Lowering Off Current in Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-Based Resistive Random Access Memory By Modulating Molecular Orientation and Doping Levels

Abstract

Resistive random-access memory (RRAM) utilizing highly tunable organic materials, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), has attracted considerable interest for high-density scaling applications due to its simple two-terminal, sandwiched structure, which enables cost-effective integration with flexibility, biocompatibility, and transient functionalities. To extend organic RRAM into integrated circuits for neuromorphic computing, it is crucial to reduce power consumption, particularly by minimizing the off current (I_off). However, I_off in vertically stacked PEDOT:PSS-based RRAM remains relatively high due to its inherently high doping level and molecular alignment in the out-of-plane direction. Herein, we introduce a sequential treatment approach to modify the molecular orientation and doping level of PEDOT:PSS thin films by employing sorbitol and potassium hydroxide (KOH), respectively, to achieve reduced I_off. We found that sorbitol addition hinders electrical conduction in the out-of-plane direction by flattening the PSS domains microscopically, while the subsequent KOH treatment effectively lowers the carrier concentration by dedoping PEDOT chains. As a result, I_off at a read voltage of 100 mV was dramatically reduced from 1.57 × 10^–3 (pristine PEDOT:PSS) to 3.20 × 10^–8 A, a value lower than those previously reported. We believe that the methods presented in this work will contribute to future research on modifying the conduction properties of PEDOT and inspire further investigation into reducing I_off in organic RRAM for practical applications.