Redox-active Organic Molecules on Silicon and Silicon Dioxide Surfaces for Hybrid Silicon-molecular Memory Devices

Download or read book Redox-active Organic Molecules on Silicon and Silicon Dioxide Surfaces for Hybrid Silicon-molecular Memory Devices written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this dissertation is on creating electronic devices that utilize unique charge storage properties of redox-active organic molecules for memory applications. A hybrid silicon-molecular approach has been adopted to make use of the advantages of the existing silicon technology, as well as to study and exploit the interaction between the organic molecules and the bulk semiconductor. As technology heads into the nano regime, this hybrid approach may prove to be the bridge between the existing Si-only technology and a future molecule-only technology. Functionalized monolayers of redox-active molecules were formed on silicon surfaces of different doping types and densities. Electrolyte-molecule-silicon test structures were electrically characterized and studied using cyclic voltammetry and impedance spectroscopy techniques. The dependence of the oxidation and reduction processes on the silicon doping type and density were analyzed and explained using voltage balance equations and surface potentials of silicon. The role played by the silicon substrate on the operation of these memory devices was identified. Multiple bits in a single cell were achieved using either molecules exhibiting multiple stable redox states or mixed monolayer of different molecules. Self-assembled monolayers of redox-active molecules were also incorporated on varying thickness of silicon dioxide on n- and p- silicon substrates in an attempt to create non-volatile memory. The dependences of read/write/erase voltages and retention times of these devices were correlated to the SiO2 thickness by using a combination of Butler-Volmer and semiconductor theories. The region of operation of the silicon surface (accumulation, depletion or inversion) and the extent of tunneling current through the silicon dioxide were found to influence the charging and discharging of the molecules in the monolayer. Increased retention times due to the presence of SiO2 can be useful in realizing non-volatile memorie.