Giant Dielectric Constant of Copper Nanowires/Amorphous SiO₂ Composite Thin Films for Supercapacitor Application

Transparent thin films comprising ultralong (within the range 52-387 μm) copper nanowires with diameter ∼7-9 nm encapsulated in amorphous silica have been successfully fabricated using an electrodeposition technique. The length and number density were controlled by electrodeposition time and concentration of precursor materials, respectively. Giant dielectric constant values (∼10¹⁰) obtained from these systems were quantitatively explained as a function of the length of the nanowires on the basis of quantum mechanical theory derived by Rice and Bernasconi. These transparent thin films offer a specific capacitance value of 550 F/g with more than 73% cyclic stability over a period of 900 cycles. Our findings demonstrate a facile pathway to control and improve the properties of metal nanowire-based transparent materials for use in supercapacitor applications.