Designing Surface Chemistry of Silver Nanocrystals for Radio-frequency Circuit Applications.

We introduce solution-based, room temperature- and atmospheric-pressure processed silver nanocrystal (Ag NC)-based electrical circuits and interconnects for applications utilizing radio-frequency (RF)/microwave frequency. We chemically designed the surface and interface states of Ag NC thin films to achieve high stability, DC and AC conductivity, and minimized RF loss through stepwise ligand exchange, shell coating, and surface cleaning. The chemical and structural properties of the circuits and interconnects affects the high-frequency electrical performance of Ag NC thin films, as confirmed by high-frequency electromagnetic field simulations. An all solution-based process is developed to build coplanar structures, in which Ag NC thin films are positioned at both sides of the substrates. In addition, we fabricated flexible transmission lines and broadband electrical circuits for resistors, interdigitated capacitors, spiral and omega-shaped inductors, and patch antennas with maximum inductance and capacitance values of 3 nH and 2.5 pF at RF/microwave frequencies up to 20 GHz. We believe that our approach will lead to a cost-effective realization of RF circuits and devices in which sensing and wireless communication capabilities are combined for internet-of-things (IoT) applications.