Covalent shaping of polyoxometalate molecular films onto ITO electrodes for charge trapping induced resistive switching

As nano-sized molecular oxides, polyoxometalates (POMs) hold great promise in non-volatile memory materials based on redox-active molecules. Materials processed from solution, by drop-casting, by embedding POMs in polymers, or using layer-by-layer deposition techniques have thus been reported and successfully investigated. Almost all of these examples are electrostatically assembled materials. We herein propose an original route for the elaboration of robust covalent POM networks, to seek the influence of the shaping process on the POM-to-POM communication and the final device performance. Capitalizing on our experience in the handling of organic-inorganic POM hybrids, we have prepared diazonium hybrids to harness the propensity of diazonium salts to form multi-layered materials upon electrochemical reduction. A few nanometers thick materials have thus been grown onto ITO electrodes and have shown to be potentially suitable for write-once-read-many (WORM) devices, with a low set voltage.