Semiconductor/High-Tc-Superconductor Hybrid ICs

NASA Technical Reports Server (NTRS)

Burns, Michael J.

1995-01-01

Hybrid integrated circuits (ICs) containing both Si-based semiconducting and YBa(2)Cu(3)O(7-x) superconducting circuit elements on sapphire substrates developed. Help to prevent diffusion of Cu from superconductors into semiconductors. These hybrid ICs combine superconducting and semiconducting features unavailable in superconducting or semiconducting circuitry alone. For example, complementary metal oxide/semiconductor (CMOS) readout and memory devices integrated with fast-switching Josephson-junction super-conducting logic devices and zero-resistance interconnections.

Atomic switches: atomic-movement-controlled nanodevices for new types of computing

PubMed Central

Hino, Takami; Hasegawa, Tsuyoshi; Terabe, Kazuya; Tsuruoka, Tohru; Nayak, Alpana; Ohno, Takeo; Aono, Masakazu

2011-01-01

Atomic switches are nanoionic devices that control the diffusion of metal cations and their reduction/oxidation processes in the switching operation to form/annihilate a metal atomic bridge, which is a conductive path between two electrodes in the on-state. In contrast to conventional semiconductor devices, atomic switches can provide a highly conductive channel even if their size is of nanometer order. In addition to their small size and low on-resistance, their nonvolatility has enabled the development of new types of programmable devices, which may achieve all the required functions on a single chip. Three-terminal atomic switches have also been developed, in which the formation and annihilation of a metal atomic bridge between a source electrode and a drain electrode are controlled by a third (gate) electrode. Three-terminal atomic switches are expected to enhance the development of new types of logic circuits, such as nonvolatile logic. The recent development of atomic switches that use a metal oxide as the ionic conductive material has enabled the integration of atomic switches with complementary metal-oxide-semiconductor (CMOS) devices, which will facilitate the commercialization of atomic switches. The novel characteristics of atomic switches, such as their learning and photosensing abilities, are also introduced in the latter part of this review. PMID:27877376

Template-switching during DNA synthesis by Thermus aquaticus DNA polymerase I.

PubMed Central

Odelberg, S J; Weiss, R B; Hata, A; White, R

1995-01-01

Recombinant DNA molecules are often generated during the polymerase chain reaction (PCR) when partially homologous templates are available [e.g., see Pääbo et al. (1990) J. Biol. Chem. 265, 4718-4721]. It has been suggested that these recombinant molecules are a consequence of truncated extension products annealing to partially homologous templates on subsequent PCR cycles. However, we demonstrate here that recombinants can be generated during a single round of primer extension in the absence of subsequent heat denaturation, indicating that template-switching produces some of these recombinant molecules. Two types of template-switches were observed: (i) switches to pre-existing templates and (ii) switches to the complementary nascent strand. Recombination is reduced several fold when the complementary template strands are physically separated by attachment to streptavidin magnetic beads. This result supports the hypothesis that either the polymerase or at least one of the two extending strands switches templates during DNA synthesis and that interaction between the complementary template strands is necessary for efficient template-switching. Images PMID:7596836

Durability-enhanced two-dimensional hole gas of C-H diamond surface for complementary power inverter applications

PubMed Central

Kawarada, Hiroshi; Yamada, Tetsuya; Xu, Dechen; Tsuboi, Hidetoshi; Kitabayashi, Yuya; Matsumura, Daisuke; Shibata, Masanobu; Kudo, Takuya; Inaba, Masafumi; Hiraiwa, Atsushi

2017-01-01

Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al2O3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and VB. PMID:28218234

Durability-enhanced two-dimensional hole gas of C-H diamond surface for complementary power inverter applications.

PubMed

Kawarada, Hiroshi; Yamada, Tetsuya; Xu, Dechen; Tsuboi, Hidetoshi; Kitabayashi, Yuya; Matsumura, Daisuke; Shibata, Masanobu; Kudo, Takuya; Inaba, Masafumi; Hiraiwa, Atsushi

2017-02-20

Complementary power field effect transistors (FETs) based on wide bandgap materials not only provide high-voltage switching capability with the reduction of on-resistance and switching losses, but also enable a smart inverter system by the dramatic simplification of external circuits. However, p-channel power FETs with equivalent performance to those of n-channel FETs are not obtained in any wide bandgap material other than diamond. Here we show that a breakdown voltage of more than 1600 V has been obtained in a diamond metal-oxide-semiconductor (MOS) FET with a p-channel based on a two-dimensional hole gas (2DHG). Atomic layer deposited (ALD) Al 2 O 3 induces the 2DHG ubiquitously on a hydrogen-terminated (C-H) diamond surface and also acts as both gate insulator and passivation layer. The high voltage performance is equivalent to that of state-of-the-art SiC planar n-channel FETs and AlGaN/GaN FETs. The drain current density in the on-state is also comparable to that of these two FETs with similar device size and V B .

Electronic switching circuit uses complementary non-linear components

NASA Technical Reports Server (NTRS)

Zucker, O. S.

1972-01-01

Inherent switching properties of saturable inductors and storage diodes are combined to perform large variety of electronic functions, such as pulse shaping, gating, and multiplexing. Passive elements replace active switching devices in generation of complex waveforms.

Resistance switching behavior of atomic layer deposited SrTiO3 film through possible formation of Sr2Ti6O13 or Sr1Ti11O20 phases

PubMed Central

Lee, Woongkyu; Yoo, Sijung; Yoon, Kyung Jean; Yeu, In Won; Chang, Hye Jung; Choi, Jung-Hae; Hoffmann-Eifert, Susanne; Waser, Rainer; Hwang, Cheol Seong

2016-01-01

Identification of microstructural evolution of nanoscale conducting phase, such as conducting filament (CF), in many resistance switching (RS) devices is a crucial factor to unambiguously understand the electrical behaviours of the RS-based electronic devices. Among the diverse RS material systems, oxide-based redox system comprises the major category of these intriguing electronic devices, where the local, along both lateral and vertical directions of thin films, changes in oxygen chemistry has been suggested to be the main RS mechanism. However, there are systems which involve distinctive crystallographic phases as CF; the Magnéli phase in TiO2 is one of the very well-known examples. The current research reports the possible presence of distinctive local conducting phase in atomic layer deposited SrTiO3 RS thin film. The conducting phase was identified through extensive transmission electron microscopy studies, which indicated that oxygen-deficient Sr2Ti6O13 or Sr1Ti11O20 phase was presumably present mainly along the grain boundaries of SrTiO3 after the unipolar set switching in Pt/TiN/SrTiO3/Pt structure. A detailed electrical characterization revealed that the samples showed typical bipolar and complementary RS after the memory cell was unipolar reset. PMID:26830978

Study on the transient properties of amorphous solar cells

NASA Astrophysics Data System (ADS)

Smrity, Manu; Dhariwal, S. R.

2016-05-01

The transient response for the solar cell when switched off from steady-state can provide useful information about the quality of the material used for fabrication of the device. In this paper we shall discuss the photovoltaic transients of amorphous silicon solar cells when switched off from open circuit configuration and illuminated by electrical pulse. The open-circuit voltage (Voc) decay can be performed by two methods, by optical excitation and by electrical pulse. When one of carriers has a concentration much higher than the other the photoconductivity is dominated by majority carriers; in that case the Voc decay which depends on the np product can be used as complementary method for obtaining information about the minority carriers. Also the series resistance drop in an electrical Voc decay method can be used to obtain a IJ't product as an additional information regarding the material of the device.

Fully-Coupled Thermo-Electrical Modeling and Simulation of Transition Metal Oxide Memristors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamaluy, Denis; Gao, Xujiao; Tierney, Brian David

2016-11-01

Transition metal oxide (TMO) memristors have recently attracted special attention from the semiconductor industry and academia. Memristors are one of the strongest candidates to replace flash memory, and possibly DRAM and SRAM in the near future. Moreover, memristors have a high potential to enable beyond-CMOS technology advances in novel architectures for high performance computing (HPC). The utility of memristors has been demonstrated in reprogrammable logic (cross-bar switches), brain-inspired computing and in non-CMOS complementary logic. Indeed, the potential use of memristors as logic devices is especially important considering the inevitable end of CMOS technology scaling that is anticipated by 2025. Inmore » order to aid the on-going Sandia memristor fabrication effort with a memristor design tool and establish a clear physical picture of resistance switching in TMO memristors, we have created and validated with experimental data a simulation tool we name the Memristor Charge Transport (MCT) Simulator.« less

High-performance hybrid complementary logic inverter through monolithic integration of a MEMS switch and an oxide TFT.

PubMed

Song, Yong-Ha; Ahn, Sang-Joon Kenny; Kim, Min-Wu; Lee, Jeong-Oen; Hwang, Chi-Sun; Pi, Jae-Eun; Ko, Seung-Deok; Choi, Kwang-Wook; Park, Sang-Hee Ko; Yoon, Jun-Bo

2015-03-25

A hybrid complementary logic inverter consisting of a microelectromechanical system switch as a promising alternative for the p-type oxide thin film transistor (TFT) and an n-type oxide TFT is presented for ultralow power integrated circuits. These heterogeneous microdevices are monolithically integrated. The resulting logic device shows a distinctive voltage transfer characteristic curve, very low static leakage, zero-short circuit current, and exceedingly high voltage gain. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection and characterization of multi-filament evolution during resistive switching

DOE PAGES

Mickel, Patrick R.; Lohn, Andrew J.; Marinella, Matthew J.

2014-08-05

We present resistive switching data in TaO x memristors displaying signatures of multi-filament switching modes, and develop a geometrically defined equivalent circuit to separate the individual resistances and powers dissipated in each filament. Using these resolved values, we compare the individual switching curves of each filament and demonstrate that the switching data of each filament collapse onto a single switching curve determined by the analytical steady-state resistive switching solution for filamentary switching. Analyzing our results in terms of this solution, we determine the switching temperature, heat flow, conductivity, and time evolving areas of each filament during resistive switching. Finally, wemore » discuss operational modes which may limit the formation of additional conducting filaments, potentially leading to increased device endurance.« less

Micro-electro-mechanically switchable near infrared complementary metamaterial absorber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pitchappa, Prakash; Pei Ho, Chong; Institute of Microelectronics

2014-05-19

We experimentally demonstrate a micro-electro-mechanically switchable near infrared complementary metamaterial absorber by integrating the metamaterial layer to be the out of plane movable microactuator. The metamaterial layer is electrostatically actuated by applying voltage across the suspended complementary metamaterial layer and the stationary bottom metallic reflector. Thus, the effective spacing between the metamaterial layer and bottom metal reflector is varied as a function of applied voltage. With the reduction of effective spacing between the metamaterial and reflector layers, a strong spectral blue shift in the peak absorption wavelength can be achieved. With spacing change of 300 nm, the spectral shift of 0.7 μmmore » in peak absorption wavelength was obtained for near infrared spectral region. The electro-optic switching performance of the device was characterized, and a striking switching contrast of 1500% was achieved at 2.1 μm. The reported micro-electro-mechanically tunable complementary metamaterial absorber device can potentially enable a wide range of high performance electro-optical devices, such as continuously tunable filters, modulators, and electro-optic switches that form the key components to facilitate future photonic circuit applications.« less

Coexistence of diode-like volatile and multilevel nonvolatile resistive switching in a ZrO2/TiO2 stack structure.

PubMed

Li, Yingtao; Yuan, Peng; Fu, Liping; Li, Rongrong; Gao, Xiaoping; Tao, Chunlan

2015-10-02

Diode-like volatile resistive switching as well as nonvolatile resistive switching behaviors in a Cu/ZrO₂/TiO₂/Ti stack are investigated. Depending on the current compliance during the electroforming process, either volatile resistive switching or nonvolatile resistive switching is observed. With a lower current compliance (<10 μA), the Cu/ZrO₂/TiO₂/Ti device exhibits diode-like volatile resistive switching with a rectifying ratio over 10(6). The permanent transition from volatile to nonvolatile resistive switching can be obtained by applying a higher current compliance of 100 μA. Furthermore, by using different reset voltages, the Cu/ZrO₂/TiO₂/Ti device exhibits multilevel memory characteristics with high uniformity. The coexistence of nonvolatile multilevel memory and diode-like volatile resistive switching behaviors in the same Cu/ZrO₂/TiO₂/Ti device opens areas of applications in high-density storage, logic circuits, neural networks, and passive crossbar memory selectors.

Organic non-volatile resistive photo-switches for flexible image detector arrays.

PubMed

Nau, Sebastian; Wolf, Christoph; Sax, Stefan; List-Kratochvil, Emil J W

2015-02-01

A unique implementation of an organic image detector using resistive photo-switchable pixels is presented. This resistive photo-switch comprises the vertical integration of an organic photodiode and an organic resistive switching memory element. The photodiodes act as a photosensitive element while the resistive switching elements simultaneously store the detected light information. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

PubMed Central

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-01-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS. PMID:26365532

Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film

NASA Astrophysics Data System (ADS)

Kyu Yang, Min; Ju, Hyunsu; Hwan Kim, Gun; Lee, Jeon-Kook; Ryu, Han-Cheol

2015-09-01

A Ta/TaOx/Pt stacked capacitor-like device for resistive switching was fabricated and examined. The tested device demonstrated stable resistive switching characteristics including uniform distribution of resistive switching operational parameters, highly promising endurance, and retention properties. To reveal the resistive switching mechanism of the device, micro structure analysis using high-resolution transmission electron microscope (HR-TEM) was performed. From the observation results, two different phases of Ta-metal clusters of cubic α-Ta and tetragonal β-Ta were founded in the amorphous TaOx mother-matrix after the device was switched from high resistance state (HRS) to low resistance state (LRS) by externally applied voltage bias. The observed Ta metal clusters unveiled the origin of the electric conduction paths in the TaOx thin film at the LRS.

Non-destructive reversible resistive switching in Cr doped Mott insulator Ca2RuO4: Interface vs bulk effects

NASA Astrophysics Data System (ADS)

Shen, Shida; Williamson, Morgan; Cao, Gang; Zhou, Jianshi; Goodenough, John; Tsoi, Maxim

2017-12-01

A non-destructive reversible resistive switching is demonstrated in single crystals of Cr-doped Mott insulator Ca2RuO4. An applied electrical bias was shown to reduce the DC resistance of the crystal by as much as 75%. The original resistance of the sample could be restored by applying an electrical bias of opposite polarity. We have studied this resistive switching as a function of the bias strength, applied magnetic field, and temperature. A combination of 2-, 3-, and 4-probe measurements provide a means to distinguish between bulk and interfacial contributions to the switching and suggests that the switching is mostly an interfacial effect. The switching was tentatively attributed to electric-field driven lattice distortions which accompany the impurity-induced Mott transition. This field effect was confirmed by temperature-dependent resistivity measurements which show that the activation energy of this material can be tuned by an applied DC electrical bias. The observed resistance switching can potentially be used for building non-volatile memory devices like resistive random access memory.

Bayesian model of signal rewiring reveals mechanisms of gene dysregulation in acquired drug resistance in breast cancer

PubMed Central

Azad, A. K. M.; Keith, Jonathan M.

2017-01-01

Small molecule inhibitors, such as lapatinib, are effective against breast cancer in clinical trials, but tumor cells ultimately acquire resistance to the drug. Maintaining sensitization to drug action is essential for durable growth inhibition. Recently, adaptive reprogramming of signaling circuitry has been identified as a major cause of acquired resistance. We developed a computational framework using a Bayesian statistical approach to model signal rewiring in acquired resistance. We used the p1-model to infer potential aberrant gene-pairs with differential posterior probabilities of appearing in resistant-vs-parental networks. Results were obtained using matched gene expression profiles under resistant and parental conditions. Using two lapatinib-treated ErbB2-positive breast cancer cell-lines: SKBR3 and BT474, our method identified similar dysregulated signaling pathways including EGFR-related pathways as well as other receptor-related pathways, many of which were reported previously as compensatory pathways of EGFR-inhibition via signaling cross-talk. A manual literature survey provided strong evidence that aberrant signaling activities in dysregulated pathways are closely related to acquired resistance in EGFR tyrosine kinase inhibitors. Our approach predicted literature-supported dysregulated pathways complementary to both node-centric (SPIA, DAVID, and GATHER) and edge-centric (ESEA and PAGI) methods. Moreover, by proposing a novel pattern of aberrant signaling called V-structures, we observed that genes were dysregulated in resistant-vs-sensitive conditions when they were involved in the switch of dependencies from targeted to bypass signaling events. A literature survey of some important V-structures suggested they play a role in breast cancer metastasis and/or acquired resistance to EGFR-TKIs, where the mRNA changes of TGFBR2, LEF1 and TP53 in resistant-vs-sensitive conditions were related to the dependency switch from targeted to bypass signaling links. Our results suggest many signaling pathway structures are compromised in acquired resistance, and V-structures of aberrant signaling within/among those pathways may provide further insights into the bypass mechanism of targeted inhibition. PMID:28288164

White-light-controlled resistive switching in ZnO/BaTiO3/C multilayer layer at room temperature

NASA Astrophysics Data System (ADS)

Wang, Junshuai; Liang, Dandan; Wu, Liangchen; Li, Xiaoping; Chen, Peng

2018-07-01

The bipolar resistance switching effect is observed in ZnO/BaTiO3/C structure. The resistance switching behavior can be modulated by white light. The resistance switch states and threshold voltage can be changed when subjected to white light. This research can help explore multi-functional materials and applications in nonvolatile memory device.

Automatic thermal control switches. [for use in Space Shuttle borne Get Away Special container

NASA Technical Reports Server (NTRS)

Wing, L. D.

1982-01-01

Two automatic, flexible connection thermal control switches have been designed and tested in a thermal vacuum facility and in the Get Away Special (GAS) container flown on the third Shuttle flight. The switches are complementary in that one switch passes heat when the plate on which it is mounted exceeds some selected temperature and the other switch will pass heat only when the mounting plate temperature is below the selected value. Both switches are driven and controlled by phase-change capsule motors and require no other power source or thermal sensors.

Self-Compliant Bipolar Resistive Switching in SiN-Based Resistive Switching Memory

PubMed Central

Kim, Sungjun; Chang, Yao-Feng; Kim, Min-Hwi; Kim, Tae-Hyeon; Kim, Yoon; Park, Byung-Gook

2017-01-01

Here, we present evidence of self-compliant and self-rectifying bipolar resistive switching behavior in Ni/SiNx/n+ Si and Ni/SiNx/n++ Si resistive-switching random access memory devices. The Ni/SiNx/n++ Si device’s Si bottom electrode had a higher dopant concentration (As ion > 1019 cm−3) than the Ni/SiNx/n+ Si device; both unipolar and bipolar resistive switching behaviors were observed for the higher dopant concentration device owing to a large current overshoot. Conversely, for the device with the lower dopant concentration (As ion < 1018 cm−3), self-rectification and self-compliance were achieved owing to the series resistance of the Si bottom electrode. PMID:28772819

Scaling Effect on Unipolar and Bipolar Resistive Switching of Metal Oxides

PubMed Central

Yanagida, Takeshi; Nagashima, Kazuki; Oka, Keisuke; Kanai, Masaki; Klamchuen, Annop; Park, Bae Ho; Kawai, Tomoji

2013-01-01

Electrically driven resistance change in metal oxides opens up an interdisciplinary research field for next-generation non-volatile memory. Resistive switching exhibits an electrical polarity dependent “bipolar-switching” and a polarity independent “unipolar-switching”, however tailoring the electrical polarity has been a challenging issue. Here we demonstrate a scaling effect on the emergence of the electrical polarity by examining the resistive switching behaviors of Pt/oxide/Pt junctions over 8 orders of magnitudes in the areas. We show that the emergence of two electrical polarities can be categorised as a diagram of an electric field and a cell area. This trend is qualitatively common for various oxides including NiOx, CoOx, and TiO2-x. We reveal the intrinsic difference between unipolar switching and bipolar switching on the area dependence, which causes a diversity of an electrical polarity for various resistive switching devices with different geometries. This will provide a foundation for tailoring resistive switching behaviors of metal oxides. PMID:23584551

Effect of oxide insertion layer on resistance switching properties of copper phthalocyanine

NASA Astrophysics Data System (ADS)

Joshi, Nikhil G.; Pandya, Nirav C.; Joshi, U. S.

2013-02-01

Organic memory device showing resistance switching properties is a next-generation of the electrical memory unit. We have investigated the bistable resistance switching in current-voltage (I-V) characteristics of organic diode based on copper phthalocyanine (CuPc) film sandwiched between aluminum (Al) electrodes. Pronounced hysteresis in the I-V curves revealed a resistance switching with on-off ratio of the order of 85%. In order to control the charge injection in the CuPc, nanoscale indium oxide buffer layer was inserted to form Al/CuPc/In2O3/Al device. Analysis of I-V measurements revealed space charge limited switching conduction at the Al/CuPc interface. The traps in the organic layer and charge blocking by oxide insertion layer have been used to explain the absence of resistance switching in the oxide buffer layered memory device cell. Present study offer potential applications for CuPc organic semiconductor in low power non volatile resistive switching memory and logic circuits.

Picoampere Resistive Switching Characteristics Realized with Vertically Contacted Carbon Nanotube Atomic Force Microscope Probe

NASA Astrophysics Data System (ADS)

Nakano, Haruhisa; Takahashi, Makoto; Sato, Motonobu; Kotsugi, Masato; Ohkochi, Takuo; Muro, Takayuki; Nihei, Mizuhisa; Yokoyama, Naoki

2013-11-01

The resistive switching characteristics of a TiO2/Ti structure have been investigated using a conductive atomic force microscopy (AFM) system with 5-nm-diameter carbon nanotube (CNT) probes. The resistive switching showed bipolar resistive random access memory (ReRAM) behaviors with extremely low switching currents in the order of Picoamperes when voltages were applied. From transmission electron microscopy (TEM) observation, we confirmed that filament-like nanocrystals, having a diameter of about 10 nm, existed in TiO2 films at resistive switching areas after not only set operation but also reset operation. Moreover, photoemission electron microscopy (PEEM) analysis showed that the anatase-type TiO2 structure did not change after set and reset operations. From these results, we suggested that the Picoampere resistive switching occurred at the interface between the TiO2 dielectric and conductive nanocrystal without any structural changes in the TiO2 film and nanocrystal. The resistive switching mechanism we suggested is highly promising to realize extremely low-power-consumption ReRAMs with vertically contacted CNT electrodes.

Multistate storage nonvolatile memory device based on ferroelectricity and resistive switching effects of SrBi2Ta2O9 films

NASA Astrophysics Data System (ADS)

Song, Zhiwei; Li, Gang; Xiong, Ying; Cheng, Chuanpin; Zhang, Wanli; Tang, Minghua; Li, Zheng; He, Jiangheng

2018-05-01

A memory device with a Pt/SrBi2Ta2O9(SBT)/Pt(111) structure was shown to have excellent combined ferroelectricity and resistive switching properties, leading to higher multistate storage memory capacity in contrast to ferroelectric memory devices. In this device, SBT polycrystalline thin films with significant (115) orientation were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates using CVD (chemical vapor deposition) method. Measurement results of the electric properties exhibit reproducible and reliable ferroelectricity switching behavior and bipolar resistive switching effects (BRS) without an electroforming process. The ON/OFF ratio of the resistive switching was found to be about 103. Switching mechanisms for the low resistance state (LRS) and high resistance state (HRS) currents are likely attributed to the Ohmic and space charge-limited current (SCLC) behavior, respectively. Moreover, the ferroelectricity and resistive switching effects were found to be mutually independent, and the four logic states were obtained by controlling the periodic sweeping voltage. This work holds great promise for nonvolatile multistate memory devices with high capacity and low cost.

Enhancement of resistive switching properties in Al2O3 bilayer-based atomic switches: multilevel resistive switching

NASA Astrophysics Data System (ADS)

Vishwanath, Sujaya Kumar; Woo, Hyunsuk; Jeon, Sanghun

2018-06-01

Atomic switches are considered to be building blocks for future non-volatile data storage and internet of things. However, obtaining device structures capable of ultrahigh density data storage, high endurance, and long data retention, and more importantly, understanding the switching mechanisms are still a challenge for atomic switches. Here, we achieved improved resistive switching performance in a bilayer structure containing aluminum oxide, with an oxygen-deficient oxide as the top switching layer and stoichiometric oxide as the bottom switching layer, using atomic layer deposition. This bilayer device showed a high on/off ratio (105) with better endurance (∼2000 cycles) and longer data retention (104 s) than single-oxide layers. In addition, depending on the compliance current, the bilayer device could be operated in four different resistance states. Furthermore, the depth profiles of the hourglass-shaped conductive filament of the bilayer device was observed by conductive atomic force microscopy.

Improved resistive switching characteristics of a Pt/HfO2/Pt resistor by controlling anode interface with forming and switching polarity

NASA Astrophysics Data System (ADS)

Jung, Yong Chan; Seong, Sejong; Lee, Taehoon; Kim, Seon Yong; Park, In-Sung; Ahn, Jinho

2018-03-01

The anode interface effects on the resistive switching characteristics of Pt/HfO2/Pt resistors are investigated by changing the forming and switching polarity. Resistive switching properties are evaluated and compared with the polarity operation procedures, such as the reset voltage (Vr), set voltage (Vs), and current levels at low and high resistance states. When the same forming and switching voltage polarity are applied to the resistor, their switching parameters are widely distributed. However, the opposite forming and switching voltage polarity procedures enhance the uniformity of the switching parameters. In particular, the Vs distribution is strongly affected by the voltage polarity variation. A model is proposed based on cone-shaped filament formation through the insulator and the cone diameter at the anode interface to explain the improved resistive switching characteristics under opposite polarity operation. The filament cone is thinner near the anode interface during the forming process; hence, the anode is altered by the application of a switching voltage with opposite polarity to the forming voltage polarity and the converted anode interface becomes the thicker part of the cone. The more uniform and stable switching behavior is attributed to control over the formation and rupture of the cone-shaped filaments at their thicker parts.

Non-volatile, solid state bistable electrical switch

NASA Technical Reports Server (NTRS)

Williams, Roger M. (Inventor)

1994-01-01

A bistable switching element is made of a material whose electrical resistance reversibly decreases in response to intercalation by positive ions. Flow of positive ions between the bistable switching element and a positive ion source is controlled by means of an electrical potential applied across a thermal switching element. The material of the thermal switching element generates heat in response to electrical current flow therethrough, which in turn causes the material to undergo a thermal phase transition from a high electrical resistance state to a low electrical resistance state as the temperature increases above a predetermined value. Application of the electrical potential in one direction renders the thermal switching element conductive to pass electron current out of the ion source. This causes positive ions to flow from the source into the bistable switching element and intercalate the same to produce a non-volatile, low resistance logic state. Application of the electrical potential in the opposite direction causes reverse current flow which de-intercalates the bistable logic switching element and produces a high resistance logic state.

Ultra-low power, highly uniform polymer memory by inserted multilayer graphene electrode

NASA Astrophysics Data System (ADS)

Jang, Byung Chul; Seong, Hyejeong; Kim, Jong Yun; Koo, Beom Jun; Kim, Sung Kyu; Yang, Sang Yoon; Gap Im, Sung; Choi, Sung-Yool

2015-12-01

Filament type resistive random access memory (RRAM) based on polymer thin films is a promising device for next generation, flexible nonvolatile memory. However, the resistive switching nonuniformity and the high power consumption found in the general filament type RRAM devices present critical issues for practical memory applications. Here, we introduce a novel approach not only to reduce the power consumption but also to improve the resistive switching uniformity in RRAM devices based on poly(1,3,5-trimethyl-3,4,5-trivinyl cyclotrisiloxane) by inserting multilayer graphene (MLG) at the electrode/polymer interface. The resistive switching uniformity was thereby significantly improved, and the power consumption was markedly reduced by 250 times. Furthermore, the inserted MLG film enabled a transition of the resistive switching operation from unipolar resistive switching to bipolar resistive switching and induced self-compliance behavior. The findings of this study can pave the way toward a new area of application for graphene in electronic devices.

Thickness-dependent resistance switching in Cr-doped SrTiO3

NASA Astrophysics Data System (ADS)

Kim, TaeKwang; Du, Hyewon; Kim, Minchang; Seo, Sunae; Hwang, Inrok; Kim, Yeonsoo; Jeon, Jihoon; Lee, Sangik; Park, Baeho

2012-09-01

The thickness-dependent bipolar resistance-switching behavior was investigated for epitaxiallygrown Cr-doped SrTiO3 (Cr-STO). All the pristine devices of different thickness showed polarity-independent symmetric current-voltage characteristic and the same space-charge-limited conduction mechanism. However, after a forming process, the resultant conduction and switching phenomena were significantly different depending on the thickness of Cr-STO. The forming process itself was highly influenced by resistance value of each pristine device. Based on our results, we suggest that the resistance-switching mechanism in Cr-STO depends not only on the insulating material's composition or the contact metal as previously reported but also on the initial resistance level determined by the geometry and the quality of the insulating material. The bipolar resistance-switching behaviors in oxide materials of different thicknesses exhibit mixed bulk and interface switching. This indicates that efforts in resistance-based memory research should be focused on scalability or process method to control a given oxide material in addition to material type and device structure.

Interplay between ferroelectric and resistive switching in doped crystalline HfO2

NASA Astrophysics Data System (ADS)

Max, Benjamin; Pešić, Milan; Slesazeck, Stefan; Mikolajick, Thomas

2018-04-01

Hafnium oxide is widely used for resistive switching devices, and recently it has been discovered that ferroelectricity can be established in (un-)doped hafnium oxide as well. Previous studies showed that both switching mechanisms are influenced by oxygen vacancies. For resistive switching, typically amorphous oxide layers with an asymmetric electrode configuration are used to create a gradient of oxygen vacancies. On the other hand, ferroelectric switching is performed by having symmetric electrodes and requires crystalline structures. The coexistence of both effects has recently been demonstrated. In this work, a detailed analysis of the reversible interplay of both switching mechanisms within a single capacitor cell is investigated. First, ferroelectric switching cycles were applied in order to drive the sample into the fatigued stage characterized by increased concentration of oxygen vacancies in the oxide layer. Afterwards, a forming step that is typical for the resistive switching devices was utilized to achieve a soft breakdown. In the next step, twofold alternation between the high and low resistance state is applied to demonstrate the resistive switching behavior of the device. Having the sample in the high resistance state with a ruptured filament, ferroelectric switching behavior is again shown within the same stack. Interestingly, the same endurance as before was observed without a hard breakdown of the device. Therefore, an effective sequence of ferroelectric—resistive—ferroelectric switching is realized. Additionally, the dependence of the forming, set, and reset voltage on the ferroelectric cycling stage (pristine, woken-up and fatigued) is analyzed giving insight into the physical device operation.

Conductance Quantization in Resistive Random Access Memory

NASA Astrophysics Data System (ADS)

Li, Yang; Long, Shibing; Liu, Yang; Hu, Chen; Teng, Jiao; Liu, Qi; Lv, Hangbing; Suñé, Jordi; Liu, Ming

2015-10-01

The intrinsic scaling-down ability, simple metal-insulator-metal (MIM) sandwich structure, excellent performances, and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication processes make resistive random access memory (RRAM) one of the most promising candidates for the next-generation memory. The RRAM device also exhibits rich electrical, thermal, magnetic, and optical effects, in close correlation with the abundant resistive switching (RS) materials, metal-oxide interface, and multiple RS mechanisms including the formation/rupture of nanoscale to atomic-sized conductive filament (CF) incorporated in RS layer. Conductance quantization effect has been observed in the atomic-sized CF in RRAM, which provides a good opportunity to deeply investigate the RS mechanism in mesoscopic dimension. In this review paper, the operating principles of RRAM are introduced first, followed by the summarization of the basic conductance quantization phenomenon in RRAM and the related RS mechanisms, device structures, and material system. Then, we discuss the theory and modeling of quantum transport in RRAM. Finally, we present the opportunities and challenges in quantized RRAM devices and our views on the future prospects.

Conductance Quantization in Resistive Random Access Memory.

PubMed

Li, Yang; Long, Shibing; Liu, Yang; Hu, Chen; Teng, Jiao; Liu, Qi; Lv, Hangbing; Suñé, Jordi; Liu, Ming

2015-12-01

The intrinsic scaling-down ability, simple metal-insulator-metal (MIM) sandwich structure, excellent performances, and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication processes make resistive random access memory (RRAM) one of the most promising candidates for the next-generation memory. The RRAM device also exhibits rich electrical, thermal, magnetic, and optical effects, in close correlation with the abundant resistive switching (RS) materials, metal-oxide interface, and multiple RS mechanisms including the formation/rupture of nanoscale to atomic-sized conductive filament (CF) incorporated in RS layer. Conductance quantization effect has been observed in the atomic-sized CF in RRAM, which provides a good opportunity to deeply investigate the RS mechanism in mesoscopic dimension. In this review paper, the operating principles of RRAM are introduced first, followed by the summarization of the basic conductance quantization phenomenon in RRAM and the related RS mechanisms, device structures, and material system. Then, we discuss the theory and modeling of quantum transport in RRAM. Finally, we present the opportunities and challenges in quantized RRAM devices and our views on the future prospects.

Resistive switching of organic–inorganic hybrid devices of conductive polymer and permeable ultra-thin SiO2 films

NASA Astrophysics Data System (ADS)

Yamamoto, Shunsuke; Kitanaka, Takahisa; Miyashita, Tokuji; Mitsuishi, Masaya

2018-06-01

We propose a resistive switching device composed of conductive polymer (PEDOT:PSS) and SiO2 ultra-thin films. The SiO2 film was fabricated from silsesquioxane polymer nanosheets as a resistive switching layer. Devices with metal (Ag or Au)∣SiO2∣PEDOT:PSS architecture show good resistive switching performance with set–reset voltages as low as several hundred millivolts. The device properties and the working mechanism were investigated by varying the electrode material, surrounding atmosphere, and SiO2 film thickness. Results show that resistive switching is based on water and ion migration at the PEDOT:PSS∣SiO2 interface.

Resistive switching of organic-inorganic hybrid devices of conductive polymer and permeable ultra-thin SiO2 films.

PubMed

Yamamoto, Shunsuke; Kitanaka, Takahisa; Miyashita, Tokuji; Mitsuishi, Masaya

2018-06-29

We propose a resistive switching device composed of conductive polymer (PEDOT:PSS) and SiO 2 ultra-thin films. The SiO 2 film was fabricated from silsesquioxane polymer nanosheets as a resistive switching layer. Devices with metal (Ag or Au)∣SiO 2 ∣PEDOT:PSS architecture show good resistive switching performance with set-reset voltages as low as several hundred millivolts. The device properties and the working mechanism were investigated by varying the electrode material, surrounding atmosphere, and SiO 2 film thickness. Results show that resistive switching is based on water and ion migration at the PEDOT:PSS∣SiO 2 interface.

Non-volatile resistive switching in the Mott insulator (V1-xCrx)2O3

NASA Astrophysics Data System (ADS)

Querré, M.; Tranchant, J.; Corraze, B.; Cordier, S.; Bouquet, V.; Députier, S.; Guilloux-Viry, M.; Besland, M.-P.; Janod, E.; Cario, L.

2018-05-01

The discovery of non-volatile resistive switching in Mott insulators related to an electric-field-induced insulator to metal transition (IMT) has paved the way for their use in a new type of non-volatile memories, the Mott memories. While most of the previous studies were dedicated to uncover the resistive switching mechanism and explore the memory potential of chalcogenide Mott insulators, we present here a comprehensive study of resistive switching in the canonical oxide Mott insulator (V1-xCrx)2O3. Our work demonstrates that this compound undergoes a non-volatile resistive switching under electric field. This resistive switching is induced by a Mott transition at the local scale which creates metallic domains closely related to existing phases of the temperature-pressure phase diagram of (V1-xCrx)2O3. Our work demonstrates also reversible resistive switching in (V1-xCrx)2O3 crystals and thin film devices. Preliminary performances obtained on 880 nm thick layers with 500 nm electrodes show the strong potential of Mott memories based on the Mott insulator (V1-xCrx)2O3.

Beverton-Holt discrete pest management models with pulsed chemical control and evolution of pesticide resistance

NASA Astrophysics Data System (ADS)

Liang, Juhua; Tang, Sanyi; Cheke, Robert A.

2016-07-01

Pest resistance to pesticides is usually managed by switching between different types of pesticides. The optimal switching time, which depends on the dynamics of the pest population and on the evolution of the pesticide resistance, is critical. Here we address how the dynamic complexity of the pest population, the development of resistance and the spraying frequency of pulsed chemical control affect optimal switching strategies given different control aims. To do this, we developed novel discrete pest population growth models with both impulsive chemical control and the evolution of pesticide resistance. Strong and weak threshold conditions which guarantee the extinction of the pest population, based on the threshold values of the analytical formula for the optimal switching time, were derived. Further, we addressed switching strategies in the light of chosen economic injury levels. Moreover, the effects of the complex dynamical behaviour of the pest population on the pesticide switching times were also studied. The pesticide application period, the evolution of pesticide resistance and the dynamic complexity of the pest population may result in complex outbreak patterns, with consequent effects on the pesticide switching strategies.

Enhancement of resistive switching properties in Al2O3 bilayer-based atomic switches: multilevel resistive switching.

PubMed

Vishwanath, Sujaya Kumar; Woo, Hyunsuk; Jeon, Sanghun

2018-06-08

Atomic switches are considered to be building blocks for future non-volatile data storage and internet of things. However, obtaining device structures capable of ultrahigh density data storage, high endurance, and long data retention, and more importantly, understanding the switching mechanisms are still a challenge for atomic switches. Here, we achieved improved resistive switching performance in a bilayer structure containing aluminum oxide, with an oxygen-deficient oxide as the top switching layer and stoichiometric oxide as the bottom switching layer, using atomic layer deposition. This bilayer device showed a high on/off ratio (10 5 ) with better endurance (∼2000 cycles) and longer data retention (10 4 s) than single-oxide layers. In addition, depending on the compliance current, the bilayer device could be operated in four different resistance states. Furthermore, the depth profiles of the hourglass-shaped conductive filament of the bilayer device was observed by conductive atomic force microscopy.

Bipolar resistive switching in Si/Ag nanostructures

NASA Astrophysics Data System (ADS)

Dias, C.; Lv, H.; Picos, R.; Aguiar, P.; Cardoso, S.; Freitas, P. P.; Ventura, J.

2017-12-01

Resistive switching devices are being intensively studied aiming a large number of promising applications such as nonvolatile memories, artificial neural networks and sensors. Here, we show nanoscale bipolar resistive switching in Pt/Si/Ag/TiW structures, with a dielectric barrier thickness of 20 nm. The observed phenomenon is based on the formation/rupture of metallic Ag filaments in the otherwise insulating Si host material. No electroforming process was required to achieve resistive switching. We obtained average values of 0.23 V and -0.24 V for the Set and Reset voltages, respectively. The stability of the switching was observed for over 100 cycles, together with a clear separation of the ON (103 Ω) and OFF (102 Ω) states. Furthermore, the influence of the Set current compliance on the ON resistance, resistances ratio and Set/Reset voltages percentage variation was also studied.

A ZnO nanowire resistive switch

NASA Astrophysics Data System (ADS)

Karthik, K. R. G.; Ramanujam Prabhakar, Rajiv; Hai, L.; Batabyal, Sudip K.; Huang, Y. Z.; Mhaisalkar, S. G.

2013-09-01

An individual ZnO nanowire resistive switch is evaluated with Pt/ZnO nanowire/Pt topology. A detailed DC I-V curve analysis is performed to bring both the conduction mechanism and the device characteristics to light. The device is further studied at various vacuum pressures to ascertain the presence of polar charges in ZnO nanowires as the phenomenon leading to the formation of the switch. The disappearance of the resistive switching is also analyzed with two kinds of fabrication approaches Focused Ion/Electron Beam involved in the making the device and a summary of both length and fabrication dependences of resistive switching in the ZnO nanowire is presented.

Selenium bond decreases ON resistance of light-activated switch

NASA Technical Reports Server (NTRS)

1965-01-01

Vitrified amorphous selenium bond decreases the ON resistance of a gallium arsenide-silicon light-activated, low-level switch. The switch is used under a pulse condition to prolong switch life and minimize errors due to heating, devitrification, and overdrawing.

First principles investigation of the unipolar resistive switching mechanism in an interfacial phase change memory based on a GeTe/Sb2Te3 superlattice

NASA Astrophysics Data System (ADS)

Shirakawa, Hiroki; Araidai, Masaaki; Shiraishi, Kenji

2018-04-01

The interfacial phase change memory (iPCM) based on a GeTe/Sb2Te3 superlattice is one of the candidates for future storage class memories. However, the atomic structures of the high and low resistance states (HRS/LRS) remain unclear and the resistive switching mechanism is still under debate. Clarifying the switching mechanism is essential for developing further high-reliability and low-power-consumption iPCM. We propose, on the basis of the results of first-principles molecular dynamics simulations, a mechanism for resistive switching, and describe the atomic structures of the high and low resistance states of iPCM for unipolar switching. Our simulations indicated that switching from HRS to LRS occurs with Joule heating only, while that from LRS to HRS occurs with both hole injection and Joule heating.

