Tip-enhanced electric field-driven efficient charge injection and transport in organic material-based resistive memories

Abstract

Organic materials show promise as switching layers for resistive random access memory (RRAM). However, practical application has been limited by inefficient charge injection and transport in typical organic materials. This study proves that local enhancement of electric fields through structured electrodes can improve charge injection and transport in organic RRAM. Specifically, pyramid-structured electrodes with an extremely sharp tip are introduced into RRAM with a polyimide (PI) switching layer. The electric field in the pyramid-structured RRAM can be significantly enhanced only at the tip, thereby facilitating charge injection at the electrode/PI interface and charge transport through the PI switching layer. Indeed, the resulting RRAM exhibits low and reliable operating voltages (SET: 1.76 V +/- 0.41 V / RESET: -0.49 V +/- 0.15 V) compared with conventional PI-based RRAMs with planar electrodes. The conductive path formed in the tip region is observed directly using conductive atomic force microscopy, demonstrating that resistive switching occurs by tip-enhanced electric fields. Also, the charge transport mechanism follows the space charge-limiting current model modified by the Poole-Frenkel effect. These results provide an effective strategy to control the charge concentration, injection, and transport in organic RRAM, for realization of low-cost, large-area, shape-deformable data storage devices. (c) 2020 Elsevier Ltd. All rights reserved.