of -187 nA (see also Table 18.3) WIL = 1000). The channel length of this transistor was 1 pm and the channel width was 1000 pm. The mean charge carrier mobility in the linear regime declined from 2 X 10 cm A s to 1.2 x 10 cm A s and the threshold voltage shifted in the negative direction from 4.8 V to -8 V. Recently, a comparable 

Therefore, further experiments have been done to differentiate between the particular gases. A chip containing an OFET of 1000 pm channel width and of 1 pm channel length was bonded, connected to the measurement setup and put into a vacuum chamber. Then, an approximately 30 nm thick layer was thermally evaporated at low deposition rate and a process pressure of 7x10 mbar. Next, the sample was characterised in high vacuum before the chamber was flooded by pure technical oxygen so that the OFET did not come into contact with the ambient atmosphere. The device was measured a second time before the chamber was evacuated again. 

The influence of the oxygen causes a shift of the threshold voltage in the opposite direction as observed by long term degradation experiments, where a detected shift in the negative direction was believed to be caused by water vapour [47] in ambient atmosphere. Therefore, further samples had to be investigated, exposed to atmospheres with defined air humidity. 

In the literature there are several reports on the degradation of OFETs and the effects on their electrical characteristics due to water vapour (e.g. [49-51 ]). The reaction of pentacene single crystals with water molecules from am- 

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