Electroforming free controlled bipolar resistive switching in Al/CoFe2O4/FTO device with self-compliance effect

NASA Astrophysics Data System (ADS)

Munjal, Sandeep; Khare, Neeraj

2018-02-01

Controlled bipolar resistive switching (BRS) has been observed in nanostructured CoFe2O4 (CFO) films using an Al (aluminum)/CoFe2O4/FTO (fluorine-doped tin oxide) device. The fabricated device shows electroforming-free uniform BRS with two clearly distinguished and stable resistance states without any application of compliance current, with a resistance ratio of the high resistance state (HRS) and the low resistance state (LRS) of >102. Small switching voltage (<1 volt) and lower current in both the resistance states confirm the fabrication of a low power consumption device. In the LRS, the conduction mechanism was found to be Ohmic in nature, while the high-resistance state (HRS/OFF state) was governed by the space charge-limited conduction mechanism, which indicates the presence of an interfacial layer with an imperfect microstructure near the top Al/CFO interface. The device shows nonvolatile behavior with good endurance properties, an acceptable resistance ratio, uniform resistive switching due to stable, less random filament formation/rupture, and a control over the resistive switching properties by choosing different stop voltages, which makes the device suitable for its application in future nonvolatile resistive random access memory.

Nanoscale RRAM-based synaptic electronics: toward a neuromorphic computing device.

PubMed

Park, Sangsu; Noh, Jinwoo; Choo, Myung-Lae; Sheri, Ahmad Muqeem; Chang, Man; Kim, Young-Bae; Kim, Chang Jung; Jeon, Moongu; Lee, Byung-Geun; Lee, Byoung Hun; Hwang, Hyunsang

2013-09-27

Efforts to develop scalable learning algorithms for implementation of networks of spiking neurons in silicon have been hindered by the considerable footprints of learning circuits, which grow as the number of synapses increases. Recent developments in nanotechnologies provide an extremely compact device with low-power consumption.In particular, nanoscale resistive switching devices (resistive random-access memory (RRAM)) are regarded as a promising solution for implementation of biological synapses due to their nanoscale dimensions, capacity to store multiple bits and the low energy required to operate distinct states. In this paper, we report the fabrication, modeling and implementation of nanoscale RRAM with multi-level storage capability for an electronic synapse device. In addition, we first experimentally demonstrate the learning capabilities and predictable performance by a neuromorphic circuit composed of a nanoscale 1 kbit RRAM cross-point array of synapses and complementary metal-oxide-semiconductor neuron circuits. These developments open up possibilities for the development of ubiquitous ultra-dense, ultra-low-power cognitive computers.

Passive electrically switchable circuit element having improved tunability and method for its manufacture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickel, Patrick R; James, Conrad D

2014-09-16

A resistive switching device and methods for making the same are disclosed. In the above said device, a resistive switching layer is interposed between opposing electrodes. The resistive switching layer comprises at least two sub-layers of switchable insulative material characterized by different ionic mobilities.

Low power consumption resistance random access memory with Pt/InOx/TiN structure

NASA Astrophysics Data System (ADS)

Yang, Jyun-Bao; Chang, Ting-Chang; Huang, Jheng-Jie; Chen, Yu-Ting; Tseng, Hsueh-Chih; Chu, Ann-Kuo; Sze, Simon M.; Tsai, Ming-Jinn

2013-09-01

In this study, the resistance switching characteristics of a resistive random access memory device with Pt/InOx/TiN structure is investigated. Unstable bipolar switching behavior is observed during the initial switching cycle, which then stabilizes after several switching cycles. Analyses indicate that the current conduction mechanism in the resistance state is dominated by Ohmic conduction. The decrease in electrical conductance can be attributed to the reduction of the cross-sectional area of the conduction path. Furthermore, the device exhibits low operation voltage and power consumption.

Multimode resistive switching in nanoscale hafnium oxide stack as studied by atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Y., E-mail: houyi@pku.edu.cn, E-mail: lfliu@pku.edu.cn; IMEC, Kapeldreef 75, B-3001 Heverlee; Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Heverlee

2016-07-11

The nanoscale resistive switching in hafnium oxide stack is investigated by the conductive atomic force microscopy (C-AFM). The initial oxide stack is insulating and electrical stress from the C-AFM tip induces nanometric conductive filaments. Multimode resistive switching can be observed in consecutive operation cycles at one spot. The different modes are interpreted in the framework of a low defect quantum point contact theory. The model implies that the optimization of the conductive filament active region is crucial for the future application of nanoscale resistive switching devices.

Highly uniform and reliable resistive switching characteristics of a Ni/WOx/p+-Si memory device

NASA Astrophysics Data System (ADS)

Kim, Tae-Hyeon; Kim, Sungjun; Kim, Hyungjin; Kim, Min-Hwi; Bang, Suhyun; Cho, Seongjae; Park, Byung-Gook

2018-02-01

In this paper, we investigate the resistive switching behavior of a bipolar resistive random-access memory (RRAM) in a Ni/WOx/p+-Si RRAM with CMOS compatibility. Highly unifrom and reliable bipolar resistive switching characteristics are observed by a DC voltage sweeping and its switching mechanism can be explained by SCLC model. As a result, the possibility of metal-insulator-silicon (MIS) structural WOx-based RRAM's application to Si-based 1D (diode)-1R (RRAM) or 1T (transistor)-1R (RRAM) structure is demonstrated.

High speed chalcogenide glass electrochemical metallization cells with various active metals.

PubMed

Hughes, Mark A; Burgess, Alexander; Hinder, Steven; Gholizadeh, A Baset; Craig, Christopher; Hewak, Daniel W

2018-08-03

We fabricated electrochemical metallization cells using a GaLaSO solid electrolyte, an InSnO inactive electrode and active electrodes consisting of various metals (Cu, Ag, Fe, Cu, Mo, Al). Devices with Ag and Cu active metals showed consistent and repeatable resistive switching behaviour, and had a retention of 3 and >43 days, respectively; both had switching speeds of <5 ns. Devices with Cr and Fe active metals displayed incomplete or intermittent resistive switching, and devices with Mo and Al active electrodes displayed no resistive switching ability. Deeper penetration of the active metal into the GaLaSO layer resulted in greater resistive switching ability of the cell. The off-state resistivity was greater for more reactive active metals which may be due to a thicker intermediate layer.

Evaluation of resistive switching properties of Si-rich oxide embedded with Ti nanodots by applying constant voltage and current

NASA Astrophysics Data System (ADS)

Ohta, Akio; Kato, Yusuke; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-06-01

We have studied the resistive switching behaviors of electron beam (EB) evaporated Si-rich oxide (SiO x ) sandwiched between Ni electrodes by applying a constant voltage and current. Additionally, the impact of Ti nanodots (NDs) embedded into SiO x on resistive switching behaviors was investigated because it is expected that NDs can trigger the formation of a conductive filament path in SiO x . The resistive switching behaviors of SiO x show that the response time during resistance switching was decreased by increasing the applied constant current or constant voltage. It was found that Ti-NDs in SiO x enhance the conductive filament path formation owing to electric field concentration by Ti-NDs.

Three-terminal resistive switching memory in a transparent vertical-configuration device

NASA Astrophysics Data System (ADS)

Ungureanu, Mariana; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E.

2014-01-01

The resistive switching phenomenon has attracted much attention recently for memory applications. It describes the reversible change in the resistance of a dielectric between two non-volatile states by the application of electrical pulses. Typical resistive switching memories are two-terminal devices formed by an oxide layer placed between two metal electrodes. Here, we report on the fabrication and operation of a three-terminal resistive switching memory that works as a reconfigurable logic component and offers an increased logic density on chip. The three-terminal memory device we present is transparent and could be further incorporated in transparent computing electronic technologies.

Effect of Electronegativity on Bipolar Resistive Switching in a WO3-Based Asymmetric Capacitor Structure.

PubMed

Kim, Jongmin; Inamdar, Akbar I; Jo, Yongcheol; Woo, Hyeonseok; Cho, Sangeun; Pawar, Sambhaji M; Kim, Hyungsang; Im, Hyunsik

2016-04-13

This study investigates the transport and switching time of nonvolatile tungsten oxide based resistive-switching (RS) memory devices. These devices consist of a highly resistive tungsten oxide film sandwiched between metal electrodes, and their RS characteristics are bipolar in the counterclockwise direction. The switching voltage, retention, endurance, and switching time are strongly dependent on the type of electrodes used, and we also find quantitative and qualitative evidence that the electronegativity (χ) of the electrodes plays a key role in determining the RS properties and switching time. We also propose an RS model based on the role of the electronegativity at the interface.

Nanocrystalline Si pathway induced unipolar resistive switching behavior from annealed Si-rich SiNx/SiNy multilayers

NASA Astrophysics Data System (ADS)

Jiang, Xiaofan; Ma, Zhongyuan; Yang, Huafeng; Yu, Jie; Wang, Wen; Zhang, Wenping; Li, Wei; Xu, Jun; Xu, Ling; Chen, Kunji; Huang, Xinfan; Feng, Duan

2014-09-01

Adding a resistive switching functionality to a silicon microelectronic chip is a new challenge in materials research. Here, we demonstrate that unipolar and electrode-independent resistive switching effects can be realized in the annealed Si-rich SiNx/SiNy multilayers with high on/off ratio of 109. High resolution transmission electron microscopy reveals that for the high resistance state broken pathways composed of discrete nanocrystalline silicon (nc-Si) exist in the Si nitride multilayers. While for the low resistance state the discrete nc-Si regions is connected, forming continuous nc-Si pathways. Based on the analysis of the temperature dependent I-V characteristics and HRTEM photos, we found that the break-and-bridge evolution of nc-Si pathway is the origin of resistive switching memory behavior. Our findings provide insights into the mechanism of the resistive switching behavior in nc-Si films, opening a way for it to be utilized as a material in Si-based memories.

Regulation of the forming process and the set voltage distribution of unipolar resistance switching in spin-coated CoFe2O4 thin films.

PubMed

Mustaqima, Millaty; Yoo, Pilsun; Huang, Wei; Lee, Bo Wha; Liu, Chunli

2015-01-01

We report the preparation of (111) preferentially oriented CoFe2O4 thin films on Pt(111)/TiO2/SiO2/Si substrates using a spin-coating process. The post-annealing conditions and film thickness were varied for cobalt ferrite (CFO) thin films, and Pt/CFO/Pt structures were prepared to investigate the resistance switching behaviors. Our results showed that resistance switching without a forming process is preferred to obtain less fluctuation in the set voltage, which can be regulated directly from the preparation conditions of the CFO thin films. Therefore, instead of thicker film, CFO thin films deposited by two times spin-coating with a thickness about 100 nm gave stable resistance switching with the most stable set voltage. Since the forming process and the large variation in set voltage have been considered as serious obstacles for the practical application of resistance switching for non-volatile memory devices, our results could provide meaningful insights in improving the performance of ferrite material-based resistance switching memory devices.

Highly uniform resistive switching properties of amorphous InGaZnO thin films prepared by a low temperature photochemical solution deposition method.

PubMed

Hu, Wei; Zou, Lilan; Chen, Xinman; Qin, Ni; Li, Shuwei; Bao, Dinghua

2014-04-09

We report on highly uniform resistive switching properties of amorphous InGaZnO (a-IGZO) thin films. The thin films were fabricated by a low temperature photochemical solution deposition method, a simple process combining chemical solution deposition and ultraviolet (UV) irradiation treatment. The a-IGZO based resistive switching devices exhibit long retention, good endurance, uniform switching voltages, and stable distribution of low and high resistance states. Electrical conduction mechanisms were also discussed on the basis of the current-voltage characteristics and their temperature dependence. The excellent resistive switching properties can be attributed to the reduction of organic- and hydrogen-based elements and the formation of enhanced metal-oxide bonding and metal-hydroxide bonding networks by hydrogen bonding due to UV irradiation, based on Fourier-transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and Field emission scanning electron microscopy analysis of the thin films. This study suggests that a-IGZO thin films have potential applications in resistive random access memory and the low temperature photochemical solution deposition method can find the opportunity for further achieving system on panel applications if the a-IGZO resistive switching cells were integrated with a-IGZO thin film transistors.

Self-assembled nanostructured resistive switching memory devices fabricated by templated bottom-up growth

PubMed Central

Song, Ji-Min; Lee, Jang-Sik

2016-01-01

Metal-oxide-based resistive switching memory device has been studied intensively due to its potential to satisfy the requirements of next-generation memory devices. Active research has been done on the materials and device structures of resistive switching memory devices that meet the requirements of high density, fast switching speed, and reliable data storage. In this study, resistive switching memory devices were fabricated with nano-template-assisted bottom up growth. The electrochemical deposition was adopted to achieve the bottom-up growth of nickel nanodot electrodes. Nickel oxide layer was formed by oxygen plasma treatment of nickel nanodots at low temperature. The structures of fabricated nanoscale memory devices were analyzed with scanning electron microscope and atomic force microscope (AFM). The electrical characteristics of the devices were directly measured using conductive AFM. This work demonstrates the fabrication of resistive switching memory devices using self-assembled nanoscale masks and nanomateirals growth from bottom-up electrochemical deposition. PMID:26739122

From dead leaves to sustainable organic resistive switching memory.

PubMed

Sun, Bai; Zhu, Shouhui; Mao, Shuangsuo; Zheng, Pingping; Xia, Yudong; Yang, Feng; Lei, Ming; Zhao, Yong

2018-03-01

An environmental-friendly, sustainable, pollution-free, biodegradable, flexible and wearable electronic device hold advanced potential applications. Here, an organic resistive switching memory device with Ag/Leaves/Ti/PET structure on a flexible polyethylene terephthalate (PET) substrate was fabricated for the first time. We observed an obvious resistive switching memory characteristic with large switching resistance ratio and stable cycle performance at room temperature. This work demonstrates that leaves, a useless waste, can be properly treated to make useful devices. Furthermore, the as-fabricated devices can be degraded naturally without damage to the environment. Copyright © 2017 Elsevier Inc. All rights reserved.

Resistive switching properties and physical mechanism of cobalt ferrite thin films

NASA Astrophysics Data System (ADS)

Hu, Wei; Zou, Lilan; Chen, Ruqi; Xie, Wei; Chen, Xinman; Qin, Ni; Li, Shuwei; Yang, Guowei; Bao, Dinghua

2014-04-01

We report reproducible resistive switching performance and relevant physical mechanism of sandwiched Pt/CoFe2O4/Pt structures in which the CoFe2O4 thin films were fabricated by a chemical solution deposition method. Uniform switching voltages, good endurance, and long retention have been demonstrated in the Pt/CoFe2O4/Pt memory cells. On the basis of the analysis of current-voltage characteristic and its temperature dependence, we suggest that the carriers transport through the conducting filaments in low resistance state with Ohmic conduction behavior, and the Schottky emission and Poole-Frenkel emission dominate the conduction mechanism in high resistance state. From resistance-temperature dependence of resistance states, we believe that the physical origin of the resistive switching refers to the formation and rupture of the oxygen vacancies related filaments. The nanostructured CoFe2O4 thin films can find applications in resistive random access memory.

Highly integrated 3×3 silicon thermo-optical switch using a single combined phase shifter for optical interconnects.

PubMed

Wang, Wanjun; Zhou, Haifeng; Yang, Jianyi; Wang, Minghua; Jiang, Xiaoqing

2012-06-15

We report on an experimental 3×3 thermo-optical switch on silicon on insulator. By controlling a single combined phase shifter, light from any input waveguide can be directed to any output waveguide, showing a simple control method and highly integrated structure as compared to the conventional multiway optical switches. Furthermore, the proposed optical switch can be generalized to be a 1×N and N×N optical switch without an extra phase shifter. The switch is fabricated by complementary metal oxide semiconductor technology. By experiment, full 3×3 switching functionality is demonstrated at a wavelength of 1.55 μm, with an average cross talk of -11.1  dB and a power consumption of 97.5 mW.

Light-controlled resistive switching characteristics in ZnO/BiFeO3/ZnO thin film

NASA Astrophysics Data System (ADS)

Liang, Dandan; Li, Xiaoping; Wang, Junshuai; Wu, Liangchen; Chen, Peng

2018-07-01

ZnO/BiFeO3/ZnO multilayer was fabricated on silicon (Si) substrate by radio-frequency magnetron sputtering system. The resistive switching characteristics in ZnO/BiFeO3/ZnO devices are observed, and the resistive switching behavior can be modulated by white light.

Fabrication of Nano-Crossbar Resistive Switching Memory Based on the Copper-Tantalum Pentoxide-Platinum Device Structure

NASA Astrophysics Data System (ADS)

Olga Gneri, Paula; Jardim, Marcos

Resistive switching memory has been of interest lately not only for its simple metal-insulator-metal (MIM) structure but also for its promising ease of scalability an integration into current CMOS technologies like the Field Programmable Gate Arrays and other non-volatile memory applications. There are several resistive switching MIM combinations but under this scope of research, attention will be paid to the bipolar resistive switching characteristics and fabrication of Tantalum Pentaoxide sandwiched between platinum and copper. By changing the polarity of the voltage bias, this metal-insulator-metal (MIM) device can be switched between a high resistive state (OFF) and low resistive state (ON). The change in states is induced by an electrochemical metallization process, which causes a formation or dissolution of Cu metal filamentary paths in the Tantalum Pentaoxide insulator. There is very little thorough experimental information about the Cu-Ta 2O5-Pt switching characteristics when scaled to nanometer dimensions. In this light, the MIM structure was fabricated in a two-dimensional crossbar format. Also, with the limited available resources, a multi-spacer technique was formulated to localize the active device area in this MIM configuration to less than 20nm. This step is important in understanding the switching characteristics and reliability of this structure when scaled to nanometer dimensions.

A graphene integrated highly transparent resistive switching memory device

NASA Astrophysics Data System (ADS)

Dugu, Sita; Pavunny, Shojan P.; Limbu, Tej B.; Weiner, Brad R.; Morell, Gerardo; Katiyar, Ram S.

2018-05-01

We demonstrate the hybrid fabrication process of a graphene integrated highly transparent resistive random-access memory (TRRAM) device. The indium tin oxide (ITO)/Al2O3/graphene nonvolatile memory device possesses a high transmittance of >82% in the visible region (370-700 nm) and exhibits stable and non-symmetrical bipolar switching characteristics with considerably low set and reset voltages (<±1 V). The vertical two-terminal device shows an excellent resistive switching behavior with a high on-off ratio of ˜5 × 103. We also fabricated a ITO/Al2O3/Pt device and studied its switching characteristics for comparison and a better understanding of the ITO/Al2O3/graphene device characteristics. The conduction mechanisms in high and low resistance states were analyzed, and the observed polarity dependent resistive switching is explained based on electro-migration of oxygen ions.

Plasma-Induced Nonvolatile Resistive Switching with Extremely Low SET Voltage in TiOxFy with AgF Nanoparticles.

PubMed

Sun, Xiangyu; Wu, Chuangui; Shuai, Yao; Pan, Xinqiang; Luo, Wenbo; You, Tiangui; Bogusz, Agnieszka; Du, Nan; Li, Yanrong; Schmidt, Heidemarie

2016-12-07

Low power consumption is crucial for the application of resistive random access memory. In this work, we present the bipolar resistive switching in an Ag/TiO x F y /Ti/Pt stack with extremely low switch-on voltage of 0.07 V. Operating current as low as 10 nA was also obtained by conductive atomic force microscopy. The highly defective TiO x F y layer was fabricated by plasma treatment using helium, oxygen, and carbon tetrafluoride orderly. During the electroforming process, AgF nanoparticles were formed due to the diffusion of Ag + which reacted with the adsorbed F - in the TiO x F y layer. These nanoparticles are of great importance to resistive switching performance because they are believed to be conductive phases and become part of the conducting path when the sample is switched to a low-resistance state.

A graphene-based non-volatile memory

NASA Astrophysics Data System (ADS)

Loisel, Loïc.; Maurice, Ange; Lebental, Bérengère; Vezzoli, Stefano; Cojocaru, Costel-Sorin; Tay, Beng Kang

2015-09-01

We report on the development and characterization of a simple two-terminal non-volatile graphene switch. After an initial electroforming step during which Joule heating leads to the formation of a nano-gap impeding the current flow, the devices can be switched reversibly between two well-separated resistance states. To do so, either voltage sweeps or pulses can be used, with the condition that VSET < VRESET , where SET is the process decreasing the resistance and RESET the process increasing the resistance. We achieve reversible switching on more than 100 cycles with resistance ratio values of 104. This approach of graphene memory is competitive as compared to other graphene approaches such as redox of graphene oxide, or electro-mechanical switches with suspended graphene. We suggest a switching model based on a planar electro-mechanical switch, whereby electrostatic, elastic and friction forces are competing to switch devices ON and OFF, and the stability in the ON state is achieved by the formation of covalent bonds between the two stretched sides of the graphene, hence bridging the nano-gap. Developing a planar electro-mechanical switch enables to obtain the advantages of electro-mechanical switches while avoiding most of their drawbacks.

Thickness effect of ultra-thin Ta2O5 resistance switching layer in 28 nm-diameter memory cell

NASA Astrophysics Data System (ADS)

Park, Tae Hyung; Song, Seul Ji; Kim, Hae Jin; Kim, Soo Gil; Chung, Suock; Kim, Beom Yong; Lee, Kee Jeung; Kim, Kyung Min; Choi, Byung Joon; Hwang, Cheol Seong

2015-11-01

Resistance switching (RS) devices with ultra-thin Ta2O5 switching layer (0.5-2.0 nm) with a cell diameter of 28 nm were fabricated. The performance of the devices was tested by voltage-driven current—voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. A Ta layer was placed beneath the Ta2O5 switching layer to act as an oxygen vacancy reservoir. The device with the smallest Ta2O5 thickness (0.5 nm) showed normal switching properties with gradual change in resistance in I-V sweep or CLPS and high reliability. By contrast, other devices with higher Ta2O5 thickness (1.0-2.0 nm) showed abrupt switching with several abnormal behaviours, degraded resistance distribution, especially in high resistance state, and much lower reliability performance. A single conical or hour-glass shaped double conical conducting filament shape was conceived to explain these behavioural differences that depended on the Ta2O5 switching layer thickness. Loss of oxygen via lateral diffusion to the encapsulating Si3N4/SiO2 layer was suggested as the main degradation mechanism for reliability, and a method to improve reliability was also proposed.

Electrochemical metallization memories--fundamentals, applications, prospects.

PubMed

Valov, Ilia; Waser, Rainer; Jameson, John R; Kozicki, Michael N

2011-06-24

This review focuses on electrochemical metallization memory cells (ECM), highlighting their advantages as the next generation memories. In a brief introduction, the basic switching mechanism of ECM cells is described and the historical development is sketched. In a second part, the full spectra of materials and material combinations used for memory device prototypes and for dedicated studies are presented. In a third part, the specific thermodynamics and kinetics of nanosized electrochemical cells are described. The overlapping of the space charge layers is found to be most relevant for the cell properties at rest. The major factors determining the functionality of the ECM cells are the electrode reaction and the transport kinetics. Depending on electrode and/or electrolyte material electron transfer, electro-crystallization or slow diffusion under strong electric fields can be rate determining. In the fourth part, the major device characteristics of ECM cells are explained. Emphasis is placed on switching speed, forming and SET/RESET voltage, R(ON) to R(OFF) ratio, endurance and retention, and scaling potentials. In the last part, circuit design aspects of ECM arrays are discussed, including the pros and cons of active and passive arrays. In the case of passive arrays, the fundamental sneak path problem is described and as well as a possible solution by two anti-serial (complementary) interconnected resistive switches per cell. Furthermore, the prospects of ECM with regard to further scalability and the ability for multi-bit data storage are addressed.

Electrochemical metallization memories—fundamentals, applications, prospects

NASA Astrophysics Data System (ADS)

Valov, Ilia; Waser, Rainer; Jameson, John R.; Kozicki, Michael N.

2011-06-01

This review focuses on electrochemical metallization memory cells (ECM), highlighting their advantages as the next generation memories. In a brief introduction, the basic switching mechanism of ECM cells is described and the historical development is sketched. In a second part, the full spectra of materials and material combinations used for memory device prototypes and for dedicated studies are presented. In a third part, the specific thermodynamics and kinetics of nanosized electrochemical cells are described. The overlapping of the space charge layers is found to be most relevant for the cell properties at rest. The major factors determining the functionality of the ECM cells are the electrode reaction and the transport kinetics. Depending on electrode and/or electrolyte material electron transfer, electro-crystallization or slow diffusion under strong electric fields can be rate determining. In the fourth part, the major device characteristics of ECM cells are explained. Emphasis is placed on switching speed, forming and SET/RESET voltage, RON to ROFF ratio, endurance and retention, and scaling potentials. In the last part, circuit design aspects of ECM arrays are discussed, including the pros and cons of active and passive arrays. In the case of passive arrays, the fundamental sneak path problem is described and as well as a possible solution by two anti-serial (complementary) interconnected resistive switches per cell. Furthermore, the prospects of ECM with regard to further scalability and the ability for multi-bit data storage are addressed.

Resistive switching characteristics of HfO2-based memory devices on flexible plastics.

PubMed

Han, Yong; Cho, Kyoungah; Park, Sukhyung; Kim, Sangsig

2014-11-01

In this study, we examine the characteristics of HfO2-based resistive switching random access memory (ReRAM) devices on flexible plastics. The Pt/HfO2/Au ReRAM devices exhibit the unipolar resistive switching behaviors caused by the conducting filaments. From the Auger depth profiles of the HfO2 thin film, it is confirmed that the relatively lower oxygen content in the interface of the bottom electrode is responsible for the resistive switching by oxygen vacancies. And the unipolar resistive switching behaviors are analyzed from the C-V characteristics in which negative and positive capacitances are measured in the low-resistance state and the high-resistance state, respectively. The devices have a high on/off ratio of 10(4) and the excellent retention properties even after a continuous bending test of two thousand cycles. The correlation between the device size and the memory characteristics is investigated as well. A relatively smaller-sized device having a higher on/off ratio operates at a higher voltage than a relatively larger-sized device.

Nanocrystalline Si pathway induced unipolar resistive switching behavior from annealed Si-rich SiN{sub x}/SiN{sub y} multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Xiaofan; Ma, Zhongyuan, E-mail: zyma@nju.edu.cn; Yang, Huafeng

2014-09-28

Adding a resistive switching functionality to a silicon microelectronic chip is a new challenge in materials research. Here, we demonstrate that unipolar and electrode-independent resistive switching effects can be realized in the annealed Si-rich SiN{sub x}/SiN{sub y} multilayers with high on/off ratio of 10{sup 9}. High resolution transmission electron microscopy reveals that for the high resistance state broken pathways composed of discrete nanocrystalline silicon (nc-Si) exist in the Si nitride multilayers. While for the low resistance state the discrete nc-Si regions is connected, forming continuous nc-Si pathways. Based on the analysis of the temperature dependent I-V characteristics and HRTEM photos,more » we found that the break-and-bridge evolution of nc-Si pathway is the origin of resistive switching memory behavior. Our findings provide insights into the mechanism of the resistive switching behavior in nc-Si films, opening a way for it to be utilized as a material in Si-based memories.« less

Tuning the resistive switching properties of TiO2-x films

NASA Astrophysics Data System (ADS)

Ghenzi, N.; Rozenberg, M. J.; Llopis, R.; Levy, P.; Hueso, L. E.; Stoliar, P.

2015-03-01

We study the electrical characteristics of TiO2-x-based resistive switching devices fabricated with different oxygen/argon flow ratio during the oxide thin film sputtering deposition. Upon minute changes in this fabrication parameter, three qualitatively different device characteristics were accessed in the same system, namely, standard bipolar resistive switching, electroforming-free devices, and devices with multi-step breakdown. We propose that small variations in the oxygen/ argon flow ratio result in relevant changes of the oxygen vacancy concentration, which is the key parameter determining the resistive switching behavior. The coexistence of percolative or non-percolative conductive filaments is also discussed. Finally, the hypothesis is verified by means of the temperature dependence of the devices in low resistance state.

The nanocoherer: an electrically and mechanically resettable resistive switching device based on gold clusters assembled on paper

NASA Astrophysics Data System (ADS)

Minnai, Chloé; Mirigliano, Matteo; Brown, Simon A.; Milani, Paolo

2018-03-01

We report the realization of a resettable resistive switching device based on a nanostructured film fabricated by supersonic cluster beam deposition of gold clusters on plain paper substrates. Through the application of suitable voltage ramps, we obtain, in the same device, either a complex pattern of resistive switchings, or reproducible and stable switchings between low resistance and high resistance states, with an amplitude up to five orders of magnitude. Our device retains a state of internal resistance following the history of the applied voltage similar to that reported for memristors. The two different switching regimes in the same device are both stable, the transition between them is reversible, and it can be controlled by applying voltage ramps or by mechanical deformation of the substrate. The device behavior can be related to the formation, growth and breaking of junctions between the loosely aggregated gold clusters forming the nanostructured films. The fact that our cluster-assembled device is mechanically resettable suggests that it can be considered as the analog of the coherer: a switching device based on metallic powders used for the first radio communication system.

Manufacture of radio frequency micromachined switches with annealing.

PubMed

Lin, Cheng-Yang; Dai, Ching-Liang

2014-01-17

The fabrication and characterization of a radio frequency (RF) micromachined switch with annealing were presented. The structure of the RF switch consists of a membrane, coplanar waveguide (CPW) lines, and eight springs. The RF switch is manufactured using the complementary metal oxide semiconductor (CMOS) process. The switch requires a post-process to release the membrane and springs. The post-process uses a wet etching to remove the sacrificial silicon dioxide layer, and to obtain the suspended structures of the switch. In order to improve the residual stress of the switch, an annealing process is applied to the switch, and the membrane obtains an excellent flatness. The finite element method (FEM) software CoventorWare is utilized to simulate the stress and displacement of the RF switch. Experimental results show that the RF switch has an insertion loss of 0.9 dB at 35 GHz and an isolation of 21 dB at 39 GHz. The actuation voltage of the switch is 14 V.

Manufacture of Radio Frequency Micromachined Switches with Annealing

PubMed Central

Lin, Cheng-Yang; Dai, Ching-Liang

2014-01-01

The fabrication and characterization of a radio frequency (RF) micromachined switch with annealing were presented. The structure of the RF switch consists of a membrane, coplanar waveguide (CPW) lines, and eight springs. The RF switch is manufactured using the complementary metal oxide semiconductor (CMOS) process. The switch requires a post-process to release the membrane and springs. The post-process uses a wet etching to remove the sacrificial silicon dioxide layer, and to obtain the suspended structures of the switch. In order to improve the residual stress of the switch, an annealing process is applied to the switch, and the membrane obtains an excellent flatness. The finite element method (FEM) software CoventorWare is utilized to simulate the stress and displacement of the RF switch. Experimental results show that the RF switch has an insertion loss of 0.9 dB at 35 GHz and an isolation of 21 dB at 39 GHz. The actuation voltage of the switch is 14 V. PMID:24445415

Power- and Low-Resistance-State-Dependent, Bipolar Reset-Switching Transitions in SiN-Based Resistive Random-Access Memory

NASA Astrophysics Data System (ADS)

Kim, Sungjun; Park, Byung-Gook

2016-08-01

A study on the bipolar-resistive switching of an Ni/SiN/Si-based resistive random-access memory (RRAM) device shows that the influences of the reset power and the resistance value of the low-resistance state (LRS) on the reset-switching transitions are strong. For a low LRS with a large conducting path, the sharp reset switching, which requires a high reset power (>7 mW), was observed, whereas for a high LRS with small multiple-conducting paths, the step-by-step reset switching with a low reset power (<7 mW) was observed. The attainment of higher nonlinear current-voltage ( I-V) characteristics in terms of the step-by-step reset switching is due to the steep current-increased region of the trap-controlled space charge-limited current (SCLC) model. A multilevel cell (MLC) operation, for which the reset stop voltage ( V STOP) is used in the DC sweep mode and an incremental amplitude is used in the pulse mode for the step-by-step reset switching, is demonstrated here. The results of the present study suggest that well-controlled conducting paths in a SiN-based RRAM device, which are not too strong and not too weak, offer considerable potential for the realization of low-power and high-density crossbar-array applications.

Characteristics of multilevel storage and switching dynamics in resistive switching cell of Al2O3/HfO2/Al2O3 sandwich structure

NASA Astrophysics Data System (ADS)

Liu, Jian; Yang, Huafeng; Ma, Zhongyuan; Chen, Kunji; Zhang, Xinxin; Huang, Xinfan; Oda, Shunri

2018-01-01

We reported an Al2O3/HfO2/Al2O3 sandwich structure resistive switching device with significant improvement of multilevel cell (MLC) operation capability, which exhibited that four stable and distinct resistance states (one low resistance state and three high resistance states) can be achieved by controlling the Reset stop voltages (V Reset-stop) during the Reset operation. The improved MLC operation capability can be attributed to the R HRS/R LRS ratio enhancement resulting from increasing of the series resistance and decreasing of leakage current by inserting two Al2O3 layers. For the high-speed switching applications, we studied the initial switching dynamics by using the measurements of the pulse width and amplitude dependence of Set and Reset switching characteristics. The results showed that under the same pulse amplitude conditions, the initial Set progress is faster than the initial Reset progress, which can be explained by thermal-assisted electric field induced rupture model in the oxygen vacancies conductive filament. Thus, proper combination of varying pulse amplitude and width can help us to optimize the device operation parameters. Moreover, the device demonstrated ultrafast program/erase speed (10 ns) and good pulse switching endurance (105 cycles) characteristics, which are suitable for high-density and fast-speed nonvolatile memory applications.

Low mass MEMS/NEMS switch for a substitute of CMOS transistor using single-walled carbon nanotube thin film

NASA Astrophysics Data System (ADS)

Jang, Min-Woo

Power dissipation is a key factor for mobile devices and other low power applications. Complementary metal oxide semiconductor (CMOS) is the dominant integrated circuit (IC) technology responsible for a large part of this power dissipation. As the minimum feature size of CMOS devices enters into the sub 50 nanometer (nm) regime, power dissipation becomes much worse due to intrinsic physical limits. Many approaches have been studied to reduce power dissipation of deeply scaled CMOS ICs. One possible candidate is the electrostatic electromechanical switch, which could be fabricated with conventional CMOS processing techniques. They have critical advantages compared to CMOS devices such as almost zero standby leakage in the off-state due to the absence of a pn junction and a gate oxide, as well as excellent drive current in the on-state due to a metallic channel. Despite their excellent standby power dissipation, the electrostatic MEMS/NEMS switches have not been considered as a viable replacement for CMOS devices due to their large mechanical delay. Moreover, previous literature reveals that their pull-in voltage and switching speed are strongly proportional to each other. This reduces their potential advantage. However, in this work, we theoretically and experimentally demonstrated that the use of single-walled carbon nanotube (SWNT) with very low mass density and strong mechanical properties could provide a route to move off of the conventional trend with respect to the pull-in voltage / switching speed tradeoff observed in the literature. We fabricated 2-terminal fixed- beam switches with aligned composite SWNT thin films. In this work, layer-by-layer (LbL) self-assembly and dielectrophoresis were selected for aligned-composite SWNT thin film deposition. The dense membranes were successfully patterned to form submicron beams by e-beam lithography and oxygen plasma etching. Fixed-fixed beam switches using these membranes successfully operated with approximately 600 psec switching delay and as low as a 3 V dc pull-in. From this we confirmed that the SWNT-based thin films have the potential to make fast MEMS switches with a low operation voltage due to its low mass density and high stiffness. However, the copolymer caused a serious reliability issue and a copolymer-free SWNT film deposition method was developed by replacing positive copolymer with a dispersion of positively functionalized SWNTs. The electrical and physical properties of pure single-walled carbon nanotube thin films deposited through a copolymer-free LbL self-assembly process are then discussed. The film thickness was proportional to the number of dipping cycles. The film resistivity was estimated as 2.19x10-3 Ω-cm after thermal treatments were performed. The estimated specific contact resistance to gold electrodes was 6.33x10-9 Ω-m2 from contact chain measurements. The fabricated 3-terminal MEMS switches using these films functioned as a beam for multiple switching cycles with a 4.5V pull-in voltage, which was operated like a 2-input NAND gate. The SWNT-based thin film switch is promising for a variety of applications to high-end nanoelectronics and high- performance MEMS/NEMS.

Resistive switching in a few nanometers thick tantalum oxide film formed by a metal oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohno, Takeo, E-mail: t-ohno@wpi-aimr.tohoku.ac.jp; Japan Science and Technology Agency; Samukawa, Seiji, E-mail: samukawa@ifs.tohoku.ac.jp

2015-04-27

Resistive switching in a Cu/Ta{sub 2}O{sub 5}/Pt structure that consisted of a few nanometer-thick Ta{sub 2}O{sub 5} film was demonstrated. The Ta{sub 2}O{sub 5} film with thicknesses of 2–5 nm was formed with a combination of Ta metal film deposition and neutral oxygen particle irradiation at room temperature. The device exhibited a bipolar resistive switching with a threshold voltage of 0.2 V and multilevel switching operation.

Identifying Read/Write Speeds for Field-Induced Interfacial Resistive Switching.

NASA Astrophysics Data System (ADS)

Tsui, Stephen; Das, Nilanjan; Wang, Yaqi; Xue, Yuyi; Chu, C. W.

2007-03-01

Efforts continue to explore new phenomena that may allow for next generation nonvolatile memory technology. Much attention has been drawn to the field-induced resistive switch occurring at the interface between a metal electrode and perovskite oxide. The switch between high (off) and low (on) resistance states is controlled by the polarity of applied voltage pulsing. Characterization of Ag-Pr0.7Ca0.3MnO3 interfaces via impedance spectroscopy shows that the resistances above 10^6 Hz are the same at the on and off states, which limits the reading speed to far slower than the applied switching pulses, or device write speed at the order of 10^7 Hz. We deduce that the switching interface is percolative in nature and that small local rearrangement of defect structures may play a major role.

Tri-state logic circuit

NASA Technical Reports Server (NTRS)

Pryor, Richard Lee (Inventor)

1977-01-01

A line driver including a pair of complementary transistors having their conduction paths serially connected between an operating and a reference potential and their bases connected through a first switch to a signal input terminal. A second switch is connected between the common base connection and the common connection of the conduction paths. With the second switch open and the first closed, an output voltage, responsive to the input signal, corresponding to first or second binary values is obtained. When the second switch is closed and the first opened, the transistor pair is turned off, disconnecting the line driver from its load, thereby providing tri-state logic operation.

Electronic interaction and bipolar resistive switching in copper oxide-multilayer graphene hybrid interface: Graphene as an oxygen ion storage and blocking layer

NASA Astrophysics Data System (ADS)

Singh, Bharti; Mehta, B. R.; Govind, Feng, X.; Müllen, Klaus

2011-11-01

This study reports a bipolar resistive switching device based on copper oxide (CuO)-multilayer graphene (MLG) hybrid interface in complete contrast to the ohmic and rectifying characteristics of junctions based on individual MLG and CuO layers. The observed shift and the occurrence of additional O1s, Cu2p, and C1s core level peaks indicate electronic interaction at the hybrid interfacial layer. Large changes in the resistive switching parameters on changing the ambient conditions from air to vacuum establish the important role of MLG as oxygen ion storage and blocking layer towards the observed resistive switching effect.

Ultra-low switching energy and scaling in electric-field-controlled nanoscale magnetic tunnel junctions with high resistance-area product

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grezes, C.; Alzate, J. G.; Cai, X.

2016-01-04

We report electric-field-induced switching with write energies down to 6 fJ/bit for switching times of 0.5 ns, in nanoscale perpendicular magnetic tunnel junctions (MTJs) with high resistance-area product and diameters down to 50 nm. The ultra-low switching energy is made possible by a thick MgO barrier that ensures negligible spin-transfer torque contributions, along with a reduction of the Ohmic dissipation. We find that the switching voltage and time are insensitive to the junction diameter for high-resistance MTJs, a result accounted for by a macrospin model of purely voltage-induced switching. The measured performance enables integration with same-size CMOS transistors in compact memorymore » and logic integrated circuits.« less

Threshold Switching Characteristics of Nb/NbO 2 /TiN Vertical Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuhan; Comes, Ryan B.; Wolf, Stuart A.

2016-01-01

Nb/NbO2/TiN vertical structures were synthesized in-situ and patterned to devices with different contact areas. The devices exhibited threshold resistive switching with minimal hysteresis and a small EThreshold (60~90 kV/cm). The switching behavior was unipolar, and demonstrated good repeatability. A less sharp but still sizable change in the device resistance was observed up to 150 °C. It was found that the resistive switching without Nb capping layer exhibited the hysteretic behavior and much larger EThreshold (~250 kV/cm) likely due to a 2-3 nm surface Nb2O5 layer. The stable threshold switching behavior well above room temperature shows the potential applications of thismore » device as an electronic switch.« less

Resistive Switching of Ta2O5-Based Self-Rectifying Vertical-Type Resistive Switching Memory

NASA Astrophysics Data System (ADS)

Ryu, Sungyeon; Kim, Seong Keun; Choi, Byung Joon

2018-01-01

To efficiently increase the capacity of resistive switching random-access memory (RRAM) while maintaining the same area, a vertical structure similar to a vertical NAND flash structure is needed. In addition, the sneak-path current through the half-selected neighboring memory cell should be mitigated by integrating a selector device with each RRAM cell. In this study, an integrated vertical-type RRAM cell and selector device was fabricated and characterized. Ta2O5 as the switching layer and TaOxNy as the selector layer were used to preliminarily study the feasibility of such an integrated device. To make the side contact of the bottom electrode with active layers, a thick Al2O3 insulating layer was placed between the Pt bottom electrode and the Ta2O5/TaOxNy stacks. Resistive switching phenomena were observed under relatively low currents (below 10 μA) in this vertical-type RRAM device. The TaOxNy layer acted as a nonlinear resistor with moderate nonlinearity. Its low-resistance-state and high-resistance-state were well retained up to 1000 s.

