The application of conventional photolithography to microscale organic resistive memory devices

We demonstrate the application of conventional photolithography to fabricate organic memory devices in an array structure with a cell area of 4 × 4 μm² without damaging the underlying organic memory layer. Applying photolithography to organic electronic devices is not trivial because the solvents used during lithography may dissolve and damage the previously coated organic layers. The application of photolithography to our organic devices was possible because of the introduction of polymethyl methacrylate (PMMA)/polyvinyl alcohol (PVA) onto the memory active layer, where PMMA functions as a buffer layer to prevent dissolution of the PVA layer during developing process, and PVA acts as a striped layer during metal lift-off process. Embedded Al bottom electrodes were particularly constructed to minimize the switching failure. The completed organic memory devices exhibited typical unipolar switching behavior and excellent memory performance in terms of their statistical memory parameters (ON and OFF currents and threshold voltages), ON/OFF ratio (>10²), endurance (>230 cycles), and retention (>10⁴ s). This convenient photolithography patterning technique is applicable for the further scaling of many types of organic devices.