Topography Study of Inkjet-printed Barium Titanate Nanoparticles and its Application in Composite Dielectric Flexible Capacitors

• Main Authors: Liang, Yen-Ju, 梁雁汝
• Other Authors: Wu, Pu-Wei
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/06735249557681557669

碩士 === 國立交通大學 === 材料科學與工程學系所 === 101 === Recently, ink-jet printing technology has become an important production means for flexible electronics. It is recognized that the topography of the inkjet-printed droplet on the substrate is very critical because its uniformity and distribution have tremendous influence over the resulting device performance. The objective of this thesis is to develop an uniformly-deposited barium titanate ink for the purpose of fabricating an all-inkjet-printed flexible capacitor with a nanocomposite dielectric to achieve low-cost, high capacitance, and low current-leakage. With the addition of suitable dispersant and the adoption of a ball-milling process, we successfully prepare a homogeneous barium titanate dispersion with barium titanate in less than 500 nm size. The formulation is optimized so the barium titanate ink can be properly printed. Observations from scanning electron microscope and white light interferometer, the undesirable “coffee ring effect” is largely mitigated when we identify a mixture including a solvent with low-boiling-point and high surface tension and another solvent with high-boiling-point and low surface tension. Without the “coffee ring” pattern, we are able to ink-jet print two-dimensional line and three-dimensional surface/plane reproducibly. By ink-jet printing barium titanate nanoparticles and commercially available negative photoresist (SU-8) sequentially on a flexible PI substrate, a nanostructured composite dielectric is successfully demonstrated. The flexible capacitor exhibits a capacitance of 8.28 pF/mm2 and a relative permittivity of 12.44. However, due to its relatively larger thickness, the recorded capacitance is less than that of organic capacitors reported in the literatures.