Effect of oxygen concentration and metal electrode on the resistive switching in MIM capacitors with transition metal oxides

NASA Astrophysics Data System (ADS)

Spassov, D.; Paskaleva, A.; Fröhlich, K.; Ivanov, Tz

2017-01-01

The influence of the oxygen content in the dielectric layer and the effect of the bottom electrode on the resistive switching in Au/Pt/TaOx/TiN and Au/Pt/TaOx/Ta structures have been studied. The sputtered TaOx layers have been prepared by using oxygen concentrations of 10 or 7% O 2 in the Ar+O2 working ambient as well as by a gradual variation of the O2 content in the deposition process from 5 to 10%. Two deposition regimes for TiN electrodes have been investigated: reactive sputtering of Ti target in Ar+N2 ambient, and sputtering of TiN target in pure Ar. Bipolar resistive switching behavior is observed in all examined structures. It is demonstrated that the resistive switching effect is affected by the oxygen content in the working ambient as well as by the type and the deposition conditions of the bottom electrodes. Most stable effect, with ON/OFF ratio above 100 is obtained in TaOx deposited with variable O2 content in the ambient. The obtained switching voltage between the high resistive and low resistive state (SET) is about -1.5 V and the reverse changeover (RESET) is ∼2 V. A well pronounced resistive switching is achieved with reactively sputtered TiN while for the other bottom electrodes the effect is negligible.

Three-dimensional crossbar arrays of self-rectifying Si/SiO 2/Si memristors

DOE PAGES

Li, Can; Han, Lili; Jiang, Hao; ...

2017-06-05

Memristors are promising building blocks for the next generation memory, unconventional computing systems and beyond. Currently common materials used to build memristors are not necessarily compatible with the silicon dominant complementary metal-oxide-semiconductor (CMOS) technology. Furthermore, external selector devices or circuits are usually required in order for large memristor arrays to function properly, resulting in increased circuit complexity. Here we demonstrate fully CMOS-compatible, all-silicon based and self-rectifying memristors that negate the need for external selectors in large arrays. It consists of p- and n-type doped single crystalline silicon electrodes and a thin chemically produced silicon oxide switching layer. The device exhibitsmore » repeatable resistance switching behavior with high rectifying ratio (10 5), high ON/OFF conductance ratio (10 4) and attractive retention at 300 °C. We further build a 5-layer 3-dimensional (3D) crossbar array of 100 nm memristors by stacking fluid supported silicon membranes. The CMOS compatibility and self-rectifying behavior open up opportunities for mass production of memristor arrays and 3D hybrid circuits on full-wafer scale silicon and flexible substrates without increasing circuit complexity.« less

Resistive switching in TiO2 nanocolumn arrays electrochemically grown

NASA Astrophysics Data System (ADS)

Marik, M.; Mozalev, A.; Hubalek, J.; Bendova, M.

2017-04-01

Resistive switching in metal oxides, especially in TiO2, has been intensively investigated for potential application in non-volatile memory microdevices. As one of the working mechanisms, a conducting filament consisting of a substoichiometric oxide phase is created within the oxide layer. With the aim of investigating the filament formation in spatially confined elements, we fabricate arrays of self-ordered TiO2 nanocolumns by porous-anodic-alumina (PAA)-assisted anodizing, incorporate them into solid-state microdevices, study their electron transport properties, and reveal that this anodizing approach is suitable for growing TiO2 nanostructures exhibiting resistive switching. The electrical properties and resistive switching behavior are both dependent on the electrolytic formation conditions, influencing the concentration and distribution of oxygen vacancies in the nanocolumn material during the film growth. Therefore, the PAA-assisted TiO2 nanocolumn arrays can be considered as a platform for investigating various phenomena related to resistive switching in valve metal oxides at the nanoscale.

Dynamic-load-enabled ultra-low power multiple-state RRAM devices.

PubMed

Yang, Xiang; Chen, I-Wei

2012-01-01

Bipolar resistance-switching materials allowing intermediate states of wide-varying resistance values hold the potential of drastically reduced power for non-volatile memory. To exploit this potential, we have introduced into a nanometallic resistance-random-access-memory (RRAM) device an asymmetric dynamic load, which can reliably lower switching power by orders of magnitude. The dynamic load is highly resistive during on-switching allowing access to the highly resistive intermediate states; during off-switching the load vanishes to enable switching at low voltage. This approach is entirely scalable and applicable to other bipolar RRAM with intermediate states. The projected power is 12 nW for a 100 × 100 nm(2) device and 500 pW for a 10 × 10 nm(2) device. The dynamic range of the load can be increased to allow power to be further decreased by taking advantage of the exponential decay of wave-function in a newly discovered nanometallic random material, reaching possibly 1 pW for a 10×10 nm(2) nanometallic RRAM device.

Coexistence of unipolar and bipolar resistive switching behaviors in NiFe2O4 thin film devices by doping Ag nanoparticles

NASA Astrophysics Data System (ADS)

Hao, Aize; Ismail, Muhammad; He, Shuai; Huang, Wenhua; Qin, Ni; Bao, Dinghua

2018-02-01

The coexistence of unipolar and bipolar resistive switching (RS) behaviors of Ag-nanoparticles (Ag-NPs) doped NiFe2O4 (NFO) based memory devices was investigated. The switching voltages of required operations in the unipolar mode were smaller than those in the bipolar mode, while ON/OFF resistance levels of both modes were identical. Ag-NPs doped NFO based devices could switch between the unipolar and bipolar modes just by preferring the polarity of RESET voltage. Besides, the necessity of identical compliance current during the SET process of unipolar and bipolar modes provided an additional advantage of simplicity in device operation. Performance characteristics and cycle-to-cycle uniformity (>103 cycles) in unipolar operation were considerably better than those in bipolar mode (>102 cycles) at 25 °C. Moreover, good endurance (>600 cycles) at 200 °C was observed in unipolar mode and excellent nondestructive retention characteristics were obtained on memory cells at 125 °C and 200 °C. On the basis of temperature dependence of resistance at low resistance state, it was believed that physical origin of the RS mechanism involved the formation/rupture of the conducting paths consisting of oxygen vacancies and Ag atoms, considering Joule heating and electrochemical redox reaction effects for the unipolar and bipolar resistive switching behaviors. Our results demonstrate that 0.5% Ag-NPs doped nickel ferrites are promising resistive switching materials for resistive access memory applications.

Studies on transient characteristics of unipolar resistive switching processes in TiO2 thin film grown by atomic layer deposition

NASA Astrophysics Data System (ADS)

Sahu, Vikas Kumar; Das, Amit K.; Ajimsha, R. S.; Misra, P.

2018-05-01

The transient characteristics of resistive switching processes have been investigated in TiO2 thin films grown by atomic layer deposition (ALD) to study the temporal evolution of the switching processes and measure the switching times. The reset and set switching times of unipolar Au/TiO2/Pt devices were found to be ~250 µs and 180 ns, respectively in the voltage windows of 0.5–0.9 V for reset and 1.9–4.8 V for set switching processes, obtained from quasi-static measurements. The reset switching time decreased exponentially with increasing amplitude of applied reset voltage pulse, while the set switching time remained insensitive to the amplitude of the set voltage pulse. A fast reset process with a switching time of ~400 ns was achieved by applying a reset voltage of ~1.8 V, higher than that of the quasi-static reset voltage window but below the set voltage window. The sluggish reset process in TiO2 thin film and the dependence of the reset switching time on the amplitude of the applied voltage pulse was understood on the basis of a self-accelerated thermal dissolution model of conducting filaments (CFs), where a higher temperature of the CFs owing to enhanced Joule heating at a higher applied voltage imposes faster diffusion of oxygen vacancies, resulting in a shorter reset switching time. Our results clearly indicate that fast resistive switching with switching times in hundreds of nanoseconds can be achieved in ALD-grown TiO2 thin films. This may find applications in fast non-volatile unipolar resistive switching memories.

Anomalous Resistance Hysteresis in Oxide ReRAM: Oxygen Evolution and Reincorporation Revealed by In Situ TEM.

PubMed

Cooper, David; Baeumer, Christoph; Bernier, Nicolas; Marchewka, Astrid; La Torre, Camilla; Dunin-Borkowski, Rafal E; Menzel, Stephan; Waser, Rainer; Dittmann, Regina

2017-06-01

The control and rational design of redox-based memristive devices, which are highly attractive candidates for next-generation nonvolatile memory and logic applications, is complicated by competing and poorly understood switching mechanisms, which can result in two coexisting resistance hystereses that have opposite voltage polarity. These competing processes can be defined as regular and anomalous resistive switching. Despite significant characterization efforts, the complex nanoscale redox processes that drive anomalous resistive switching and their implications for current transport remain poorly understood. Here, lateral and vertical mapping of O vacancy concentrations is used during the operation of such devices in situ in an aberration corrected transmission electron microscope to explain the anomalous switching mechanism. It is found that an increase (decrease) in the overall O vacancy concentration within the device after positive (negative) biasing of the Schottky-type electrode is associated with the electrocatalytic release and reincorporation of oxygen at the electrode/oxide interface and is responsible for the resistance change. This fundamental insight presents a novel perspective on resistive switching processes and opens up new technological opportunities for the implementation of memristive devices, as anomalous switching can now be suppressed selectively or used deliberately to achieve the desirable so-called deep Reset. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct observation of oxygen vacancy-driven structural and resistive phase transitions in La2/3Sr1/3MnO3

NASA Astrophysics Data System (ADS)

Yao, Lide; Inkinen, Sampo; van Dijken, Sebastiaan

2017-02-01

Resistive switching in transition metal oxides involves intricate physical and chemical behaviours with potential for non-volatile memory and memristive devices. Although oxygen vacancy migration is known to play a crucial role in resistive switching of oxides, an in-depth understanding of oxygen vacancy-driven effects requires direct imaging of atomic-scale dynamic processes and their real-time impact on resistance changes. Here we use in situ transmission electron microscopy to demonstrate reversible switching between three resistance states in epitaxial La2/3Sr1/3MnO3 films. Simultaneous high-resolution imaging and resistance probing indicate that the switching events are caused by the formation of uniform structural phases. Reversible horizontal migration of oxygen vacancies within the manganite film, driven by combined effects of Joule heating and bias voltage, predominantly triggers the structural and resistive transitions. Our findings open prospects for ionotronic devices based on dynamic control of physical properties in complex oxide nanostructures.

High power operation of a nitrogen doped, vanadium compensated, 6H-SiC extrinsic photoconductive switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sullivan, J. S.

2014-04-28

We report the high power operation of nitrogen doped, vanadium compensated, 6H-SiC, extrinsic photoconductive switches with improved vanadium and nitrogen dopant density. Photoconductive switching tests are performed on 1 mm thick, m-plane, switch substrates at switch voltage and currents up to 17 kV and 1.5 kA, respectively. Sub-ohm minimum switch on resistance is achieved for peak optical intensities ≥35 MW/cm{sup 2} at 532 nm applied to the switch facet. A reduction of greater than nine orders of magnitude is observed in switch material resistivity between dark and illuminated states.

Genetic analysis of the response to eleven Colletotrichum lindemuthianum races in a RIL population of common bean (Phaseolus vulgaris L.)

PubMed Central

2014-01-01

Background Bean anthracnose is caused by the fungus Colletotrichum lindemuthianum (Sacc. & Magnus) Lams.- Scrib. Resistance to C. lindemuthianum in common bean (Phaseolus vulgaris L.) generally follows a qualitative mode of inheritance. The pathogen shows extensive pathogenic variation and up to 20 anthracnose resistance loci (named Co-), conferring resistance to specific races, have been described. Anthracnose resistance has generally been investigated by analyzing a limited number of isolates or races in segregating populations. In this work, we analyzed the response against eleven C. lindemuthianum races in a recombinant inbred line (RIL) common bean population derived from the cross Xana × Cornell 49242 in which a saturated linkage map was previously developed. Results A systematic genetic analysis was carried out to dissect the complex resistance segregations observed, which included contingency analyses, subpopulations and genetic mapping. Twenty two resistance genes were identified, some with a complementary mode of action. The Cornell 49242 genotype carries a complex cluster of resistance genes at the end of linkage group (LG) Pv11 corresponding to the previously described anthracnose resistance cluster Co-2. In this position, specific resistance genes to races 3, 6, 7, 19, 38, 39, 65, 357, 449 and 453 were identified, with one of them showing a complementary mode of action. In addition, Cornell 49242 had an independent gene on LG Pv09 showing a complementary mode of action for resistance to race 453. Resistance genes in genotype Xana were located on three regions involving LGs Pv01, Pv02 and Pv04. All resistance genes identified in Xana showed a complementary mode of action, except for two controlling resistance to races 65 and 73 located on LG Pv01, in the position of the previously described anthracnose resistance cluster Co-1. Conclusions Results shown herein reveal a complex and specific interaction between bean and fungus genotypes leading to anthracnose resistance. Organization of specific resistance genes in clusters including resistance genes with different modes of action (dominant and complementary genes) was also confirmed. Finally, new locations for anthracnose resistance genes were identified in LG Pv09. PMID:24779442

Switching dynamics of TaOx-based threshold switching devices

NASA Astrophysics Data System (ADS)

Goodwill, Jonathan M.; Gala, Darshil K.; Bain, James A.; Skowronski, Marek

2018-03-01

Bi-stable volatile switching devices are being used as access devices in solid-state memory arrays and as the active part of compact oscillators. Such structures exhibit two stable states of resistance and switch between them at a critical value of voltage or current. A typical resistance transient under a constant amplitude voltage pulse starts with a slow decrease followed by a rapid drop and leveling off at a low steady state value. This behavior prompted the interpretation of initial delay and fast transition as due to two different processes. Here, we show that the entire transient including incubation time, transition time, and the final resistance values in TaOx-based switching can be explained by one process, namely, Joule heating with the rapid transition due to the thermal runaway. The time, which is required for the device in the conducting state to relax back to the stable high resistance one, is also consistent with the proposed mechanism.

Resistive switching characteristic of electrolyte-oxide-semiconductor structures

NASA Astrophysics Data System (ADS)

Chen, Xiaoyu; Wang, Hao; Sun, Gongchen; Ma, Xiaoyu; Gao, Jianguang; Wu, Wengang

2017-08-01

The resistive switching characteristic of SiO2 thin film in electrolyte-oxide-semiconductor (EOS) structures under certain bias voltage is reported. To analyze the mechanism of the resistive switching characteristic, a batch of EOS structures were fabricated under various conditions and their electrical properties were measured with a set of three-electrode systems. A theoretical model based on the formation and rupture of conductive filaments in the oxide layer is proposed to reveal the mechanism of the resistive switching characteristic, followed by an experimental investigation of Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) to verify the proposed theoretical model. It is found that different threshold voltage, reverse leakage current and slope value features of the switching I-V characteristic can be observed in different EOS structures with different electrolyte solutions as well as different SiO2 layers made by different fabrication processes or in different thicknesses. With a simple fabrication process and significant resistive switching characteristic, the EOS structures show great potential for chemical/biochemical applications. Project supported by the National Natural Science Foundation of China (No. 61274116) and the National Basic Research Program of China (No. 2015CB352100).

Measurement of resistance switching dynamics in copper sulfide memristor structures

NASA Astrophysics Data System (ADS)

McCreery, Kaitlin; Olson, Matthew; Teitsworth, Stephen

Resistance switching materials are the subject of current research in large part for their potential to enable novel computing devices and architectures such as resistance random access memories and neuromorphic chips. A common feature of memristive structures is the hysteretic switching between high and low resistance states which is induced by the application of a sufficiently large electric field. Here, we describe a relatively simple wet chemistry process to fabricate Cu2 S / Cu memristive structures with Cu2 S film thickness ranging up to 150 micron. In this case, resistance switching is believed to be mediated by electromigration of Cu ions from the Cu substrate into the Cu2 S film. Hysteretic current-voltage curves are measured and reveal switching voltages of about 0.8 Volts with a relatively large variance and independent of film thickness. In order to gain insight into the dynamics and variability of the switching process, we have measured the time-dependent current response to voltage pulses of varying height and duration with a time resolution of 1 ns. The transient response consists of a deterministic RC component as well as stochastically varying abrupt current steps that occur within a few microseconds of the pulse application.

A vacancy-modulated self-selective resistive switching memory with pronounced nonlinear behavior

NASA Astrophysics Data System (ADS)

Ma, Haili; Feng, Jie; Gao, Tian; Zhu, Xi

2017-12-01

In this study, we report a self-selective (nonlinear) resistive switching memory cell, with high on-state half-bias nonlinearity of 650, sub-μA operating current, and high On/Off ratios above 100×. Regarding the cell structure, a thermal oxidized HfO x layer in combination with a sputtered Ta2O5 layer was configured as an active stack, with Pt and Hf as top and bottom electrodes, respectively. The Ta2O5 acts as a selective layer as well as a series resistor, which could make the resistive switching happened in HfO x layer. Through the analysis of the physicochemical properties and electrical conduction mechanisms at each state, a vacancy-modulated resistance switching model was proposed to explain the switching behavior. The conductivity of HfO x layer was changed by polarity-dependent drift of the oxygen vacancy ( V o), resulting in an electron hopping distance change during switching. With the help of Ta2O5 selective layer, high nonlinearity observed in low resistance state. The proposed material stack shows a promising prospect to act as a self-selective cell for 3D vertical RRAM application.

Ultra-compact 32 × 32 strictly-non-blocking Si-wire optical switch with fan-out LGA interposer.

PubMed

Tanizawa, Ken; Suzuki, Keijiro; Toyama, Munehiro; Ohtsuka, Minoru; Yokoyama, Nobuyuki; Matsumaro, Kazuyuki; Seki, Miyoshi; Koshino, Keiji; Sugaya, Toshio; Suda, Satoshi; Cong, Guangwei; Kimura, Toshio; Ikeda, Kazuhiro; Namiki, Shu; Kawashima, Hitoshi

2015-06-29

We demonstrate a 32 × 32 path-independent-insertion-loss optical path switch that integrates 1024 thermooptic Mach-Zehnder switches and 961 intersections on a small, 11 × 25 mm2 die. The switch is fabricated on a 300-mm-diameter silicon-on-insulator wafer by a complementary metal-oxide semiconductor-compatible process with advanced ArF immersion lithography. For reliable electrical packaging, the switch chip is flip-chip bonded to a ceramic interposer that arranges the electrodes in a 0.5-mm pitch land grid array. The on-chip loss is measured to be 15.8 ± 1.0 dB, and successful switching is demonstrated for digital-coherent 43-Gb/s QPSK signals. The total crosstalk of the switch is estimated to be less than -20 dB at the center wavelength of 1545 nm. The bandwidth narrowing caused by dimensional errors that arise during fabrication is discussed.

Improvement of Bipolar Switching Properties of Gd:SiOx RRAM Devices on Indium Tin Oxide Electrode by Low-Temperature Supercritical CO2 Treatment.

PubMed

Chen, Kai-Huang; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Liang, Shu-Ping; Young, Tai-Fa; Syu, Yong-En; Sze, Simon M

2016-12-01

Bipolar switching resistance behaviors of the Gd:SiO2 resistive random access memory (RRAM) devices on indium tin oxide electrode by the low-temperature supercritical CO2-treated technology were investigated. For physical and electrical measurement results obtained, the improvement on oxygen qualities, properties of indium tin oxide electrode, and operation current of the Gd:SiO2 RRAM devices were also observed. In addition, the initial metallic filament-forming model analyses and conduction transferred mechanism in switching resistance properties of the RRAM devices were verified and explained. Finally, the electrical reliability and retention properties of the Gd:SiO2 RRAM devices for low-resistance state (LRS)/high-resistance state (HRS) in different switching cycles were also measured for applications in nonvolatile random memory devices.

Direct Observation of Conducting Filaments in Tungsten Oxide Based Transparent Resistive Switching Memory.

PubMed

Qian, Kai; Cai, Guofa; Nguyen, Viet Cuong; Chen, Tupei; Lee, Pooi See

2016-10-05

Transparent nonvolatile memory has great potential in integrated transparent electronics. Here, we present highly transparent resistive switching memory using stoichiometric WO 3 film produced by cathodic electrodeposition with indium tin oxide electrodes. The memory device demonstrates good optical transmittance, excellent operative uniformity, low operating voltages (+0.25 V/-0.42 V), and long retention time (>10 4 s). Conductive atomic force microscopy, ex situ transmission electron microscopy, and X-ray photoelectron spectroscopy experiments directly confirm that the resistive switching effects occur due to the electric field-induced formation and annihilation of the tungsten-rich conductive channel between two electrodes. Information on the physical and chemical nature of conductive filaments offers insightful design strategies for resistive switching memories with excellent performances. Moreover, we demonstrate the promising applicability of the cathodic electrodeposition method for future resistive memory devices.

Low Temperature Resistive Switching Behavior in a Manganite

NASA Astrophysics Data System (ADS)

Salvo, Christopher; Lopez, Melinda; Tsui, Stephen

2012-02-01

The development of new nonvolatile memory devices remains an important field of consumer electronics. A possible candidate is bipolar resistive switching, a method by which the resistance of a material changes when a voltage is applied. Although there is a great deal of research on this topic, not much has been done at low temperatures. In this work, we compare the room temperature and low temperature behaviors of switching in a manganite thin film. The data indicates that the switching is suppressed upon cooling to cryogenic temperatures, and the presence of crystalline charge traps is tied to the physical mechanism.

Investigation of resistive switching behaviours in WO3-based RRAM devices

NASA Astrophysics Data System (ADS)

Li, Ying-Tao; Long, Shi-Bing; Lü, Hang-Bing; Liu, Qi; Wang, Qin; Wang, Yan; Zhang, Sen; Lian, Wen-Tai; Liu, Su; Liu, Ming

2011-01-01

In this paper, a WO3-based resistive random access memory device composed of a thin film of WO3 sandwiched between a copper top and a platinum bottom electrodes is fabricated by electron beam evaporation at room temperature. The reproducible resistive switching, low power consumption, multilevel storage possibility, and good data retention characteristics demonstrate that the Cu/WO3/Pt memory device is very promising for future nonvolatile memory applications. The formation and rupture of localised conductive filaments is suggested to be responsible for the observed resistive switching behaviours.

Dual operation characteristics of resistance random access memory in indium-gallium-zinc-oxide thin film transistors

NASA Astrophysics Data System (ADS)

Yang, Jyun-Bao; Chang, Ting-Chang; Huang, Jheng-Jie; Chen, Yu-Chun; Chen, Yu-Ting; Tseng, Hsueh-Chih; Chu, Ann-Kuo; Sze, Simon M.

2014-04-01

In this study, indium-gallium-zinc-oxide thin film transistors can be operated either as transistors or resistance random access memory devices. Before the forming process, current-voltage curve transfer characteristics are observed, and resistance switching characteristics are measured after a forming process. These resistance switching characteristics exhibit two behaviors, and are dominated by different mechanisms. The mode 1 resistance switching behavior is due to oxygen vacancies, while mode 2 is dominated by the formation of an oxygen-rich layer. Furthermore, an easy approach is proposed to reduce power consumption when using these resistance random access memory devices with the amorphous indium-gallium-zinc-oxide thin film transistor.

A steep-slope transistor based on abrupt electronic phase transition

NASA Astrophysics Data System (ADS)

Shukla, Nikhil; Thathachary, Arun V.; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G.; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

2015-08-01

Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep (`sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

A steep-slope transistor based on abrupt electronic phase transition.

PubMed

Shukla, Nikhil; Thathachary, Arun V; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

2015-08-07

Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep ('sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

E-field induced resistive switch in metal/praseodymium calcium manganite interfaces: A model for future nonvolatile memory devices

NASA Astrophysics Data System (ADS)

Das, Nilanjan

Among the various candidates for non-volatile random access memory (RAM), interfacial resistive switch in Ag/Pr0.7Ca0.3 MnO3 (PCMO) configuration has drawn major attention in recent years due to its potential as a high storage density (˜ terabyte) device. However, the diverse nature of the resistive switch in different systems makes the development of a unifying model for its underlying physics very difficult. This dissertation will address both issues, namely, characterization of switches for device applications and development of a system-independent generic model, in detail. In our work, we have studied the properties electric pulse induced interfacial switch in electrode/PCMO system. A very fast speed ("write speed") of 100 ns, threshold ("programming voltage") as low as 2 V (for micro electrodes), and non-volatility ("data retention") of switched states have been achieved. A clear distinction between fast switch and sub-threshold slow quasistatic-dc switch has been made. Results obtained from time-dependence studies and impedance spectroscopy suggest that defect creation/annihilation, such as broken bonds (under very high field at interface, 107V/cm), is likely the mechanism for the sub-micros fast switching. On the other hand, slow accumulative process, such as electromigration of point defects, are responsible for the subthreshold quasi-dc switch. Scanning probe imaging has revealed the nanoscale inhomogeneity of the switched surfaces, essential for observing a resistive switch. Evolution of such structures has been observed under surface pre-training. Device scalability has been tested by creating reversible modification of surface conductivities with atomic force microscopy, thus creating the "nano-switch" (limited to a region of 10--100 nm).

Forming-free bipolar resistive switching in nonstoichiometric ceria films

NASA Astrophysics Data System (ADS)

Ismail, Muhammad; Huang, Chun-Yang; Panda, Debashis; Hung, Chung-Jung; Tsai, Tsung-Ling; Jieng, Jheng-Hong; Lin, Chun-An; Chand, Umesh; Rana, Anwar Manzoor; Ahmed, Ejaz; Talib, Ijaz; Nadeem, Muhammad Younus; Tseng, Tseung-Yuen

2014-01-01

The mechanism of forming-free bipolar resistive switching in a Zr/CeO x /Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrO y layer at the Zr/CeO x interface. X-ray diffraction studies of CeO x films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeO x film and in the nonstoichiometric ZrO y interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

CMOS analog switches for adaptive filters

NASA Technical Reports Server (NTRS)

Dixon, C. E.

1980-01-01

Adaptive active low-pass filters incorporate CMOS (Complimentary Metal-Oxide Semiconductor) analog switches (such as 4066 switch) that reduce variation in switch resistance when filter is switched to any selected transfer function.

Gain-Scheduled Complementary Filter Design for a MEMS Based Attitude and Heading Reference System

PubMed Central

Yoo, Tae Suk; Hong, Sung Kyung; Yoon, Hyok Min; Park, Sungsu

2011-01-01

This paper describes a robust and simple algorithm for an attitude and heading reference system (AHRS) based on low-cost MEMS inertial and magnetic sensors. The proposed approach relies on a gain-scheduled complementary filter, augmented by an acceleration-based switching architecture to yield robust performance, even when the vehicle is subject to strong accelerations. Experimental results are provided for a road captive test during which the vehicle dynamics are in high-acceleration mode and the performance of the proposed filter is evaluated against the output from a conventional linear complementary filter. PMID:22163824

Single-Trial Analysis of Inter-Beat Interval Perturbations Accompanying Single-Switch Scanning: Case Series of Three Children With Severe Spastic Quadriplegic Cerebral Palsy.

PubMed

Leung, Brian; Chau, Tom

2016-02-01

Single-switch access in conjunction with scanning remains a fundamental solution in restoring communication for many children with profound physical disabilities. However, untimely switch inaction and unintentional switch activations can lead to user frustration and impede functional communication. A previous preliminary study, in the context of a case series with three single-switch users, reported that correct, accidental and missed switch activations could elicit cardiac deceleration and increased phasic skin conductance on average, while deliberate switch non-use was associated with autonomic nonresponse. The present study investigated the possibility of using blood volume pulse recordings from the same three pediatric single-switch users to track the aforementioned switch events on a single-trial basis. Peaks of the line length time series derived from the empirical mode decomposition of the inter-beat interval time series matched, on average, a high percentage (above 80%) of single-switch events, while unmatched peaks coincided moderately (below 37%) with idle time during scanning. These results encourage further study of autonomic measures as complementary information channels to enhance single-switch access.

Evidence of electrochemical resistive switching in the hydrated alumina layers of Cu/CuTCNQ/(native AlOx)/Al junctions

NASA Astrophysics Data System (ADS)

Knorr, Nikolaus; Bamedi, Ameneh; Karipidou, Zoi; Wirtz, René; Sarpasan, Mustafa; Rosselli, Silvia; Nelles, Gabriele

2013-09-01

We have investigated bipolar resistive switching of Cu/CuTCNQ/Al cross-junctions in both vacuum and different gas environments. While the generally observed S-shaped I-V hysteresis was reproduced in ambient air, it was reversibly suppressed in well-degassed samples in vacuum and in dry N2. The OFF-switching currents in ambient air peaked when approximately +2.6 V was applied to the Al electrode at low voltage sweep rates. OFF-switching at constant bias was accelerated in humid and oxygen-rich atmospheres. For unbiased samples stored in air, ON-state (RON) and OFF-state (ROFF) resistances increased with time, and RON surpassed the initial ROFF after approximately one week. Retention times were enhanced for samples stored in vacuum and those with a larger cross-junction area. We suggest that resistive switching occurs in a hydrated native alumina layer at the CuTCNQ/Al interface that grows in thickness during exposure to ambient humidity: ON-switching by electrochemical metallization of free Al and/or Cu ions and OFF-switching by anodic oxidation of the Al electrode and previously grown metal filaments.

Unnecessary antiretroviral treatment switches and accumulation of HIV resistance mutations; two arguments for viral load monitoring in Africa.

PubMed

Sigaloff, Kim C E; Hamers, Raph L; Wallis, Carole L; Kityo, Cissy; Siwale, Margaret; Ive, Prudence; Botes, Mariette E; Mandaliya, Kishor; Wellington, Maureen; Osibogun, Akin; Stevens, Wendy S; van Vugt, Michèle; de Wit, Tobias F Rinke

2011-09-01

This study aimed to investigate the consequences of using clinicoimmunological criteria to detect antiretroviral treatment (ART) failure and guide regimen switches in HIV-infected adults in sub-Saharan Africa. Frequencies of unnecessary switches, patterns of HIV drug resistance, and risk factors for the accumulation of nucleoside reverse transcriptase inhibitor (NRTI)-associated mutations were evaluated. Cross-sectional analysis of adults switching ART regimens at 13 clinical sites in 6 African countries was performed. Two types of failure identification were compared: diagnosis of clinicoimmunological failure without viral load testing (CIF only) or CIF with local targeted viral load testing (targeted VL). After study enrollment, reference HIV RNA and genotype were determined retrospectively. Logistic regression assessed factors associated with multiple thymidine analogue mutations (TAMs) and NRTI cross-resistance (≥2 TAMs or Q151M or K65R/K70E). Of 250 patients with CIF switching to second-line ART, targeted VL was performed in 186. Unnecessary switch at reference HIV RNA <1000 copies per milliliter occurred in 46.9% of CIF only patients versus 12.4% of patients with targeted VL (P < 0.001). NRTI cross-resistance was observed in 48.0% of 183 specimens available for genotypic analysis, comprising ≥2 TAMs (37.7%), K65R (7.1%), K70E (3.3%), or Q151M (3.3%). The presence of NRTI cross-resistance was associated with the duration of ART exposure and zidovudine use. Clinicoimmunological monitoring without viral load testing resulted in frequent unnecessary regimen switches. Prolonged treatment failure was indicated by extensive NRTI cross-resistance. Access to virological monitoring should be expanded to prevent inappropriate switches, enable early failure detection and preserve second-line treatment options in Africa.

HIV-1 Drug Resistance and Second-Line Treatment in Children Randomized to Switch at Low Versus Higher RNA Thresholds.

PubMed

Harrison, Linda; Melvin, Ann; Fiscus, Susan; Saidi, Yacine; Nastouli, Eleni; Harper, Lynda; Compagnucci, Alexandra; Babiker, Abdel; McKinney, Ross; Gibb, Diana; Tudor-Williams, Gareth

2015-09-01

The PENPACT-1 trial compared virologic thresholds to determine when to switch to second-line antiretroviral therapy (ART). Using PENPACT-1 data, we aimed to describe HIV-1 drug resistance accumulation on first-line ART by virologic threshold. PENPACT-1 had a 2 × 2 factorial design, randomizing HIV-infected children to start protease inhibitor (PI) versus nonnucleoside reverse transcriptase inhibitor (NNRTI)-based ART, and switch at a 1000 copies/mL versus 30,000 copies/mL threshold. Switch criteria were not achieving the threshold by week 24, confirmed rebound above the threshold thereafter, or Center for Disease Control and Prevention stage C event. Resistance tests were performed on samples ≥1000 copies/mL before switch, resuppression, and at 4-years/trial end. Sixty-seven children started PI-based ART and were randomized to switch at 1000 copies/mL (PI-1000), 64 PIs and 30,000 copies/mL (PI-30,000), 67 NNRTIs and 1000 copies/mL (NNRTI-1000), and 65 NNRTI and 30,000 copies/mL (NNRTI-30,000). Ninety-four (36%) children reached the 1000 copies/mL switch criteria during 5-year follow-up. In 30,000 copies/mL threshold arms, median time from 1000 to 30,000 copies/mL switch criteria was 58 (PI) versus 80 (NNRTI) weeks (P = 0.81). In NNRTI-30,000, more nucleoside reverse transcriptase inhibitor (NRTI) resistance mutations accumulated than other groups. NNRTI mutations were selected before switching at 1000 copies/mL (23% NNRTI-1000, 27% NNRTI-30,000). Sixty-two children started abacavir + lamivudine, 166 lamivudine + zidovudine or stavudine, and 35 other NRTIs. The abacavir + lamivudine group acquired fewest NRTI mutations. Of 60 switched to second-line, 79% PI-1000, 63% PI-30,000, 64% NNRTI-1000, and 100% NNRTI-30,000 were <400 copies/mL 24 weeks later. Children on first-line NNRTI-based ART who were randomized to switch at a higher virologic threshold developed the most resistance, yet resuppressed on second-line. An abacavir + lamivudine NRTI combination seemed protective against development of NRTI resistance.

Resistive Switching and Voltage Induced Modulation of Tunneling Magnetoresistance in Nanosized Perpendicular Organic Spin Valves

NASA Astrophysics Data System (ADS)

Schmidt, Georg; Goeckeritz, Robert; Homonnay, Nico; Mueller, Alexander; Fuhrmann, Bodo

Resistive switching has already been reported in organic spin valves (OSV), however, its origin is still unclear. We have fabricated nanosized OSV based on La0.7Sr0.3MnO3/Alq3/Co. These devices show fully reversible resistive switching of up to five orders of magnitude. The magnetoresistance (MR) is modulated during the switching process from negative (-70%) to positive values (+23%). The results are reminiscent of experiments claiming magnetoelectric coupling in LSMO based tunneling structures using ferroelectric barriers. By analyzing the I/V characteristics of the devices we can show that transport is dominated by tunneling through pinholes. The resistive switching is caused by voltage induced creation and motion of oxygen vacancies at the LSMO surface, however, the resulting tunnel barrier is complemented by a second adjacent barrier in the organic semiconductor. Our model shows that the barrier in the organic material is constant, causing the initial MR while the barrier in the LMSO can be modulated by the voltage resulting in the resistive switching and the modulation of the MR as the coupling to the states in the LSMO changes. A switching caused by LSMO only is also supported by the fact that replacing ALQ3 by H2PC yields almost identical results. Supported by the DFG in the SFB762.

Kinetic Self-Assembly of DNA Tiles and Bricks

DTIC Science & Technology

2016-08-26

research, and educa- tion. This is achieved by freeze drying cell-free systems into paper and other porous substrates to create materials with the...different toehold switches on paper . Experiments were performed by freeze drying the recombinant PT7 expression system onto paper discs, along with linear...DNA encoding specific switch RNAs. The paper discs were rehy- drated with or without the complementary RNA trigger 24 hr after drying and then

Impulse voltage control of continuously tunable bipolar resistive switching in Pt/Bi0.9Eu0.1FeO3/Nb-doped SrTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Wei, Maocai; Liu, Meifeng; Wang, Xiuzhang; Li, Meiya; Zhu, Yongdan; Zhao, Meng; Zhang, Feng; Xie, Shuai; Hu, Zhongqiang; Liu, Jun-Ming

2017-03-01

Epitaxial Bi0.9Eu0.1FeO3 (BEFO) thin films are deposited on Nb-doped SrTiO3 (NSTO) substrates by pulsed laser deposition to fabricate the Pt/BEFO/NSTO (001) heterostructures. These heterostructures possess bipolar resistive switching, where the resistances versus writing voltage exhibits a distinct hysteresis loop and a memristive behavior with good retention and anti-fatigue characteristics. The local resistive switching is confirmed by the conductive atomic force microscopy (C-AFM), suggesting the possibility to scale down the memory cell size. The observed memristive behavior could be attributed to the ferroelectric polarization effect, which modulates the height of potential barrier and width of depletion region at the BEFO/NSTO interface. The continuously tunable resistive switching behavior could be useful to achieve non-volatile, high-density, multilevel random access memory with low energy consumption.

Bipolar resistive switching in graphene oxide based metal insulator metal structure for non-volatile memory applications

NASA Astrophysics Data System (ADS)

Singh, Rakesh; Kumar, Ravi; Kumar, Anil; Kashyap, Rajesh; Kumar, Mukesh; Kumar, Dinesh

2018-05-01

Graphene oxide based devices have attracted much attention recently because of their possible application in next generation electronic devices. In this study, bipolar resistive switching characteristics of graphene oxide based metal insulator metal structure were investigated for nonvolatile memories. The graphene oxide was prepared by the conventional Hummer's method and deposited on ITO coated glass by spin-coating technique. The dominant mechanism of resistive switching is the formation and rupture of the conductive filament inside the graphene oxide. The conduction mechanism for low and high resistance states are dominated by two mechanism the ohmic conduction and space charge limited current (SCLC) mechanism, respectively. Atomic Force Microscopy, X-ray diffraction, Cyclic-Voltammetry were conducted to observe the morphology, structure and behavior of the material. The fabricated device with Al/GO/ITO structure exhibited reliable bipolar resistive switching with set & reset voltage of -2.3 V and 3V respectively.

EFFECTS OF TiOx INTERLAYER ON RESISTANCE SWITCHING OF Pt/TiOx/ZnO/n+-Si STRUCTURES

NASA Astrophysics Data System (ADS)

Li, Hongxia; Lv, Xiaojun; Xi, Junhua; Wu, Xin; Mao, Qinan; Liu, Qingmin; Ji, Zhenguo

2014-08-01

In this paper, we fabricated Pt/TiOx/ZnO/n+-Si structures by inserting TiOx interlayer between Pt top electrode (TE) and ZnO thin film for non-volatile resistive random access memory (ReRAM) applications. Effects of TiOx interlayer with different thickness on the resistance switching of Pt/TiOx/ZnO/n+-Si structures were investigated. Conduction behaviors in high and low resistance state (HRS and LRS) fit well with the trap-controlled space-charge-limited conduction (SCLC) and Ohmic behavior, respectively. Variations of set and reset voltages and HRS and LRS resistances of Pt/TiOx/ZnO/n+-Si structures were investigated as a function of TiOx thickness. Switching cycling tests were attempted to evaluate the endurance reliability of Pt/TiOx/ZnO/n+-Si structures. Additionally, the switching mechanism was analyzed by the filament model.

Impacts of Co doping on ZnO transparent switching memory device characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simanjuntak, Firman Mangasa; Wei, Kung-Hwa; Prasad, Om Kumar

2016-05-02

The resistive switching characteristics of indium tin oxide (ITO)/Zn{sub 1−x}Co{sub x}O/ITO transparent resistive memory devices were investigated. An appropriate amount of cobalt dopant in ZnO resistive layer demonstrated sufficient memory window and switching stability. In contrast, pure ZnO devices demonstrated a poor memory window, and using an excessive dopant concentration led to switching instability. To achieve suitable memory performance, relying only on controlling defect concentrations is insufficient; the grain growth orientation of the resistive layer must also be considered. Stable endurance with an ON/OFF ratio of more than one order of magnitude during 5000 cycles confirmed that the Co-doped ZnOmore » device is a suitable candidate for resistive random access memory application. Additionally, fully transparent devices with a high transmittance of up to 90% at wavelength of 550 nm have been fabricated.« less

Resistive switching characteristics of thermally oxidized TiN thin films

NASA Astrophysics Data System (ADS)

Biju, K. P.

2018-04-01

Resistive switching characteristics of thermally oxidized TiN thin films and mechanisms were investigated.XPS results indicates Ti-O content decreases with sputter etching and Ti 2p peak shift towards lower binding energy due to formation of Ti-O-N and Ti-N. Pt/TiO2/TiON/TiN stack exhibits both clockwise switching (CWS) and counter clockwise switching(CCWS) characteristic depending on polarity of the applied voltage. However the transition from CCWS to CWS is irreversible. Two stable switching modes with opposite switching polarity and different electrical characteristics are found to coexist in the same memory cell. Clockwise switching shows filamentary characteristics that lead to faster switching with excellent retention at high temperature. Counter-clockwise switching exhibits homogeneous conduction with slower switching and moderate retention. The field-induced switching in both CCWS and CWS might be due to inhomogeneous defect distribution due to thermal oxidation.

