Achieving highly tunable negative permittivity in titanium nitride/polyimide nanocomposites via controlled DC bias

Metacomposites with negative permittivity that derived from random structures have drawn considerable attention. Nowadays, negative permittivity was commonly realized in percolative composites via controlling the compositions and microstructures. Herein, highly tunable plasma-like negative permittivities were successfully achieved in titanium nitride/polyimide nanocomposites via applying external DC bias. It is indicated that the trapped charges at the interfaces between titanium nitride and polyimide can escape from the interfaces after absorbing energy from DC bias, resulting in elevated concentration of free charges and enhanced plasma oscillations, hence the enhanced plasma frequencies and negative permittivities. This work demonstrated that applying DC bias is an effective way to achieve highly tailorable negative permittivity, which is of great significance to the exploration of high-performance negative-k metacomposites. (C) 2018 Elsevier B.V. All rights reserved.