Materials effects on the electrode-sensitive bipolar resistive switches of polymer: gold nanoparticle memory devices

Electronic devices with an polystyrene (PS) layer blended with Au nanoparticles capped with conjugated 2-naphthalenethiol (Au-2NT NPs) sandwiched between Au and Al electrodes exhibit bipolar resistive switches sensitive to the electrodes. This paper reports the effects of materials, including electrode materials, capping ligands of Au nanoparticles and matrix polymers, on the electrical behavior of the polymer:nanoparticle memory devices. Although the devices using Cu to replace Au as the top electrode exhibit resistive switches similar to those with Au, the threshold voltage for the resistive switch is higher, and the current density for the devices in the low conductivity state is lower. However, the threshold voltage and the current density are almost the same as those with Au as the top electrode, when a semiconductor, MoO3, is used to replace Au as the top electrode of the devices. The effects of these electrodes are attributed to the charge transfer at the contacts between Au-2NT NPs and the electrodes. The resistive switches are also sensitive to the capping organic ligand of the Au nanoparticles. The threshold voltage decreases and the current density increases, when conjugated benzenethiol is used to replace 2-naphthalenethiol. However, the current density dramatically decreases and the threshold voltage increases, when 2-benzeneethanethiol, a partially conjugated molecule, is adopted as the capping ligand of the Au nanoparticles. The effect of the capping ligands is ascribed to their effect on the charge tunneling across the Au-2NT NPs in the active layer and the contacts between Au-2NT NPs and electrodes. The devices with poly(methyl methacrylate) (PMMA) replacing PS as the polymer matrix exhibit resistive switches almost the same as those with PS, which indicates that the Au-2NT NPs rather than the polymer is the active material responsible for the resistive switches. (C) 2013 Elsevier B. V. All rights reserved.