Nonpolar resistive memory switching with all four possible resistive switching modes in amorphous LaHoO{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Yogesh; Pavunny, Shojan P.; Katiyar, Ram S., E-mail: rkatiyar@hpcf.upr.edu

2015-09-07

We studied the resistive memory switching in pulsed laser deposited amorphous LaHoO{sub 3} (a-LHO) thin films for non-volatile resistive random access memory applications. Nonpolar resistive switching (RS) was achieved in Pt/a-LHO/Pt memory cells with all four possible RS modes (i.e., positive unipolar, positive bipolar, negative unipolar, and negative bipolar) having high R{sub ON}/R{sub OFF} ratios (in the range of ∼10{sup 4}–10{sup 5}) and non-overlapping switching voltages (set voltage, V{sub ON} ∼ ±3.6–4.2 V and reset voltage, V{sub OFF} ∼ ±1.3–1.6 V) with a small variation of about ±5–8%. Temperature dependent current-voltage (I–V) characteristics indicated the metallic conduction in low resistance states (LRS). We believe that themore » formation (set) and rupture (reset) of mixed conducting filaments formed out of oxygen vacancies and metallic Ho atoms could be responsible for the change in the resistance states of the memory cell. Detailed analysis of I–V characteristics further corroborated the formation of conductive nanofilaments based on metal-like (Ohmic) conduction in LRS. Simmons-Schottky emission was found to be the dominant charge transport mechanism in the high resistance state.« less

Conductive atomic force microscopy study of the photoexcitation effect on resistive switching in ZrO2(Y) films with Au nanoparticles

NASA Astrophysics Data System (ADS)

Novikov, A. S.; Filatov, D. O.; Antonov, D. A.; Antonov, I. N.; Shenina, M. E.; Gorshkov, O. N.

2018-03-01

We report on the experimental observation of the effect of optical excitation on resistive switching in ultrathin ZrO2(Y) films with single-layered arrays of Au nanoparticles. The samples were prepared by depositing nanometer-thick Au films sandwiched between two ZrO2(Y) layers by magnetron sputtering followed by annealing. Resistive switching was studied by conductive atomic force microscopy by measuring cyclic current-voltage curves of a probe-to-sample contact. The contact area was illuminated by radiation of a semiconductor laser diode with the wavelength corresponding to the plasmon resonance in an Au nanoparticle array. The enhancement of the hysteresis in cyclic current-voltage curves due to bipolar resistive switching under illumination was observed. The effect was attributed to heating of Au nanoparticles due to plasmonic optical absorption and a plasmon resonance, which enhances internal photoemission of electrons from the Fermi level in Au nanoparticles into the conduction band of ZrO2(Y). Both factors promote resistive switching in a ZrO2(Y) matrix.

Controlling the ferroelectric and resistive switching properties of a BiFeO3 thin film prepared using sub-5 nm dimension nanoparticles.

PubMed

Shirolkar, Mandar M; Li, Jieni; Dong, Xiaolei; Li, Ming; Wang, Haiqian

2017-10-04

In recent years, BiFeO 3 has attracted significant attention as an interesting multiferroic material in the exploration of fundamental science and development of novel applications. Our previous study (Phys. Chem. Chem. Phys.18, 2016, 25409) highlighted the interesting physicochemical features of BiFeO 3 of sub-5 nm dimension. The study also accentuated the existence of weak ferroelectricity at sub-5 nm dimensions in BiFeO 3 . Based on this feature, we have prepared thin films using sub-5 nm BiFeO 3 nanoparticles and explored various physicochemical properties of the thin film. We report that during the formation of the thin film, the nanoparticles aggregated; particularly, annihilation of their nanotwinning nature was observed. Qualitatively, the Gibbs free energy change ΔG governed the abovementioned processes. The thin film exhibited an R3c phase and enhanced Bi-O-Fe coordination as compared to the sub-5 nm nanoparticles. Raman spectroscopy under the influence of a magnetic field shows a magnetoelectric effect, spin phonon coupling, and magnetic anisotropy. We report room-temperature ferroelectric behavior in the thin film, which enhances with the application of a magnetic field; this confirms the multiferroic nature of the thin film. The thin film shows polarization switching ability at multiple voltages and read-write operation at low bias (±0.5 V). Furthermore, the thin film shows negative differential-complementary resistive switching behavior in the nano-microampere current range. We report nearly stable 1-bit operation for 10 2 cycles, 10 5 voltage pulses, and 10 5 s, demonstrating the paradigm device applications. The observed results thus show that the thin films prepared using sub-5 nm BiFeO 3 nanoparticles are a promising candidate for future spintronics and memory applications. The reported approach can also be pertinent to explore the physicochemical properties and develop potential applications of several other nanoparticles.

Investigating the origins of high multilevel resistive switching in forming free Ti/TiO2-x-based memory devices through experiments and simulations

NASA Astrophysics Data System (ADS)

Bousoulas, P.; Giannopoulos, I.; Asenov, P.; Karageorgiou, I.; Tsoukalas, D.

2017-03-01

Although multilevel capability is probably the most important property of resistive random access memory (RRAM) technology, it is vulnerable to reliability issues due to the stochastic nature of conducting filament (CF) creation. As a result, the various resistance states cannot be clearly distinguished, which leads to memory capacity failure. In this work, due to the gradual resistance switching pattern of TiO2-x-based RRAM devices, we demonstrate at least six resistance states with distinct memory margin and promising temporal variability. It is shown that the formation of small CFs with high density of oxygen vacancies enhances the uniformity of the switching characteristics in spite of the random nature of the switching effect. Insight into the origin of the gradual resistance modulation mechanisms is gained by the application of a trap-assisted-tunneling model together with numerical simulations of the filament formation physical processes.

Resistive switching characteristics of interfacial phase-change memory at elevated temperature

NASA Astrophysics Data System (ADS)

Mitrofanov, Kirill V.; Saito, Yuta; Miyata, Noriyuki; Fons, Paul; Kolobov, Alexander V.; Tominaga, Junji

2018-04-01

Interfacial phase-change memory (iPCM) devices were fabricated using W and TiN for the bottom and top contacts, respectively, and the effect of operation temperature on the resistive switching was examined over the range between room temperature and 200 °C. It was found that the high-resistance (RESET) state in an iPCM device drops sharply at around 150 °C to a low-resistance (SET) state, which differs by ˜400 Ω from the SET state obtained by electric-field-induced switching. The iPCM device SET state resistance recovered during the cooling process and remained at nearly the same value for the RESET state. These resistance characteristics greatly differ from those of the conventional Ge-Sb-Te (GST) alloy phase-change memory device, underscoring the fundamentally different switching nature of iPCM devices. From the thermal stability measurements of iPCM devices, their optimal temperature operation was concluded to be less than 100 °C.

Additional Electrochemical Treatment Effects on the Switching Characteristics of Anodic Porous Alumina Resistive Switching Memory

NASA Astrophysics Data System (ADS)

Otsuka, Shintaro; Takeda, Ryouta; Furuya, Saeko; Shimizu, Tomohiro; Shingubara, Shouso; Iwata, Nobuyuki; Watanabe, Tadataka; Takano, Yoshiki; Takase, Kouichi

2012-06-01

We have investigated the current-voltage characteristics of a resistive switching memory (ReRAM), especially the reproducibility of the switching voltage between an insulating state and a metallic state. The poor reproducibility hinders the practical use of this memory. According to a filament model, the variation of the switching voltage may be understood in terms of the random choice of filaments with different conductivities and lengths at each switching. A limitation of the number of conductive paths is expected to lead to the suppression of the variation of switching voltage. In this study, two strategies for the limitation have been proposed using an anodic porous alumina (APA). The first is the reduction of the number of conductive paths by restriction of the contact area between the top electrodes and the insulator. The second is the lowering of the resistivity of the insulator, which makes it possible to grow filaments with the same characteristics by electrochemical treatments using a pulse-electroplating technique.

Formation of template-switching artifacts by linear amplification.

PubMed

Chakravarti, Dhrubajyoti; Mailander, Paula C

2008-07-01

Linear amplification is a method of synthesizing single-stranded DNA from either a single-stranded DNA or one strand of a double-stranded DNA. In this protocol, molecules of a single primer DNA are extended by multiple rounds of DNA synthesis at high temperature using thermostable DNA polymerases. Although linear amplification generates the intended full-length single-stranded product, it is more efficient over single-stranded templates than double-stranded templates. We analyzed linear amplification over single- or double-stranded mouse H-ras DNA (exon 1-2 region). The single-stranded H-ras template yielded only the intended product. However, when the double-stranded template was used, additional artifact products were observed. Increasing the concentration of the double-stranded template produced relatively higher amounts of these artifact products. One of the artifact DNA bands could be mapped and analyzed by sequencing. It contained three template-switching products. These DNAs were formed by incomplete DNA strand extension over the template strand, followed by switching to the complementary strand at a specific Ade nucleotide within a putative hairpin sequence, from which DNA synthesis continued over the complementary strand.

Resistive Switching of Sub-10 nm TiO2 Nanoparticle Self-Assembled Monolayers

PubMed Central

Schmidt, Dirk Oliver; Raab, Nicolas; Santhanam, Venugopal; Dittmann, Regina; Simon, Ulrich

2017-01-01

Resistively switching devices are promising candidates for the next generation of non-volatile data memories. Such devices are up to now fabricated mainly by means of top-down approaches that apply thin films sandwiched between electrodes. Recent works have demonstrated that resistive switching (RS) is also feasible on chemically synthesized nanoparticles (NPs) in the 50 nm range. Following this concept, we developed this approach further to the sub-10 nm range. In this work, we report RS of sub-10 nm TiO2 NPs that were self-assembled into monolayers and transferred onto metallic substrates. We electrically characterized these monolayers in regard to their RS properties by means of a nanorobotics system in a scanning electron microscope, and found features typical of bipolar resistive switching. PMID:29113050

Enhanced bipolar resistive switching behavior in polar Cr-doped barium titanate thin films without electro-forming process

NASA Astrophysics Data System (ADS)

Thakre, Atul; Kumar, Ashok

2017-12-01

An enhanced, repeatable and robust resistive switching phenomenon was observed in Cr substituted BaTiO3 polar ferroelectric thin films; fabricated and deposited by the sol-gel approach and spin coating technique, respectively. An enhanced bistable bipolar resistive switching (BRS) phenomenon without electro-forming process, low switching voltage (˜ 2 V) and moderate retention characteristics of 104 s along with a high Roff/Ron resistance ratio ˜103 was achieved. The current conduction analysis showed that the space charge limited conduction (SCLC) and Schottky emission conduction dominate in the high voltage range, while thermally active charge carriers (ohmic) in the lower voltage range. The impedance spectroscopy study indicates the formation of current conducting path and rupturing of oxygen vacancies during SET and RESET process.

Microstructure evolution characteristics induced by oxygen vacancy generation in anatase TiO2 based resistive switching devices

NASA Astrophysics Data System (ADS)

Liu, Chen; Gao, Bin; Huang, Peng; Kang, Jinfeng

2017-03-01

In this work, first principle calculations are employed to study the microstructure characteristics of the anatase TiO2 resistive switching material associated with the generation of oxygen vacancy (V o) based nanofilaments during the switching process. The calculations indicate that both the magnéli phase Ti4O7 and V o-defect phase of anatase TiO2 may be formed with the generation of oxygen vacancies during the forming and SET processes. Based on the calculations, a new physical insight is proposed to clarify the microstructure evolution characteristics of the anatase TiO2 resistive switching material and the correlation with resistive switching behaviors. During the forming or SET process, the anatase TiO2 is first excited to a transition state with the generation of oxygen vacancies, then fully relaxes to a stable V o-defect state. This V o-defect state may either recover to the original state with the recombination of the oxygen vacancies, which causes the reversible resistive switching behavior, or further transform to a much more stable state—the magnéli phase Ti4O7, through a phase transition process with the generation of many more oxygen vacancies. The phase transition from V o- defective anatase phase to magnéli phase Ti4O7 causes the failure of the resistive switching due to the significantly reduced possibility of the reversible phase transition from the magnéli phase to the anatase phase, compared with the possibility of the recombination from the V o-defective anatase.

Application of nanomaterials in two-terminal resistive-switching memory devices

PubMed Central

Ouyang, Jianyong

2010-01-01

Nanometer materials have been attracting strong attention due to their interesting structure and properties. Many important practical applications have been demonstrated for nanometer materials based on their unique properties. This article provides a review on the fabrication, electrical characterization, and memory application of two-terminal resistive-switching devices using nanomaterials as the active components, including metal and semiconductor nanoparticles (NPs), nanotubes, nanowires, and graphenes. There are mainly two types of device architectures for the two-terminal devices with NPs. One has a triple-layer structure with a metal film sandwiched between two organic semiconductor layers, and the other has a single polymer film blended with NPs. These devices can be electrically switched between two states with significant different resistances, i.e. the ‘ON’ and ‘OFF’ states. These render the devices important application as two-terminal non-volatile memory devices. The electrical behavior of these devices can be affected by the materials in the active layer and the electrodes. Though the mechanism for the electrical switches has been in argument, it is generally believed that the resistive switches are related to charge storage on the NPs. Resistive switches were also observed on crossbars formed by nanotubes, nanowires, and graphene ribbons. The resistive switches are due to nanoelectromechanical behavior of the materials. The Coulombic interaction of transient charges on the nanomaterials affects the configurable gap of the crossbars, which results into significant change in current through the crossbars. These nanoelectromechanical devices can be used as fast-response and high-density memory devices as well. PMID:22110862

Effect of AlN layer on the bipolar resistive switching behavior in TiN thin film based ReRAM device for non-volatile memory application

NASA Astrophysics Data System (ADS)

Prakash, Ravi; Kaur, Davinder

2018-05-01

The effect of an additional AlN layer in the Cu/TiN/AlN/Pt stack configuration deposited using sputtering has been investigated. The Cu/TiN/AlN/Pt device shows a tristate resistive switching. Multilevel switching is facilitated by ionic and metallic filament formation, and the nature of the filaments formed is confirmed by performing a resistance vs. temperature measurement. Ohmic behaviour and trap controlled space charge limited current (SCLC) conduction mechanisms are confirmed as dominant conduction mechanism at low resistance state (LRS) and high resistance state (HRS). High resistance ratio (102) corresponding to HRS and LRS, good write/erase endurance (105) and non-volatile long retention (105s) are also observed. Higher thermal conductivity of the AlN layer is the main reasons for the enhancement of resistive switching performance in Cu/TiN/AlN/Pt cell. The above result suggests the feasibility of Cu/TiN/AlN/Pt devices for multilevel nonvolatile ReRAM application.

Sustained Resistive Switching in a Single Cu:7,7,8,8-tetracyanoquinodimethane Nanowire: A Promising Material for Resistive Random Access Memory

PubMed Central

Basori, Rabaya; Kumar, Manoranjan; Raychaudhuri, Arup K.

2016-01-01

We report a new type of sustained and reversible unipolar resistive switching in a nanowire device made from a single strand of Cu:7,7,8,8-tetracyanoquinodimethane (Cu:TCNQ) nanowire (diameter <100 nm) that shows high ON/OFF ratio (~103), low threshold voltage of switching (~3.5 V) and large cycling endurance (>103). This indicates a promising material for high density resistive random access memory (ReRAM) device integration. Switching is observed in Cu:TCNQ single nanowire devices with two different electrode configuration: symmetric (C-Pt/Cu:TCNQ/C-Pt) and asymmetric (Cu/Cu:TCNQ/C-Pt), where contacts connecting the nanowire play an important role. This report also developed a method of separating out the electrode and material contributions in switching using metal-semiconductor-metal (MSM) device model along with a direct 4-probe resistivity measurement of the nanowire in the OFF as well as ON state. The device model was followed by a phenomenological model of current transport through the nanowire device which shows that lowering of potential barrier at the contacts likely occur due to formation of Cu filaments in the interface between nanowire and contact electrodes. We obtain quantitative agreement of numerically analyzed results with the experimental switching data. PMID:27245099

Switching synchronization in one-dimensional memristive networks

NASA Astrophysics Data System (ADS)

Slipko, Valeriy A.; Shumovskyi, Mykola; Pershin, Yuriy V.

2015-11-01

We report on a switching synchronization phenomenon in one-dimensional memristive networks, which occurs when several memristive systems with different switching constants are switched from the high- to low-resistance state. Our numerical simulations show that such a collective behavior is especially pronounced when the applied voltage slightly exceeds the combined threshold voltage of memristive systems. Moreover, a finite increase in the network switching time is found compared to the average switching time of individual systems. An analytical model is presented to explain our observations. Using this model, we have derived asymptotic expressions for memory resistances at short and long times, which are in excellent agreement with results of our numerical simulations.

Ultra-high-extinction-ratio 2 × 2 silicon optical switch with variable splitter.

PubMed

Suzuki, Keijiro; Cong, Guangwei; Tanizawa, Ken; Kim, Sang-Hun; Ikeda, Kazuhiro; Namiki, Shu; Kawashima, Hitoshi

2015-04-06

We demonstrate a record-high extinction-ratio of 50.4 dB in a 2 × 2 silicon Mach-Zehnder switch equipped with a variable splitter as the front 3-dB splitter. The variable splitter is adjusted to compensate for the splitting-ratio mismatch between the front and rear 3-dB splitters. The high extinction ratio does not rely on waveguide crossings and meets a strong demand in applications to multiport circuit switches. Large fabrication tolerance will make the high extinction ratio compatible with a volume production with standard complementary metal-oxide semiconductor fabrication facilities.

Emerging memories: resistive switching mechanisms and current status

NASA Astrophysics Data System (ADS)

Jeong, Doo Seok; Thomas, Reji; Katiyar, R. S.; Scott, J. F.; Kohlstedt, H.; Petraru, A.; Hwang, Cheol Seong

2012-07-01

The resistance switching behaviour of several materials has recently attracted considerable attention for its application in non-volatile memory (NVM) devices, popularly described as resistive random access memories (RRAMs). RRAM is a type of NVM that uses a material(s) that changes the resistance when a voltage is applied. Resistive switching phenomena have been observed in many oxides: (i) binary transition metal oxides (TMOs), e.g. TiO2, Cr2O3, FeOx and NiO; (ii) perovskite-type complex TMOs that are variously functional, paraelectric, ferroelectric, multiferroic and magnetic, e.g. (Ba,Sr)TiO3, Pb(Zrx Ti1-x)O3, BiFeO3 and PrxCa1-xMnO3 (iii) large band gap high-k dielectrics, e.g. Al2O3 and Gd2O3; (iv) graphene oxides. In the non-oxide category, higher chalcogenides are front runners, e.g. In2Se3 and In2Te3. Hence, the number of materials showing this technologically interesting behaviour for information storage is enormous. Resistive switching in these materials can form the basis for the next generation of NVM, i.e. RRAM, when current semiconductor memory technology reaches its limit in terms of density. RRAMs may be the high-density and low-cost NVMs of the future. A review on this topic is of importance to focus concentration on the most promising materials to accelerate application into the semiconductor industry. This review is a small effort to realize the ambitious goal of RRAMs. Its basic focus is on resistive switching in various materials with particular emphasis on binary TMOs. It also addresses the current understanding of resistive switching behaviour. Moreover, a brief comparison between RRAMs and memristors is included. The review ends with the current status of RRAMs in terms of stability, scalability and switching speed, which are three important aspects of integration onto semiconductors.

Electrical Characterization of Temperature Dependent Resistive Switching in Pr0.7C0.3MnO3

NASA Astrophysics Data System (ADS)

Lopez, Melinda; Salvo, Christopher; Tsui, Stephen

2012-02-01

Resistive switching offers a non-volatile and reversible means to possibly create a more physically compact yet larger access capacity in memory technology. While there has been a great deal of research conducted on this electrical property in oxide materials, there is still more to be learned about this at both high voltage pulsing and cryogenic temperatures. In this work, the electrical properties of a PCMO-metal interface switch were examined after application of voltage pulsing varying from 100 V to 1000 V and at temperatures starting at 293 K and lowered to 80 K. What was discovered was that below temperatures of 150 K, the resistive switching began to decrease across all voltage pulsing and that at all temperatures before this cessation, the change in resistive switching increased with higher voltage pulsing. We suggest that a variable density of charge traps at the interface is a likely mechanism, and work continues to extract more details.

Role of Al2O3 thin layer on improving the resistive switching properties of Ta5Si3-based conductive bridge random accesses memory device

NASA Astrophysics Data System (ADS)

Kumar, Dayanand; Aluguri, Rakesh; Chand, Umesh; Tseng, Tseung-Yuen

2018-04-01

Ta5Si3-based conductive bridge random access memory (CBRAM) devices have been investigated to improve their resistive switching characteristics for their application in future nonvolatile memory technology. Changes in the switching characteristics by the addition of a thin Al2O3 layer of different thicknesses at the bottom electrode interface of a Ta5Si3-based CBRAM devices have been studied. The double-layer device with a 1 nm Al2O3 layer has shown improved resistive switching characteristics over the single layer one with a high on/off resistance ratio of 102, high endurance of more than 104 cycles, and good retention for more than 105 s at the temperature of 130 °C. The higher thermal conductivity of Al2O3 over Ta5Si3 has been attributed to the enhanced switching properties of the double-layer devices.

Excellent Resistive Switching Performance of Cu-Se-Based Atomic Switch Using Lanthanide Metal Nanolayer at the Cu-Se/Al2O3 Interface.

PubMed

Woo, Hyunsuk; Vishwanath, Sujaya Kumar; Jeon, Sanghun

2018-03-07

The next-generation electronic society is dependent on the performance of nonvolatile memory devices, which has been continuously improving. In the last few years, many memory devices have been introduced. However, atomic switches are considered to be a simple and reliable basis for next-generation nonvolatile devices. In general, atomic switch-based resistive switching is controlled by electrochemical metallization. However, excess ion injection from the entire area of the active electrode into the switching layer causes device nonuniformity and degradation of reliability. Here, we propose the fabrication of a high-performance atomic switch based on Cu x -Se 1- x by inserting lanthanide (Ln) metal buffer layers such as neodymium (Nd), samarium (Sm), dysprosium (Dy), or lutetium (Lu) between the active metal layer and the electrolyte. Current-atomic force microscopy results confirm that Cu ions penetrate through the Ln-buffer layer and form thin conductive filaments inside the switching layer. Compared with the Pt/Cu x -Se 1- x /Al 2 O 3 /Pt device, the optimized Pt/Cu x -Se 1- x /Ln/Al 2 O 3 /Pt devices show improvement in the on/off resistance ratio (10 2 -10 7 ), retention (10 years/85 °C), endurance (∼10 000 cycles), and uniform resistance state distribution.

Migration of interfacial oxygen ions modulated resistive switching in oxide-based memory devices

NASA Astrophysics Data System (ADS)

Chen, C.; Gao, S.; Zeng, F.; Tang, G. S.; Li, S. Z.; Song, C.; Fu, H. D.; Pan, F.

2013-07-01

Oxides-based resistive switching memory induced by oxygen ions migration is attractive for future nonvolatile memories. Numerous works had focused their attentions on the sandwiched oxide materials for depressing the characteristic variations, but the comprehensive studies of the dependence of electrodes on the migration behavior of oxygen ions are overshadowed. Here, we investigated the interaction of various metals (Ni, Co, Al, Ti, Zr, and Hf) with oxygen atoms at the metal/Ta2O5 interface under electric stress and explored the effect of top electrode on the characteristic variations of Ta2O5-based memory device. It is demonstrated that chemically inert electrodes (Ni and Co) lead to the scattering switching characteristics and destructive gas bubbles, while the highly chemically active metals (Hf and Zr) formed a thick and dense interfacial intermediate oxide layer at the metal/Ta2O5 interface, which also degraded the resistive switching behavior. The relatively chemically active metals (Al and Ti) can absorb oxygen ions from the Ta2O5 film and avoid forming the problematic interfacial layer, which is benefit to the formation of oxygen vacancies composed conduction filaments in Ta2O5 film thus exhibit the minimum variations of switching characteristics. The clarification of oxygen ions migration behavior at the interface can lead further optimization of resistive switching performance in Ta2O5-based memory device and guide the rule of electrode selection for other oxide-based resistive switching memories.

Thin TiOx layer as a voltage divider layer located at the quasi-Ohmic junction in the Pt/Ta2O5/Ta resistance switching memory.

PubMed

Li, Xiang Yuan; Shao, Xing Long; Wang, Yi Chuan; Jiang, Hao; Hwang, Cheol Seong; Zhao, Jin Shi

2017-02-09

Ta 2 O 5 has been an appealing contender for the resistance switching random access memory (ReRAM). The resistance switching (RS) in this material is induced by the repeated formation and rupture of the conducting filaments (CFs) in the oxide layer, which are accompanied by the almost inevitable randomness of the switching parameters. In this work, a 1 to 2 nm-thick Ti layer was deposited on the 10 nm-thick Ta 2 O 5 RS layer, which greatly improved the RS performances, including the much-improved switching uniformity. The Ti metal layer was naturally oxidized to TiO x (x < 2) and played the role of a series resistor, whose resistance value was comparable to the on-state resistance of the Ta 2 O 5 RS layer. The series resistor TiO x efficiently suppressed the adverse effects of the voltage (or current) overshooting at the moment of switching by the appropriate voltage partake effect, which increased the controllability of the CF formation and rupture. The switching cycle endurance was increased by two orders of magnitude even during the severe current-voltage sweep tests compared with the samples without the thin TiO x layer. The Ti deposition did not induce any significant overhead to the fabrication process, making the process highly promising for the mass production of a reliable ReRAM.

Study of Ag/RGO/ITO sandwich structure for resistive switching behavior deposited on plastic substrate

NASA Astrophysics Data System (ADS)

Vartak, Rajdeep; Rag, Adarsh; De, Shounak; Bhat, Somashekhara

2018-05-01

We report here the use of facile and environmentally benign way synthesized reduced graphene oxide (RGO) for low-voltage non-volatile memory device as charge storing element. The RGO solutions have been synthesized using electrochemical exfoliation of battery electrode. The solution processed based RGO solution is suitable for large area and low-cost processing on plastic substrate. Room-temperature current-voltage characterisation has been carried out in Ag/RGO/ITO PET sandwich configuration to study the type of trap distribution. It is observed that in the low-voltage sweep, ohmic current is the main mechanism of current flow and trap filled/assisted conduction is observed at high-sweep voltage region. The Ag/RGO/ITO PET sandwich structure showed bipolar resistive switching behavior. These mechanisms can be analyzed based on oxygen availability and vacancies in the RGO giving rise to continuous least resistive path (conductive) and high resistance path along the structure. An Ag/RGO/ITO arrangement demonstrates long retention time with low operating voltage, low set/reset voltage, good ON/OFF ratio of 103 (switching transition between lower resistance state and higher resistance state and decent switching performance. The RGO memory showed decent results with an almost negligible degradation in switching properties which can be used for low-voltage and low-cost advanced flexible electronics.

Light-activated resistance switching in SiOx RRAM devices

NASA Astrophysics Data System (ADS)

Mehonic, A.; Gerard, T.; Kenyon, A. J.

2017-12-01

We report a study of light-activated resistance switching in silicon oxide (SiOx) resistive random access memory (RRAM) devices. Our devices had an indium tin oxide/SiOx/p-Si Metal/Oxide/Semiconductor structure, with resistance switching taking place in a 35 nm thick SiOx layer. The optical activity of the devices was investigated by characterising them in a range of voltage and light conditions. Devices respond to illumination at wavelengths in the range of 410-650 nm but are unresponsive at 1152 nm, suggesting that photons are absorbed by the bottom p-type silicon electrode and that generation of free carriers underpins optical activity. Applied light causes charging of devices in the high resistance state (HRS), photocurrent in the low resistance state (LRS), and lowering of the set voltage (required to go from the HRS to LRS) and can be used in conjunction with a voltage bias to trigger switching from the HRS to the LRS. We demonstrate negative correlation between set voltage and applied laser power using a 632.8 nm laser source. We propose that, under illumination, increased electron injection and hence a higher rate of creation of Frenkel pairs in the oxide—precursors for the formation of conductive oxygen vacancy filaments—reduce switching voltages. Our results open up the possibility of light-triggered RRAM devices.

Spatial nonuniformity in resistive-switching memory effects of NiO.

PubMed

Oka, Keisuke; Yanagida, Takeshi; Nagashima, Kazuki; Kanai, Masaki; Kawai, Tomoji; Kim, Jin-Soo; Park, Bae Ho

2011-08-17

Electrically driven resistance change phenomenon in metal/NiO/metal junctions, so-called resistive switching (RS), is a candidate for next-generation universal nonvolatile memories. However, the knowledge as to RS mechanisms is unfortunately far from comprehensive, especially the spatial switching location, which is crucial information to design reliable devices. In this communication, we demonstrate the identification of the spatial switching location of bipolar RS by introducing asymmetrically passivated planar NiO nanowire junctions. We have successfully identified that the bipolar RS in NiO occurs near the cathode rather than the anode. This trend can be interpreted in terms of an electrochemical redox model based on ion migration and p-type conduction.

Non-exponential resistive switching in Ag2S memristors: a key to nanometer-scale non-volatile memory devices.

PubMed

Gubicza, Agnes; Csontos, Miklós; Halbritter, András; Mihály, György

2015-03-14

The dynamics of resistive switchings in nanometer-scale metallic junctions formed between an inert metallic tip and an Ag film covered by a thin Ag2S layer are investigated. Our thorough experimental analysis and numerical simulations revealed that the resistance change upon a switching bias voltage pulse exhibits a strongly non-exponential behaviour yielding markedly different response times at different bias levels. Our results demonstrate the merits of Ag2S nanojunctions as nanometer-scale non-volatile memory cells with stable switching ratios, high endurance as well as fast response to write/erase, and an outstanding stability against read operations at technologically optimal bias and current levels.

Improvement of multi-level resistive switching characteristics in solution-processed AlO x -based non-volatile resistive memory using microwave irradiation

NASA Astrophysics Data System (ADS)

Kim, Seung-Tae; Cho, Won-Ju

2018-01-01

We fabricated a resistive random access memory (ReRAM) device on a Ti/AlO x /Pt structure with solution-processed AlO x switching layer using microwave irradiation (MWI), and demonstrated multi-level cell (MLC) operation. To investigate the effect of MWI power on the MLC characteristics, post-deposition annealing was performed at 600-3000 W after AlO x switching layer deposition, and the MLC operation was compared with as-deposited (as-dep) and conventional thermally annealing (CTA) treated devices. All solution-processed AlO x -based ReRAM devices exhibited bipolar resistive switching (BRS) behavior. We found that these devices have four-resistance states (2 bits) of MLC operation according to the modulation of the high-resistance state (HRSs) through reset voltage control. Particularly, compared to the as-dep and CTA ReRAM devices, the MWI-treated ReRAM devices showed a significant increase in the memory window and stable endurance for multi-level operation. Moreover, as the MWI power increased, excellent MLC characteristics were exhibited because the resistance ratio between each resistance state was increased. In addition, it exhibited reliable retention characteristics without deterioration at 25 °C and 85 °C for 10 000 s. Finally, the relationship between the chemical characteristics of the solution-processed AlO x switching layer and BRS-based multi-level operation according to the annealing method and MWI power was investigated using x-ray photoelectron spectroscopy.

Methods for resistive switching of memristors

DOEpatents

Mickel, Patrick R.; James, Conrad D.; Lohn, Andrew; Marinella, Matthew; Hsia, Alexander H.

2016-05-10

The present invention is directed generally to resistive random-access memory (RRAM or ReRAM) devices and systems, as well as methods of employing a thermal resistive model to understand and determine switching of such devices. In particular example, the method includes generating a power-resistance measurement for the memristor device and applying an isothermal model to the power-resistance measurement in order to determine one or more parameters of the device (e.g., filament state).

High-performance black phosphorus top-gate ferroelectric transistor for nonvolatile memory applications

NASA Astrophysics Data System (ADS)

Lee, Young Tack; Hwang, Do Kyung; Choi, Won Kook

2016-10-01

Two-dimensional (2D) van der Waals (vdW) atomic crystals have been extensively studied and significant progress has been made. The newest 2D vdW material, called black phosphorus (BP), has attracted considerable attention due to its unique physical properties, such as its being a singlecomponent material like graphene, and its having a high mobility and direct band gap. Here, we report on a high-performance BP nanosheet based ferroelectric field effect transistor (FeFET) with a poly(vinylidenefluoride-trifluoroethylene) top-gate insulator for a nonvolatile memory application. The BP FeFETs show the highest linear hole mobility of 563 cm2/Vs and a clear memory window of more than 15 V. For more advanced nonvolatile memory circuit applications, two different types of resistive-load and complementary ferroelectric memory inverters were implemented, which showed distinct memory on/off switching characteristics.

Influence of oxygen doping on resistive-switching characteristic of a-Si/c-Si device

NASA Astrophysics Data System (ADS)

Zhang, Jiahua; Chen, Da; Huang, Shihua

2017-12-01

The influence of oxygen doping on resistive-switching characteristics of Ag/a-Si/p+-c-Si device was investigated. By oxygen doping in the growth process of amorphous silicon, the device resistive-switching performances, such as the ON/OFF resistance ratios, yield and stability were improved, which may be ascribed to the significant reduction of defect density because of oxygen incorporation. The device I-V characteristics are strongly dependent on the oxygen doping concentration. As the oxygen doping concentration increases, the Si-rich device gradually transforms to an oxygen-rich device, and the device yield, switching characteristics, and stability may be improved for silver/oxygen-doped a-Si/p+-c-Si device. Finally, the device resistive-switching mechanism was analyzed. Project supported by the Zhejiang Provincial Natural Science Foundation of China (No. LY17F040001), the Open Project Program of Surface Physics Laboratory (National Key Laboratory) of Fudan University (No. KF2015_02), the Open Project Program of National Laboratory for Infrared Physics, Chinese Academy of Sciences (No. M201503), the Zhejiang Provincial Science and Technology Key Innovation Team (No. 2011R50012), and the Zhejiang Provincial Key Laboratory (No. 2013E10022).

Three-dimensional resistivity and switching between correlated electronic states in 1T-TaS2

NASA Astrophysics Data System (ADS)

Svetin, Damjan; Vaskivskyi, Igor; Brazovskii, Serguei; Mihailovic, Dragan

2017-04-01

Recent demonstrations of controlled switching between different ordered macroscopic states by impulsive electromagnetic perturbations in complex materials have opened some fundamental questions on the mechanisms responsible for such remarkable behavior. Here we experimentally address the question of whether two-dimensional (2D) Mott physics can be responsible for unusual switching between states of different electronic order in the layered dichalcogenide 1T-TaS2, or it is a result of subtle inter-layer “orbitronic” re-ordering of its stacking structure. We report on in-plane (IP) and out-of-plane (OP) resistance switching by current-pulse injection at low temperatures. Elucidating the controversial theoretical predictions, we also report on measurements of the anisotropy of the electrical resistivity below room temperature. From the T-dependence of ρ⊥ and ρ||, we surmise that the resistivity is more consistent with collective motion than single particle diffusive or band-like transport. The relaxation dynamics of the metastable state for both IP and OP electron transport are seemingly governed by the same mesoscopic quantum re-ordering process. We conclude that 1T-TaS2 shows resistance switching arising from an interplay of both IP and OP correlations.

Engineering the switching dynamics of TiOx-based RRAM with Al doping

NASA Astrophysics Data System (ADS)

Trapatseli, Maria; Khiat, Ali; Cortese, Simone; Serb, Alexantrou; Carta, Daniela; Prodromakis, Themistoklis

2016-07-01

Titanium oxide (TiOx) has attracted a lot of attention as an active material for resistive random access memory (RRAM), due to its versatility and variety of possible crystal phases. Although existing RRAM materials have demonstrated impressive characteristics, like ultra-fast switching and high cycling endurance, this technology still encounters challenges like low yields, large variability of switching characteristics, and ultimately device failure. Electroforming has been often considered responsible for introducing irreversible damage to devices, with high switching voltages contributing to device degradation. In this paper, we have employed Al doping for tuning the resistive switching characteristics of titanium oxide RRAM. The resistive switching threshold voltages of undoped and Al-doped TiOx thin films were first assessed by conductive atomic force microscopy. The thin films were then transferred in RRAM devices and tested with voltage pulse sweeping, demonstrating that the Al-doped devices could on average form at lower potentials compared to the undoped ones and could support both analog and binary switching at potentials as low as 0.9 V. This work demonstrates a potential pathway for implementing low-power RRAM systems.

Switching kinetics of SiC resistive memory for harsh environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, K. A., E-mail: kam2g11@soton.ac.uk; Huang, R.; Groot, C. H. de

2015-07-15

Cu/a-SiC/Au resistive memory cells are measured using voltage pulses and exhibit the highest R{sub OFF}/R{sub ON} ratio recorded for any resistive memory. The switching kinetics are investigated and fitted to a numerical model, using thermal conductivity and resistivity properties of the dielectric. The SET mechanism of the Cu/a-SiC/Au memory cells is found to be due to ionic motion without joule heating contributions, whereas the RESET mechanism is found to be due to thermally assisted ionic motion. The conductive filament diameter is extracted to be around 4nm. The high thermal conductivity and resistivity for the Cu/a-SiC/Au memory cells result in slowmore » switching but with high thermal reliability and stability, showing potential for use in harsh environments. Radiation properties of SiC memory cells are investigated. No change was seen in DC sweep or pulsed switching nor in conductive mechanisms, up to 2Mrad(Si) using {sup 60}Co gamma irradiation.« less

Bipolar resistive switching of single gold-in-Ga2O3 nanowire.

PubMed

Hsu, Chia-Wei; Chou, Li-Jen

2012-08-08

We have fabricated single nanowire chips on gold-in-Ga(2)O(3) core-shell nanowires using the electron-beam lithography techniques and realized bipolar resistive switching characteristics having invariable set and reset voltages. We attribute the unique property of invariance to the built-in conduction path of gold core. This invariance allows us to fabricate many resistive switching cells with the same operating voltage by simple depositing repetitive metal electrodes along a single nanowire. Other characteristics of these core-shell resistive switching nanowires include comparable driving electric field with other thin film and nanowire devices and a remarkable on/off ratio more than 3 orders of magnitude at a low driving voltage of 2 V. A smaller but still impressive on/off ratio of 10 can be obtained at an even lower bias of 0.2 V. These characteristics of gold-in-Ga(2)O(3) core-shell nanowires make fabrication of future high-density resistive memory devices possible.

Change from lung adenocarcinoma to small cell lung cancer as a mechanism of resistance to afatinib.

PubMed

Manca, Paolo; Russano, Marco; Pantano, Francesco; Tonini, Giuseppe; Santini, Daniele

2017-08-29

We report the case of a patient affected by advanced EGFR mutation-positive lung who experienced resistance to therapy during treatment with Afatinib through the occurrence of a switch of tumor histotype to small cell lung cancer (SCLC) with features of a G3 neuroendocrine carcinoma. Unexpectedly, the switch to SCLC histotype occurred in the only site not responsive to afatinib and subsequently the most responsive to chemotherapy. Our case shows that occurrence of switch to SCLC is a possible mechanism of resistance during treatment with Afatinib.

Effects of Gibbs free energy of interfacial metal oxide on resistive switching characteristics of solution-processed HfOx films

NASA Astrophysics Data System (ADS)

Hsu, Chih-Chieh; Sun, Jhen-Kai; Tsao, Che-Chang; Chuang, Po-Yang

2017-08-01

Effects of bottom electrodes (BEs) of Al, Mo, and Pt on resistive switching characteristics of sol-gel HfOx films were investigated in this work. To avoid influences of plasma or thermal energy on HfOx RS characteristic, the top electrodes were formed by pressing indium balls onto the HfOx surface rather than by using a sputter or an evaporator. When using Mo as the BE, the as-deposited HfOx film can give a forming-free resistive switching behavior with low set/reset voltages of 0.28 V / - 0.54 V. In contrast, non-switching characteristics of the HfOx films were observed when using Al and Pt as the BEs. The HfOx conduction current was found to be highly dependent on the BE. However, when an annealing process at 350 °C in an oxygen ambient was performed to the HfOx films on different BEs, the resistive switching behavior of the HfOx/Mo was absent while it can be found in the HfOx/Al sample. Differences in I-V characteristics of the HfOx films on different BEs were explained by considering Gibbs free energies of interfacial oxide layers. X-ray photoelectron spectroscopy (XPS) depth profile was used to examine the interfacial oxide layer. The resistive switching mechanism was also studied.

