Tunneling Negative Differential Resistance in Flexible Silicone Graphite Composites

S.D. Littlejohn, A. Nogaret, S. Crampin
University of Bath, UK

Keywords: negative differential resistance, graphite, nano-particles, flexible

Summary:

Developing flexible electronic materials with the ability to amplify signals is a major challenge for bioelectronics. The next step in developing an active nervous system calls for a flexible electronic material that produces a signal gain. The ability to tune the electrical conductivity of the graphene bilayer with an electric field provides a route for addressing this challenge through the generation of negative differential resistance (NDR). We demonstrate a wide NDR region in the current-voltage characteristics of silicone filled with graphitic nanoparticles. At the peak, the conductor breaks up into domains of constant electric field separated by highly resistive domain boundaries. These boundaries are identified as individual graphite nanoparticles whose orientation in the electric field favours conduction across just two graphene layers. Increasing the electric field opens a partial energy gap at the Fermi level which causes the current carrying bilayer to undergo a semimetal-to-insulator transition. This explains the dependence of the I-V curves on the concentration of graphitic nanoparticles, temperature, channel length, as well as the disappearance of the NDR when the graphitic nanoparticles are replaced with amorphous carbon nanoparticles.