Capacitive tunnels in single-walled carbon nanotube networks on flexible substrate

Abstract

We report the analysis of single-walled carbon nanotube networks, which are expected to be suitable as miniaturized flexible radio frequency RC filters and also have important implications for high frequency devices. The surface morphology obtained by atomic force microscopy shows that most of the growth on polypropylene carbonate substrate is homogeneous. The large value of peak intensity ratio of G and D band in Raman spectra indicates the high purity network. Nyquist plots of carbon nanotube networks on a flexible substrate are close to real circles, indicating that the material is conducting, and suggest a simple equivalent circuit having a resistor in parallel with a capacitor. The Bode plots give the dependence of real and imaginary impedances on frequency. While at high frequency, the impedance decreases, due to generation of capacitance between a single-walled carbon nanotube; at low frequency, it shows the normal behavior, having constant value. The tunnels among different carbon nanotubes are capable of storing electric charge. The accumulative capacitances of tunnels for three varied concentrations are calculated by electrochemical impedance spectroscopy simulations to fit the observed Nyquist plots.