In-operando hard X-ray photoelectron spectroscopy study on the impact of current compliance and switching cycles on oxygen and carbon defects in resistive switching Ti/HfO{sub 2}/TiN cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sowinska, Malgorzata, E-mail: sowinska@ihp-microelectronics.com; Bertaud, Thomas; Walczyk, Damian

2014-05-28

In this study, direct experimental materials science evidence of the important theoretical prediction for resistive random access memory (RRAM) technologies that a critical amount of oxygen vacancies is needed to establish stable resistive switching in metal-oxide-metal samples is presented. In detail, a novel in-operando hard X-ray photoelectron spectroscopy technique is applied to non-destructively investigates the influence of the current compliance and direct current voltage sweep cycles on the Ti/HfO{sub 2} interface chemistry and physics of resistive switching Ti/HfO{sub 2}/TiN cells. These studies indeed confirm that current compliance is a critical parameter to control the amount of oxygen vacancies in themore » conducting filaments in the oxide layer during the RRAM cell operation to achieve stable switching. Furthermore, clear carbon segregation towards the Ti/HfO{sub 2} interface under electrical stress is visible. Since carbon impurities impact the oxygen vacancy defect population under resistive switching, this dynamic carbon segregation to the Ti/HfO{sub 2} interface is suspected to negatively influence RRAM device endurance. Therefore, these results indicate that the RRAM materials engineering needs to include all impurities in the dielectric layer in order to achieve reliable device performance.« less

Effect of forming-gas annealing on the resistance switching effect of heteroepitaxial Nb:SrTiO3 film on Si substrate

NASA Astrophysics Data System (ADS)

Xiang, Wenfeng; Hu, Minghao; Liu, Yi

2017-12-01

The influence of forming-gas annealing (FGA) on the resistance switching effect of epitaxial Nb:SrTiO3 [Nb-doped strontium titanates (NbSTO)] films on Si substrate has been investigated. The resistance values at low and high resistance states for NbSTO films after FGA are about two orders of magnitude lower than those of the as-deposited sample, which may effectively decrease the power dissipation of devices. Hysteretic I-V characteristic curves show that the stability of FGA sample was improved. The resistance ratio of NbSTO films measured via pulse voltage increased from 1.0-1.2 to 3.2-3.6 after FGA. Moreover, the resistance ratio of the FGA sample gradually increased with increasing number of cycles. These results indicate that FGA improves the resistance switching characteristics of NbSTO films. In addition, the underlying mechanism was discussed.

Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

NASA Astrophysics Data System (ADS)

Long, Shibing; Liu, Qi; Lv, Hangbing; Li, Yingtao; Wang, Yan; Zhang, Sen; Lian, Wentai; Zhang, Kangwei; Wang, Ming; Xie, Hongwei; Liu, Ming

2011-03-01

Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO2 film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO2:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I- V relationship of low resistance state (LRS) and the dependence of LRS resistance ( R ON) and reset current ( I reset) on the set current compliance ( I comp) indicate that the observed resistive switching characteristics of the Ag/ZrO2:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.

Low-power resistive random access memory by confining the formation of conducting filaments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Yi-Jen; Lee, Si-Chen, E-mail: sclee@ntu.edu.tw; Shen, Tzu-Hsien

2016-06-15

Owing to their small physical size and low power consumption, resistive random access memory (RRAM) devices are potential for future memory and logic applications in microelectronics. In this study, a new resistive switching material structure, TiO{sub x}/silver nanoparticles/TiO{sub x}/AlTiO{sub x}, fabricated between the fluorine-doped tin oxide bottom electrode and the indium tin oxide top electrode is demonstrated. The device exhibits excellent memory performances, such as low operation voltage (<±1 V), low operation power, small variation in resistance, reliable data retention, and a large memory window. The current-voltage measurement shows that the conducting mechanism in the device at the high resistancemore » state is via electron hopping between oxygen vacancies in the resistive switching material. When the device is switched to the low resistance state, conducting filaments are formed in the resistive switching material as a result of accumulation of oxygen vacancies. The bottom AlTiO{sub x} layer in the device structure limits the formation of conducting filaments; therefore, the current and power consumption of device operation are significantly reduced.« less

Gallium Nitride Monolithic Microwave Integrated Circuit Designs Using 0.25-micro m Qorvo Process

DTIC Science & Technology

2017-07-27

and sensor systems of interest to US Defense Department applications, particularly for next-generation radar systems. Broadband, efficient, high...A simple GaN high-electron-mobility-transistor (HEMT) TR single-pull double- throw (SPDT) switch consists of at least 2 series- and 2 shunt... simple TR switch that works well up to 6 GHz is shown in Figs. 4 (layout) and 5 (simulation). Complementary DC-bias voltages are applied at inputs A

Attaching Copper Wires to Magnetic-Reed-Switch Leads

NASA Technical Reports Server (NTRS)

Kamila, Rudolf

1987-01-01

Bonding method reliably joins copper wires to short iron-alloy leads from glass-encased dry magnetic-reed switch without disturbing integrity of glass-to-metal seal. Joint resistant to high temperatures and has low electrical resistance.

Observation of indium ion migration-induced resistive switching in Al/Mg{sub 0.5}Ca{sub 0.5}TiO{sub 3}/ITO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Zong-Han; Wang, Yeong-Her, E-mail: yhw@ee.ncku.edu.tw

2016-08-01

Understanding switching mechanisms is very important for resistive random access memory (RRAM) applications. This letter reports an investigation of Al/Mg{sub 0.5}Ca{sub 0.5}TiO{sub 3} (MCTO)/ITO RRAM, which exhibits bipolar resistive switching behavior. The filaments that connect Al electrodes with indium tin oxide electrodes across the MCTO layer at a low-resistance state are identified. The filaments composed of In{sub 2}O{sub 3} crystals are observed through energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, nanobeam diffraction, and comparisons of Joint Committee on Powder Diffraction Standards (JCPDS) cards. Finally, a switching mechanism resulting from an electrical field induced by In{sup 3+} ion migration is proposed.more » In{sup 3+} ion migration forms/ruptures the conductive filaments and sets/resets the RRAM device.« less

Improved multi-level capability in Si3N4-based resistive switching memory using continuous gradual reset switching

NASA Astrophysics Data System (ADS)

Kim, Sungjun; Park, Byung-Gook

2017-01-01

In this letter, we compare three different types of reset switching behavior in a bipolar resistive random-access memory (RRAM) system that is housed in a Ni/Si3N4/Si structure. The abrupt, step-like gradual and continuous gradual reset transitions are largely determined by the low-resistance state (LRS). For abrupt reset switching, the large conducting path shows ohmic behavior or has a weak nonlinear current-voltage (I-V) characteristics in the LRS. For gradual switching, including both the step-like and continuous reset types, trap-assisted direct tunneling is dominant in the low-voltage regime, while trap-assisted Fowler-Nordheim tunneling is dominant in the high-voltage regime, thus causing nonlinear I-V characteristics. More importantly, we evaluate the multi-level capabilities of the two different gradual switching types, including both step-like and continuous reset behavior, using identical and incremental voltage conditions. Finer control of the conductance level with good uniformity is achieved in continuous gradual reset switching when compared to that in step-like gradual reset switching. For continuous reset switching, a single conducting path, which initially has a tunneling gap, gradually responds to pulses with even and identical amplitudes, while for step-like reset switching, the multiple conducting paths only respond to incremental pulses to obtain effective multi-level states.

Highly sensitive self-complementary DNA nanoswitches triggered by polyelectrolytes.

PubMed

Wu, Jincai; Yu, Feng; Zhang, Zheng; Chen, Yong; Du, Jie; Maruyama, Atsushi

2016-01-07

Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(L-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation.

High-speed low-power photonic transistor devices based on optically-controlled gain or absorption to affect optical interference.

PubMed

Huang, Yingyan; Ho, Seng-Tiong

2008-10-13

We show that a photonic transistor device can be realized via the manipulation of optical interference by optically controlled gain or absorption in novel ways, resulting in efficient transistor signal gain and switching action. Exemplary devices illustrate two complementary device types with high operating speed, microm size, microW switching power, and switching gain. They can act in tandem to provide a wide variety of operations including wavelength conversion, pulse regeneration, and logical operations. These devices could have a Transistor Figure-of-Merits >10(5) times higher than current chi((3)) approaches and are highly attractive.

Electromechanical resistive switching via back-to-back Schottky junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Lijie, E-mail: L.Li@swansea.ac.uk

The physics of the electromechanical resistive switching is uncovered using the theory of back-to-back Schottky junctions combined with the quantum domain space charge transport. A theoretical model of the basic element of resistive switching devices realized by the metal-ZnO nanowires-metal structure has been created and analyzed. Simulation results show that the reverse biased Schottky junction and the air gap impedance dominate the current-voltage relation at higher external voltages; thereby electromechanically varying the air gap thickness causes the device exhibit resistive tuning characteristics. As the device dimension is in nanometre scale, investigation of the model based on quantum mechanics has alsomore » been conducted.« less

Abnormal bipolar resistive switching behavior in a Pt/GaO{sub 1.3}/Pt structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, D. Y.; Wu, Z. P.; Zhang, L. J.

2015-07-20

A stable and repeatable abnormal bipolar resistive switching behavior was observed in a Pt/GaO{sub 1.3}/Pt sandwich structure without an electroforming process. The low resistance state (LRS) and the high resistance state (HRS) of the device can be distinguished clearly and be switched reversibly under a train of the voltage pulses. The LRS exhibits a conduction of electron tunneling, while the HRS shows a conduction of Schottky-type. The observed phenomena are considered to be related to the migration of oxygen vacancies which changes the space charge region width of the metal/semiconductor interface and results in a different electron transport mechanism.

Few-Layer MoS2-Organic Thin-Film Hybrid Complementary Inverter Pixel Fabricated on a Glass Substrate.

PubMed

Lee, Hee Sung; Shin, Jae Min; Jeon, Pyo Jin; Lee, Junyeong; Kim, Jin Sung; Hwang, Hyun Chul; Park, Eunyoung; Yoon, Woojin; Ju, Sang-Yong; Im, Seongil

2015-05-13

Few-layer MoS2-organic thin-film hybrid complementary inverters demonstrate a great deal of device performance with a decent voltage gain of ≈12, a few hundred pW power consumption, and 480 Hz switching speed. As fabricated on glass, this hybrid CMOS inverter operates as a light-detecting pixel as well, using a thin MoS2 channel. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomic Layer Deposited Oxide-Based Nanocomposite Structures with Embedded CoPtx Nanocrystals for Resistive Random Access Memory Applications.

PubMed

Wang, Lai-Guo; Cao, Zheng-Yi; Qian, Xu; Zhu, Lin; Cui, Da-Peng; Li, Ai-Dong; Wu, Di

2017-02-22

Al 2 O 3 - or HfO 2 -based nanocomposite structures with embedded CoPt x nanocrystals (NCs) on TiN-coated Si substrates have been prepared by combination of thermal atomic layer deposition (ALD) and plasma-enhanced ALD for resistive random access memory (RRAM) applications. The impact of CoPt x NCs and their average size/density on the resistive switching properties has been explored. Compared to the control sample without CoPt x NCs, ALD-derived Pt/oxide/100 cycle-CoPt x NCs/TiN/SiO 2 /Si exhibits a typical bipolar, reliable, and reproducible resistive switching behavior, such as sharp distribution of RRAM parameters, smaller set/reset voltages, stable resistance ratio (≥10 2 ) of OFF/ON states, better switching endurance up to 10 4 cycles, and longer data retention over 10 5 s. The possible resistive switching mechanism based on nanocomposite structures of oxide/CoPt x NCs has been proposed. The dominant conduction mechanisms in low- and high-resistance states of oxide-based device units with embedded CoPt x NCs are Ohmic behavior and space-charge-limited current, respectively. The insertion of CoPt x NCs can effectively improve the formation of conducting filaments due to the CoPt x NC-enhanced electric field intensity. Besides excellent resistive switching performances, the nanocomposite structures also simultaneously present ferromagnetic property. This work provides a flexible pathway by combining PEALD and TALD compatible with state-of-the-art Si-based technology for multifunctional electronic devices applications containing RRAM.

Opportunity of spinel ferrite materials in nonvolatile memory device applications based on their resistive switching performances.

PubMed

Hu, Wei; Qin, Ni; Wu, Guangheng; Lin, Yanting; Li, Shuwei; Bao, Dinghua

2012-09-12

The opportunity of spinel ferrites in nonvolatile memory device applications has been demonstrated by the resistive switching performance characteristics of a Pt/NiFe(2)O(4)/Pt structure, such as low operating voltage, high device yield, long retention time (up to 10(5) s), and good endurance (up to 2.2 × 10(4) cycles). The dominant conduction mechanisms are Ohmic conduction in the low-resistance state and in the lower-voltage region of the high-resistance state and Schottky emission in the higher-voltage region of the high-resistance state. On the basis of measurements of the temperature dependence of the resistances and magnetic properties in different resistance states, we explain the physical mechanism of resistive switching of Pt/NiFe(2)O(4)/Pt devices using the model of formation and rupture of conducting filaments by considering the thermal effect of oxygen vacancies and changes in the valences of cations due to the redox effect.

An electromagnetically actuated fiber optic switch using magnetized ferromagnetic materials

NASA Astrophysics Data System (ADS)

Pandojirao-S, Praveen; Dhaubanjar, Naresh; Phuyal, Pratibha C.; Chiao, Mu; Chiao, J.-C.

2008-03-01

This paper presents the design, fabrication and testing of a fiber optic switch actuated electromagnetically. The ferromagnetic gel coated optical fiber is actuated using external electromagnetic fields. The ferromagnetic gel consists of ferromagnetic powders dispersed in epoxy. The fabrication utilizes a simple cost-effective coating setup. A direct fiberto-fiber alignment eliminates the need for complementary optical parts and the displacement of fiber switches the laser coupling. The magnetic characteristics of magnetized ferromagnetic materials are performed using alternating gradient magnetometer and the magnetic hysteresis curves are measured for different ferromagnetic materials including iron, cobalt, and nickel. Optical fiber switches with various fiber lengths are actuated and their static and dynamic responses for the same volume of ferromagnetic gel are summarized. The highest displacement is 1.345 mm with an input current of 260mA. In this paper, the performance of fiber switches with various coating materials is presented.

RF MEMS microswitches design and characterization

NASA Astrophysics Data System (ADS)

Lafontan, Xavier; Dufaza, Christian; Robert, Michel; Perez, Guy; Pressecq, Francis

2000-08-01

This paper presents the work performed in MUMPs on RF MEMS micro-switch. Concepts, design and characterization of switches are studied. The study particularly focuses on the electrical resistance characterization and modelization. The switches developed uses two different principle: overflowed gold and hinged beam. The realized contacts exhibited high on resistance (~20(Omega) ) due to nanoscopics asperities of contacts and insulating interfacial films. Results of a typical contact cleaning method are also presented.

Forming-free colossal resistive switching effect in rare-earth-oxide Gd2O3 films for memristor applications

NASA Astrophysics Data System (ADS)

Cao, Xun; Li, Xiaomin; Gao, Xiangdong; Yu, Weidong; Liu, Xinjun; Zhang, Yiwen; Chen, Lidong; Cheng, Xinhong

2009-10-01

The reproducible forming-free resistive switching (RS) behavior in rare-earth-oxide Gd2O3 polycrystalline thin film was demonstrated. The characteristic of this forming-free RS was similar to that of other forming-necessary binary RS materials except that its initial resistance starts from not the high resistance state (HRS) but the low resistance state (LRS). An ultrahigh resistance switching ratio from HRS to LRS of about six to seven orders of magnitude was achieved at a bias voltage of 0.6 V. Mechanism analysis indicated that the existence of metallic Gd in the Gd2O3 films plays an important role in the forming-free RS performance. Our work provides a novel material with interesting RS behavior, which is beneficial to deepen our understanding of the origin of RS phenomenon.

Color tunable electroluminescence and resistance switching from a ZnO-nanorod-TaOx-p-GaN heterojunction.

PubMed

Zhao, J L; Teo, K L; Zheng, K; Sun, X W

2016-03-18

Well-aligned ZnO nanorods have been prepared on p-GaN-sapphire using a vapor phase transport (VPT) technique. A thin sputtered layer of TaOx is employed as the intermediate layer and an n-ZnO-TaOx-p-GaN heterojunction device has been achieved. The current transport of the heterojunction exhibited a typical resistance switching behavior, which originated from the filament forming and breaking in the TaOx layer. Color controllable electroluminescence (EL) was observed from the biased heterojunction at room temperature. Bluish-white wide band emission is achieved from the forward biased device in both the high resistance and low resistance states, while red emission can only be observed for the reverse biased device in the low resistance state. The correlation between the EL and resistance switching has been analyzed in-depth based on the interface band diagram of the heterojunction.

High resistance ratio of bipolar resistive switching in a multiferroic/high-K Bi(Fe0.95Cr0.05)O3/ZrO2/Pt heterostructure

NASA Astrophysics Data System (ADS)

Dong, B. W.; Miao, Jun; Han, J. Z.; Shao, F.; Yuan, J.; Meng, K. K.; Wu, Y.; Xu, X. G.; Jiang, Y.

2018-03-01

An novel heterostructure composed of multiferroic Bi(Fe0.95Cr0.05)O3 (BFCO) and high-K ZrO2 (ZO) layers is investigated. Ferroelectric and electrical properties of the BFZO/ZO heterostructure have been investigated. A pronounced bipolar ferroelectric resistive switching characteristic was achieved in the heterostructure at room temperature. Interestingly, the BFCO/ZO structures exhibit a reproducible resistive switching with a high On/Off resistance ratio ∼2×103 and long retention time. The relationship between polarization and band structure at the interface of BFCO/ZO bilayer under the positive and negative sweepings has been discussed. As a result, the BFCO/ZO multiferroic/high-K heterostructure with high On/Off resistance ratio and long retention characterizes, exhibits a potential in future nonvolatile memory application.

Resistive switching based on filaments in metal/PMMA/metal thin film devices

NASA Astrophysics Data System (ADS)

Wolf, Christoph; Nau, Sebastian; Sax, Stefan; Busby, Yan; Pireaux, Jean-Jacques; List-Kratochvil, Emil J. W.

2015-12-01

The working mechanism of unipolar organic resistive switching thin-film devices is investigated. On the basis of a metal/poly(methyl methacrylate)/metal model system, direct spectroscopic evidence for filament formation is obtained by three-dimensional (3D) imaging with time-of-flight secondary ion mass spectrometry. By means of alternative fabrication methods the claimed influence of metal implantation in the organic layer during fabrication is ruled out. Further, the stability of the resistive switches under oxygen and humidity is investigated leading to a deeper understanding of the processes governing the formation and rupture of filaments.

Electrode with transparent series resistance for uniform switching of optical modulation devices

DOEpatents

Tench, D Morgan [Camarillo, CA; Cunningham, Michael A [Thousand Oaks, CA; Kobrin, Paul H [Newbury Park, CA

2008-01-08

Switching uniformity of an optical modulation device for controlling the propagation of electromagnetic radiation is improved by use of an electrode comprising an electrically resistive layer that is transparent to the radiation. The resistive layer is preferably an innerlayer of a wide-bandgap oxide sandwiched between layers of indium tin oxide or another transparent conductor, and may be of uniform thickness, or may be graded so as to provide further improvement in the switching uniformity. The electrode may be used with electrochromic and reversible electrochemical mirror (REM) smart window devices, as well as display devices based on various technologies.

Composition-ratio influence on resistive switching behavior of solution-processed InGaZnO-based thin-film.

PubMed

Hwang, Yeong-Hyeon; Hwang, Inchan; Cho, Won-Ju

2014-11-01

The influence of composition ratio on the bipolar resistive switching behavior of resistive switching memory devices based on amorphous indium-gallium-zinc-oxide (a-IGZO) using the spin-coating process was investigated. To study the stoichiometric effects of the a-IGZO films on device characteristics, four devices with In/Ga/Zn stoichiometries of 1:1:1, 3:1:1, 1:3:1, and 1:1:3 were fabricated and characterized. The 3:1:1 film showed an ohmic behavior and the 1:1:3 film showed a rectifying switching behavior. The current-voltage characteristics of the a-IGZO films with stoichiometries of 1:1:1 and 1:3:1, however, showed a bipolar resistive memory switching behavior. We found that the three-fold increase in the gallium content ratio reduces the reset voltage from -0.9 to - 0.4 V and enhances the current ratio of high to low resistive states from 0.7 x 10(1) to 3 x 10(1). Our results show that the increase in the Ga composition ratio in the a-IGZO-based ReRAM cells effectively improves the device performance and reliability by increasing the initial defect density in the a-IGZO films.

Manipulating Conduction in Metal Oxide Semiconductors: Mechanism Investigation and Conductance Tuning in Doped Fe2O3 Hematite and Metal/Ga2O3/Metal Heterostructure

NASA Astrophysics Data System (ADS)

Zhao, Bo

This study aims at understanding the fundamental mechanisms of conduction in several metal oxide semiconductors, namely alpha-Fe2O 3 and beta-Ga2O3, and how it could be tuned to desired values/states to enable a wide range of application. In the first effort, by adding Ti dopant, we successfully turned Fe2O3 from insulating to conductive by fabricated compositionally and structurally well-defined epitaxial alpha-(TixFe1-x)2 O3(0001) films for x ≤ 0.09. All films were grown by oxygen plasma assisted molecular beam epitaxy on Al2O3(0001) sapphire substrate with a buffer layer of Cr2O3 to relax the strain from lattice mismatch. Van der Pauw resistivity and Hall effect measurements reveal carrier concentrations between 1019 and 1020 cm-3 at room temperature and mobilities in the range of 0.1 to 0.6 cm2/V˙s. Such low mobility, unlike conventional band-conduction semiconductor, was attributed to hopping mechanism due to strong electron-phonon interaction in the lattice. More interestingly, conduction mechanism transitions from small-polaron hopping at higher temperatures to variable range hopping at lower temperatures with a transition temperature between 180 to 140 K. Consequently, by adding Ti dopant, conductive Fe 2O3 hematite thin films were achieved with a well-understood conducting mechanism that could guide further device application such as spin transistor and water splitting. In the case of Ga2O3, while having a band gap as high as 5 eV, they are usually conductive for commercially available samples due to unintentional Si doping. However, we discovered the conductance could be repeatedly switched between high resistance state and low resistance state when made into metal/Ga2O3 /metal heterostructure. However, to obtain well controlled switching process with consistent switching voltages and resistances, understanding switching mechanism is the key. In this study, we fabricated resistive switching devices utilizing a Ni/Ga2O3/Ir heterostructure. Bipolar switching, non-volatility, and repeatable switching are tested for the devices fabricated. Following previous discoveries on Ni/Ga2O3 single crystal which shows interface barrier type change (Schottky ↔ Ohmic) upon annealing accompanied by defects migration, characterization of the interface behavior on resistive switching cell Ni/Ga2O 3(thin film)/Ir under two different resistive states was performed using X-ray photoemission spectroscopy (XPS). Most interestingly, feathers in XPS spectrum of Ga allow for a unique nondestructive approach to investigate interface by XPS through electron transparent top contact. Theoretical modeling shows that Ga migrate towards the interface upon switching to low resistive state, indicating a possible mechanism that involves interfacial switch through barrier height modifying. Such device holds potential to become the next generation of non-volatile memory device, resistive RAM.

Flexible non-volatile memory devices based on organic semiconductors

NASA Astrophysics Data System (ADS)

Cosseddu, Piero; Casula, Giulia; Lai, Stefano; Bonfiglio, Annalisa

2015-09-01

The possibility of developing fully organic electronic circuits is critically dependent on the ability to realize a full set of electronic functionalities based on organic devices. In order to complete the scene, a fundamental element is still missing, i.e. reliable data storage. Over the past few years, a considerable effort has been spent on the development and optimization of organic polymer based memory elements. Among several possible solutions, transistor-based memories and resistive switching-based memories are attracting a great interest in the scientific community. In this paper, a route for the fabrication of organic semiconductor-based memory devices with performances beyond the state of the art is reported. Both the families of organic memories will be considered. A flexible resistive memory based on a novel combination of materials is presented. In particular, high retention time in ambient conditions are reported. Complementary, a low voltage transistor-based memory is presented. Low voltage operation is allowed by an hybrid, nano-sized dielectric, which is also responsible for the memory effect in the device. Thanks to the possibility of reproducibly fabricating such device on ultra-thin substrates, high mechanical stability is reported.

Zero energy-storage ballast for compact fluorescent lamps

DOEpatents

Schultz, W.N.; Thomas, R.J.

1999-08-31

A CFL ballast includes complementary-type switching devices connected in series with their gates connected together at a control node. The switching devices supply a resonant tank circuit which is tuned to a frequency near, but slightly lower than, the resonant frequency of a resonant control circuit. As a result, the tank circuit restarts oscillations immediately following each zero crossing of the bus voltage. Such rapid restarts avoid undesirable flickering while maintaining the operational advantages and high efficacy of the CFL ballast. 4 figs.

Zero energy-storage ballast for compact fluorescent lamps

DOEpatents

Schultz, William Newell; Thomas, Robert James

1999-01-01

A CFL ballast includes complementary-type switching devices connected in series with their gates connected together at a control node. The switching devices supply a resonant tank circuit which is tuned to a frequency near, but slightly lower than, the resonant frequency of a resonant control circuit. As a result, the tank circuit restarts oscillations immediately following each zero crossing of the bus voltage. Such rapid restarts avoid undesirable flickering while maintaining the operational advantages and high efficacy of the CFL ballast.

The Role of Working Memory Capacity and Interference Resolution Mechanisms in Task Switching

PubMed Central

Pettigrew, Corinne; Martin, Randi C.

2015-01-01

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response-distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response-distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching. PMID:26594895

The role of working memory capacity and interference resolution mechanisms in task switching.

PubMed

Pettigrew, Corinne; Martin, Randi C

2016-12-01

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response-distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. A total of 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response-distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores, which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching.

Metabolic impact of switching antipsychotic therapy to aripiprazole after weight gain: a pilot study.

PubMed

Kim, Sun H; Ivanova, Oxana; Abbasi, Fahim A; Lamendola, Cindy A; Reaven, Gerald M; Glick, Ira D

2007-08-01

Switching antipsychotic regimen to agents with low weight gain potential has been suggested in patients who gain excessive weight on their antipsychotic therapy. In an open-label pilot study, we evaluated the metabolic and psychiatric efficacy of switching to aripiprazole in 15 (9 men, 6 women) outpatients with schizophrenia who had gained at least 10 kg on their previous antipsychotic regimen. Individuals had evaluation of glucose tolerance, insulin resistance (insulin suppression test), lipid concentrations, and psychiatric status before and after switching to aripiprazole for 4 months. A third of the individuals could not psychiatrically tolerate switching to aripiprazole. In the remaining individuals, psychiatric symptoms significantly improved with decline in Clinical Global Impression Scale (by 26%, P = 0.015) and Positive and Negative Syndrome Scale (by 22%, P = 0.023). Switching to aripiprazole did not alter weight or metabolic outcomes (fasting glucose, insulin resistance, and lipid concentrations) in the patients of whom 73% were insulin resistant and 47% had impaired or diabetic glucose tolerance at baseline. In conclusion, switching to aripiprazole alone does not ameliorate the highly prevalent metabolic abnormalities in the schizophrenia population who have gained weight on other second generation antipsychotic medications.

Ferroelectric domain switching dynamics and memristive behaviors in BiFeO3-based magnetoelectric heterojunctions

NASA Astrophysics Data System (ADS)

Huang, Weichuan; Liu, Yukuai; Luo, Zhen; Hou, Chuangming; Zhao, Wenbo; Yin, Yuewei; Li, Xiaoguang

2018-06-01

The ferroelectric domain reversal dynamics and the corresponding resistance switching as well as the memristive behaviors in epitaxial BiFeO3 (BFO, ~150 nm) based multiferroic heterojunctions were systematically investigated. The ferroelectric domain reversal dynamics could be described by the nucleation-limited-switching model with the Lorentzian distribution of logarithmic domain-switching times. By engineering the domain states, multi and even continuously tunable resistances states, i.e. memristive states, could be non-volatilely achieved. The resistance switching speed can be as fast as 30 ns in the BFO-based multiferroic heterojunctions with a write voltage of ~20 V. By reducing the thickness of BFO, the La0.6Sr0.4MnO3/BFO (~5 nm)/La0.6Sr0.4MnO3 multiferroic tunnel junction (MFTJ) shows an even a quicker switching speed (20 ns) with a much lower operation voltage (~4 V). Importantly, the MFTJ exhibits a tunable interfacial magnetoelectric coupling related to the ferroelectric domain switching dynamics. These findings enrich the potential applications of multiferroic BFO based devices in high-speed, low-power, and high-density memories as well as future neuromorphic computational architectures.

Different threshold and bipolar resistive switching mechanisms in reactively sputtered amorphous undoped and Cr-doped vanadium oxide thin films

NASA Astrophysics Data System (ADS)

Rupp, Jonathan A. J.; Querré, Madec; Kindsmüller, Andreas; Besland, Marie-Paule; Janod, Etienne; Dittmann, Regina; Waser, Rainer; Wouters, Dirk J.

2018-01-01

This study investigates resistive switching in amorphous undoped and Cr-doped vanadium oxide thin films synthesized by sputtering deposition at low oxygen partial pressure. Two different volatile threshold switching characteristics can occur as well as a non-volatile bipolar switching mechanism, depending on device stack symmetry and Cr-doping. The two threshold switching types are associated with different crystalline phases in the conduction filament created during an initial forming step. The first kind of threshold switching, observed for undoped vanadium oxide films, was, by its temperature dependence, proven to be associated with a thermally triggered insulator-to-metal transition in a crystalline VO2 phase, whereas the threshold switch observed in chromium doped films is stable up to 90 °C and shows characteristics of an electronically induced Mott transition. This different behaviour for undoped versus doped films has been attributed to an increased stability of V3+ due to the Cr3+ doping (as evidenced by X-ray photoelectron spectroscopy analysis), probably favouring the creation of a crystalline Cr-doped V2O3 phase (rather than a Cr-doped VO2 phase) during the energetic forming step. The symmetric Pt/a-(VCr)Ox/Pt device showing high temperature stable threshold switching may find interesting applications as a possible new selector device for resistive switching memory (ReRAM) crossbar arrays.

Resistive switching effect of N-doped MoS2-PVP nanocomposites films for nonvolatile memory devices

NASA Astrophysics Data System (ADS)

Wu, Zijin; Wang, Tongtong; Sun, Changqi; Liu, Peitao; Xia, Baorui; Zhang, Jingyan; Liu, Yonggang; Gao, Daqiang

2017-12-01

Resistive memory technology is very promising in the field of semiconductor memory devices. According to Liu et al, MoS2-PVP nanocomposite can be used as an active layer material for resistive memory devices due to its bipolar resistive switching behavior. Recent studies have also indicated that the doping of N element can reduce the band gap of MoS2 nanosheets, which is conducive to improving the conductivity of the material. Therefore, in this paper, we prepared N-doped MoS2 nanosheets and then fabricated N-doped MoS2-PVP nanocomposite films by spin coating. Finally, the resistive memory [C. Tan et al., Chem. Soc. Rev. 44, 2615 (2015)], device with ITO/N-doped MoS2-PVP/Pt structure was fabricated. Study on the I-V characteristics shows that the device has excellent resistance switching effect. It is worth mentioning that our device possesses a threshold voltage of 0.75 V, which is much better than 3.5 V reported previously for the undoped counterparts. The above research shows that N-doped MoS2-PVP nanocomposite films can be used as the active layer of resistive switching memory devices, and will make the devices have better performance.

Negative voltage modulated multi-level resistive switching by using a Cr/BaTiOx/TiN structure and quantum conductance through evidence of H2O2 sensing mechanism.

PubMed

Chakrabarti, Somsubhra; Ginnaram, Sreekanth; Jana, Surajit; Wu, Zong-Yi; Singh, Kanishk; Roy, Anisha; Kumar, Pankaj; Maikap, Siddheswar; Qiu, Jian-Tai; Cheng, Hsin-Ming; Tsai, Ling-Na; Chang, Ya-Ling; Mahapatra, Rajat; Yang, Jer-Ren

2017-07-05

Negative voltage modulated multi-level resistive switching with quantum conductance during staircase-type RESET and its transport characteristics in Cr/BaTiO x /TiN structure have been investigated for the first time. The as-deposited amorphous BaTiO x film has been confirmed by high-resolution transmission electron microscopy. X-ray photo-electron spectroscopy shows different oxidation states of Ba in the switching material, which is responsible for tunable more than 10 resistance states by varying negative stop voltage owing to slow decay value of RESET slope (217.39 mV/decade). Quantum conductance phenomenon has been observed in staircase RESET cycle of the memory devices. By inspecting the oxidation states of Ba + and Ba 2+ through measuring H 2 O 2 with a low concentration of 1 nM in electrolyte/BaTiO x /SiO 2 /p-Si structure, the switching mechanism of each HRS level as well as the multi-level phenomenon has been explained by gradual dissolution of oxygen vacancy filament. Along with negative stop voltage modulated multi-level, current compliance dependent multi-level has also been demonstrated and resistance ratio up to 2000 has been achieved even for a thin (<5 nm) switching material. By considering oxidation-reduction of the conducting filaments, the current-voltage switching curve has been simulated as well. Hence, multi-level resistive switching of Cr/BaTiO x /TiN structure implies the promising applications in high dense, multistate non-volatile memories in near future.

Resistive switching mechanisms in random access memory devices incorporating transition metal oxides: TiO2, NiO and Pr0.7Ca0.3MnO3.

PubMed

Magyari-Köpe, Blanka; Tendulkar, Mihir; Park, Seong-Geon; Lee, Hyung Dong; Nishi, Yoshio

2011-06-24

Resistance change random access memory (RRAM) cells, typically built as MIM capacitor structures, consist of insulating layers I sandwiched between metal layers M, where the insulator performs the resistance switching operation. These devices can be electrically switched between two or more stable resistance states at a speed of nanoseconds, with long retention times, high switching endurance, low read voltage, and large switching windows. They are attractive candidates for next-generation non-volatile memory, particularly as a flash successor, as the material properties can be scaled to the nanometer regime. Several resistance switching models have been suggested so far for transition metal oxide based devices, such as charge trapping, conductive filament formation, Schottky barrier modulation, and electrochemical migration of point defects. The underlying fundamental principles of the switching mechanism still lack a detailed understanding, i.e. how to control and modulate the electrical characteristics of devices incorporating defects and impurities, such as oxygen vacancies, metal interstitials, hydrogen, and other metallic atoms acting as dopants. In this paper, state of the art ab initio theoretical methods are employed to understand the effects that filamentary types of stable oxygen vacancy configurations in TiO(2) and NiO have on the electronic conduction. It is shown that strong electronic interactions between metal ions adjacent to oxygen vacancy sites results in the formation of a conductive path and thus can explain the 'ON' site conduction in these materials. Implication of hydrogen doping on electroforming is discussed for Pr(0.7)Ca(0.3)MnO(3) devices based on electrical characterization and FTIR measurements.

Electrically tunable transport and resistive switching in doped Ca2RuO4

NASA Astrophysics Data System (ADS)

Shen, Shida; Williamson, Morgan; Cao, Gang; Zhou, Jianshi; Goodenough, John; Tsoi, Maxim

We study electronic transport properties of Cr doped (2.5%) Mott insulator Ca2RuO4 where electric fields were previously found to induce an insulator-to-metal switching with potential industrial applications. In our experiments we observe a continuous reduction in the resistivity of Ca2RuO4 as a function of increasing electrical bias followed by an abrupt switching at higher biases. Interestingly, the observed switching is non-destructive and requires opposite bias polarities to switch from high-to-low and low-to-high resistance states. Combination of 2-, 3-, and 4-probe measurements provide a means to shed light on the origin of the switching and distinguish between its bulk and interfacial contributions. This work was supported in part by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA, by NSF Grants DMR-1600057, DMR-1265162, and DMR-1122603, and by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2015-CRG4-2626.

Resistive switching memory devices composed of binary transition metal oxides using sol-gel chemistry.

PubMed

Lee, Chanwoo; Kim, Inpyo; Choi, Wonsup; Shin, Hyunjung; Cho, Jinhan

2009-04-21

We describe a novel and versatile approach for preparing resistive switching memory devices based on binary transition metal oxides (TMOs). Titanium isopropoxide (TIPP) was spin-coated onto platinum (Pt)-coated silicon substrates using a sol-gel process. The sol-gel-derived layer was converted into a TiO2 film by thermal annealing. A top electrode (Ag electrode) was then coated onto the TiO2 films to complete device fabrication. When an external bias was applied to the devices, a switching phenomenon independent of the voltage polarity (i.e., unipolar switching) was observed at low operating voltages (about 0.6 VRESET and 1.4 VSET). In addition, it was confirmed that the electrical properties (i.e., retention time, cycling test and switching speed) of the sol-gel-derived devices were comparable to those of vacuum deposited devices. This approach can be extended to a variety of binary TMOs such as niobium oxides. The reported approach offers new opportunities for preparing the binary TMO-based resistive switching memory devices allowing a facile solution processing.

Self-learning ability realized with a resistive switching device based on a Ni-rich nickel oxide thin film

NASA Astrophysics Data System (ADS)

Liu, Y.; Chen, T. P.; Liu, Z.; Yu, Y. F.; Yu, Q.; Li, P.; Fung, S.

2011-12-01

The resistive switching device based on a Ni-rich nickel oxide thin film exhibits an inherent learning ability of a neural network. The device has the short-term-memory and long-term-memory functions analogous to those of the human brain, depending on the history of its experience of voltage pulsing or sweeping. Neuroplasticity could be realized with the device, as the device can be switched from a high-resistance state to a low-resistance state due to the formation of stable filaments by a series of electrical pulses, resembling the changes such as the growth of new connections and the creation of new neurons in the brain in response to experience.

Time-programmable drug dosing allows the manipulation, suppression and reversal of antibiotic drug resistance in vitro

NASA Astrophysics Data System (ADS)

Yoshida, Mari; Reyes, Sabrina Galiñanes; Tsuda, Soichiro; Horinouchi, Takaaki; Furusawa, Chikara; Cronin, Leroy

2017-06-01

Multi-drug strategies have been attempted to prolong the efficacy of existing antibiotics, but with limited success. Here we show that the evolution of multi-drug-resistant Escherichia coli can be manipulated in vitro by administering pairs of antibiotics and switching between them in ON/OFF manner. Using a multiplexed cell culture system, we find that switching between certain combinations of antibiotics completely suppresses the development of resistance to one of the antibiotics. Using this data, we develop a simple deterministic model, which allows us to predict the fate of multi-drug evolution in this system. Furthermore, we are able to reverse established drug resistance based on the model prediction by modulating antibiotic selection stresses. Our results support the idea that the development of antibiotic resistance may be potentially controlled via continuous switching of drugs.

A 0.2 V Micro-Electromechanical Switch Enabled by a Phase Transition.

PubMed

Dong, Kaichen; Choe, Hwan Sung; Wang, Xi; Liu, Huili; Saha, Bivas; Ko, Changhyun; Deng, Yang; Tom, Kyle B; Lou, Shuai; Wang, Letian; Grigoropoulos, Costas P; You, Zheng; Yao, Jie; Wu, Junqiao

2018-04-01

Micro-electromechanical (MEM) switches, with advantages such as quasi-zero leakage current, emerge as attractive candidates for overcoming the physical limits of complementary metal-oxide semiconductor (CMOS) devices. To practically integrate MEM switches into CMOS circuits, two major challenges must be addressed: sub 1 V operating voltage to match the voltage levels in current circuit systems and being able to deliver at least millions of operating cycles. However, existing sub 1 V mechanical switches are mostly subject to significant body bias and/or limited lifetimes, thus failing to meet both limitations simultaneously. Here 0.2 V MEM switching devices with ≳10 6 safe operating cycles in ambient air are reported, which achieve the lowest operating voltage in mechanical switches without body bias reported to date. The ultralow operating voltage is mainly enabled by the abrupt phase transition of nanolayered vanadium dioxide (VO 2 ) slightly above room temperature. The phase-transition MEM switches open possibilities for sub 1 V hybrid integrated devices/circuits/systems, as well as ultralow power consumption sensors for Internet of Things applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zero-static power radio-frequency switches based on MoS2 atomristors.

PubMed

Kim, Myungsoo; Ge, Ruijing; Wu, Xiaohan; Lan, Xing; Tice, Jesse; Lee, Jack C; Akinwande, Deji

2018-06-28

Recently, non-volatile resistance switching or memristor (equivalently, atomristor in atomic layers) effect was discovered in transitional metal dichalcogenides (TMD) vertical devices. Owing to the monolayer-thin transport and high crystalline quality, ON-state resistances below 10 Ω are achievable, making MoS 2 atomristors suitable as energy-efficient radio-frequency (RF) switches. MoS 2 RF switches afford zero-hold voltage, hence, zero-static power dissipation, overcoming the limitation of transistor and mechanical switches. Furthermore, MoS 2 switches are fully electronic and can be integrated on arbitrary substrates unlike phase-change RF switches. High-frequency results reveal that a key figure of merit, the cutoff frequency (f c ), is about 10 THz for sub-μm 2 switches with favorable scaling that can afford f c above 100 THz for nanoscale devices, exceeding the performance of contemporary switches that suffer from an area-invariant scaling. These results indicate a new electronic application of TMDs as non-volatile switches for communication platforms, including mobile systems, low-power internet-of-things, and THz beam steering.

Modeling and experimental study of resistive switching in vertically aligned carbon nanotubes

NASA Astrophysics Data System (ADS)

Ageev, O. A.; Blinov, Yu F.; Ilina, M. V.; Ilin, O. I.; Smirnov, V. A.

2016-08-01

Model of the resistive switching in vertically aligned carbon nanotube (VA CNT) taking into account the processes of deformation, polarization and piezoelectric charge accumulation have been developed. Origin of hysteresis in VA CNT-based structure is described. Based on modeling results the VACNTs-based structure has been created. The ration resistance of high-resistance to low-resistance states of the VACNTs-based structure amounts 48. The correlation the modeling results with experimental studies is shown. The results can be used in the development nanoelectronics devices based on VA CNTs, including the nonvolatile resistive random-access memory.

