Browsing by Author "Wang, Gunuk"

Now showing 1 - 6 of 6
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    Addressable SiOX memory array with incorporated diodes
    (2016-07-05) Tour, James M.; Yao, Jun; Lin, Jian; Wang, Gunuk; Palem, Krishna; Rice University; Nanyang Technological University; United States Patent and Trademark Office
    Various embodiments of the resistive memory cells and arrays discussed herein comprise: (1) a first electrode; (2) a second electrode; (3) resistive memory material; and (4) a diode. The resistive memory material is selected from the group consisting of SiOx, SiOxH, SiOxNy, SiOxNyH, SiOxCz, SiOxCzH, and combinations thereof, wherein each of x, y and z are equal to or greater than 1 and equal to or less than 2. The diode may be any suitable diode, such as n-p diodes, p-n diodes, and Schottky diodes.
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    Nanoporous metal-oxide memory
    (2017-11-28) Tour, James M.; Wang, Gunuk; Yang, Yang; Rice University; United States Patent and Trademark Office
    A nanoporous (NP) memory may include a non-porous layer and a nanoporous layer sandwiched between the bottom and top electrodes. The memory may be free of diodes, selectors, and/or transistors that may be necessary in other memories to mitigate crosstalk. The nanoporous material of the nanoporous layer may be a metal oxide, metal chalcogenide, or a combination thereof. Further, the memory may lack any additional components. Further, the memory may be free from requiring an electroformation process to allow switching between ON/OFF states.
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    Porous SiOx materials for improvement in SiOx switching device performances
    (2018-06-12) Tour, James M.; Wang, Gunuk; Yang, Yang; Ji, Yongsung; Rice University; United States Patent and Trademark Office
    A porous memory device, such as a memory or a switch, may provide a top and bottom electrodes with a memory material layer (e.g. SiOx) positioned between the electrodes. The memory material layer may provide a nanoporous structure. In some embodiments, the nanoporous structure may be formed electrochemically, such as from anodic etching. Electroformation of a filament through the memory material layer may occur internally through the layer rather than at an edge at extremely low electro-forming voltages. The porous memory device may also provide multi-bit storage, high on-off ratios, long high-temperature lifetime, excellent cycling endurance, fast switching, and lower power consumption.
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    Rebar Graphene from Functionalized Boron Nitride Nanotubes
    (American Chemical Society, 2015) Li, Yilun; Peng, Zhiwei; Larios, Eduardo; Wang, Gunuk; Lin, Jian; Yan, Zheng; Ruiz-Zepeda, Francisco; José-Yacamán, Miguel; Tour, James M.; Richard E. Smalley Institute for Nanoscale Science and Technology
    The synthesis of rebar graphene on Cu substrates is described using functionalized boron nitride nanotubes (BNNTs) that were annealed or subjected to chemical vapor deposition (CVD) growth of graphene. Characterization shows that the BNNTs partially unzip and form a reinforcing bar (rebar) network within the graphene layer that enhances the mechanical strength through covalent bonds. The rebar graphene is transferrable to other substrates without polymer assistance. The optical transmittance and conductivity of the hybrid rebar graphene film was tested, and a field effect transistor was fabricated to explore its electrical properties. This method of synthesizing 2D hybrid graphene/BN structures should enable the hybridization of various 1D nanotube and 2D layered structures with enhanced mechanical properties.
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    Three-Dimensional Nanoporous Fe2O3/Fe3C-Graphene Heterogeneous Thin Films for Lithium-Ion Batteries
    (American Chemical Society, 2014) Yang, Yang; Fan, Xiujun; Casillas, Gilberto; Peng, Zhiwei; Ruan, Gedeng; Wang, Gunuk; Yacaman, Miguel Jose; Tour, James M.; Smalley Institute for Nanoscale Science and Technology
    Three-dimensional self-organized nanoporous thin films integrated into a heterogeneous Fe2O3/Fe3C-graphene structure were fabricated using chemical vapor deposition. Few-layer graphene coated on the nanoporous thin film was used as a conductive passivation layer, and Fe3C was introduced to improve capacity retention and stability of the nanoporous layer. A possible interfacial lithium storage effect was anticipated to provide additional charge storage in the electrode. These nanoporous layers, when used as an anode in lithium-ion batteries, deliver greatly enhanced cyclability and rate capacity compared with pristine Fe2O3: a specific capacity of 356 μAh cm–2 μm–1 (3560 mAh cm–3 or ∼1118 mAh g–1) obtained at a discharge current density of 50 μA cm–2 (∼0.17 C) with 88% retention after 100 cycles and 165 μAh cm–2 μm–1(1650 mAh cm–3 or ∼518 mAh g–1) obtained at a discharge current density of 1000 μA cm–2(∼6.6 C) for 1000 cycles were achieved. Meanwhile an energy density of 294 μWh cm–2 μm–1(2.94 Wh cm–3 or ∼924 Wh kg–1) and power density of 584 μW cm–2 μm–1 (5.84 W cm–3 or ∼1834 W kg–1) were also obtained, which may make these thin film anodes promising as a power supply for micro- or even nanosized portable electronic devices.
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    Three-Dimensional Networked Nanoporous Ta2O5–x Memory System for Ultrahigh Density Storage
    (American Chemical Society, 2015) Wang, Gunuk; Lee, Jae-Hwang; Yang, Yang; Ruan, Gedeng; Kim, Nam Dong; Ji, Yongsung; Tour, James M.; Richard E. Smalley Institute of Nanoscale Science and Technology
    Oxide-based resistive memory systems have high near-term promise for use in nonvolatile memory. Here we introduce a memory system employing a three-dimensional (3D) networked nanoporous (NP) Ta2O5-x structure and graphene for ultrahigh density storage. The devices exhibit a self-embedded highly nonlinear I-V switching behavior with an extremely low leakage current (on the order of pA) and good endurance. Calculations indicated that this memory architecture could be scaled up to a ∼162 Gbit crossbar array without the need for selectors or diodes normally used in crossbar arrays. In addition, we demonstrate that the voltage point for a minimum current is systematically controlled by the applied set voltage, thereby offering a broad range of switching characteristics. The potential switching mechanism is suggested based upon the transformation from Schottky to Ohmic-like contacts, and vice versa, depending on the movement of oxygen vacancies at the interfaces induced by the voltage polarity, and the formation of oxygen ions in the pores by the electric field.