Physical mechanisms involved in the formation and operation of memory devices based on a monolayer of gold nanoparticles-polythiophene hybrid materials

TL;DR

This study investigates the physical and chemical mechanisms in a monolayer gold nanoparticle-polymer hybrid memory device, revealing nanoparticle growth, organic layer rearrangement, and charge transport behavior through combined in situ physical, chemical, and electrical analyses.

Contribution

It provides a comprehensive in situ analysis of the physical and chemical changes during device forming and operation, which was previously inaccessible without destructive methods.

Findings

Gold nanoparticles grow fourfold during forming

Organic layer transforms from sp3 to sp2 amorphous carbon

Charge transport follows trap-filled space charge limited current

Abstract

Understanding the physical and chemical mechanisms occurring during the forming process and operation of an organic resistive memory device is a major issue for better performances. Various mechanisms were suggested in vertically stacked memory structures, but the analysis remains indirect and needs destructive characterization (e.g. cross-section to access the organic layers sandwiched between electrodes). Here, we report a study on a planar, monolayer thick, hybrid nanoparticle/molecule device (10 nm gold nanoparticles embedded in an electro-generated poly(2-thienyl-3,4-(ethylenedioxy)thiophene) layer), combining, in situ, on the same device, physical (scanning electron microscope, physico-chemical (thermogravimetry and mass spectroscopy, Raman spectroscopy) and electrical (temperature dependent current-voltage) characterizations. We demonstrate that the forming process causes an increase in the gold particle size, almost 4 times larger than the starting nanoparticles, and that the organic layer undergoes a significant chemical rearrangement from a sp3 to sp2 amorphous carbon material. Temperature dependent electrical characterizations of this nonvolatile memory confirm that the charge transport mechanism in the device is consistent with a trap-filled space charge limited current in the off state, the sp2 amorphous carbon material containing many electrically active defects.