Dielectric Behavior of Thin Polymerized Composite Layers Fabricated by Inkjet-Printing

A detailed study of the dielectric behavior of printed capacitors is given, in which the dielectric consists of a thin (<1 mu m) ceramic/polymer composite layer with high permittivities of epsilon(r) 20-69. The used ink contains surface-modified Ba0.6Sr0.4TiO3 (BST), a polymeric crosslinking agent and a thermal initiator, which allows the immediate polymerization of the ink during printing, leading to homogenous layers. To validate the results of the calculated permittivities, different layer thicknesses of the dielectric are printed and the capacitances, as well as the loss factors, are measured. Afterwards, the exact layer thicknesses are determined with cross sectional SEM images of ion-etched samples. Then, the permittivities are calculated with the known effective area of the capacitors. Furthermore, the ink composition is varied to obtain different ceramic/polymer ratios and thus different permittivities. The packing density of all composites is analyzed via SEM to show possible pores and validate the target ratio, respectively. The correlation between the chosen ratio and the measured permittivity is discussed using models from the literature. In addition, the leakage current of some capacitors is measured and discussed. For that, the dielectric was printed on different bottom electrodes as the nature of the electrode was found to be crucial for the performance.

Automated summary

A thorough investigation of dielectric behavior in printed capacitors using a ceramic/polymer composite layer is presented. The ink used contains Ba0.6Sr0.4TiO3 with modified surface properties, a crosslinking agent, and a thermal initiator for immediate ink polymerization. The capacitors with different dielectric layer thicknesses were printed to measure capacitance and loss factor values. The exact layer thicknesses were determined using cross-sectional SEM images, and the permittivities were calculated based on the known effective area. Varying the ink composition yielded different ceramic/polymer ratios and permittivities, which were validated through SEM analysis. Furthermore, the leakage current and the choice of bottom electrode were measured and discussed for performance optimization.