Studies on field effect transistors with conjugated polymer and high permittivity gate dielectrics using pulsed plasma polymerization.

摘要

The aim of this Ph.D. project is to explore the operating mechanism of polymer field effect transistors (PFETs) to improve their performance. Polymer semiconductors are composed of pi-conjugated polymers and have the advantage of easy processing. Their solution processibility at room temperature makes them an attractive candidate for light-weight, large-area, flexible electronics. However, the performance of PFETs is currently limited by low carrier mobility and high driving voltages. This dissertation presents thin film insulators as new gate dielectric materials to relax the requirement for driving voltages and illustrates some unique features of field dependent mobility in PFETs. Light responsive PFETs based on new polymer semiconductors are also demonstrated as a potential application of PFETs.; Pulsed plasma deposited polymer insulating films were investigated for their potential application as the gate dielectric in PFETs. The work on pulsed plasma polymerized (PPP) thin film insulators put emphasis on improving the dielectric constant of the thin polymer films. The driving voltage of a PFET can be reduced by using gate insulators with a high dielectric constants. Early work on PPP allylamine films indicated that the chamber temperature during pulsed plasma polymerization has an effect on the dielectric constant. PPP allylamine films were employed as the insulating layers and tested as metal-insulator-semiconductor (MIS) capacitors. The insulating polymer films were deposited at plasma reactor temperatures of 25°C and 100°C. Multiple frequency capacitance-voltage (C-V) measurements indicated that an in-situ heat treatment during film deposition increased the insulator dielectric constant. The dielectric constant, calculated from the C-V data, rose from 3.03 for samples with no heat treatment to 3.55 for samples with an in-situ heat treatment. For both sample sets, the I-V data demonstrates a low leakage current value (0.65 pA/mm2) up to 100V.; Later work on PPP insulators took advantage of engineering ability of the dielectric constant of the polymer film by the judicious selection of a monomer possessing a high polarizability. Polymerized dichlorotetramethyldisiloxane (DCTMDS) films deposited by radio frequency pulsed plasma polymerization (PPP) demonstrated very high dielectric constants for an organic-based system, in the range of 7 to 10. (Abstract shortened by UMI.)