Demonstration of Synaptic Behaviors and Resistive Switching Characterizations by Proton Exchange Reactions in Silicon Oxide

PubMed Central

Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Pan, Chih-Hung; Chang, Ting-Chang; Lee, Jack C.

2016-01-01

We realize a device with biological synaptic behaviors by integrating silicon oxide (SiOx) resistive switching memory with Si diodes. Minimal synaptic power consumption due to sneak-path current is achieved and the capability for spike-induced synaptic behaviors is demonstrated, representing critical milestones for the use of SiO2–based materials in future neuromorphic computing applications. Biological synaptic behaviors such as long-term potentiation (LTP), long-term depression (LTD) and spike-timing dependent plasticity (STDP) are demonstrated systematically using a comprehensive analysis of spike-induced waveforms, and represent interesting potential applications for SiOx-based resistive switching materials. The resistive switching SET transition is modeled as hydrogen (proton) release from (SiH)2 to generate the hydrogen bridge defect, and the RESET transition is modeled as an electrochemical reaction (proton capture) that re-forms (SiH)2. The experimental results suggest a simple, robust approach to realize programmable neuromorphic chips compatible with large-scale CMOS manufacturing technology. PMID:26880381

Forming free and ultralow-power erase operation in atomically crystal TiO2 resistive switching

NASA Astrophysics Data System (ADS)

Dai, Yawei; Bao, Wenzhong; Hu, Linfeng; Liu, Chunsen; Yan, Xiao; Chen, Lin; Sun, Qingqing; Ding, Shijin; Zhou, Peng; Zhang, David Wei

2017-06-01

Two-dimensional layered materials (2DLMs) have attracted broad interest from fundamental sciences to industrial applications. Their applications in memory devices have been demonstrated, yet much still remains to explore optimal materials and device structure for practical application. In this work, a forming-free, bipolar resistive switching behavior are demonstrated in 2D TiO2-based resistive random access memory (RRAM). Physical adsorption method is adopted to achieve high quality, continuous 2D TiO2 network efficiently. The 2D TiO2 RRAM devices exhibit superior properties such as fast switching capability (20 ns of erase operation) and extremely low erase energy consumption (0.16 fJ). Furthermore, the resistive switching mechanism is attributed to the formation and rupture of oxygen vacancies-based percolation path in 2D TiO2 crystals. Our results pave the way for the implementation of high performance 2DLMs-based RRAM in the next generation non-volatile memory (NVM) application.

Demonstration of Synaptic Behaviors and Resistive Switching Characterizations by Proton Exchange Reactions in Silicon Oxide

NASA Astrophysics Data System (ADS)

Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Pan, Chih-Hung; Chang, Ting-Chang; Lee, Jack C.

2016-02-01

We realize a device with biological synaptic behaviors by integrating silicon oxide (SiOx) resistive switching memory with Si diodes. Minimal synaptic power consumption due to sneak-path current is achieved and the capability for spike-induced synaptic behaviors is demonstrated, representing critical milestones for the use of SiO2-based materials in future neuromorphic computing applications. Biological synaptic behaviors such as long-term potentiation (LTP), long-term depression (LTD) and spike-timing dependent plasticity (STDP) are demonstrated systematically using a comprehensive analysis of spike-induced waveforms, and represent interesting potential applications for SiOx-based resistive switching materials. The resistive switching SET transition is modeled as hydrogen (proton) release from (SiH)2 to generate the hydrogen bridge defect, and the RESET transition is modeled as an electrochemical reaction (proton capture) that re-forms (SiH)2. The experimental results suggest a simple, robust approach to realize programmable neuromorphic chips compatible with large-scale CMOS manufacturing technology.

The role of oxygen vacancies in resistive switching behavior of organic-TiO2 hybrid composite

NASA Astrophysics Data System (ADS)

Zhang, Jiahua; Chen, Da; Huang, Shihua

2017-10-01

Effects of polyethylene glycol (PEG) on resistive switching behaviors and mechanisms in organic-TiO2 hybrid composites were investigated. The reversed current-voltage curves in the negative bias during the initial voltage sweeps were first observed in the composites annealed at 150, 200 and 250 °C, which is ascribed to the accumulation of oxygen vacancies and the inhibition effect of polarities of PEG chains. In addition, the volatility of composites with relatively high content of PEG is caused by the inhibition effect of PEG on creating oxygen vacancies. The formation and rupture of oxygen-vacancy filaments was considered as the resistive switching mechanism. Finally, the charging and discharging process in PEG-TiO2 composite annealed at 150 °C results in the instability of the electron-occupied oxygen vacancies and the inhibition of PEG chains. This study demonstrates a new way to investigate the interaction between polymers and TiO2 for understanding the resistive switching mechanism of TiO2-based memories.

Analysis of the Bipolar Resistive Switching Behavior of a Biocompatible Glucose Film for Resistive Random Access Memory.

PubMed

Park, Sung Pyo; Tak, Young Jun; Kim, Hee Jun; Lee, Jin Hyeok; Yoo, Hyukjoon; Kim, Hyun Jae

2018-06-01

Resistive random access memory (RRAM) devices are fabricated through a simple solution process using glucose, which is a natural biomaterial for the switching layer of RRAM. The fabricated glucose-based RRAM device shows nonvolatile bipolar resistive switching behavior, with a switching window of 10 3 . In addition, the endurance and data retention capability of glucose-based RRAM exhibit stable characteristics up to 100 consecutive cycles and 10 4 s under constant voltage stress at 0.3 V. The interface between the top electrode and the glucose film is carefully investigated to demonstrate the bipolar switching mechanism of the glucose-based RRAM device. The glucose based-RRAM is also evaluated on a polyimide film to verify the possibility of a flexible platform. Additionally, a cross-bar array structure with a magnesium electrode is prepared on various substrates to assess the degradability and biocompatibility for the implantable bioelectronic devices, which are harmless and nontoxic to the human body. It is expected that this research can provide meaningful insights for developing the future bioelectronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Uniting Gradual and Abrupt set Processes in Resistive Switching Oxides

NASA Astrophysics Data System (ADS)

Fleck, Karsten; La Torre, Camilla; Aslam, Nabeel; Hoffmann-Eifert, Susanne; Böttger, Ulrich; Menzel, Stephan

2016-12-01

Identifying limiting factors is crucial for a better understanding of the dynamics of the resistive switching phenomenon in transition-metal oxides. This improved understanding is important for the design of fast-switching, energy-efficient, and long-term stable redox-based resistive random-access memory devices. Therefore, this work presents a detailed study of the set kinetics of valence change resistive switches on a time scale from 10 ns to 104 s , taking Pt /SrTiO3/TiN nanocrossbars as a model material. The analysis of the transient currents reveals that the switching process can be subdivided into a linear-degradation process that is followed by a thermal runaway. The comparison with a dynamical electrothermal model of the memory cell allows the deduction of the physical origin of the degradation. The origin is an electric-field-induced increase of the oxygen-vacancy concentration near the Schottky barrier of the Pt /SrTiO3 interface that is accompanied by a steadily rising local temperature due to Joule heating. The positive feedback of the temperature increase on the oxygen-vacancy mobility, and thereby on the conductivity of the filament, leads to a self-acceleration of the set process.

Switching characteristics in Cu:SiO2 by chemical soak methods for resistive random access memory (ReRAM)

NASA Astrophysics Data System (ADS)

Chin, Fun-Tat; Lin, Yu-Hsien; Yang, Wen-Luh; Liao, Chin-Hsuan; Lin, Li-Min; Hsiao, Yu-Ping; Chao, Tien-Sheng

2015-01-01

A limited copper (Cu)-source Cu:SiO2 switching layer composed of various Cu concentrations was fabricated using a chemical soaking (CS) technique. The switching layer was then studied for developing applications in resistive random access memory (ReRAM) devices. Observing the resistive switching mechanism exhibited by all the samples suggested that Cu conductive filaments formed and ruptured during the set/reset process. The experimental results indicated that the endurance property failure that occurred was related to the joule heating effect. Moreover, the endurance switching cycle increased as the Cu concentration decreased. In high-temperature tests, the samples demonstrated that the operating (set/reset) voltages decreased as the temperature increased, and an Arrhenius plot was used to calculate the activation energy of the set/reset process. In addition, the samples demonstrated stable data retention properties when baked at 85 °C, but the samples with low Cu concentrations exhibited short retention times in the low-resistance state (LRS) during 125 °C tests. Therefore, Cu concentration is a crucial factor in the trade-off between the endurance and retention properties; furthermore, the Cu concentration can be easily modulated using this CS technique.

Resistive switching characteristics of manganese oxide thin film and nanoparticle assembly hybrid devices

NASA Astrophysics Data System (ADS)

Abbas, Haider; Park, Mi Ra; Abbas, Yawar; Hu, Quanli; Kang, Tae Su; Yoon, Tae-Sik; Kang, Chi Jung

2018-06-01

Improved resistive switching characteristics are demonstrated in a hybrid device with Pt/Ti/MnO (thin film)/MnO (nanoparticle)/Pt structure. The hybrid devices of MnO thin film and nanoparticle assembly were fabricated. MnO nanoparticles with an average diameter of ∼30 nm were chemically synthesized and assembled as a monolayer on a Pt bottom electrode. A MnO thin film of ∼40 nm thickness was deposited on the nanoparticle assembly to form the hybrid structure. Resistive switching could be induced by the formation and rupture of conducting filaments in the hybrid oxide layers. The hybrid device exhibited very stable unipolar switching with good endurance and retention characteristics. It showed a larger and stable memory window with a uniform distribution of SET and RESET voltages. Moreover, the conduction mechanisms of ohmic conduction, space-charge-limited conduction, Schottky emission, and Poole–Frenkel emission have been investigated as possible conduction mechanisms for the switching of the devices. Using MnO nanoparticles in the thin film and nanoparticle heterostructures enabled the appropriate control of resistive random access memory (RRAM) devices and markedly improved their memory characteristics.

Ultralow Power Consumption Flexible Biomemristors.

PubMed

Kim, Min-Kyu; Lee, Jang-Sik

2018-03-28

Low power consumption is the important requirement in memory devices for saving energy. In particular, improved energy efficiency is essential in implantable electronic devices for operation under a limited power supply. Here, we demonstrate the use of κ-carrageenan (κ-car) as the resistive switching layer to achieve memory that has low power consumption. A carboxymethyl (CM) group is introduced to the κ-car to increase its ionic conductivity. Ag was doped in CM:κ-car to improve the resistive switching properties of the devices. Memory devices based on Ag-doped CM:κ-car showed electroforming-free resistive switching. This device exhibited low reset voltage (∼0.05 V), fast switching speed (50 ns), and high on/off ratio (>10 3 ) under low compliance current (10 -5 A). Its power consumption (∼0.35 μW) is much lower than those of the previously reported biomemristors. The resistive switching may be a result of an electrochemical redox process and Ag filament formation in the CM:κ-car under an electric field. This biopolymer memory can also be fabricated on flexible substrate. This study verifies the feasibility of using biopolymers for applications to future implantable and biocompatible nanoelectronics.

Electrical control of exchange bias via oxygen migration across CoO-ZnO nanocomposite barrier

NASA Astrophysics Data System (ADS)

Li, Q.; Yan, S. S.; Xu, J.; Li, S. D.; Zhao, G. X.; Long, Y. Z.; Shen, T. T.; Zhang, K.; Zhang, J.

2016-12-01

We proposed a nanocomposite barrier CoO-ZnO for magnetism manipulation in Co/CoO-ZnO/Ag heterojunctions. Both electrical control of magnetism and resistive switching were realized in this junction. An electrical tunable exchange bias of CoO1-v (v denotes O vacancies) on Co films was realized using voltages below 1 volt. The magnetism modulation associated with resistive switching can be attributed to the oxygen ions migration between the insulating CoO1-v layer and the semiconductive ZnO1-v layer, which can cause both ferromagnetic phase and resistance switching of CoO1-v layer.

Study on Resistive Switching Property of Ti Doped Novel NiO Thin Films

NASA Astrophysics Data System (ADS)

Li, Y.; Zhao, G. Y.; Kou, Z. B.; Liu, J. C.; Zhu, R.

2018-01-01

Ti doped nickel oxide thin films have been fabricated by sol-gel dip-coating process using nickel acetate and tetrabutyl titanate as source materials. The effect of the amount of Ti dopant on the surface roughness, optical, chemical state and electrical properties of NiO: Ti thin films was observed by atomic force microscopy (AFM), Uv-vis spectroscopy, X-ray photoelectron spectroscopy(XPS) and I-V measurement, respectively. Results show that the Ti doping is an effective ways to improve the resistive switching behaviors and it is a convenient way to understand the mechanism of the resistive switching behaviors.

Piezotronic nanowire-based resistive switches as programmable electromechanical memories.

PubMed

Wu, Wenzhuo; Wang, Zhong Lin

2011-07-13

We present the first piezoelectrically modulated resistive switching device based on piezotronic ZnO nanowire (NW), through which the write/read access of the memory cell is programmed via electromechanical modulation. Adjusted by the strain-induced polarization charges created at the semiconductor/metal interface under externally applied deformation by the piezoelectric effect, the resistive switching characteristics of the cell can be modulated in a controlled manner, and the logic levels of the strain stored in the cell can be recorded and read out, which has the potential for integrating with NEMS technology to achieve micro/nanosystems capable for intelligent and self-sufficient multidimensional operations.

Strategies for dynamic soft-landing in capacitive microelectromechanical switches

NASA Astrophysics Data System (ADS)

Jain, Ankit; Nair, Pradeep R.; Alam, Muhammad A.

2011-06-01

Electromechanical dielectric degradation associated with the hard landing of movable electrode is a technology-inhibiting reliability concern for capacitive RF-MEMS switches. In this letter, we propose two schemes for dynamic soft-landing that obviate the need for external feedback circuitry. Instead, the proposed resistive and capacitive braking schemes can reduce impact velocity significantly without compromising other performance characteristics like pull-in voltage and pull-in time. Resistive braking is achieved by inserting a resistance in series with the voltage source whereas capacitive braking requires patterning of the electrode or the dielectric. Our results have important implications to the design and optimization of reliability aware electrostatically actuated MEMS switches.

A coaxial radial opening switch for a distributed-energy-store rail launcher

NASA Astrophysics Data System (ADS)

Upshaw, J. L.; Zowarka, R. C.

1984-03-01

The design, fabrication, and initial testing results for a coaxial radial opening switch for a distributed-energy-store rail launcher are presented. In this nonarcing switch, the voltage needed to transfer current to the rail launcher is generated in a fixed resistor sized to absorb the energy required to accomplish the switching. The coaxial geometry consisting of concentric rings allowed flexibility in defining the conductive and resistive portions of the switch, and also provided tight coupling by minimizing the inductance of the current path between the charging path and the load path to minimize the energy absorption requirements. The resistive portion of the switch is composed of a series of stacked circular steel ring laminations. Switching is completed in three intervals through radial actuation. The switch parts were machined from ETP 110 electrical tough pitch copper plate, 2000 series aluminum plate, and close-tolerance standed GFR epoxy. Current may be transferred at levels less than 20 kA.

Oxygen migration during resistance switching and failure of hafnium oxide memristors

DOE PAGES

Kumar, Suhas; Wang, Ziwen; Huang, Xiaopeng; ...

2017-03-06

While the recent establishment of the role of thermophoresis/diffusion-driven oxygen migration during resistance switching in metal oxide memristors provided critical insights required for memristor modeling, extended investigations of the role of oxygen migration during ageing and failure remain to be detailed. Such detailing will enable failure-tolerant design, which can lead to enhanced performance of memristor-based next-generation storage-class memory. Furthermore, we directly observed lateral oxygen migration using in-situ synchrotron x-ray absorption spectromicroscopy of HfO x memristors during initial resistance switching, wear over millions of switching cycles, and eventual failure, through which we determined potential physical causes of failure. Using this information,more » we reengineered devices to mitigate three failure mechanisms and demonstrated an improvement in endurance of about three orders of magnitude.« less

A resistance ratio change phenomenon observed in Al doped ZnO (AZO)/Cu(In1-xGax)Se2/Mo resistive switching memory device

NASA Astrophysics Data System (ADS)

Guo, Tao; Sun, Bai; Mao, Shuangsuo; Zhu, Shouhui; Xia, Yudong; Wang, Hongyan; Zhao, Yong; Yu, Zhou

2018-03-01

In this work, the Cu(In1-xGax)Se2 (CIGS), Al doped ZnO (AZO) and Mo has been used for constructing a resistive switching device with AZO/CIGS/Mo sandwich structure grown on a transparent glass substrate. The device represents a high-performance memory characteristics under ambient temperature. In particularly, a resistance ratio change phenomenon have been observed in our device for the first time.

Surviving bacterial sibling rivalry: inducible and reversible phenotypic switching in Paenibacillus dendritiformis.

PubMed

Be'er, Avraham; Florin, E-L; Fisher, Carolyn R; Swinney, Harry L; Payne, Shelley M

2011-01-01

Natural habitats vary in available nutrients and room for bacteria to grow, but successful colonization can lead to overcrowding and stress. Here we show that competing sibling colonies of Paenibacillus dendritiformis bacteria survive overcrowding by switching between two distinct vegetative phenotypes, motile rods and immotile cocci. Growing colonies of the rod-shaped bacteria produce a toxic protein, Slf, which kills cells of encroaching sibling colonies. However, sublethal concentrations of Slf induce some of the rods to switch to Slf-resistant cocci, which have distinct metabolic and resistance profiles, including resistance to cell wall antibiotics. Unlike dormant spores of P. dendritiformis, the cocci replicate. If cocci encounter conditions that favor rods, they secrete a signaling molecule that induces a switch to rods. Thus, in contrast to persister cells, P. dendritiformis bacteria adapt to changing environmental conditions by inducible and reversible phenotypic switching. In favorable environments, species may face space and nutrient limits due to overcrowding. Bacteria provide an excellent model for analyzing principles underlying overcrowding and regulation of density in nature, since their population dynamics can be easily and accurately assessed under controlled conditions. We describe a newly discovered mechanism for survival of a bacterial population during overcrowding. When competing with sibling colonies, Paenibacillus dendritiformis produces a lethal protein (Slf) that kills cells at the interface of encroaching colonies. Slf also induces a small proportion of the cells to switch from motile, rod-shaped cells to nonmotile, Slf-resistant, vegetative cocci. When crowding is reduced and nutrients are no longer limiting, the bacteria produce a signal that induces cocci to switch back to motile rods, allowing the population to spread. Genes encoding components of this phenotypic switching pathway are widespread among bacterial species, suggesting that this survival mechanism is not unique to P. dendritiformis.

Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

PubMed Central

Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

2017-01-01

Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region. PMID:28079056

A spot laser modulated resistance switching effect observed on n-type Mn-doped ZnO/SiO2/Si structure.

PubMed

Lu, Jing; Tu, Xinglong; Yin, Guilin; Wang, Hui; He, Dannong

2017-11-09

In this work, a spot laser modulated resistance switching (RS) effect is firstly observed on n-type Mn-doped ZnO/SiO 2 /Si structure by growing n-type Mn-doped ZnO film on Si wafer covered with a 1.2 nm native SiO 2 , which has a resistivity in the range of 50-80 Ω∙cm. The I-V curve obtained in dark condition evidences the structure a rectifying junction, which is further confirmed by placing external bias. Compared to the resistance state modulated by electric field only in dark (without illumination), the switching voltage driving the resistance state of the structure from one state to the other, shows clear shift under a spot laser illumination. Remarkably, the switching voltage shift shows a dual dependence on the illumination position and power of the spot laser. We ascribe this dual dependence to the electric filed produced by the redistribution of photo-generated carriers, which enhance the internal barrier of the hetero-junction. A complete theoretical analysis based on junction current and diffusion equation is presented. The dependence of the switching voltage on spot laser illumination makes the n-type Mn-doped ZnO/SiO 2 /Si structure sensitive to light, which thus allows for the integration of an extra functionality in the ZnO-based photoelectric device.

Investigation of resistance switching in SiO x RRAM cells using a 3D multi-scale kinetic Monte Carlo simulator

NASA Astrophysics Data System (ADS)

Sadi, Toufik; Mehonic, Adnan; Montesi, Luca; Buckwell, Mark; Kenyon, Anthony; Asenov, Asen

2018-02-01

We employ an advanced three-dimensional (3D) electro-thermal simulator to explore the physics and potential of oxide-based resistive random-access memory (RRAM) cells. The physical simulation model has been developed recently, and couples a kinetic Monte Carlo study of electron and ionic transport to the self-heating phenomenon while accounting carefully for the physics of vacancy generation and recombination, and trapping mechanisms. The simulation framework successfully captures resistance switching, including the electroforming, set and reset processes, by modeling the dynamics of conductive filaments in the 3D space. This work focuses on the promising yet less studied RRAM structures based on silicon-rich silica (SiO x ) RRAMs. We explain the intrinsic nature of resistance switching of the SiO x layer, analyze the effect of self-heating on device performance, highlight the role of the initial vacancy distributions acting as precursors for switching, and also stress the importance of using 3D physics-based models to capture accurately the switching processes. The simulation work is backed by experimental studies. The simulator is useful for improving our understanding of the little-known physics of SiO x resistive memory devices, as well as other oxide-based RRAM systems (e.g. transition metal oxide RRAMs), offering design and optimization capabilities with regard to the reliability and variability of memory cells.

Rugged switch responds to minute pressure differentials

NASA Technical Reports Server (NTRS)

Friend, L. C.; Shaub, K. D.

1967-01-01

Pressure responsive switching device exhibits high sensitivity but is extremely rugged and resistant to large amplitude shock and velocity loading. This snap-action, single pole-double throw switch operates over a wide temperature range.

Resistive switching and memory effects of AgI thin film

NASA Astrophysics Data System (ADS)

Liang, X. F.; Chen, Y.; Shi, L.; Lin, J.; Yin, J.; Liu, Z. G.

2007-08-01

A memory device has been fabricated using an AgI film sandwiched between a Pt film and an Ag film with the lateral size of the device scaled down to 300 nm. The AgI film was made by the iodination of the Ag film at room temperature and under ambient pressure. The switching between high- and low-resistance states can be realized by applying voltages of different polarities. The switching can be performed under the application of voltage pulses with a 100 Hz frequency for ~103 times. The switching times are in the order of microseconds and the retention time is about a week. The switching effects are explained as the electrochemical growth and dissolution of Ag in AgI.

Hardware Acceleration Of Multi-Deme Genetic Algorithm for DNA Codeword Searching

DTIC Science & Technology

2008-01-01

C and G are complementary to each other. A Watson - Crick complement of a DNA sequence is another DNA sequence which replaces all the A with T or vise...versa and replaces all the T with A or vise versa, and also switches the 5’ and 3’ ends. A DNA sequence binds most stably with its Watson - Crick ...bind with 5 Watson - Crick pairs. The length of the longest complementary sequence between two flexible DNA strands, A and B, is the same as the

Ferroelectric behavior and reproducible Bi-stable resistance switching property in K-doped ZnO thin films as candidate for application in non-volatile memories

NASA Astrophysics Data System (ADS)

Lee, J. W.; Subramaniam, N. G.; Kang, T. W.; Shon, Yoon; Kim, E. K.

2015-05-01

Potassium-doped ZnO thin films electrodeposited on indium tin oxide (ITO) coated glass substrates exhibited ferroelectric behavior with a remnant polarization of 0.2 μC/cm2. Especially, wave forms showing the applied input voltage Vi and output voltage Vo were obtained for Al/ZnO:K/ITO structure. It exhibits a superposition of Vi (input) and Vo (output) signal from Al/ZnO:K/ITO structure with a clear phase shift between the two wave forms which again confirms that the observed ferroelectric hysteresis curve is not related to leaky dielectric materials. The current-voltage characteristics of Al/ZnO:K/ITO structures measured for several cycles revealed bi-stable switching characteristics. The reproducible bi-stable switching characteristics for the mentioned structures had good retention in one particular resistance state. Around one order of switching was realized between low and high resistance states. The switching property thought to be polarization induced originating out from the ferroelectric properties of the potassium doped ZnO thin film. The switching between ZnO:K/ITO interface is assumed to be critical for stability in switching for several cycles. Possible application of this structure in non-volatile memories is explored.

Designing Predictive Diagnose Method for Insulation Resistance Degradation of the Electrical Power Cables from Neutral Insulated Power Networks

NASA Astrophysics Data System (ADS)

Dobra, R.; Pasculescu, D.; Risteiu, M.; Buica, G.; Jevremović, V.

2017-06-01

This paper describe some possibilities to minimize voltages switching-off risks from the mining power networks, in case of insulated resistance faults by using a predictive diagnose method. The cables from the neutral insulated power networks (underground mining) are designed to provide a flexible electrical connection between portable or mobile equipment and a point of supply, including main feeder cable for continuous miners, pump cable, and power supply cable. An electronic protection for insulated resistance of mining power cables can be made using this predictive strategy. The main role of electronic relays for insulation resistance degradation of the electrical power cables, from neutral insulated power networks, is to provide a permanent measurement of the insulated resistance between phases and ground, in order to switch-off voltage when the resistance value is below a standard value. The automat system of protection is able to signalize the failure and the human operator will be early informed about the switch-off power and will have time to take proper measures to fix the failure. This logic for fast and automat switch-off voltage without aprioristic announcement is suitable for the electrical installations, realizing so a protection against fires and explosion. It is presented an algorithm and an anticipative relay for insulated resistance control from three-phase low voltage installations with insulated neutral connection.

Room-temperature ferroelectric resistive switching in ultrathin Pb(Zr 0.2 Ti 0.8)O3 films.

PubMed

Pantel, Daniel; Goetze, Silvana; Hesse, Dietrich; Alexe, Marin

2011-07-26

Spontaneous polarization of ferroelectric materials has been for a long time proposed as binary information support, but it suffers so far from destructive readout. A nondestructive resistive readout of the ferroelectric polarization state in a metal-ferroelectric-metal capacitor would thus be advantageous for data storage applications. Combing conducting force microscopy and piezoelectric force microscopy, we unambiguously show that ferroelectric polarization direction and resistance state are correlated for epitaxial ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) nanoscale capacitors prepared by self-assembly methods. For intermediate ferroelectric layer thickness (∼9 nm) sandwiched between copper and La(0.7)Sr(0.3)MnO(3) electrodes we achieved giant electroresistance with a resistance ratio of >1500 and high switching current densities (>10 A/cm(2)) necessary for effective resistive readout. The present approach uses metal-ferroelectric-metal devices at room temperature and, therefore, significantly advances the use of ferroelectric-based resistive switching.

Electric field-induced resistive switching, magnetism, and photoresponse modulation in a Pt/Co0.03Zn0.97O/Nb:SrTiO3 multi-function heterostructure

NASA Astrophysics Data System (ADS)

Luo, Zhipeng; Pei, Ling; Li, Meiya; Zhu, Yongdan; Xie, Shuai; Cheng, Xiangyang; Liu, Jiaxian; Ding, Huaqi; Xiong, Rui

2018-04-01

A Co0.03Zn0.97O (CZO) thin film was epitaxially grown on a Nb doped (001) SrTiO3 (NSTO) single-crystal substrate by pulsed laser deposition to form a Pt/CZO/NSTO heterostructure. This device exhibits stable bipolar resistive switching, well retention and endurance, multilevel memories, and a resistance ratio of high resistance state (HRS)/low resistance state (LRS) up to 7 × 105. Under the illumination of a 405 nm laser, the HRS of the device showed distinct photoelectricity with an open-circuit voltage of 0.5 V. A stronger ferromagnetism was observed at the HRS than at the LRS. The above phenomenon is attributable to the accumulation and migration of oxygen vacancies at the interface of CZO/NSTO. Our results demonstrated a pathway towards making multifunctional devices that simultaneously exhibit resistive switching, photoelectricity, and ferromagnetism.

Finite Ground Coplanar Waveguide Shunt MEMS Switches for Switched Line Phase Shifters

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Simons, Rainee N.; Scardelletti, Maximillian; Varaljay, Nicholas C.

2000-01-01

Switches with low insertion loss and high isolation are required for switched line phase shifters and the transmit/receive switch at the front end of communication systems. A Finite Ground Coplanar (FGC) waveguide capacitive, shunt MEMS switch has been implemented on high resistivity Si. The switch has demonstrated an insertion loss of less than 0.3 dB and a return loss greater than 15 dB from 10 to 20, GHz. The switch design, fabrication, and characteristics are presented.

Origin of the OFF state variability in ReRAM cells

NASA Astrophysics Data System (ADS)

Salaoru, Iulia; Khiat, Ali; Li, Qingjiang; Berdan, Radu; Papavassiliou, Christos; Prodromakis, Themistoklis

2014-04-01

This work exploits the switching dynamics of nanoscale resistive random access memory (ReRAM) cells with particular emphasis on the origin of the observed variability when cells are consecutively cycled/programmed at distinct memory states. It is demonstrated that this variance is a common feature of all ReRAM elements and is ascribed to the formation and rupture of conductive filaments that expand across the active core, independently of the material employed as the active switching core, the causal physical switching mechanism, the switching mode (bipolar/unipolar) or even the unit cells' dimensions. Our hypothesis is supported through both experimental and theoretical studies on TiO2 and In2O3 : SnO2 (ITO) based ReRAM cells programmed at three distinct resistive states. Our prototypes employed TiO2 or ITO active cores over 5 × 5 µm2 and 100 × 100 µm2 cell areas, with all tested devices demonstrating both unipolar and bipolar switching modalities. In the case of TiO2-based cells, the underlying switching mechanism is based on the non-uniform displacement of ionic species that foster the formation of conductive filaments. On the other hand, the resistive switching observed in the ITO-based devices is considered to be due to a phase change mechanism. The selected experimental parameters allowed us to demonstrate that the observed programming variance is a common feature of all ReRAM devices, proving that its origin is dependent upon randomly oriented local disorders within the active core that have a substantial impact on the overall state variance, particularly for high-resistive states.

Memristive switching induced by 100 MeV Ag7+ ion irradiation in Ag/La0.7Sr0.3MnO3/Ag planar structures

NASA Astrophysics Data System (ADS)

Bhavsar, K. H.; Joshi, U. S.; Mistry, B. V.; Khan, S. A.; Avasthi, D. K.

2011-09-01

Resistive random access memory is one of the candidate technologies for the promising next generation non-volatile memories with fast switching speed, low power consumption and non-destructive readout. The swift heavy ion (SHI)-induced resistive switching behavior of Ag/La0.7Sr0.3MnO3/Ag planar structures, grown on SiO2 substrates by the chemical solution deposition technique, has been investigated. Five identical samples were irradiated by 100 MeV Ag7+ ions with fluence values ranging from 1×1011 to 5×1013 ions/cm2 at the Materials Science beamline of the IUAC, New Delhi. Upon irradiation, systematic amorphization and grain elongation was observed in the grazing incidence X-ray diffraction and atomic force microscopy, respectively. Four-terminal I-V curves indicate typical non-ohmic behavior of pristine Ag/La0.7Sr0.3MnO3/Ag planar geometry at room temperature for several voltage-sweeping cycles. On the other hand, well-defined hysteresis loops with sharp on-off transition in the I-V curves were observed for the sample irradiated with 100 MeV Ag7+ ions at 1×1012 ions/cm2, indicating that the sample possesses low resistance state and high resistance state. A symmetrical resistance ratio (R high/R low) of ∼ 330% at-1.7 V has been achieved. The resistance switching is bipolar and may be attributed to SHI-induced defects in the device. Such defect-induced resistive switching has recently been proposed theoretically, and our results are direct evidence of the phenomenon.

Critical role of a double-layer configuration in solution-based unipolar resistive switching memories.

PubMed

Carlos, Emanuel; Kiazadeh, Asal; Deuermeier, Jonas; Branquinho, Rita; Martins, Rodrigo; Fortunato, Elvira

2018-08-24

Lately, resistive switching memories (ReRAM) have been attracting a lot of attention due to their possibilities of fast operation, lower power consumption and simple fabrication process and they can also be scaled to very small dimensions. However, most of these ReRAM are produced by physical methods and nowadays the industry demands more simplicity, typically associated with low cost manufacturing. As such, ReRAMs in this work are developed from a solution-based aluminum oxide (Al 2 O 3 ) using a simple combustion synthesis process. The device performance is optimized by two-stage deposition of the Al 2 O 3 film. The resistive switching properties of the bilayer devices are reproducible with a yield of 100%. The ReRAM devices show unipolar resistive switching behavior with good endurance and retention time up to 10 5 s at 85 °C. The devices can be programmed in a multi-level cell operation mode by application of different reset voltages. Temperature analysis of various resistance states reveals a filamentary nature based on the oxygen vacancies. The optimized film was stacked between ITO and indium zinc oxide, targeting a fully transparent device for applications on transparent system-on-panel technology.

Hf layer thickness dependence of resistive switching characteristics of Ti/Hf/HfO2/Au resistive random access memory device

NASA Astrophysics Data System (ADS)

Nakajima, Ryo; Azuma, Atsushi; Yoshida, Hayato; Shimizu, Tomohiro; Ito, Takeshi; Shingubara, Shoso

2018-06-01

Resistive random access memory (ReRAM) devices with a HfO2 dielectric layer have been studied extensively owing to the good reproducibility of their SET/RESET switching properties. Furthermore, it was reported that a thin Hf layer next to a HfO2 layer stabilized switching properties because of the oxygen scavenging effect. In this work, we studied the Hf thickness dependence of the resistance switching characteristics of a Ti/Hf/HfO2/Au ReRAM device. It is found that the optimum Hf thickness is approximately 10 nm to obtain good reproducibility of SET/RESET voltages with a small RESET current. However, when the Hf thickness was very small (∼2 nm), the device failed after the first RESET process owing to the very large RESET current. In the case of a very thick Hf layer (∼20 nm), RESET did not occur owing to the formation of a leaky dielectric layer. We observed the occurrence of multiple resistance states in the RESET process of the device with a Hf thickness of 10 nm by increasing the RESET voltage stepwise.

Exploring the energy landscape of resistive switching in antiferromagnetic S r3I r2O7

NASA Astrophysics Data System (ADS)

Williamson, Morgan; Shen, Shida; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

2018-04-01

We study the resistive switching triggered by an applied electrical bias in the antiferromagnetic Mott insulator S r3I r2O7 . The switching was previously associated with an electric-field-driven structural transition. Here we use time-resolved measurements to probe the thermal activation behavior of the switching process and acquire information about the energy barrier associated with the transition. We quantify the changes in the energy-barrier height with respect to the applied bias and find a linear decrease of the barrier with increasing bias. Our observations support the potential of antiferromagnetic transition-metal oxides for spintronic applications.

An X-Band SOS Resistive Gate-Insulator-Semiconductor /RIS/ switch

NASA Astrophysics Data System (ADS)

Kwok, S. P.

1980-02-01

The new X-Band Resistive Gate-Insulator-Semiconductor (RIS) switch has been fabricated on silicon-on-sapphire, and its equivalent circuit model characterized. An RIS SPST switch with 20-dB on/off isolation, 1.2-dB insertion loss, and power handling capacity in excess of 20-W peak has been achieved at X band. The device switching time is on the order of 600 ns, and it requires negligible control holding current in both on and off states. The device is compatible with monolithic integrated-circuit technology and thus is suitable for integration into low-cost monolithic phase shifters or other microwave integrated circuits.

Memristive switching of MgO based magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Krzysteczko, Patryk; Reiss, Günter; Thomas, Andy

2009-09-01

Here we demonstrate that both, tunnel magnetoresistance (TMR) and resistive switching (RS), can be observed simultaneously in nanoscale magnetic tunnel junctions. The devices show bipolar RS of 6% and TMR ratios of about 100%. For each magnetic state, multiple resistive states are created depending on the bias history, which provides a method for multibit data storage and logic. The electronic transport measurements are discussed in the framework of a memristive system. Differently prepared MgO barriers are compared to gain insight into the switching mechanism.

Charged Defects-Induced Resistive Switching in Sb2Te3 Memristor

NASA Astrophysics Data System (ADS)

Zhang, J. J.; Liu, N.; Sun, H. J.; Yan, P.; Li, Y.; Zhong, S. J.; Xie, S.; Li, R. J.; Miao, X. S.

2016-02-01

Resistive switching (RS) characteristics of Ta/Sb2Te3/Ta and Ag/Sb2Te3/Ta memory devices have been investigated. The I- V curves show the bipolar RS at room temperature. We have demonstrated that the redistribution and migration of charged defects are responsible for the memristive switching. By using Ag electrode instead of Ta, more defects can be created near the Ag/Sb2Te3 interface, which is a feasible method to eliminate the electroforming process.

Switching behavior of resistive change memory using oxide nanowires

NASA Astrophysics Data System (ADS)

Aono, Takashige; Sugawa, Kosuke; Shimizu, Tomohiro; Shingubara, Shoso; Takase, Kouichi

2018-06-01

Resistive change random access memory (ReRAM), which is expected to be the next-generation nonvolatile memory, often has wide switching voltage distributions due to many kinds of conductive filaments. In this study, we have tried to suppress the distribution through the structural restriction of the filament-forming area using NiO nanowires. The capacitor with Ni metal nanowires whose surface is oxidized showed good switching behaviors with narrow distributions. The knowledge gained from our study will be very helpful in producing practical ReRAM devices.

Genetic analysis of the resistance to eight anthracnose races in the common bean differential cultivar Kaboon.

PubMed

Campa, Ana; Giraldez, Ramón; Ferreira, Juan José

2011-06-01

Resistance to the eight races (3, 7, 19, 31, 81, 449, 453, and 1545) of the pathogenic fungus Colletotrichum lindemuthianum (anthracnose) was evaluated in F(3) families derived from the cross between the anthracnose differential bean cultivars Kaboon and Michelite. Molecular marker analyses were carried out in the F(2) individuals in order to map and characterize the anthracnose resistance genes or gene clusters present in Kaboon. The analysis of the combined segregations indicates that the resistance present in Kaboon against these eight anthracnose races is determined by 13 different race-specific genes grouped in three clusters. One of these clusters, corresponding to locus Co-1 in linkage group (LG) 1, carries two dominant genes conferring specific resistance to races 81 and 1545, respectively, and a gene necessary (dominant complementary gene) for the specific resistance to race 31. A second cluster, corresponding to locus Co-3/9 in LG 4, carries six dominant genes conferring specific resistance to races 3, 7, 19, 449, 453, and 1545, respectively, and the second dominant complementary gene for the specific resistance to race 31. A third cluster of unknown location carries three dominant genes conferring specific resistance to races 449, 453, and 1545, respectively. This is the first time that two anthracnose resistance genes with a complementary mode of action have been mapped in common bean and their relationship with previously known Co- resistance genes established.

Spintronic logic: from switching devices to computing systems

NASA Astrophysics Data System (ADS)

Friedman, Joseph S.

2017-09-01

Though numerous spintronic switching devices have been proposed or demonstrated, there has been significant difficulty in translating these advances into practical computing systems. The challenge of cascading has impeded the integration of multiple devices into a logic family, and several proposed solutions potentially overcome these challenges. Here, the cascading techniques by which the output of each spintronic device can drive the input of another device are described for several logic families, including spin-diode logic (in particular, all-carbon spin logic), complementary magnetic tunnel junction logic (CMAT), and emitter-coupled spin-transistor logic (ECSTL).

A Review on Resistive Switching in High-k Dielectrics: A Nanoscale Point of View Using Conductive Atomic Force Microscope

PubMed Central

Lanza, Mario

2014-01-01

Metal-Insulator-Metal (MIM) structures have raised as the most promising configuration for next generation information storage, leading to great performance and fabrication-friendly Resistive Random Access Memories (RRAM). In these cells, the memory concept is no more based on the charge storage, but on tuning the electrical resistance of the insulating layer by applying electrical stresses to reach a high resistive state (HRS or “0”) and a low resistive state (LRS or “1”), which makes the memory point. Some high-k dielectrics show this unusual property and in the last years high-k based RRAM have been extensively analyzed, especially at the device level. However, as resistance switching (in the most promising cells) is a local phenomenon that takes place in areas of ~100 nm2, the use of characterization tools with high lateral spatial resolution is necessary. In this paper the status of resistive switching in high-k materials is reviewed from a nanoscale point of view by means of conductive atomic force microscope analyses. PMID:28788561

Realization of the Switching Mechanism in Resistance Random Access Memory™ Devices: Structural and Electronic Properties Affecting Electron Conductivity in a Hafnium Oxide-Electrode System Through First-Principles Calculations

NASA Astrophysics Data System (ADS)

Aspera, Susan Meñez; Kasai, Hideaki; Kishi, Hirofumi; Awaya, Nobuyoshi; Ohnishi, Shigeo; Tamai, Yukio

2013-01-01

The resistance random access memory (RRAM™) device, with its electrically induced nanoscale resistive switching capacity, has attracted considerable attention as a future nonvolatile memory device. Here, we propose a mechanism of switching based on an oxygen vacancy migration-driven change in the electronic properties of the transition-metal oxide film stimulated by set pulse voltages. We used density functional theory-based calculations to account for the effect of oxygen vacancies and their migration on the electronic properties of HfO2 and Ta/HfO2 systems, thereby providing a complete explanation of the RRAM™ switching mechanism. Furthermore, computational results on the activation energy barrier for oxygen vacancy migration were found to be consistent with the set and reset pulse voltage obtained from experiments. Understanding this mechanism will be beneficial to effectively realizing the materials design in these devices.

Resistive switching characteristics of polymer non-volatile memory devices in a scalable via-hole structure.

