Nonvolatile Ferroelectric Memory Transistors Using PVDF, P(VDF-TrFE) and Blended PVDF/P(VDF-TrFE) Thin Films

Abstract

In this work, metal–ferroelectric–semiconductor field-effect transistors (MFSFETs) have been fabricated for the first time using poly(vinylidene fluoride) (PVDF) and polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] thin films as ferroelectric layer. PVDF and P(VDF-TrFE) thin films were fabricated by sol–gel method on Si(100) wafers. The drain current–gate voltage (I_D–V_G) characteristics of the fabricated MFSFETs with PVDF and P(VDF-TrFE) thin films exhibited very good ferroelectric hysteretic curves with counterclockwise loop same to those of other ferroelectric materials. It also demonstrates a realizable possibility of one-transistor type (1T-type) ferroelectric memory without a buffer layer using thin organic material. The absence of a buffer layer presents many advantages such as the elimination of the depolarization field, leakage current influence of the thin buffer layer, reduction of the process steps, low-operational voltage, and low-power consumption. The MFSFETs using PVDF and P(VDF-TrFE) thin films as ferroelectric layer have promising potential for use in low-voltage operable and flexible 1T-type ferroelectric random access memory (FeRAM) using organic material. On the other hand, it also has been attempted to make ferroelectric field-effect transistors (FeFETs) with blended PVDF/P(VDF-TrFE) films in order to compare the P(VDF-TrFE) films. The ferroelectric films for metal–ferroelectric-metal (MFM) capacitors have been fabricated using the blended PVDF/P(VDF-TrFE) solutions with different concentrations by sol–gel method. Ferroelectric field-effect transistors using poly(3-hexylthiopene) (P3HT) channel layer have also been fabricated on TiN substrates in order to compare the device characteristics of the pure P(VDF-TrFE) and blended PVDF/P(VDF-TrFE) thin films in this study.