초록 |
In organic thin film transistor devices, obtaining good dielectric characteristics and mechanical flexibility simultaneously has been a question of great interest. In order to achieve high on/off ratio, the leakage current should be low enough. For this purpose, nanocomposite can be a useful choice for the gate dielectric layer. Because of high dielectric constant and high thermal stability, in this work, barium titanate ceramic particles (BaTiO3) were used as the filler in the polymer matrix of poly 4-vinyl phenol (PVP). A kind of coupling agent was applied on to BaTiO3 particles before dispersing in the polymer to form PVP-BaTiO3 nanocomposite. The thickness of this dielectric layer was 400 nm. The AFM images showed that the surface roughness of the nanocomposite layer increases with the increase of BaTiO3 content. This is due to the agglomeration of the particles. The surface roughness was about 3 nm for the sample with 25 wt% of BaTiO3. For the flexibility test of the dielectric layer, the cyclic bending experiment was carried out. Leakage current of the sample was measured before and after bending test. Compared to the results before bending, the leakage current of the samples after being bended was higher. However, the leakage has not increased when the number of cyclic bending was increased. Nanocomposite gate dielectric layer was shown to have higher capacitance and lower leakage current compared to those of pure PVP gate dielectric layer. |