As semiconductor device scaling is reaching the 45 nm node, the need for novel device concept, architecture and new materials has never been so pressing as today. Flash memories, the driving force of semiconductor memory market in recent years, also face the same or maybe more severe challenges to meet the demands for high-density, low-cost, low-power, high-speed, better endurance and longer retention time. As traditional continuous floating gate flash struggles to balance the trade-off between high speed and retention requirement, nanocrystal (NC) floating gate flash has attracted more and more interest recently due to its advantages over traditional flash memories in many areas such as better device scaling, lower power consumption and improved charge retention. However, there are still two major challenges remaining for embedded NC synthesis: the deposition method and the size and distribution control. Nowadays using bio-nano techniques such as DNA, virus or protein for NC synthesis and assembly has become a hot topic and feasible for actual electronic device fabrication. In this dissertation a new method for NC deposition wherein a colloidal suspension of commercially-available NCs was organized using a self-assembled chaperonin array. The chaperonin array was applied as a scaffold to mediate NCs into an assembly with uniform spatial distribution on Si wafers. By using this method, we demonstrated that colloidal PbSe and Co NCs in suspension can self-assemble into ordered arrays with a high density of up to 10¹²cm⁻². MOSCAP and MOSFET memory devices were successfully fabricated with the chaperonin protein mediated NCs, showing promising memory functions such as a large charge storage capacity, long retention time and good endurance. The charge storage capacity with respect to material work function, NC size and density was explored. In addition to NC engineering, the tunnel barrier was engineered by replacing traditional SiO₂ by high-k material HfO₂, giving a higher write/erase speed with a reduced effective oxide thickness (EOT). Suggestions for future research in this direction are presented in the last part of this work. / text

Mainstream non-volatile memory technology dominated by the planar Flash transistor with continuous floating-gate has been historically improved in density and performance primarily by means of process scaling, but is currently faced with significant hindrances to its future scaling due to fundamental constraints of electrostatics and reliability. This dissertation is based on exploring two pathways for circumventing scaling limitations of the state-of-the-art Flash memory technology. The first part of the dissertation is based on demonstrating a vertical Flash memory transistor with nanocrystal floating-gate, while the second part is based on developing fundamental understanding of the operation of Phase Change Memory. A vertical Flash transistor can allow the theoretical minimum cell area and a nanocrystal floating-gate on the sidewalls is shown to allow a thinner gate-stack further conducive to scaling while still providing good reliability. Subsequently, the application of a technique of protein-mediated assembly of preformed nanocrystals to the sidewalls of the vertical Flash transistor is also demonstrated and characterized. This technique of ordering pre-formed nanocrystals is beneficial towards achieving reproducible nanocrystal size uniformity and ordering especially in a highly scaled vertical Flash cell, rendering it more amenable to scaling and manufacturability. In both forms, the vertical Flash memory cell is shown to have good electrical characteristics and reliability for the viability of this cell design and implementation. In the remaining part of this dissertation, studies are undertaken towards developing fundamental understanding of the operational characteristics of Phase Change Memory (PCM) technology that is expected to replace floating-gate Flash technology based on its potential for scaling. First, a phenomenon of improving figures of merit of the PCM cell with operational cycles is electrically characterized. Based on the electrical characterization and published material characterization data, a physical model of an evolving "active region" of the cell is proposed to explain the improvement of the cell parameters with operational cycles. Then, basic understanding is developed on early and erratic retention failure in a statistically significant number of cells in a large array and, electrical characterization and physical modeling is used to explain the mechanism behind the early retention failure.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 76-78). Also available in electronic version.

Thesis (Ph.D.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

This thesis is dedicated to developing three different types of ferrocene-containing polymers for organic lithium-ion battery and resistive memory applications. Chapter 1 gives an overview of organic cathode-active materials, polymeric resistive memories and ferrocene-containing polymers. Furthermore, the previously reported applications of ferrocene-containing polymeric systems in electrochemical energy storage and electronical memory devices were also comprehensively summarized. In chapter 2, conjugated ferrocene-containing side-chain metallopolymers PFcFE1, PFcFE2, PFcFE3 and PFcFE4 were designed and synthesized via Sonogashira cross-coupling polycondensation. The charging-discharging processes of triphenyamine-based PFcFE1 and thiophene-modified PFcFE4 have been successfully studied as cathode materials. PFcFE1 composite electrode showed a capacity of 90 mAh g-1 and the cathode composed of PFcFE4 retained over 90% of the initial capacity after 100 charging-discharging cycles at 10 C. These results demonstrate the great potentials of these ferrocene-containing side-chain polymers as active cathode materials for organic lithium-ion battery applicaitons. Besides, all prepared ferrocene-containing metallopolymers PFcFE1, PFcFE2, PFcFE3 and PFcFE4 also exhibited nonvolatile resistive switching behaviors with the flash memory effect of PFcFE1, PFcFE2 and PFcFE3 as well as the WORM memory feature of PFcFE4, indicating the easily tuned memory properties by changing the chemical structures of the active polymeric backbones. It is also worth noting that the ITO/PFcFE1/Al memory device showed a high ON/OFF current ratio of 103 to 104, a low switch-on voltage of -1.0 V, a long retention time of 1000 s and a large read cycle number up to 105, which is superior to other reported ferrocene-containing memory examples. Chapter 3 focuses on the development of non-conjugated ferrocene-containing copolymers PVFVM1, PVFVM1-1, PVFVM2, PVFVM3, PVFVM4, PVFVM5 and PVFVM6 based on different heteroaromatic moieties which were prepared by AIBN initiated chain addition polymerization. The as-prepared copolymers PVFVM1 and PVFVM1-1 exhibited electrochemical characteristics of both ferrocene and triphenylamine pendants with reversible multiple redox waves at the half potentials of E1/2 = --0.06, 0.30, and 0.42 V (vs. Fc/Fc+). Notably, the composite electrode based on PVFVM1 afforded a discharge capacity of 102 mAh g--1 at 10 C, corresponding to 98% of its theoretical capacity. The cycle endurances of the active polymer electrodes composed of PVFVM1 or PVFVM1-1 were both evaluated for over 50 numbers and no significant capacity reduction over cycles were observed. On the other hand, initial I-V results of memory devices based on PVFVM1, PVFVM1-1, PVFVM2, PVFVM3, PVFVM4 and PVFVM6 also revealed their huge potentials in electronic information storage. The stability and reproducibility of the corresponding memory devices based on these materials will be futher evaluated in the near future. We used 1,1'-ferrocenediboronic acid bis(pinacol) ester to develop conjugated ferrocene-containing main-chain metallopolymers in chapter 4. All these rational designed metallopolymers FcMMP1, FcMMP2, FcMMP3 and FcMMP4 with one or two ferrocene moieties were produced via Suzuki cross-coupling polycondensation. Their structural information, molecular masses, photophysical features and thermal properties have been well studied. Electrochemical performances of the formed polymers were also examined to clarify their potential as cathode-active materials. Other charge-storage characteristics and switching behaviors of these prepared ferrocene-containing main-chain metallopolymers for organic battery and memory applications are under further investigation.

No description available.

Thesis (M.S.)--State University of New York at Binghamton, Department of Physics, 2006. / Includes bibliographical references.