Resistive switching and transport characteristics of an all-carbon memristor

We describe the structural and electrical characteristics of a resistive switching device fabricated from amorphous carbon. The device consisted of two low resistance sp2-rich contacts separated by a resistive layer with mixed sp2 and sp3 hybridisation states deposited using energetic deposition. Systematic bipolar switching between high- and low-resistance states (HRS/LRS) was observed. The ratio between the HRS and LRS exceeded 100:1 and the device provided stable operation up to at least 10 k cycles. Unlike conventional metal-oxide memristors, this device does not rely on the formation and breakage of conductive metal filaments. A mechanism based on the formation of conductive pathways caused by transitions between sp2 and sp3 hybridisation states is proposed. The current-voltage characteristics were modelled assuming a conducting pathway formed either at the interface regions where barriers could be present or within the interior of the resistive layer where Poole-Frenkel conduction occurred. The switching was attributed to reversible electric field induced alteration of the hybridisation states of carbon atoms. The ability to fabricate these devices entirely from carbon suggests the possibility of a large scale manufacture of durable, biocompatible memristors.