| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 봄 (04/14 ~ 04/15, 전경련회관) |
| 권호 | 30권 1호, p.351 |
| 발표분야 | 고분자 구조 및 물성 |
| 제목 | Ferroelectric properties of poly(vinylidenefluoride-trifluoroethylene) copolymer thin films |
| 초록 | Since P(VDF/TrFE) copolymer with VDF content between 50 and 80 mole% forms a ferroelectric β-phase directly upon crystallization, it might be good candidate for polymeric nonvolatile memory materials. Ferro-electric polymers, however, have not been actually used up to now due to their long switching time and limited thermal stability. Recently, investigations showed that suitable copolymers based on P(VDF/TrFE) copolymers in ultra-thin layers could achieve switching times of ≤100 ns and many studies are being carried out to construct the polymeric memory devices with that copolymers. To be used as a nonvolatile memory materials, copolymer of P(VDF/TrFE) should be coated as thin film of about 100nm thickness on a suitable substrate. For the thin film of that thickness, the surface effect can be enormous. In this work, many characteristics P(VDF/TrFE) copolymers had showed as a bulk material have been re-measured with thin sample and the surface effect were evaluated. The ferroelectric-to-paraelectric transition (Curie transition) of this copolymer sample was evaluated with FTIR spectroscopy using specular reflection mode. The switching of CF2 dipoles upon application of external electric field was also confirmed with FTIR method as well as X-ray diffraction method using grazing incidence angle. It was generally confirmed that many characteristics such as Curie transition and dipole switching upon poling process could be successfully monitored even for the thin copolymer films of about 100nm thickness. Figures 1 to 4 show the infrared spectra of the copolymer as a function of temperature, annealing treatment, and electric field application. In Figure 1, the 1290cm-1 band and 849cm-1 band are assigned to the symmetric CF2 stretching vibration coupled to the backbone stretching and bending vibrations. These peaks are observed only with the copolymer sample in ferroelectric phase and they disappear above the Curie transition temperature. As shown with the increased 1290cm-1 band intensity in Figure 2, higher ferroelectric crystallinity can be obtained by annealing the sample above the Curie temperature. Poling process upon application of electric field was also monitored and its results are shown in Figure 3 and 4. Two spectra in those figures show very different intensity. The increased intensity of 1290 and 849cm-1 bands and the decreased intensity of 1186 and 883cm-1 band indicate that the CF2 dipole in the ferroelectric phases can be successfully aligned along the electric field even the thin copolymer sample. This study was supported by "The National Research Program for the 0.1 Terabit Non-Volatile Memory Development Sponsored by Korea Ministry of Science & Technology" |
| 저자 | 김성옥1, 이한섭1, 김갑진2 |
| 소속 | 1인하대, 2경희대 |
| 키워드 | P(VDF/TrFE) copolymer; Ferroelectric; Curie transition; |
