Recently, it was proposed in the literature that the electron trap on a hydroxyl-containing dielectric interface of an organic field effect transistor (OFET) hinders its n type operation. The authors fabricated pentacene and fullerene OFETs with a hydroxyl-free insulating material, a long-chain alkane, i.e., tetratetracontate (TTC), C44 H90 layer coated on the Si O2 dielectric layer. The displacement current measurements clearly demonstrated that the electron trap of the Si O2 surface is suppressed by the TTC layer. For a pentacene FET with an Al electrode and Si O2 dielectric layer, a p type operation was observed, while the operation mode was switched to the n type by the insertion of TTC on the Si O2 interface. By simple patterning of the TTC layer to produce a bipolar injection, the authors fabricated an ambipolar pentacene FET with a single kind of metal electrode. Thus TTC is a good material for the surface modification of a dielectric layer in OFETs.
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