PubMed

Kim, Tae-Wook; Choi, Hyejung; Oh, Seung-Hwan; Jo, Minseok; Wang, Gunuk; Cho, Byungjin; Kim, Dong-Yu; Hwang, Hyunsang; Lee, Takhee

2009-01-14

The resistive switching characteristics of polyfluorene-derivative polymer material in a sub-micron scale via-hole device structure were investigated. The scalable via-hole sub-microstructure was fabricated using an e-beam lithographic technique. The polymer non-volatile memory devices varied in size from 40 x 40 microm(2) to 200 x 200 nm(2). From the scaling of junction size, the memory mechanism can be attributed to the space-charge-limited current with filamentary conduction. Sub-micron scale polymer memory devices showed excellent resistive switching behaviours such as a large ON/OFF ratio (I(ON)/I(OFF) approximately 10(4)), excellent device-to-device switching uniformity, good sweep endurance, and good retention times (more than 10,000 s). The successful operation of sub-micron scale memory devices of our polyfluorene-derivative polymer shows promise to fabricate high-density polymer memory devices.

Laterally configured resistive switching device based on transition-metal nano-gap electrode on Gd oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakita, Masatoshi; Okabe, Kyota; Kimura, Takashi

2016-01-11

We have developed a fabrication process for a laterally configured resistive switching device based on a Gd oxide. A nano-gap electrode connected by a Gd oxide with the ideal interfaces has been created by adapting the electro-migration method in a metal/GdO{sub x} bilayer system. Bipolar set and reset operations have been clearly observed in the Pt/GdO{sub x} system similarly in the vertical device based on GdO{sub x}. Interestingly, we were able to observe a clear bipolar switching also in a ferromagnetic CoFeB nano-gap electrode with better stability compared to the Pt/GdO{sub x} device. The superior performance of the CoFeB/GdO{sub x}more » device implies the importance of the spin on the resistive switching.« less

Resistive switching: An investigation of the bipolar–unipolar transition in Co-doped ZnO thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, Daniel A.A., E-mail: danielandrade.ufs@gmail.com; Department of Physics, University at Buffalo, The State University of New York, Buffalo, NY 14260; Zeng, Hao

2015-06-15

Highlights: • A purely bipolar behavior on a Co-doped ZnO thin film has been demonstrated. • We have shown what can happen if a unipolar test is performed in a purely bipolar device. • An explanation for how a sample can show a purely bipolar switching behavior was suggested. • An important open issue about resistive switching effect was put in debate. - Abstract: In order to investigate the resistive switching effect we built devices in a planar structure in which two Al contacts were deposited on the top of the film and separated by a small gap using amore » shadow mask. Therefore, two samples of 10% Co-doped ZnO thin films were sputtered on glass substrate. High resolution X-ray diffraction (HRXRD) revealed a highly c-axis oriented crystalline structure, without secondary phase. The high resolution scanning electron microscopy (HRSEM) showed a flat surface with good coverage and thickness about 300 nm. A Keithley 2425 semiconductor characterization system was used to perform the resistive switching tests in the bipolar and unipolar modes. Considering only the effect of compliance current (CC), the devices showed a purely bipolar behavior since an increase in CC did not induce a transition to unipolar behavior.« less

Low temperature grown GaNAsSb: A promising material for photoconductive switch application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, K. H.; Yoon, S. F.; Wicaksono, S.

2013-09-09

We report a photoconductive switch using low temperature grown GaNAsSb as the active material. The GaNAsSb layer was grown at 200 °C by molecular beam epitaxy in conjunction with a radio frequency plasma-assisted nitrogen source and a valved antimony cracker source. The low temperature growth of the GaNAsSb layer increased the dark resistivity of the switch and shortened the carrier lifetime. The switch exhibited a dark resistivity of 10{sup 7} Ω cm, a photo-absorption of up to 2.1 μm, and a carrier lifetime of ∼1.3 ps. These results strongly support the suitability of low temperature grown GaNAsSb in the photoconductivemore » switch application.« less

Nd2-xCexCuO4-y/Nd2-xCexOy boundary and resistive switchings in mesoscopic structures on base of epitaxial Nd1.86Ce0.14CuO4-у films

NASA Astrophysics Data System (ADS)

Tulina, N. A.; Rossolenko, A. N.; Ivanov, A. A.; Sirotkin, V. V.; Shmytko, I. M.; Borisenko, I. Yu.; Ionov, A. M.

2016-08-01

Reverse and stable bipolar resistive switching effect (BRSE) was observed in planar Nd2-xCex CuO4-y/Nd2-xCexOx/Ag heterostructure. It was shown that the СVС of the BRSE observed has a diode character. Simulations were used to consider the influence of the nonuniform distribution of an electric field at the interface of a heterojunction on the effect of bipolar resistive switching in investigated structures. The inhomogeneous distribution of the electric field near the contact edge creates regions of higher electric field strength which, in turn, stimulates motion and redistribution of defects, changes of the resistive properties of the whole structure and formation of a percolation channel.

Multilevel resistance switching effect in Au/La2/3Ba1/3MnO3/Pt heterostructure manipulated by external fields

NASA Astrophysics Data System (ADS)

Wen, Jiahong; Zhao, Xiaoyu; Li, Qian; Zhang, Sheng; Wang, Dunhui; Du, Youwei

2018-04-01

Multilevel resistance switching (RS) effect has attracted more and more attention due to its promising potential for the increase of storage density in memory devices. In this work, the transport properties are investigated in an Au/La2/3Ba1/3MnO3 (LBMO)/Pt heterostructure. Taking advantage of the strong interplay among the spin, charge, orbital and lattice of LBMO, the Au/LBMO/Pt device can exhibit bipolar RS effect and magnetoresistance effect simultaneously. Under the coaction of electric field and magnetic field, four different resistance states are achieved in this device. These resistance states show excellent repeatability and retentivity and can be switched between any two states, which suggest the potential applications in the multilevel RS memory devices with enhanced storage density.

Effect of La3+ substitution with Gd3+ on the resistive switching properties of La0.7Sr0.3MnO3 thin films

NASA Astrophysics Data System (ADS)

Lee, Hong-Sub; Park, Chang-Sun; Park, Hyung-Ho

2014-05-01

This study demonstrated that the resistive switching voltage of perovskite manganite material could be controlled by A-site cation substitution in "A" MnO3 perovskite manganite structure. A partial substitution of La3+ in La0.7Sr0.3MnO3 with smaller cation Gd3+ induced A-site vacancy of the largest Sr2+ cation with surface segregation of SrOy due to ionic size mismatch, and the induced vacancies reduced migration energy barrier. The operating voltage decreased from 3.5 V to 2.5 V due to a favorable condition for electrochemical migration and redox of oxygen ions. Moreover, surface-segregated SrOy was enhanced with Gd-substitution and the SrOy reduced Schottky-like barrier height and resistive switching ratio from the potential drop and screening effect. The relationship between A-site vacancy generation resulting in surface segregation of SrOy and resistive switching behavior was also investigated by energy resolved x-ray photoelectron spectroscopy, O 1s near edge x-ray absorption spectroscopy, and current voltage measurement.

Key concepts behind forming-free resistive switching incorporated with rectifying transport properties

PubMed Central

Shuai, Yao; Ou, Xin; Luo, Wenbo; Mücklich, Arndt; Bürger, Danilo; Zhou, Shengqiang; Wu, Chuangui; Chen, Yuanfu; Zhang, Wanli; Helm, Manfred; Mikolajick, Thomas; Schmidt, Oliver G.; Schmidt, Heidemarie

2013-01-01

This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO3/Pt/Ti capacitor-like structures. Polycrystalline BiFeO3 thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO2/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600°C. The current-voltage (I–V) curves indicate that resistive switching can only be achieved in Au/BiFeO3/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO3 thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits. PMID:23860408

A complementary switching mechanism for organic memory devices to regulate the conductance of binary states

NASA Astrophysics Data System (ADS)

Vyas, Giriraj; Dagar, Parveen; Sahu, Satyajit

2016-06-01

We have fabricated an organic non-volatile memory device wherein the ON/OFF current ratio has been controlled by varying the concentration of a small organic molecule, 2,3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ), in an insulating matrix of a polymer Poly(4-vinylphenol) (PVP). A maximum ON-OFF ratio of 106 is obtained when the concentration of DDQ is half or 10 wt. % of PVP. In this process, the switching direction for the devices has also been altered, indicating the disparity in conduction mechanism. Conduction due to metal filament formation through the active material and the voltage dependent conformational change of the organic molecule seem to be the motivation behind the gradual change in the switching direction.

Conduction Channel Formation and Dissolution Due to Oxygen Thermophoresis/Diffusion in Hafnium Oxide Memristors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Suhas; Wang, Ziwen; Huang, Xiaopeng

Due to the favorable operating power, endurance, speed, and density., transition-metal-oxide memristors, or resistive random-access memory (RRAM) switches, are under intense development for storage-class memory. Their commercial deployment critically depends on predictive compact models based on understanding nanoscale physiocochemical forces, which remains elusive and controversial owing to the difficulties in directly observing atomic motions during resistive switching, Here, using scanning transmission synchrotron X-ray spectromicroscopy to study in situ switching of hafnium oxide memristors, we directly observed the formation of a localized oxygen-deficiency-derived conductive channel surrounded by a low-conductivity ring of excess oxygen. Subsequent thermal annealing homogenized the segregated oxygen, resettingmore » the cells toward their as-grown resistance state. We show that the formation and dissolution of the conduction channel are successfully modeled by radial thermophoresis and Fick diffusion of oxygen atoms driven by Joule heating. This confirmation and quantification of two opposing nanoscale radial forces that affect bipolar memristor switching are important components for any future physics-based compact model for the electronic switching of these devices.« less

Examination of the temperature dependent electronic behavior of GeTe for switching applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Champlain, James G.; Ruppalt, Laura B.; Guyette, Andrew C.

2016-06-28

The DC and RF electronic behaviors of GeTe-based phase change material switches as a function of temperature, from 25 K to 375 K, have been examined. In its polycrystalline (ON) state, GeTe behaved as a degenerate p-type semiconductor, exhibiting metal-like temperature dependence in the DC regime. This was consistent with the polycrystalline (ON) state RF performance of the switch, which exhibited low resistance S-parameter characteristics. In its amorphous (OFF) state, the GeTe presented significantly greater DC resistance that varied considerably with bias and temperature. At low biases (<1 V) and temperatures (<200 K), the amorphous GeTe low-field resistance dramatically increased, resulting in exceptionally highmore » amorphous-polycrystalline (OFF-ON) resistance ratios, exceeding 10{sup 9} at cryogenic temperatures. At higher biases and temperatures, the amorphous GeTe exhibited nonlinear current-voltage characteristics that were best fit by a space-charge limited conduction model that incorporates the effect of a defect band. The observed conduction behavior suggests the presence of two regions of localized traps within the bandgap of the amorphous GeTe, located at approximately 0.26–0.27 eV and 0.56–0.57 eV from the valence band. Unlike the polycrystalline state, the high resistance DC behavior of amorphous GeTe does not translate to the RF switch performance; instead, a parasitic capacitance associated with the RF switch geometry dominates OFF state RF transmission.« less

Clinical Outcomes of Virologically-Suppressed Patients with Pre-existing HIV-1 Drug Resistance Mutations Switching to Rilpivirine/Emtricitabine/Tenofovir Disoproxil Fumarate in the SPIRIT Study.

PubMed

Porter, Danielle P; Toma, Jonathan; Tan, Yuping; Solberg, Owen; Cai, Suqin; Kulkarni, Rima; Andreatta, Kristen; Lie, Yolanda; Chuck, Susan K; Palella, Frank; Miller, Michael D; White, Kirsten L

2016-02-01

Antiretroviral regimen switching may be considered for HIV-1-infected, virologically-suppressed patients to enable treatment simplification or improve tolerability, but should be guided by knowledge of pre-existing drug resistance. The current study examined the impact of pre-existing drug resistance mutations on virologic outcomes among virologically-suppressed patients switching to Rilpivirine (RPV)/emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF). SPIRIT was a phase 3b study evaluating the safety and efficacy of switching to RPV/FTC/TDF in virologically-suppressed HIV-1-infected patients. Pre-existing drug resistance at baseline was determined by proviral DNA genotyping for 51 RPV/FTC/TDF-treated patients with known mutations by historical RNA genotype and matched controls and compared with clinical outcome at Week 48. Drug resistance mutations in protease or reverse transcriptase were detected in 62.7% of patients by historical RNA genotype and in 68.6% by proviral DNA genotyping at baseline. Proviral DNA sequencing detected 89% of occurrences of NRTI and NNRTI resistance-associated mutations reported by historical genotype. Mutations potentially affecting RPV activity, including E138A/G/K/Q, Y181C, and H221Y, were detected in isolates from 11 patients by one or both assays. None of the patients with single mutants had virologic failure through Week 48. One patient with pre-existing Y181Y/C and M184I by proviral DNA genotyping experienced virologic failure. Nineteen patients with K103N present by historical genotype were confirmed by proviral DNA sequencing and 18/19 remained virologically-suppressed. Virologic success rates were high among virologically-suppressed patients with pre-existing NRTI and NNRTI resistance-associated mutations who switched to RPV/FTC/TDF in the SPIRIT study. While plasma RNA genotyping remains preferred, proviral DNA genotyping may provide additional value in virologically-suppressed patients for whom historical resistance data are unavailable.

Resistance switching mechanism of La0.8Sr0.2MnO3-δ thin films

NASA Astrophysics Data System (ADS)

Luo, X. D.; Gao, R. L.; Fu, C. L.; Cai, W.; Chen, G.; Deng, X. L.; Zhang, H. R.; Sun, J. R.

2016-02-01

Effects of oxygen vacancies on the electrical transport properties of oxygen stoichiometric La0.8Sr0.2MnO3 and oxygen-deficient La0.8Sr0.2MnO3-δ films have been investigated. The result presents that the oxygen-deficient films annealed in vacuum show obvious increase of resistance and lattice parameter. With the sweeping voltage or temperature increasing, the resistance exhibits obvious bipolar switching effect, no forming process was needed. Oxygen deficiency in the annealed film leads to the formation of a structural disorder in the Mn-O-Mn conduction channel due to the accumulation of oxygen vacancies under high external electric field or temperatures and hence is believed to be responsible for the bipolar resistance switching effect and the enhanced resistivity compared with oxygen stoichiometric La0.8Sr0.2MnO3 film. These results may be important for practical applications in photoelectric or storage devices and point to a useful direction for other oxidizing materials.

Influence of Thermal Annealing Treatment on Bipolar Switching Properties of Vanadium Oxide Thin-Film Resistance Random-Access Memory Devices

NASA Astrophysics Data System (ADS)

Chen, Kai-Huang; Cheng, Chien-Min; Kao, Ming-Cheng; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Wu, Sean; Su, Feng-Yi

2017-04-01

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current-voltage ( I- V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Effect of dysprosium and lutetium metal buffer layers on the resistive switching characteristics of Cu-Sn alloy-based conductive-bridge random access memory.

PubMed

Vishwanath, Sujaya Kumar; Woo, Hyunsuk; Jeon, Sanghun

2018-06-18

Conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates for non-volatile memory in next-generation information and communication technology. The resistive switching mechanism of CBRAM depends on the formation/annihilation of the conductive filament (CF) between the active metal electrode and the inert electrode. However, excessive ion injection from the active electrode into the solid electrolyte is reduces the uniformity and reliability of the resistive switching devices. To solve this problem, we investigated the resistive switching characteristics of a modified active electrode with different compositions of Cu_x-Sn_{_1-x}(0.13 < X < 0.55). The resistive switching characteristics were further improved by inserting a dysprosium (Dy) or lutetium (Lu) buffer layer at the interface of Cu_x-Sn_1-x/Al₂O₃. Electrical analysis of the optimal Cu_0.27-Sn_0.73/Lu-based CBRAM exhibited stable resistive switching behavior with low operation voltage (SET: 0.7 V and RESET: -0.3 V), a high on/off resistive ratio (10⁶), cyclic endurance (>10⁴), and long-term retention (85℃/10 years). To achieve these performance parameters, CFs were locally formed inside the electrolyte using a modified CuSn active electrode, and the amount of Cu-ion injection was reduced by inserting the Dy or Lu buffer layer between the CuSn active electrode and the electrolyte. In particular, conductive-atomic force microscopy results at the Dy/ or Lu/Al₂O₃ interface directly showed and defined the diameter of the CF. © 2018 IOP Publishing Ltd.

Scalability of voltage-controlled filamentary and nanometallic resistance memory devices.

PubMed

Lu, Yang; Lee, Jong Ho; Chen, I-Wei

2017-08-31

Much effort has been devoted to device and materials engineering to realize nanoscale resistance random access memory (RRAM) for practical applications, but a rational physical basis to be relied on to design scalable devices spanning many length scales is still lacking. In particular, there is no clear criterion for switching control in those RRAM devices in which resistance changes are limited to localized nanoscale filaments that experience concentrated heat, electric current and field. Here, we demonstrate voltage-controlled resistance switching, always at a constant characteristic critical voltage, for macro and nanodevices in both filamentary RRAM and nanometallic RRAM, and the latter switches uniformly and does not require a forming process. As a result, area-scalability can be achieved under a device-area-proportional current compliance for the low resistance state of the filamentary RRAM, and for both the low and high resistance states of the nanometallic RRAM. This finding will help design area-scalable RRAM at the nanoscale. It also establishes an analogy between RRAM and synapses, in which signal transmission is also voltage-controlled.

The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices

NASA Astrophysics Data System (ADS)

Rezvanian, O.; Brown, C.; Zikry, M. A.; Kingon, A. I.; Krim, J.; Irving, D. L.; Brenner, D. W.

2008-07-01

It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation.

Study of self-compliance behaviors and internal filament characteristics in intrinsic SiO{sub x}-based resistive switching memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Yao-Feng, E-mail: yfchang@utexas.edu; Zhou, Fei; Chen, Ying-Chen

2016-01-18

Self-compliance characteristics and reliability optimization are investigated in intrinsic unipolar silicon oxide (SiO{sub x})-based resistive switching (RS) memory using TiW/SiO{sub x}/TiW device structures. The program window (difference between SET voltage and RESET voltage) is dependent on external series resistance, demonstrating that the SET process is due to a voltage-triggered mechanism. The program window has been optimized for program/erase disturbance immunity and reliability for circuit-level applications. The SET and RESET transitions have also been characterized using a dynamic conductivity method, which distinguishes the self-compliance behavior due to an internal series resistance effect (filament) in SiO{sub x}-based RS memory. By using amore » conceptual “filament/resistive gap (GAP)” model of the conductive filament and a proton exchange model with appropriate assumptions, the internal filament resistance and GAP resistance can be estimated for high- and low-resistance states (HRS and LRS), and are found to be independent of external series resistance. Our experimental results not only provide insights into potential reliability issues but also help to clarify the switching mechanisms and device operating characteristics of SiO{sub x}-based RS memory.« less

Electroformed silicon nitride based light emitting memory device

NASA Astrophysics Data System (ADS)

Anutgan, Tamila; Anutgan, Mustafa; Atilgan, Ismail; Katircioglu, Bayram

2017-07-01

The resistive memory switching effect of an electroformed nanocrystal silicon nitride thin film light emitting diode (LED) is demonstrated. For this purpose, current-voltage (I-V) characteristics of the diode were systematically scanned, paying particular attention to the sequence of the measurements. It was found that when the voltage polarity was changed from reverse to forward, the previously measured reverse I-V behavior was remembered until some critical forward bias voltage. Beyond this critical voltage, the I-V curve returns to its original state instantaneously, and light emission switches from the OFF state to the ON state. The kinetics of this switching mechanism was studied for different forward bias stresses by measuring the corresponding time at which the switching occurs. Finally, the switching of resistance and light emission states was discussed via energy band structure of the electroformed LED.

Electron holography on HfO2/HfO2-x bilayer structures with multilevel resistive switching properties

NASA Astrophysics Data System (ADS)

Niu, G.; Schubert, M. A.; Sharath, S. U.; Zaumseil, P.; Vogel, S.; Wenger, C.; Hildebrandt, E.; Bhupathi, S.; Perez, E.; Alff, L.; Lehmann, M.; Schroeder, T.; Niermann, T.

2017-05-01

Unveiling the physical nature of the oxygen-deficient conductive filaments (CFs) that are responsible for the resistive switching of the HfO2-based resistive random access memory (RRAM) devices represents a challenging task due to the oxygen vacancy related defect nature and nanometer size of the CFs. As a first important step to this goal, we demonstrate in this work direct visualization and a study of physico-chemical properties of oxygen-deficient amorphous HfO2-x by carrying out transmission electron microscopy electron holography as well as energy dispersive x-ray spectroscopy on HfO2/HfO2-x bilayer heterostructures, which are realized by reactive molecular beam epitaxy. Furthermore, compared to single layer devices, Pt/HfO2/HfO2-x /TiN bilayer devices show enhanced resistive switching characteristics with multilevel behavior, indicating their potential as electronic synapses in future neuromorphic computing applications.

The Role of Work Function and Band Gap in Resistive Switching Behaviour of ZnTe Thin Films

NASA Astrophysics Data System (ADS)

Rowtu, Srinu; Sangani, L. D. Varma; Krishna, M. Ghanashyam

2018-02-01

Resistive switching behavior by engineering the electrode work function and band gap of ZnTe thin films is demonstrated. The device structures Au/ZnTe/Au, Au/ZnTe/Ag, Al/ZnTe/Ag and Pt/ZnTe/Ag were fabricated. ZnTe was deposited by thermal evaporation and the stoichiometry and band gap were controlled by varying the source-substrate distance. Band gap could be varied between 1.0 eV to approximately 4.0 eV with the larger band gap being attributed to the partial oxidation of ZnTe. The transport characteristics reveal that the low-resistance state is ohmic in nature which makes a transition to Poole-Frenkel defect-mediated conductivity in the high-resistance states. The highest R off-to- R on ratio achieved is 109. Interestingly, depending on stoichiometry, both unipolar and bipolar switching can be realized.

Filamentary model in resistive switching materials

NASA Astrophysics Data System (ADS)

Jasmin, Alladin C.

2017-12-01

The need for next generation computer devices is increasing as the demand for efficient data processing increases. The amount of data generated every second also increases which requires large data storage devices. Oxide-based memory devices are being studied to explore new research frontiers thanks to modern advances in nanofabrication. Various oxide materials are studied as active layers for non-volatile memory. This technology has potential application in resistive random-access-memory (ReRAM) and can be easily integrated in CMOS technologies. The long term perspective of this research field is to develop devices which mimic how the brain processes information. To realize such application, a thorough understanding of the charge transport and switching mechanism is important. A new perspective in the multistate resistive switching based on current-induced filament dynamics will be discussed. A simple equivalent circuit of the device gives quantitative information about the nature of the conducting filament at different resistance states.

Forming-free resistive switching characteristics of Ag/CeO2/Pt devices with a large memory window

NASA Astrophysics Data System (ADS)

Zheng, Hong; Kim, Hyung Jun; Yang, Paul; Park, Jong-Sung; Kim, Dong Wook; Lee, Hyun Ho; Kang, Chi Jung; Yoon, Tae-Sik

2017-05-01

Ag/CeO2(∼45 nm)/Pt devices exhibited forming-free bipolar resistive switching with a large memory window (low-resistance-state (LRS)/high-resistance-state (HRS) ratio >106) at a low switching voltage (<±1 ∼ 2 V) in voltage sweep condition. Also, they retained a large memory window (>104) at a pulse operation (±5 V, 50 μs). The high oxygen ionic conductivity of the CeO2 layer as well as the migration of silver facilitated the formation of filament for the transition to LRS at a low voltage without a high voltage forming operation. Also, a certain amount of defects in the CeO2 layer was required for stable HRS with space-charge-limited-conduction, which was confirmed comparing the devices with non-annealed and annealed CeO2 layers.

High-explosive driven crowbar switch

DOEpatents

Dike, Robert S.; Kewish, Jr., Ralph W.

1976-01-13

The disclosure relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a hard current contact with a supportive annular conductor.

Ultra-Lightweight Resistive Switching Memory Devices Based on Silk Fibroin.

PubMed

Wang, Hong; Zhu, Bowen; Wang, Hua; Ma, Xiaohua; Hao, Yue; Chen, Xiaodong

2016-07-01

Ultra-lightweight resistive switching memory based on protein has been demonstrated. The memory foil is 0.4 mg cm(-2) , which is 320-fold lighter than silicon substrate, 20-fold lighter than office paper and can be sustained by a human hair. Additionally, high resistance OFF/ON ratio of 10(5) , retention time of 10(4) s, and excellent flexibility (bending radius of 800 μm) have been achieved. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature-dependent resistance switching in SrTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jian-kun; University of Chinese Academy of Sciences, Beijing 100049; Ma, Chao

2016-06-13

Resistance switching phenomena were studied by varying temperature in SrTiO{sub 3} single crystal. The resistance hysteresis loops appear at a certain temperature ranging from 340 K to 520 K. With the assistance of 375 nm ultraviolet continuous laser, the sample resistance is greatly reduced, leading to a stable effect than that in dark. These resistance switching phenomena only exist in samples with enough oxygen vacancies, which is confirmed by spherical aberration-corrected scanning transmission electron microscopy measurements, demonstrating an important role played by oxygen vacancies. At temperatures above 340 K, positively charged oxygen vacancies become mobile triggered by external electric field, and the resistance switchingmore » effect emerges. Our theoretical results based on drift-diffusion model reveal that the built-in field caused by oxygen vacancies can be altered under external electric field. Therefore, two resistance states are produced under the cooperative effect of built-in field and external field. However, the increasing mobility of oxygen vacancies caused by higher temperature promotes internal electric field to reach equilibrium states quickly, and suppresses the hysteresis loops above 420 K.« less

Contact material optimization and contact physics in metal-contact microelectromechanical systems (MEMS) switches

NASA Astrophysics Data System (ADS)

Yang, Zhenyin

Metal-contact MEMS switches hold great promise for implementing agile radio frequency (RF) systems because of their small size, low fabrication cost, low power consumption, wide operational band, excellent isolation and exceptionally low signal insertion loss. Gold is often utilized as a contact material for metal-contact MEMS switches due to its excellent electrical conductivity and corrosion resistance. However contact wear and stiction are the two major failure modes for these switches due to its material softness and high surface adhesion energy. To strengthen the contact material, pure gold was alloyed with other metal elements. We designed and constructed a new micro-contacting test facility that closely mimic the typical MEMS operation and utilized this facility to efficiently evaluate optimized contact materials. Au-Ni binary alloy system as the candidate contact material for MEMS switches was systematically investigated. A correlation between contact material properties (etc. microstructure, micro-hardness, electrical resistivity, topology, surface structures and composition) and micro-contacting performance was established. It was demonstrated nano-scale graded two-phase Au-Ni film could possibly yield an improved device performance. Gold micro-contact degradation mechanisms were also systematically investigated by running the MEMS switching tests under a wide range of test conditions. According to our quantitative failure analysis, field evaporation could be the dominant failure mode for highfield (> critical threshold field) hot switching; transient thermal-assisted wear could be the dominant failure mode for low-field hot switching; on the other hand, pure mechanical wear and steady current heating (1 mA) caused much less contact degradation in cold switching tests. Results from low-force (50 muN/micro-contact), low current (0.1 mA) tests on real MEMS switches indicated that continuous adsorbed films from ambient air could degrade the switch contact resistance. Our work also contributes to the field of general nano-science and technology by resolving the transfer directionality of field evaporation of gold in atomic force microscope (AFM)/scanning tunneling microscope (STM).

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

PubMed Central

Niu, Gang; Kim, Hee-Dong; Roelofs, Robin; Perez, Eduardo; Schubert, Markus Andreas; Zaumseil, Peter; Costina, Ioan; Wenger, Christian

2016-01-01

With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption. PMID:27312225

Material insights of HfO2-based integrated 1-transistor-1-resistor resistive random access memory devices processed by batch atomic layer deposition

NASA Astrophysics Data System (ADS)

Niu, Gang; Kim, Hee-Dong; Roelofs, Robin; Perez, Eduardo; Schubert, Markus Andreas; Zaumseil, Peter; Costina, Ioan; Wenger, Christian

2016-06-01

With the continuous scaling of resistive random access memory (RRAM) devices, in-depth understanding of the physical mechanism and the material issues, particularly by directly studying integrated cells, become more and more important to further improve the device performances. In this work, HfO2-based integrated 1-transistor-1-resistor (1T1R) RRAM devices were processed in a standard 0.25 μm complementary-metal-oxide-semiconductor (CMOS) process line, using a batch atomic layer deposition (ALD) tool, which is particularly designed for mass production. We demonstrate a systematic study on TiN/Ti/HfO2/TiN/Si RRAM devices to correlate key material factors (nano-crystallites and carbon impurities) with the filament type resistive switching (RS) behaviours. The augmentation of the nano-crystallites density in the film increases the forming voltage of devices and its variation. Carbon residues in HfO2 films turn out to be an even more significant factor strongly impacting the RS behaviour. A relatively higher deposition temperature of 300 °C dramatically reduces the residual carbon concentration, thus leading to enhanced RS performances of devices, including lower power consumption, better endurance and higher reliability. Such thorough understanding on physical mechanism of RS and the correlation between material and device performances will facilitate the realization of high density and reliable embedded RRAM devices with low power consumption.

Resistive switching phenomena: A review of statistical physics approaches

DOE PAGES

Lee, Jae Sung; Lee, Shinbuhm; Noh, Tae Won

2015-08-31

Here we report that resistive switching (RS) phenomena are reversible changes in the metastable resistance state induced by external electric fields. After discovery ~50 years ago, RS phenomena have attracted great attention due to their potential application in next-generation electrical devices. Considerable research has been performed to understand the physical mechanisms of RS and explore the feasibility and limits of such devices. There have also been several reviews on RS that attempt to explain the microscopic origins of how regions that were originally insulators can change into conductors. However, little attention has been paid to the most important factor inmore » determining resistance: how conducting local regions are interconnected. Here, we provide an overview of the underlying physics behind connectivity changes in highly conductive regions under an electric field. We first classify RS phenomena according to their characteristic current–voltage curves: unipolar, bipolar, and threshold switchings. Second, we outline the microscopic origins of RS in oxides, focusing on the roles of oxygen vacancies: the effect of concentration, the mechanisms of channel formation and rupture, and the driving forces of oxygen vacancies. Third, we review RS studies from the perspective of statistical physics to understand connectivity change in RS phenomena. We discuss percolation model approaches and the theory for the scaling behaviors of numerous transport properties observed in RS. Fourth, we review various switching-type conversion phenomena in RS: bipolar-unipolar, memory-threshold, figure-of-eight, and counter-figure-of-eight conversions. Finally, we review several related technological issues, such as improvement in high resistance fluctuations, sneak-path problems, and multilevel switching problems.« less

Switching mechanism transition induced by annealing treatment in nonvolatile Cu/ZnO/Cu/ZnO/Pt resistive memory: From carrier trapping/detrapping to electrochemical metallization

NASA Astrophysics Data System (ADS)

Yang, Y. C.; Pan, F.; Zeng, F.; Liu, M.

2009-12-01

ZnO/Cu/ZnO trilayer films sandwiched between Cu and Pt electrodes were prepared for nonvolatile resistive memory applications. These structures show resistance switching under electrical bias both before and after a rapid thermal annealing (RTA) treatment, while it is found that the resistive switching effects in the two cases exhibit distinct characteristics. Compared with the as-fabricated device, the memory cell after RTA demonstrates remarkable device parameter improvements including lower threshold voltages, lower write current, and higher Roff/Ron ratio. A high-voltage forming process is avoided in the annealed device as well. Furthermore, the RTA treatment has triggered a switching mechanism transition from a carrier trapping/detrapping type to an electrochemical-redox-reaction-controlled conductive filament formation/rupture process, as indicated by different features in current-voltage characteristics. Both scanning electron microscopy observations and Auger electron spectroscopy depth profiles reveal that the Cu charge trapping layer in ZnO/Cu/ZnO disperses uniformly into the storage medium after RTA, while x-ray diffraction and x-ray photoelectron spectroscopy analyses demonstrate that the Cu atoms have lost electrons to become Cu2+ ions after dispersion. The above experimental facts indicate that the altered status of Cu in the ZnO/Cu/ZnO trilayer films during RTA treatment should be responsible for the switching mechanism transition. This study is envisioned to open the door for understanding the interrelation between different mechanisms that currently exist in the field of resistive memories.

Mechanisms of charge transport and resistive switching in composite films of semiconducting polymers with nanoparticles of graphene and graphene oxide

NASA Astrophysics Data System (ADS)

Berestennikov, A. S.; Aleshin, A. N.

2017-11-01

We have investigated the effect of the resistive switching in the composite films based on polyfunctional polymers - PVK, PFD and PVC mixed with particles of Gr and GO with the concentration of ˜ 1 - 3 wt.%. We have developed the solution processed hybrid memory structures based on PVK and GO particles composite films. The effect of the resistive switching in Al/PVK(PFD; PVC):Gr(GO)/ITO/PET structures manifests itself as a sharp change of the electrical resistance from a low-conducting state to a relatively high-conducting state when applying a bias to Al-ITO electrodes of ˜ 0.2-0.4 V. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK(PFD; PVC):Gr(GO)/ITO/PET structures, with the switching time in the range from 1 to 30 μs. The mechanism of resistive switching associated with the processes of capture and accumulation of charge carriers by Gr(GO) particles introduced into the matrixes of the PVK polymer due to the reduction/oxidation processes. The possible mechanisms of energy transfer between organic and inorganic components in PVK(PFD; PVC):GO(Gr) films causes increase mobility are discussed. Incorporating of Gr (GO) particles into the polymer matrix is a promising route to enhance the performance of hybrid memory structures, as well as it is an effective medium for memory cells.

Transparent resistive switching memory using aluminum oxide on a flexible substrate

NASA Astrophysics Data System (ADS)

Yeom, Seung-Won; Shin, Sang-Chul; Kim, Tan-Young; Ha, Hyeon Jun; Lee, Yun-Hi; Shim, Jae Won; Ju, Byeong-Kwon

2016-02-01

Resistive switching memory (ReRAM) has attracted much attention in recent times owing to its fast switching, simple structure, and non-volatility. Flexible and transparent electronic devices have also attracted considerable attention. We therefore fabricated an Al2O3-based ReRAM with transparent indium-zinc-oxide (IZO) electrodes on a flexible substrate. The device transmittance was found to be higher than 80% in the visible region (400-800 nm). Bended states (radius = 10 mm) of the device also did not affect the memory performance because of the flexibility of the two transparent IZO electrodes and the thin Al2O3 layer. The conduction mechanism of the resistive switching of our device was explained by ohmic conduction and a Poole-Frenkel emission model. The conduction mechanism was proved by oxygen vacancies in the Al2O3 layer, as analyzed by x-ray photoelectron spectroscopy analysis. These results encourage the application of ReRAM in flexible and transparent electronic devices.

Unipolar resistive switching behaviors and mechanisms in an annealed Ni/ZrO2/TaN memory device

NASA Astrophysics Data System (ADS)

Tsai, Tsung-Ling; Ho, Tsung-Han; Tseng, Tseung-Yuen

2015-01-01

The effects of Ni/ZrO2/TaN resistive switching memory devices without and with a 400 °C annealing process on switching properties are investigated. The devices exhibit unipolar resistive switching behaviors with low set and reset voltages because of a large amount of Ni diffusion with no reaction with ZrO2 after the annealing process, which is confirmed by ToF-SIMS and XPS analyses. A physical model based on a Ni filament is constructed to explain such phenomena. The device that undergoes the 400 °C annealing process exhibits an excellent endurance of more than 1.5  ×  104 cycles. The improvement can be attributed to the enhancement of oxygen ion migration along grain boundaries, which result in less oxygen ion consumption during the reset process. The device also performs good retention up to 105 s at 150 °C. Therefore, it has great potential for high-density nonvolatile memory applications.

Novel Role of Endogenous Catalase in Macrophage Polarization in Adipose Tissue.

PubMed

Park, Ye Seul; Uddin, Md Jamal; Piao, Lingjuan; Hwang, Inah; Lee, Jung Hwa; Ha, Hunjoo

2016-01-01

Macrophages are important components of adipose tissue inflammation, which results in metabolic diseases such as insulin resistance. Notably, obesity induces a proinflammatory phenotypic switch in adipose tissue macrophages, and oxidative stress facilitates this switch. Thus, we examined the role of endogenous catalase, a key regulator of oxidative stress, in the activity of adipose tissue macrophages in obese mice. Catalase knockout (CKO) exacerbated insulin resistance, amplified oxidative stress, and accelerated macrophage infiltration into epididymal white adipose tissue in mice on normal or high-fat diet. Interestingly, catalase deficiency also enhanced classical macrophage activation (M1) and inflammation but suppressed alternative activation (M2) regardless of diet. Similarly, pharmacological inhibition of catalase activity using 3-aminotriazole induced the same phenotypic switch and inflammatory response in RAW264.7 macrophages. Finally, the same phenotypic switch and inflammatory responses were observed in primary bone marrow-derived macrophages from CKO mice. Taken together, the data indicate that endogenous catalase regulates the polarization of adipose tissue macrophages and thereby inhibits inflammation and insulin resistance.

Simultaneous Bistability of a Qubit and Resonator in Circuit Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

Mavrogordatos, Th. K.; Tancredi, G.; Elliott, M.; Peterer, M. J.; Patterson, A.; Rahamim, J.; Leek, P. J.; Ginossar, E.; Szymańska, M. H.

2017-01-01

We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switching.

Improved Thermal-Switch Disks Protect Batteries

NASA Technical Reports Server (NTRS)

Darcy, Eric; Bragg, Bobby

1990-01-01

Improved thermal-switch disks help protect electrical batteries against high currents like those due to short circuits or high demands for power in circuits supplied by batteries. Protects batteries against excessive temperatures. Centered by insulating fiberglass washer. Contains conductive polymer that undergoes abrupt increase in electrical resistance when excessive current raises its temperature above specific point. After cooling, polymer reverts to low resistance. Disks reusable.

Effect of sputtering atmosphere on the characteristics of ZrOx resistive switching memory

NASA Astrophysics Data System (ADS)

He, Pin; Ye, Cong; Wu, Jiaji; Wei, Wei; Wei, Xiaodi; Wang, Hao; Zhang, Rulin; Zhang, Li; Xia, Qing; Wang, Hanbin

2017-05-01

A ZrOx switching layer with different oxygen content for TiN/ZrOx/Pt resistive switching (RS) memory was prepared by magnetron sputtering in different atmospheres such as N2/Ar mixture, O2/Ar mixture as well as pure Ar. The morphology, structure and RS characteristics were systemically investigated and it was found that the RS performance is highly dependent on the sputtering atmosphere. For the memory device sputtered in N2/Ar mixture, with 8.06% nitrogen content in the ZrOx switching layer, the highest uniformity with smallest distribution of V set and high resistance states (HRS)/low resistance states (LRS) values were achieved. By analyzing the current conduction mechanisms combined with possible RS mechanisms for three devices, we deduce that for the device with a ZrOx layer sputtered in N2/Ar mixture, oxygen ions (O2-), which are decisive to the disruption/formation of the conductive filament, will gather around the tip of the filament due to the existence of doping nitrogen, and lead to the reduction of O2- migration randomness in the operation process, so that the uniformity of the N-doped ZrOx device can be improved.

Performance analysis of resistive switching devices based on BaTiO3 thin films

NASA Astrophysics Data System (ADS)

Samardzic, Natasa; Kojic, Tijana; Vukmirovic, Jelena; Tripkovic, Djordjije; Bajac, Branimir; Srdic, Vladimir; Stojanovic, Goran

2016-03-01

Resitive switching devices, memristors, have recenty attracted much attention due to promising performances and potential applications in the field of logic and memory devices. Here, we present thin film BaTiO3 based memristor fabricated using ink-jet printing technique. Active material is a single layer barium titanate film with thickness of ̴100 nm, sandwitched between metal electodes. Printing parameters were optimized aiming to achieve stable drop flow and uniform printed layer. Current-voltage characteristics show typical memristive behavior with pinched hysteresis loop crossed at the origin, with marked differences between High Resistive State (HRS) and Low Resistive State (LRS). Obtained resistive states are stable during numerous switching processes. The device also shows unipolar switching effect for negative voltage impulses. Variable voltage impulse amplitudes leads to the shifting of the energy levels of electode contacts resulting in changing of the overall current through the device. Structural charcterization have been performed using XRD analysis and SEM micrography. High-temperature current-voltage measurements combined with transport parameter analysis using Hall efect measurement system (HMS 3000) and Impedance Analyzer AC measurements allows deeper insigth into conduction mechanism of ferroelectric memristors.

Energy loss in spark gap switches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Lavrinovich, I. V.; National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk

2014-04-15

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Cost-effectiveness of HIV drug resistance testing to inform switching to second line antiretroviral therapy in low income settings.

