Low-frequency negative capacitance effect in systems of metallic nanoparticles embedded in dielectric matrix

A negative capacitance (NC) effect in a low-frequency range $\left(4–8\times {10}^5\mathrm{Hz}\right)$ , previously shown to take place mainly in semiconductor structures, is evidenced in a nanometric system constituted by metallic $\left(\mathrm{Ga}\right)$ nanoparticles embedded in an insulating $\left({\mathrm{SiO}}_x\text{with}x~1\right)$ matrix. The dependence of the $\mathrm{NC}$ phenomenon on the time-dependent transient current through the system is evidenced. A remarkable enhancement of the effect with size reduction of the nanoparticles is manifested. The physical mechanism responsible for the current inertia appears to be related to the space charges located at the multiple insulator–metal interfaces.