Since the discovery of conducting polymers , organic-based electronics such as organic light-emitting diodes, transistors, photovoltaics, and memory devices have been spotlighted as potentially innovative devices given their easy and lowcost fabrication by spin-coating or ink-jet printing, and their fl exibility. Among these, organic memories have been extensively investigated for data-storage application. [ 11 , 14 , 16-21 ] However, organic memories so far have been fabricated in single cells or in arrayed cells with low memory cell density , which constitutes an obstacle to their more practical application. In this regard, the three-dimensional (3D) stacking of memory devices provides a way to achieve a great increase in memory cell density. Unlike silicon or inorganic-based memory devices, which can be fabricated in complicated vertically stacked multi-layers, organic devices are built from organically active-and thus chemically unstable in multi-layer stackingmaterials that are not trivial to stack. The success of multi-layer stacked device fabrication by the spin-coating process depends to a great extent on the chemical and thermal robustness of the organic material because the stacked over-layer may dissolve the below-layer with excess solvent during the spin-coating.
Here we demonstrate the fabrication of 3D-stacked 8 ร 8 cross-bar array polymer resistive memory devices with a composite of polyimide (PI) and 6-phenyl-C61 butyric acid methyl ester (PCBM) as the memory element by using simple spincoating processes to deposit the active layers. Individual memory cells in the different layers can be independently controled and monitored and they exhibited excellent memory performance in terms of ON/OFF ratio, cycling, and retention time. Our demonstration of 3D stackable organic memory devices will bring closer the prospect of achieving highly integrable organic memory devices and other organic-based electronics.
A conceptual schematic of the 3D-stacked 8 ร 8 crossbar multi-layer organic memory devices is illustrated in Figure .