Making Plastic Remember: Electrically Rewritable Polymer Memory Devices

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Making Plastic Remember: Electrically Rewritable Polymer Memory Devices Dominic Prime, and Shashi Paul Emerging Technologies Research Centre, De Montfort University, Hawthorn Building, The Gateway, Leicester, LE1 9BH, United Kingdom ABSTRACT Organic based electronic memory devices are currently receiving an unprecedented amount attention as possible alternatives for conventional semiconductor memories, due to their simple device structures, ease of fabrication, compatibility with flexible substrates and low cost. Polymer memory devices (PMDs) based on active layers containing gold nanoparticles (Q-Au) with 8-hydroxyquinoline (8HQ) will be presented in this report. Memory performance attributes will also be presented, which are less reported in literature, but still essential for the realisation of viable organic memory technologies. INTRODUCTION In recent years there has been a growing interest in both academia and industry in the field of organic electronic materials as low cost, easily processible alternatives to silicon and other inorganic semiconductors. There have so far been large advancements in organic devices such as organic field effect transistors (OFETs), organic solar cells and organic light emitting diodes (OLEDs), with OLEDís being the main organic devices to have achieved commercial success. In the field of non-volatile polymer memory devices there has been considerably less research conducted. To make a viable memory device any new organic memory must have acceptable levels of performance in terms of retention time, memory cycles and power consumption [1]; criteria which so far polymer memories fail to meet sufficiently one, or more areas. Among the most promising PMDs to date are devices consisting of an admixture of organic polymer, nanoparticles and small organic molecules deposited between top and bottom metal electrodes to form a crossbar structure [2, 3]. When voltages are applied, the device can switch between two different conductivity states, with the state being read by an intermediate voltage. Polymer memory devices based on active layers consisting of gold nanoparticles passivated with octadecylamine and tri-n-octylphosphine (Q-Au) and 8HQ in a polystyrene (PS) matrix have been studied, as shown in figure 1. The gold nanoparticles used in the study had a size distribution in the range of 5-10nm, with an average size of 7nm. Information regarding the on/off current ratio, i.e. the difference between the measured current in the on state compared to the current in the off state, is reported by a number of authors [3, 6]. However information on how the devices perform in regards to retention time, and also memory cycles before failure is rarely reported. In this report we investigate the retention time of PMDs and the effect of read, write and erase (RWE) cycles on their performance.

Aluminium contacts

Active admixture layer

Glass substrate Figure 1. Polymer memory device structure (not to scale). EXPERIMENT PMDs were fabricated through the following process. Bottom aluminiu