平成２１年度　実績報告書

103/156

教育研究プラットフォームIDER研究成果/ポストドクター・GCOE研究員y t i s n e t n I y t i s n e t n I Figure 1. XPS spectra of C 1s for 10% The effects of an electric - field application on properties of P(VDF - TeFE) thin film Jong - Hyeon Jeong D ivision of Electrical, Electronic and Information Engineering , Graduate School of Engineering , Osaka University Sugino Laboratory Abstract In the processes to form a P(VDF - TeFE) thin film, we have studied about the thin film formation with various conditions of a spin - coat speed, a concentration and a type of solvents, and annealing temperature. As a molecular structure of the film is changed by concentrations or types of solvent, the annealing in electric field is carried out to prevent the changes. We have investigated the film formed by annealing with and without electric field, al so confirmed the rising of permanent polarization. The conventional energy storage techniques based on chemicals have demerits such as finite lifetime and large scale. We have studied the fabrication of a micro - generator which is activated by acoustic wav e on a level with human voices. Because of the nature of the source wave, the material of a m embrane should have low density and elasticity and be compatible with LSI processes to apply to MEMS processes. P(VDF - TeFE) (Poly - vinylidene difluoride and tetrafl uoroethylene) (supported by Daikin Co.Ltd.) closely resembles PVDF in a molecular structure. For average mechanical parameters of P ( VDF - TeFE) and PVDF f ilm , a resonant frequency of PVDF film is almost double compared with P(VDF - TeFE) film because elastic m odulus of PVDF is higher than that of P(VDF - TeFE) . Using the 3 - types of solvents such as Methyl - Ethyl - Ketone (MEK), Dimethylacetoamide (DMA) and mixed solvent with MEK and DMA, the P(VDF - TeFE) thin film wa s formed by spin - coating method on a surface of a Pt/Ta - deposited silicon substrate. In a c ase of casting in only DMA, the adhesion of the film is very bad. Moreover the roughness of film surface wa s changed by annealing temperature, and the roughness affects a n electric performance. Fig. 1 show s that XPS spectra and FTIR spectra of the samples formed with single solution (MEK 100%) and mixed solution (MEK:DMA=3:1) by 10 % concentration. In Fig. 1 - (a), the cases of annealing in electric field are very different from the cases of annealing in none field. In the region of 284 ~ 286 eV, particularly, C - C bonds and C - H bonds didn ’ t appear in a case of annealing in electric field. Fig. 2 show s the case o f 4% concentration. As shown Fig. 1 , there are not big changes of molecule structure . H owever, the quantity of C - C bonds and C - F bonds is very different from the spectra of Fig. 1 . Contrary to a case of 10% solvent, the absorption of C - C bonds is low, and it will be expected that the chain of C - C bonds is cut. In a case of 4% single solvents, the resu l ts show a simple difference of polarization. In a case of mixed solvents, however, the quantity of polarization is changed largely by a frequency of bias voltag es. In order to apply the P(VDF - TeFE) film to a piezoelectric membrane of a micro generator, we have achieved a film forming process for various conditions and also achieved the improvement of film characteristics wi th annealing method in electric field and types of solvents. Figure 2 . XPS spectra of C 1s for 4 % 99

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