| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Nanomaterials | Wednesday Sessions |
| Session NM-WeP |
| Session: | Nanomaterials Poster Session |
| Presenter: | Atsushi Kohno, Fukuoka University, Japan |
| Authors: | A. Kohno, Fukuoka University, Japan T. Tajiri, Fukuoka University, Japan |
| Correspondent: | Click to Email |
Integration of size-controlled nanoparticles into thin films is attractive for applications to functional materials and devices owing to their unique properties related to the reduced size. We have synthesized the nanoparticles of dielectric materials in the one-dimensional pores of mesoporous silicate SBA-15 thin films formed on silicon and quartz substrates and have investigated the characteristics of nanoparticles. Ferroelectric nanoparticles are attractive for memory application especially as ultra-small scale devices, and the ferroelectricity of nanoparticle is interesting from the viewpoint of materials sciences. In this research we focus on the nanoparticles of perovskite-type ferroelectric materials. The synthesis of barium titanate (BaTiO3) nanoparticles in the pores of SBA-15 thin film were developed, and the electrical and optical properties of the nanoparticles have been investigated.
Mesoporous silicate SBA-15 has been synthesized using Ethylene oxide/propylene oxide/ethylene oxide triblock copolymer and tetraethylorthosilicate. The mixture solution was coated on p-Si(100) and quartz substrates by spin-coating, and then the coated samples were dried and sintered. The SBA-15 thin film samples were dipped in BaTiO3 precursor solution. The SBA-15 films which contained BaTiO3 precursor solution in the pores were sintered in a furnace at 700 °C for crystallization. In the case of electrical measurement Au electrodes were made on the films.
X-ray diffraction showed that the one-dimensional pores in SBA-15 thin film were aligned parallel to the surface and stacked keeping well-ordered hexagonal symmetry. The pore diameter was estimated to be about 5 nm from the analyses of X-ray diffraction and reflectivity, as detail of the evaluation method was reported elsewhere. It was confirmed that the stacked pore structure was never affected by the synthesis of BaTiO3 nanoparticles. The elemental composition and chemical states of BaTiO3 nanoparticles in the thin films were checked by XPS measurement as compared with the bulk material. The optical absorption of BaTiO3 nanoparticles was clearly observed and the absorption edge is estimated to be about 3.7 eV which is much larger than the bandgap of the bulk material.
The clockwise hysteresis was clearly observed in the capacitance-voltage characteristics of Au/BaTiO3-containing SBA-15/p-Si capacitor and the hysteresis voltage width was increased and saturated as increased the applied voltage. These results suggest that the hysteresis was caused by ferroelectricity of BaTiO3 nanoparticles. The properties of the BaTiO3 nanoparticles will be discussed in the conference.