Properties of MFS Structures Using Ferroelectric VF2-TrFE Copolymer Film Gate

Ferroelectric vinylidene fluoride-trifluoroethylene (VF₂-TrFE) copolymer films were directly deposited on degenerated Si (n⁺, 0.002 Omegaldrcm) using by spin coating method. A 1-5 wt% diluted solution of purified vinylidene fluoride-trifluoroethylene (VF₂:TrFE = 70:30) in a dimethylformamide (DMF) solvent were prepared and deposited on silicon wafers at a spin rate of 2000-4000 rpm for 2~30 seconds. After annealing in a vacuum ambient at 100~200degC for 60 min, upper aluminum, gold and platinum electrodes were deposited for electrical measurement. X-ray diffraction results showed that the VF₂-TrFE films on Si substrates had beta-phase of copolymer structures. The capacitance on highly doped Si wafer showed hysteresis behavior like a butterfly shape and this result indicates clearly that the copolymer films have ferroelectric properties. The typical measured remnant polarization (P_r) and coercive filed (E_C) values were about 5.8 muC/cm² and 470 kV/cm, respectively, in an applied electric field of plusmn 1 MV/cm. The measured switching times (t_sw) was less than 20 ns. The leakage current densities measured at room temperature was less than 1 times 10^-6 A/cm² under a field of 1 MV/cm.