PubMed

Phillips, Andrew; Cambiano, Valentina; Nakagawa, Fumiyo; Mabugu, Travor; Magubu, Travor; Miners, Alec; Ford, Debbie; Pillay, Deenan; De Luca, Andrea; Lundgren, Jens; Revill, Paul

2014-01-01

To guide future need for cheap resistance tests for use in low income settings, we assessed cost-effectiveness of drug resistance testing as part of monitoring of people on first line ART - with switching from first to second line ART being conditional on NNRTI drug resistance mutations being identified. An individual level simulation model of HIV transmission, progression and the effect of ART which accounts for adherence and resistance development was used to compare outcomes of various potential monitoring strategies in a typical low income setting in sub-Saharan Africa. Underlying monitoring strategies considered were based on clinical disease, CD4 count or viral load. Within each we considered a strategy in which no further measures are performed, one with a viral load measure to confirm failure, and one with both a viral load measure and a resistance test. Predicted outcomes were assessed over 2015-2025 in terms of viral suppression, first line failure, switching to second line regimen, death, HIV incidence, disability-adjusted-life-years averted and costs. Potential future low costs of resistance tests ($30) were used. The most effective strategy, in terms of DALYs averted, was one using viral load monitoring without confirmation. The incremental cost-effectiveness ratio for this strategy was $2113 (the same as that for viral load monitoring with confirmation). ART monitoring strategies which involved resistance testing did not emerge as being more effective or cost effective than strategies not using it. The slightly reduced ART costs resulting from use of resistance testing, due to less use of second line regimens, was of similar magnitude to the costs of resistance tests. Use of resistance testing at the time of first line failure as part of the decision whether to switch to second line therapy was not cost-effective, even though the test was assumed to be very inexpensive.

Tri-state resistive switching characteristics of MnO/Ta2O5 resistive random access memory device by a controllable reset process

NASA Astrophysics Data System (ADS)

Lee, N. J.; Kang, T. S.; Hu, Q.; Lee, T. S.; Yoon, T.-S.; Lee, H. H.; Yoo, E. J.; Choi, Y. J.; Kang, C. J.

2018-06-01

Tri-state resistive switching characteristics of bilayer resistive random access memory devices based on manganese oxide (MnO)/tantalum oxide (Ta2O5) have been studied. The current–voltage (I–V) characteristics of the Ag/MnO/Ta2O5/Pt device show tri-state resistive switching (RS) behavior with a high resistance state (HRS), intermediate resistance state (IRS), and low resistance state (LRS), which are controlled by the reset process. The MnO/Ta2O5 film shows bipolar RS behavior through the formation and rupture of conducting filaments without the forming process. The device shows reproducible and stable RS both from the HRS to the LRS and from the IRS to the LRS. In order to elucidate the tri-state RS mechanism in the Ag/MnO/Ta2O5/Pt device, transmission electron microscope (TEM) images are measured in the LRS, IRS and HRS. White lines like dendrites are observed in the Ta2O5 film in both the LRS and the IRS. Poole–Frenkel conduction, space charge limited conduction, and Ohmic conduction are proposed as the dominant conduction mechanisms for the Ag/MnO/Ta2O5/Pt device based on the obtained I–V characteristics and TEM images.

Method and apparatus for controlling current in inductive loads such as large diameter coils

DOEpatents

Riveros, Carlos A.

1981-01-01

A method and apparatus for controlling electric current in loads that are essentially inductive, such that sparking and "ringing" current problems are reduced or eliminated. The circuit apparatus employs a pair of solid state switches (each of which switch may be an array of connected or parallel solid state switching devices such as transistors) and means for controlling those switches such that a power supply supplying two d.c. voltages (e.g. positive 150 volts d.c. and negative 150 volts d.c.) at low resistance may be connected across an essentially inductive load (e.g. a 6 gauge wire loop one hundred meters in diameter) alternatively and such that the first solid state switch is turned off and the second is turned on such that both are not on at the same time but the first turned on and the other on in less time than the inductive time constant (L/R) so that the load is essentially always presented with a low resistance path across its input. In this manner a steady AC current may be delivered to the load at a frequency desired. Shut-off problems are avoided by gradually shortening the period of switching to less than the time constant so that the maximum energy contained in the inductive load is reduced to approximately zero and dissipated in the inherent resistance. The invention circuit may be employed by adjusting the timing of switching to deliver a desired waveform (such as sinusoidal) to the load.

Biomolecule nanoparticle-induced nanocomposites with resistive switching nonvolatile memory properties

NASA Astrophysics Data System (ADS)

Ko, Yongmin; Ryu, Sook Won; Cho, Jinhan

2016-04-01

Resistive switching behavior-based memory devices are considered promising candidates for next-generation data storage because of their simple structure configuration, low power consumption, and rapid operating speed. Here, the resistive switching nonvolatile memory properties of Fe2O3 nanocomposite (NC) films prepared from the thermal calcination of layer-by-layer (LbL) assembled ferritin multilayers were successfully investigated. For this study, negatively charged ferritin nanoparticles were alternately deposited onto the Pt-coated Si substrate with positively charged poly(allylamine hydrochloride) (PAH) by solution-based electrostatic LbL assembly, and the formed multilayers were thermally calcinated to obtain a homogeneous transition metal oxide NC film through the elimination of organic components, including the protein shell of ferritin. The formed memory device exhibits a stable ON/OFF current ratio of approximately 103, with nanosecond switching times under an applied external bias. In addition, these reversible switching properties were kept stable during the repeated cycling tests of above 200 cycles and a test period of approximately 105 s under atmosphere. These solution-based approaches can provide a basis for large-area inorganic nanoparticle-based electric devices through the design of bio-nanomaterials at the molecular level.

The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM

NASA Astrophysics Data System (ADS)

Sedghi, N.; Li, H.; Brunell, I. F.; Dawson, K.; Potter, R. J.; Guo, Y.; Gibbon, J. T.; Dhanak, V. R.; Zhang, W. D.; Zhang, J. F.; Robertson, J.; Hall, S.; Chalker, P. R.

2017-03-01

The role of nitrogen doping on the stability and memory window of resistive state switching in N-doped Ta2O5 deposited by atomic layer deposition is elucidated. Nitrogen incorporation increases the stability of resistive memory states which is attributed to neutralization of electronic defect levels associated with oxygen vacancies. The density functional simulations with the screened exchange hybrid functional approximation show that the incorporation of nitrogen dopant atoms in the oxide network removes the O vacancy midgap defect states, thus nullifying excess defects and eliminating alternative conductive paths. By effectively reducing the density of vacancy-induced defect states through N doping, 3-bit multilevel cell switching is demonstrated, consisting of eight distinctive resistive memory states achieved by either controlling the set current compliance or the maximum voltage during reset. Nitrogen doping has a threefold effect: widening the switching memory window to accommodate the more intermediate states, improving the stability of states, and providing a gradual reset for multi-level cell switching during reset. The N-doped Ta2O5 devices have relatively small set and reset voltages (< 1 V) with reduced variability due to doping.

Improvement of fatigue resistance for multilayer lead zirconate titanate (PZT)-based ceramic actuators by external mechanical loads

NASA Astrophysics Data System (ADS)

Yang, Gang; Yue, Zhenxing; Ji, Ye; Chu, Xiangcheng; Li, Longtu

2008-12-01

The influence of external compressive loads, applied along a direction perpendicular to polarization, on fatigue behaviors of multilayer lead zirconate titanate (PZT)-based ceramic actuators was investigated. Under no external mechanical load, a normal fatigue behavior was observed, demonstrating that both switching polarization (Pswitching) and remnant polarization (Pr) progressively decreased with increasing switching cycles due to domain pinning by charge point defects. However, an anomalous enhancement in both switching and remnant polarizations was observed upon application of the external compressive loads. After 5×106 cycles of polarization switching, Pswitching and Pr increase by about 13% and 6% at 40 MPa, respectively, while Pswitching and Pr increase by about 11% and 21% at 60 MPa, respectively. The improvement of fatigue resistance can be attributed to non-180° domain switching and suppression of microcracking, triggered by external mechanical loads.

Plane-wave scattering by self-complementary metasurfaces in terms of electromagnetic duality and Babinet's principle

NASA Astrophysics Data System (ADS)

Nakata, Yosuke; Urade, Yoshiro; Nakanishi, Toshihiro; Kitano, Masao

2013-11-01

We investigate theoretically electromagnetic plane-wave scattering by self-complementary metasurfaces. By using Babinet's principle extended to metasurfaces with resistive elements, we show that the frequency-independent transmission and reflection are realized for normal incidence of a circularly polarized plane wave onto a self-complementary metasurface, even if there is diffraction. Next, we consider two special classes of self-complementary metasurfaces. We show that self-complementary metasurfaces with rotational symmetry can act as coherent perfect absorbers, and those with translational symmetry compatible with their self-complementarity can split the incident power equally, even for oblique incidences.

Set statistics in conductive bridge random access memory device with Cu/HfO{sub 2}/Pt structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Meiyun; Long, Shibing, E-mail: longshibing@ime.ac.cn; Wang, Guoming

2014-11-10

The switching parameter variation of resistive switching memory is one of the most important challenges in its application. In this letter, we have studied the set statistics of conductive bridge random access memory with a Cu/HfO{sub 2}/Pt structure. The experimental distributions of the set parameters in several off resistance ranges are shown to nicely fit a Weibull model. The Weibull slopes of the set voltage and current increase and decrease logarithmically with off resistance, respectively. This experimental behavior is perfectly captured by a Monte Carlo simulator based on the cell-based set voltage statistics model and the Quantum Point Contact electronmore » transport model. Our work provides indications for the improvement of the switching uniformity.« less

Resistive switching and voltage induced modulation of tunneling magnetoresistance in nanosized perpendicular organic spin valves

NASA Astrophysics Data System (ADS)

Göckeritz, Robert; Homonnay, Nico; Müller, Alexander; Fuhrmann, Bodo; Schmidt, Georg

2016-04-01

Nanoscale multifunctional perpendicular organic spin valves have been fabricated. The devices based on an La0.7Sr0.3MnO3/Alq3/Co trilayer show resistive switching of up to 4-5 orders of magnitude and magnetoresistance as high as -70% the latter even changing sign when voltage pulses are applied. This combination of phenomena is typically observed in multiferroic tunnel junctions where it is attributed to magnetoelectric coupling between a ferromagnet and a ferroelectric material. Modeling indicates that here the switching originates from a modification of the La0.7Sr0.3MnO3 surface. This modification influences the tunneling of charge carriers and thus both the electrical resistance and the tunneling magnetoresistance which occurs at pinholes in the organic layer.

System and method for determining stator winding resistance in an AC motor

DOEpatents

Lu, Bin [Kenosha, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Theisen, Peter J [West Bend, WI

2011-05-31

A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

Reflective HTS switch

DOEpatents

Martens, Jon S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.

1994-01-01

A HTS switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time.

Selection by current compliance of negative and positive bipolar resistive switching behaviour in ZrO2-x /ZrO2 bilayer memory

NASA Astrophysics Data System (ADS)

Huang, Ruomeng; Yan, Xingzhao; Morgan, Katrina A.; Charlton, Martin D. B.; (Kees de Groot, C. H.

2017-05-01

We report here a ZrO2-x /ZrO2-based bilayer resistive switching memory with unique properties that enables the selection of the switching mode by applying different electroforming current compliances. Two opposite polarity modes, positive bipolar and negative bipolar, correspond to the switching in the ZrO2 and ZrO2-x layer, respectively. The ZrO2 layer is proved to be responsible for the negative bipolar mode which is also observed in a ZrO2 single layer device. The oxygen deficient ZrO2-x layer plays the dominant role in the positive bipolar mode, which is exclusive to the bilayer memory. A systematic investigation of the ZrO2-x composition in the bilayer memory suggests that ZrO1.8 layer demonstrates optimum switching performance with low switching voltage, narrow switching voltage distribution and good cycling endurance. An excess of oxygen vacancies, beyond this composition, leads to a deterioration of switching properties. The formation and dissolution of the oxygen vacancy filament model has been proposed to explain both polarity switching behaviours and the improved properties in the bilayer positive bipolar mode are attributed to the confined oxygen vacancy filament size within the ZrO2-x layer.

Cell-type-specific genome editing with a microRNA-responsive CRISPR–Cas9 switch

PubMed Central

Hirosawa, Moe; Fujita, Yoshihiko; Parr, Callum J. C.; Hayashi, Karin; Kashida, Shunnichi; Hotta, Akitsu; Woltjen, Knut

2017-01-01

Abstract The CRISPR–Cas9 system is a powerful genome-editing tool useful in a variety of biotechnology and biomedical applications. Here we developed a synthetic RNA-based, microRNA (miRNA)-responsive CRISPR–Cas9 system (miR-Cas9 switch) in which the genome editing activity of Cas9 can be modulated through endogenous miRNA signatures in mammalian cells. We created miR-Cas9 switches by using a miRNA-complementary sequence in the 5΄-UTR of mRNA encoding Streptococcus pyogenes Cas9. The miR-21-Cas9 or miR-302-Cas9 switches selectively and efficiently responded to miR-21-5p in HeLa cells or miR-302a-5p in human induced pluripotent stem cells, and post-transcriptionally attenuated the Cas9 activity only in the target cells. Moreover, the miR-Cas9 switches could differentially control the genome editing by sensing endogenous miRNA activities within a heterogeneous cell population. Our miR-Cas9 switch system provides a promising framework for cell-type selective genome editing and cell engineering based on intracellular miRNA information. PMID:28525578

Cardioprotection Resulting from Glucagon-Like Peptide-1 Administration Involves Shifting Metabolic Substrate Utilization to Increase Energy Efficiency in the Rat Heart.

PubMed

Aravindhan, Karpagam; Bao, Weike; Harpel, Mark R; Willette, Robert N; Lepore, John J; Jucker, Beat M

2015-01-01

Previous studies have shown that glucagon-like peptide-1 (GLP-1) provides cardiovascular benefits independent of its role on peripheral glycemic control. However, the precise mechanism(s) by which GLP-1 treatment renders cardioprotection during myocardial ischemia remain unresolved. Here we examined the role for GLP-1 treatment on glucose and fatty acid metabolism in normal and ischemic rat hearts following a 30 min ischemia and 24 h reperfusion injury, and in isolated cardiomyocytes (CM). Relative carbohydrate and fat oxidation levels were measured in both normal and ischemic hearts using a 1-13C glucose clamp coupled with NMR-based isotopomer analysis, as well as in adult rat CMs by monitoring pH and O2 consumption in the presence of glucose or palmitate. In normal heart, GLP-1 increased glucose uptake (↑64%, p<0.05) without affecting glycogen levels. In ischemic hearts, GLP-1 induced metabolic substrate switching by increasing the ratio of carbohydrate versus fat oxidation (↑14%, p<0.01) in the LV area not at risk, without affecting cAMP levels. Interestingly, no substrate switching occurred in the LV area at risk, despite an increase in cAMP (↑106%, p<0.05) and lactate (↑121%, p<0.01) levels. Furthermore, in isolated CMs GLP-1 treatment increased glucose utilization (↑14%, p<0.05) and decreased fatty acid oxidation (↓15%, p<0.05) consistent with in vivo finding. Our results show that this benefit may derive from distinct and complementary roles of GLP-1 treatment on metabolism in myocardial sub-regions in response to this injury. In particular, a switch to anaerobic glycolysis in the ischemic area provides a compensatory substrate switch to overcome the energetic deficit in this region in the face of reduced tissue oxygenation, whereas a switch to more energetically favorable carbohydrate oxidation in more highly oxygenated remote regions supports maintaining cardiac contractility in a complementary manner.

Instability evolution of the viscous elliptic liquid jet in the Rayleigh regime

NASA Astrophysics Data System (ADS)

Gu, Shibo; Wang, Lipo; Hung, David L. S.

2017-06-01

For jet flow emanating from noncircular orifices, an unbalanced surface tension force leads to capillary instability, which is independent of influence from the ambient air in the Rayleigh regime. In the present article, the dynamic behavior of incompressible elliptical jets in the Rayleigh regime is investigated. Theoretically, with the consideration of the fluid viscosity, the solution of the Cosserat equation consists of a particular solution and a complementary solution. For the complementary solution the wave number of disturbance modes has two complex conjugate roots, which are responsible for the jet breakup. To match the nonzero particular solution, a spatial wave needs to be introduced, which is independent of external perturbations. Physically, such a spatial wave is interpreted as the axis-switching phenomenon. The predicted features of the axis-switching wavelength and the damping effect from the fluid viscosity have been successfully verified by experimental results. Moreover, the dispersion relations from the present theory suggest that the growth rate of spatial instability is influenced by orifice eccentricity, the Weber number, and the Ohnesorge number.

Instability evolution of the viscous elliptic liquid jet in the Rayleigh regime.

PubMed

Gu, Shibo; Wang, Lipo; Hung, David L S

2017-06-01

For jet flow emanating from noncircular orifices, an unbalanced surface tension force leads to capillary instability, which is independent of influence from the ambient air in the Rayleigh regime. In the present article, the dynamic behavior of incompressible elliptical jets in the Rayleigh regime is investigated. Theoretically, with the consideration of the fluid viscosity, the solution of the Cosserat equation consists of a particular solution and a complementary solution. For the complementary solution the wave number of disturbance modes has two complex conjugate roots, which are responsible for the jet breakup. To match the nonzero particular solution, a spatial wave needs to be introduced, which is independent of external perturbations. Physically, such a spatial wave is interpreted as the axis-switching phenomenon. The predicted features of the axis-switching wavelength and the damping effect from the fluid viscosity have been successfully verified by experimental results. Moreover, the dispersion relations from the present theory suggest that the growth rate of spatial instability is influenced by orifice eccentricity, the Weber number, and the Ohnesorge number.

The effect of body bias of the metal-oxide-semiconductor field-effect transistor in the resistive network on spatial current distribution in a bio-inspired complementary metal-oxide-semiconductor vision chip

NASA Astrophysics Data System (ADS)

Kong, Jae-Sung; Hyun, Hyo-Young; Seo, Sang-Ho; Shin, Jang-Kyoo

2008-11-01

Complementary metal-oxide-semiconductor (CMOS) vision chips for edge detection based on a resistive circuit have recently been developed. These chips help in the creation of neuromorphic systems of a compact size, high speed of operation, and low power dissipation. The output of the vision chip depends predominantly upon the electrical characteristics of the resistive network which consists of a resistive circuit. In this paper, the body effect of the metal-oxide-semiconductor field-effect transistor for current distribution in a resistive circuit is discussed with a simple model. In order to evaluate the model, two 160 × 120 CMOS vision chips have been fabricated using a standard CMOS technology. The experimental results nicely match our prediction.

Electric field-triggered metal-insulator transition resistive switching of bilayered multiphasic VOx

NASA Astrophysics Data System (ADS)

Won, Seokjae; Lee, Sang Yeon; Hwang, Jungyeon; Park, Jucheol; Seo, Hyungtak

2018-01-01

Electric field-triggered Mott transition of VO2 for next-generation memory devices with sharp and fast resistance-switching response is considered to be ideal but the formation of single-phase VO2 by common deposition techniques is very challenging. Here, VOx films with a VO2-dominant phase for a Mott transition-based metal-insulator transition (MIT) switching device were successfully fabricated by the combined process of RF magnetron sputtering of V metal and subsequent O2 annealing to form. By performing various material characterizations, including scanning transmission electron microscopy-electron energy loss spectroscopy, the film is determined to have a bilayer structure consisting of a VO2-rich bottom layer acting as the Mott transition switching layer and a V2O5/V2O3 mixed top layer acting as a control layer that suppresses any stray leakage current and improves cyclic performance. This bilayer structure enables excellent electric field-triggered Mott transition-based resistive switching of Pt-VOx-Pt metal-insulator-metal devices with a set/reset current ratio reaching 200, set/reset voltage of less than 2.5 V, and very stable DC cyclic switching upto 120 cycles with a great set/reset current and voltage distribution less than 5% of standard deviation at room temperature, which are specifications applicable for neuromorphic or memory device applications. [Figure not available: see fulltext.

Reflective HTS switch

DOEpatents

Martens, J.S.; Hietala, V.M.; Hohenwarter, G.K.G.

1994-09-27

A HTS (High Temperature Superconductor) switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time. 6 figs.

Megavolt, Multigigawatt Pulsed Plasma Switch

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Choi, Sang H.; Song, Kyo D.

1996-01-01

Plasma switch proposed for use in high-voltage, high-current pulse power system. Designed not only to out-perform conventional spark-gap switch but also relatively compact and lightweight. Features inverse-pinch configuration to prevent constriction of current sheets into filaments, plus multiple-ring-electrode structure to resist high-voltage breakdown.

MEMS, Ka-Band Single-Pole Double-Throw (SPDT) Switch for Switched Line Phase Shifters

NASA Technical Reports Server (NTRS)

Scardelletti, Maximilian C.; Ponchak, George E.; Varaljay, Nicholas C.

2002-01-01

Ka-band MEMS doubly anchored cantilever beam capacitive shunt devices are used to demonstrate a MEMS SPDT switch fabricated on high resistivity silicon (HRS) utilizing finite ground coplanar waveguide (FGC) transmission lines. The SPDT switch has an insertion loss (IL), return loss (RL), and isolation of 0.3dB, 40dB, and 30 dB, respectively at Ka-band.

Modulation of resistive switching characteristics for individual BaTiO3 microfiber by surface oxygen vacancies

NASA Astrophysics Data System (ADS)

Miao, Zhilei; Chen, Lei; Zhou, Fang; Wang, Qiang

2018-01-01

Different from traditional thin-film BaTiO3 (BTO) RRAM device with planar structure, individual microfiber-shaped RRAM device, showing promising application potentials in the micro-sized non-volatile memory system, has not been investigated so far to demonstrate resistive switching behavior. In this work, individual sol-gel BTO microfiber has been formed using the draw-bench method, followed by annealing in different atmospheres of air and argon, respectively. The resistive switching characteristics of the individual BTO microfiber have been investigated by employing double-probe SEM measurement system, which shows great convenience to test local electrical properties by modulating the contact sites between the W probes and the BTO microfiber. For the sample annealed in air, the average resistive ON/OFF ratio is as high as 108, enhanced about four orders in comparison with the counterpart that annealed in Argon. For the sample annealed in argon ambience, the weakened resistive ON/OFF ratio can be attributed to the increased presence of oxygen vacancies in the surface of BTO fibers, and the underlying electrical conduction mechanisms are also discussed.

Bipolar resistive switching in Cu/AlN/Pt nonvolatile memory device

NASA Astrophysics Data System (ADS)

Chen, C.; Yang, Y. C.; Zeng, F.; Pan, F.

2010-08-01

Highly stable and reproducible bipolar resistive switching effects are reported on Cu/AlN/Pt devices. Memory characteristics including large memory window of 103, long retention time of >106 s and good endurance of >103 were demonstrated. It is concluded that the reset current decreases as compliance current decreases, which provides an approach to suppress power consumption. The dominant conduction mechanisms of low resistance state and high resistance state were verified by Ohmic behavior and trap-controlled space charge limited current, respectively. The memory effect is explained by the model concerning redox reaction mediated formation and rupture of the conducting filament in AlN films.

Mechanism of the reset process in bipolar-resistance-switching Ta/TaOx/Pt capacitors based on observation of the capacitance and resistance

NASA Astrophysics Data System (ADS)

Na, Sang-Chul; Kim, Jae-Jun; Chul Chun, Min; Hee Jin, Da; Ahn, Seung-Eon; Soo Kang, Bo

2014-03-01

The capacitance (C) and the resistance (R) were measured at various states as the reset process progressed in bipolar-resistance-switching Ta/TaOx/Pt thin film capacitors. The reset process was found to undergo three sequential stages where C and R showed different behavior: increasing C and constant R before an abrupt reset transition, the rapid increase of both C and R upon transition, and saturated C thereafter. These behaviors can be explained in terms of the annihilation of the oxygen vacancies followed by rupture of the conducting channels.

Enhanced switching stability in Ta2O5 resistive RAM by fluorine doping

NASA Astrophysics Data System (ADS)

Sedghi, N.; Li, H.; Brunell, I. F.; Dawson, K.; Guo, Y.; Potter, R. J.; Gibbon, J. T.; Dhanak, V. R.; Zhang, W. D.; Zhang, J. F.; Hall, S.; Robertson, J.; Chalker, P. R.

2017-08-01

The effect of fluorine doping on the switching stability of Ta2O5 resistive random access memory devices is investigated. It shows that the dopant serves to increase the memory window and improve the stability of the resistive states due to the neutralization of oxygen vacancies. The ability to alter the current in the low resistance state with set current compliance coupled with large memory window makes multilevel cell switching more favorable. The devices have set and reset voltages of <1 V with improved stability due to the fluorine doping. Density functional modeling shows that the incorporation of fluorine dopant atoms at the two-fold O vacancy site in the oxide network removes the defect state in the mid bandgap, lowering the overall density of defects capable of forming conductive filaments. This reduces the probability of forming alternative conducting paths and hence improves the current stability in the low resistance states. The doped devices exhibit more stable resistive states in both dc and pulsed set and reset cycles. The retention failure time is estimated to be a minimum of 2 years for F-doped devices measured by temperature accelerated and stress voltage accelerated retention failure methods.

Elucidation and Optimization of Resistive Random Access Memory Switching Behavior for Advanced Computing Applications

NASA Astrophysics Data System (ADS)

Alamgir, Zahiruddin

RRAM has recently emerged as a strong candidate for non-volatile memory (NVM). Beyond memory applications, RRAM holds promise for use in performing logic functions, mimicking neuromorphic activities, enabling multi-level switching, and as one of the key elements of hardware based encryption or signal processing systems. It has been shown previously that RRAM resistance levels can be changed by adjusting compliance current or voltage level. This characteristic makes RRAM suitable for use in setting the synaptic weight in neuromorphic computing circuits. RRAM is also considered as a key element in hardware encryption systems, to produce unique and reproducible signals. However, a key challenge to implement RRAM in these applications is significant cycle to cycle performance variability. We sought to develop RRAM that can be tuned to different resistance levels gradually, with high reliability, and low variability. To achieve this goal, we focused on elucidating the conduction mechanisms underlying the resistive switching behavior for these devices. Electrical conduction mechanisms were determined by curve fitting I-V data using different current conduction equations. Temperature studies were also performed to corroborate these data. It was found that Schottky barrier height and width modulation was one of the key parameters that could be tuned to achieve different resistance levels, and for switching resistance states, primarily via oxygen vacancy movement. Oxygen exchange layers with different electronegativity were placed between top electrode and the oxide layer of TaOx devices to determine the effect of oxygen vacancy concentrations and gradients in these devices. It was found that devices with OELs with lower electronegativity tend to yield greater separation in the OFF vs. ON state resistance levels. As an extension of this work, TaOx based RRAM with Hf as the OEL was fabricated and could be tuned to different resistance level using pulse width and height modulation, yielding excellent uniformity and reliability. These findings improve our understanding of conduction within TaO x-based RRAM devices, providing a physical basis for switching in these devices. The value of this work lies in the demonstration of devices with excellent performance and demonstrated devices constitute a significant step toward real-world applications.

Concepts, characterization, and modeling of MEMS microswitches with gold contacts in MUMPs

NASA Astrophysics Data System (ADS)

Lafontan, Xavier; Dufaza, Christian; Robert, Michel; Pressecq, Francis; Perez, Guy

2001-04-01

This paper demonstrates that RF MEMS micro-switches can be realized with a low cost MEMS technology such as MUMPs. Two different switches are proposed, namely the hinged beam switch and the gold overflowing switch. Their concepts, design and characterization are described in details. On-resistance as low as 5 - 6 (Omega) for the gold overflowing switch and 2 - 3 (Omega) for the hinged beam switch have been measured. Finally, experimental measurements showed that force and electrical current had strong influences on the overall electrical contact.

Efficacy and safety of raltegravir in treatment-experienced HIV-1-infected patients switching from enfuvirtide-based regimens: 48 week results of the randomized EASIER ANRS 138 trial.

PubMed

Gallien, Sébastien; Braun, Joséphine; Delaugerre, Constance; Charreau, Isabelle; Reynes, Jacques; Jeanblanc, François; Verdon, Renaud; de Truchis, Pierre; May, Thierry; Madelaine-Chambrin, Isabelle; Aboulker, Jean-Pierre; Molina, Jean-Michel

2011-09-01

To assess the sustainable efficacy and safety of a switch from enfuvirtide to raltegravir in patients with multidrug-resistant HIV infection. One hundred and seventy patients with multidrug-resistant HIV infection and suppressed plasma HIV RNA levels < 400 copies/mL under an enfuvirtide-based regimen were randomized to maintain their regimen or to switch to a raltegravir-based regimen (immediate group) in a 48 week prospective, randomized, open-label trial. At week 24, patients in the maintenance arm also switched to raltegravir (deferred group). Baseline genotypic susceptibility scores (GSSs) were calculated using available historical resistance tests. Efficacy was assessed by the cumulative proportion of patients with virological failure, defined as a confirmed plasma HIV RNA ≥ 400 copies/mL up to week 48. The EASIER ANRS 138 trial is registered at ClinicalTrials.gov (NCT00454337). At baseline, 86% of patients had plasma HIV RNA levels <50 copies/mL and 86% had a GSS ≥ 1. Through to week 48, in the on-treatment analysis, only one patient in the immediate group, with a GSS of 0, developed virological failure. At week 48, 90% of patients in both the immediate and deferred groups had plasma HIV-1 RNA levels <50 copies/mL. Median CD4 cell counts remained stable during follow-up. Of note, 12 of 66 (18.2%) patients receiving a regimen combining raltegravir and ritonavir-boosted tipranavir experienced alanine aminotransferase elevations, which led to a switch from tipranavir to darunavir in 8 cases, without discontinuation of raltegravir. In well-suppressed patients with multidrug-resistant HIV infection, a switch from enfuvirtide to raltegravir is generally well tolerated and has sustained antiviral efficacy when combined with a potent background regimen.

Logic computation in phase change materials by threshold and memory switching.

PubMed

Cassinerio, M; Ciocchini, N; Ielmini, D

2013-11-06

Memristors, namely hysteretic devices capable of changing their resistance in response to applied electrical stimuli, may provide new opportunities for future memory and computation, thanks to their scalable size, low switching energy and nonvolatile nature. We have developed a functionally complete set of logic functions including NOR, NAND and NOT gates, each utilizing a single phase-change memristor (PCM) where resistance switching is due to the phase transformation of an active chalcogenide material. The logic operations are enabled by the high functionality of nanoscale phase change, featuring voltage comparison, additive crystallization and pulse-induced amorphization. The nonvolatile nature of memristive states provides the basis for developing reconfigurable hybrid logic/memory circuits featuring low-power and high-speed switching. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Schottky Emission Distance and Barrier Height Properties of Bipolar Switching Gd:SiOx RRAM Devices under Different Oxygen Concentration Environments

PubMed Central

Chen, Kai-Huang; Tsai, Tsung-Ming; Cheng, Chien-Min; Huang, Shou-Jen; Chang, Kuan-Chang; Liang, Shu-Ping; Young, Tai-Fa

2017-01-01

In this study, the hopping conduction distance and bipolar switching properties of the Gd:SiOx thin film by (radio frequency, rf) rf sputtering technology for applications in RRAM devices were calculated and investigated. To discuss and verify the electrical switching mechanism in various different constant compliance currents, the typical current versus applied voltage (I-V) characteristics of gadolinium oxide RRAM devices was transferred and fitted. Finally, the transmission electrons’ switching behavior between the TiN bottom electrode and Pt top electrode in the initial metallic filament forming process of the gadolinium oxide thin film RRAM devices for low resistance state (LRS)/high resistance state (HRS) was described and explained in a simulated physical diagram model. PMID:29283368

On the origin of resistive switching volatility in Ni/TiO{sub 2}/Ni stacks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cortese, Simone, E-mail: simone.cortese@soton.ac.uk; Trapatseli, Maria; Khiat, Ali

2016-08-14

Resistive switching and resistive random access memories have attracted huge interest for next generation nonvolatile memory applications, also thought to be able to overcome flash memories limitations when arranged in crossbar arrays. A cornerstone of their potential success is that the toggling between two distinct resistance states, usually a High Resistive State (HRS) and a Low Resistive State (LRS), is an intrinsic non-volatile phenomenon with the two states being thermodynamically stable. TiO{sub 2} is one of the most common materials known to support non-volatile RS. In this paper, we report a volatile resistive switching in a titanium dioxide thin filmmore » sandwiched by two nickel electrodes. The aim of this work is to understand the underlying physical mechanism that triggers the volatile effect, which is ascribed to the presence of a NiO layer at the bottom interface. The NiO layer alters the equilibrium between electric field driven filament formation and thermal enhanced ion diffusion, resulting in the volatile behaviour. Although the volatility is not ideal for non-volatile memory applications, it shows merit for access devices in crossbar arrays due to its high LRS/HRS ratio, which are also briefly discussed.« less

Comparison of resistive switching characteristics using copper and aluminum electrodes on GeOx/W cross-point memories

PubMed Central

2013-01-01

Comparison of resistive switching memory characteristics using copper (Cu) and aluminum (Al) electrodes on GeOx/W cross-points has been reported under low current compliances (CCs) of 1 nA to 50 μA. The cross-point memory devices are observed by high-resolution transmission electron microscopy (HRTEM). Improved memory characteristics are observed for the Cu/GeOx/W structures as compared to the Al/GeOx/W cross-points owing to AlOx formation at the Al/GeOx interface. The RESET current increases with the increase of the CCs varying from 1 nA to 50 μA for the Cu electrode devices, while the RESET current is high (>1 mA) and independent of CCs varying from 1 nA to 500 μA for the Al electrode devices. An extra formation voltage is needed for the Al/GeOx/W devices, while a low operation voltage of ±2 V is needed for the Cu/GeOx/W cross-point devices. Repeatable bipolar resistive switching characteristics of the Cu/GeOx/W cross-point memory devices are observed with CC varying from 1 nA to 50 μA, and unipolar resistive switching is observed with CC >100 μA. High resistance ratios of 102 to 104 for the bipolar mode (CCs of 1 nA to 50 μA) and approximately 108 for the unipolar mode are obtained for the Cu/GeOx/W cross-points. In addition, repeatable switching cycles and data retention of 103 s are observed under a low current of 1 nA for future low-power, high-density, nonvolatile, nanoscale memory applications. PMID:24305116

Programmable resistive-switch nanowire transistor logic circuits.

PubMed

Shim, Wooyoung; Yao, Jun; Lieber, Charles M

2014-09-10

Programmable logic arrays (PLA) constitute a promising architecture for developing increasingly complex and functional circuits through nanocomputers from nanoscale building blocks. Here we report a novel one-dimensional PLA element that incorporates resistive switch gate structures on a semiconductor nanowire and show that multiple elements can be integrated to realize functional PLAs. In our PLA element, the gate coupling to the nanowire transistor can be modulated by the memory state of the resistive switch to yield programmable active (transistor) or inactive (resistor) states within a well-defined logic window. Multiple PLA nanowire elements were integrated and programmed to yield a working 2-to-4 demultiplexer with long-term retention. The well-defined, controllable logic window and long-term retention of our new one-dimensional PLA element provide a promising route for building increasingly complex circuits with nanoscale building blocks.

Resistive switching behaviors of Au/pentacene/Si-nanowire arrays/heavily doped n-type Si devices for memory applications

NASA Astrophysics Data System (ADS)

Tsao, Hou-Yen; Lin, Yow-Jon

2014-02-01

The fabrication of memory devices based on the Au/pentacene/heavily doped n-type Si (n+-Si), Au/pentacene/Si nanowires (SiNWs)/n+-Si, and Au/pentacene/H2O2-treated SiNWs/n+-Si structures and their resistive switching characteristics were reported. A pentacene memory structure using SiNW arrays as charge storage nodes was demonstrated. The Au/pentacene/SiNWs/n+-Si devices show hysteresis behavior. H2O2 treatment may lead to the hysteresis degradation. However, no hysteresis-type current-voltage characteristics were observed for Au/pentacene/n+-Si devices, indicating that the resistive switching characteristic is sensitive to SiNWs and the charge trapping effect originates from SiNWs. The concept of nanowires within the organic layer opens a promising direction for organic memory devices.

Internal filament modulation in low-dielectric gap design for built-in selector-less resistive switching memory application

NASA Astrophysics Data System (ADS)

Chen, Ying-Chen; Lin, Chih-Yang; Huang, Hui-Chun; Kim, Sungjun; Fowler, Burt; Chang, Yao-Feng; Wu, Xiaohan; Xu, Gaobo; Chang, Ting-Chang; Lee, Jack C.

2018-02-01

Sneak path current is a severe hindrance for the application of high-density resistive random-access memory (RRAM) array designs. In this work, we demonstrate nonlinear (NL) resistive switching characteristics of a HfO x /SiO x -based stacking structure as a realization for selector-less RRAM devices. The NL characteristic was obtained and designed by optimizing the internal filament location with a low effective dielectric constant in the HfO x /SiO x structure. The stacking HfO x /SiO x -based RRAM device as the one-resistor-only memory cell is applicable without needing an additional selector device to solve the sneak path issue with a switching voltage of ~1 V, which is desirable for low-power operating in built-in nonlinearity crossbar array configurations.

CD4 count-based failure criteria combined with viral load monitoring may trigger worse switch decisions than viral load monitoring alone.

PubMed

Hoffmann, Christopher J; Maritz, Jean; van Zyl, Gert U

2016-02-01

CD4 count decline often triggers antiretroviral regimen switches in resource-limited settings, even when viral load testing is available. We therefore compared CD4 failure and CD4 trends in patients with viraemia with or without antiretroviral resistance. Retrospective cohort study investigating the association of HIV drug resistance with CD4 failure or CD4 trends in patients on first-line antiretroviral regimens during viraemia. Patients with viraemia (HIV RNA >1000 copies/ml) from two HIV treatment programmes in South Africa (n = 350) were included. We investigated the association of M184V and NNRTI resistance with WHO immunological failure criteria and CD4 count trends, using chi-square tests and linear mixed models. Fewer patients with the M184V mutation reached immunologic failure criteria than those without: 51 of 151(34%) vs. 90 of 199 (45%) (P = 0.03). Similarly, 79 of 220 (36%) patients, who had major NNRTI resistance, had immunological failure, whereas 62 of 130 (48%) without (chi-square P = 0.03) did. The CD4 count decline among patients with the M184V mutation was 2.5 cells/mm(3) /year, whereas in those without M184V it was 14 cells/mm(3) /year (P = 0.1), but the difference in CD4 count decline with and without NNRTI resistance was marginal. Our data suggest that CD4 count monitoring may lead to inappropriate delayed therapy switches for patients with HIV drug resistance. Conversely, patients with viraemia but no drug resistance are more likely to have a CD4 count decline and thus may be more likely to be switched to a second-line regimen. © 2015 John Wiley & Sons Ltd.

Influence of Ta doping in resistive switching behavior of TiO2

NASA Astrophysics Data System (ADS)

Barman, Arabinda; Saini, Chetan P.; Deshmukh, Sujit; Dhar, Sankar; Kanjilal, Aloke

An approach has been made to understand the resistive switching behavior in Ta-doped TiO2 films on Pt substrates. Prior to thin film deposition, Ta-doped TiO2 powder has been synthesized chemically using Ta and Ti precursor solutions. However, the Ta doping has seriously been affected by increasing Ta concentration above 1 at% due to the segregation of Ta2O5 phase. The Ta-doped TiO2 targets have been prepared for pulsed laser deposition of the films on Pt substrates using an excitation wavelength of 248 nm. The structural and chemical properties of the Ta-doped TiO2 films have been investigated in details with the help of XRD, SIMS, XAS and XPS. The stoichiometry of the Ta-doped TiO2 films with increasing depth has been verified initially by SIMS. The electrical study of the corresponding device structures further suggests that the optimized resistive switching effect can be accomplished up to a threshold Ta-doping of 1 at%. Nevertheless, a highly conducting behavior has been shown when the TiO2 films are doped with 2 at% Ta. These results will be discussed in details in the light of defect induced resistive switching phenomenon.

Hydrogen-peroxide-modified egg albumen for transparent and flexible resistive switching memory

NASA Astrophysics Data System (ADS)

Zhou, Guangdong; Yao, Yanqing; Lu, Zhisong; Yang, Xiude; Han, Juanjuan; Wang, Gang; Rao, Xi; Li, Ping; Liu, Qian; Song, Qunliang

2017-10-01

Egg albumen is modified by hydrogen peroxide with concentrations of 5%, 10%, 15% and 30% at room temperature. Compared with devices without modification, a memory cell of Ag/10% H2O2-egg albumen/indium tin oxide exhibits obviously enhanced resistive switching memory behavior with a resistance ratio of 104, self-healing switching endurance for 900 cycles and a prolonged retention time for a 104 s @ 200 mV reading voltage after being bent 103 times. The breakage of massive protein chains occurs followed by the recombination of new protein chain networks due to the oxidation of amidogen and the synthesis of disulfide during the hydrogen peroxide modifying egg albumen. Ions such as Fe3+, Na+, K+, which are surrounded by protein chains, are exposed to the outside of protein chains to generate a series of traps during the egg albumen degeneration process. According to the fitting results of the double logarithm I-V curves and the current-sensing atomic force microscopy (CS-AFM) images of the ON and OFF states, the charge transfer from one trap center to its neighboring trap center is responsible for the resistive switching memory phenomena. The results of our work indicate that hydrogen- peroxide-modified egg albumen could open up a new avenue of biomaterial application in nanoelectronic systems.

Inverse polarity of the resistive switching effect and strong inhomogeneity in nanoscale YBCO-metal contacts

NASA Astrophysics Data System (ADS)

Truchly, M.; Plecenik, T.; Zhitlukhina, E.; Belogolovskii, M.; Dvoranova, M.; