(728b) Electrostatically Assisted Assembling of Silver-Dielectric Core/Shell Nanoparticle Thin Film Capacitor With Uniform Metal Nanoparticle Distribution and Controlled Spacing

New dielectric materials are sought after for keeping up with device miniaturization and for emerging applications (e.g. energy conservation and storage). Previous reports give great promise to composite dielectric materials for achieving high dielectric constant (k).  Conductive filler/polymer composite material, identified as conductor-insulator percolative system, is one of these promising method to achieve high-k. We present a novel approach to preparation of metal-dielectric composites where metal volume fractions significantly higher than in simple metal particle-polymer mixtures can be achieved. The approach is based on using metal-dielectric core-shell particles, where each individual metal particle is coated with a uniform shell of a dielectric or insulating material. The shell prevents electrical contact between two neighboring metal cores. Changing shell thickness enables to control the separation distance between metal cores and also the metal volume fraction for the same size of metal particles. Additionally, volume fraction of metal core can be varied with changing metal core size.

In our system, silica shell serving as insulating interlayers could cause potential barriers so as to reduce the tunnel current between neighboring Ag cores, endowing the core/shell nanocomposites with stable and relatively high dielectric constants (k) and low dielectric loss (D). We fabricated and characterized Ag@SiO₂ core-shell particle thin film based parallel plate capacitors. To the best of our knowledge, there are no reports on thickness dependence of k and D in metal-dielectric composites. For most dielectrics, D decreases with thickness. Our thin film composites (1-3 um in thickness) thus show promising D values. The dielectric loss tangent of our thin film composites filling with Ag@SiO₂ were below 0.1, which meets the requirement for embedded decoupling capacitors. These results suggest that the conductive metal core of silver effectively enhances the dielectric constant while maintaining the low dielectric loss of the metal-dielectric composites. In addition, detailed dielectric property measurements revealed that the dielectric properties of the thin film Ag-dielectric composites were related to the incorporation and volume fraction of Ag nanoparitcles in the composites film.