Showing papers by "Meyya Meyyappan published in 2008"

Chalcogenide-Nanowire-Based Phase Change Memory

Abstract: We report fabrication of phase change random access memory (PRAM) using nanowires (NWs) of GeTe and In2Se3. NWs were grown by a vapor-liquid-solid technique and ranged from 40 to 80 nm in diameter and several micrometers long. A dynamic switching ratio (on/off ratio) of 2200 and 2 times 105 was realized for GeTe and indium selenide devices, respectively. The programming power for the RESET operation is only tens of microwatts compared to the milliwatt power levels required by the conventional thin-film-based PRAM.

Germanium Antimonide Phase-Change Nanowires for Memory Applications

Abstract: GeSb nanowires (NWs) have been grown using a vapor-liquid-solid approach for the fabrication of electrically operated phase-change random access memory device. The NWs are 40-100 nm in diameter and have approximately 90% Sb for fast crystallization. Memory devices show an on/off resistance ratio of 104, reset programming current of 0.7 mA, and set programming current of 60 nA.

Special Issue on Nanowire Transistors: Modeling, Device Design, and Technology

Abstract: The primary goal of this special issue is, therefore, to compile advances in different aspects of nanowire-based devices including device physics and modeling, device design, characterization techniques, technology, and applications so that this special issue will not only be of great archival value but also attract new researchers into this area for further accelerating the application of nanowires in building cheaper and higher performance electronic systems.

Nanotechnology: Challenges and the Way Forward

Abstract: Countless investors, both large and small, are interested in nanotechnology simply because they believe that, if they wait long enough, they will eventually see substantial financial returns. Such windfalls, however, will not happen automatically (Kennedy, ch. 1; Currall et al., ch. 7; Sutcliffe, ch. 16). Even if investments help produce a marketable product, there may be little or no financial gain if the product cannot be scaled up in production or if it is not adopted. In this chapter, Meyyappan presents a number of “threats” to the economic success of nanotechnology. These threats, which he contrasts to the promise of benefits, include negative public perceptions of nanotechnology as well as a “potential derailing campaign” (compare Foladori and Invernizzi, ch. 2; ETC Group, ch. 10; and Miller, ch. 19). Meyyappan, a veteran promoter of nanotechnology, has followed—and indeed helped shape— the development of nanotechnology over the last decade as Director of NASA’s program on nanotechnology. Despite the fact that his day-to-day work is in a government funded laboratory, his vision of the future entails the commercialization of nanotechnology products. To reap the benefits he envisions from the research he oversees, Meyyappan urges all those hoping for a nanotechnology enabled future to help overcome likely challenges to commercialization. – Eds.

One-Dimensional Phase-Change Nanomaterials for Information Storage Applications

Abstract: The electrically operated phase-change random access memory (PRAM) features faster write/read, improved endurance, and much simpler fabrication as compared with the traditional transistor-based nonvolatile semiconductor memories. Low-dimensional phase-change materials in nanoscale dimensions offer advantages over their bulk or thin-film counterparts in several aspects such as reduced programmable volume and reduced thermal energies in phase transition. These features contribute to low-power operation, excellent scalability, and fast write/erase time. In this chapter, we present a general bottom-up synthesis approach and systematic material analysis study of one-dimensional chalcogenide-based phase-change materials including germanium telluride (GeTe), and indium selenide (In2Se3) nanowires that are targeted for nonvolatile resistive switching data storage. The phase-change nanowires have been synthesized via thermal evaporation method under vaporliquid—solid (VLS) mechanism. The morphology, composition, and crystal structure of the synthesized nanowires were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The as-synthesized nanowires are structurally uniform with single crystalline structures. The one-dimensional phase-change chalcogenide nanowires exhibit significantly reduced melting points, low activation energy, and excellent morphology, making them promising nanomaterials for data storage devices with very low energy consumption and excellent scalability.