Sensor applications of polymer field effect transistors

This thesis presents the fabrication and characterization of organic eld eecttransistors (OFETs) for sensor applications using polymeric semiconductor of poly (3-hexyl thiophene)(P3HT). Utilizing deionized (DI) water as gate insulator, operationvoltages of polymer eld eect transistors (polymer FETs) are reduced below 1V. Toease the microuidic channel integration of polymer FETs, a novel structure calledplanar OFET is designed and introduced. Comparing the output characteristics ofplanar OFET with the one of top-gate, bottom-contact OFET using gate probe instead of deposited gate electrode, it is shown that this planar OFET topology operatessuccessfully as eld eect transistor providing on-o ratio of about 50. It is statedthat P3HT lm deposition by spin-coating method leads higher on-o ratios thandrop-casting method for top-gate, bottom-contact OFET topology. Then, durabilityof P3HT to microfabrication processes is examined. In addition, sensitivity of P3HTto NaCl and KCl solutions is searched. Finally, microuidic channel encapsulation ofplanar polymer FETs with three dierent materials, polyvinyl alcohol (PVA), paryleneand polydimethylsiloxane (PDMS) is searched. PVA microuidic channels providingliquid ow are successfully formed. On-o ratios of 4 and 10 are obtained with planarpolymer FETs integrated into parylene and PDMS microuidic channels, respectively.