We are developing a molecular approach for information storage that has features superior to those of semiconductors. The basic idea is to store information in distinct oxidation states of molecules that are attached to an electroactive surface. We have elected to employ cationic oxidation states rather than anionic states given the greater stability of the positively charged states under real-world conditions. The advantages over semiconductors include (1) molecular rather than bulk properties, affording scalability to molecular dimensions, (2) charge-retention times in the tens of minutes (several orders of magnitude greater than semiconductors), (3) storage of multiple bits per molecule, and (4) low power operation. This approach may ultimately enable the storage of 1014 bytes/cm3 which in a single cubic centimeter is ~10-times the content of all printed materials in the Library of Congress (~10,000 Gb). The basic outline of our approach is illustrated in the color diagram below [see papers 104 and 108-112 in the publication list]. In this diagram, each crossing of the two electrodes defines a memory cell. A given memory cell contains a sizeable number of identical molecules (in other words, we are not attempting "single-molecule electronics"), thereby affording defect tolerance.
This project is intensely collaborative and involves chemical synthesis by our group at North Carolina State Univeristy, physical chemical characterization (Prof. David Bocian, UC-Riverside), electrochemical characterization (Prof. Werner Kuhr, UC-Riverside), theoretical chemistry (Prof. Mark Ratner, Northwestern University), computer chip fabrication (Prof. Veena Misra, NC State Electrical Engineering), circuit simulation and analysis (Prof. Wentai Liu, NC State Electrical Engineering), and computer architecture design and simulation (Prof. Eric Rotenberg, NC State Electrical Engineering). Chemical synthesis makes this project possible, but must be done in the context of our larger objectives in molecular electronics in order to have substantive impact. To date we have synthesized about 100 molecules for investigation of suitability for molecular-based information storage.
Examples of the molecules we have created are shown below. Our goals are to push into the low-potential regime and to achieve multibit operation.
A "winged-spider" for studies of multibit information storage at sites proximal and distal to the surface.
A dimer comprised of essentially identical units for studies of multibit information storage.
A triple decker for studies of multibit information storage at low oxidation potentials.
A dyad of triple deckers for studies of multibit information storage at sites proximal and distal to the surface.
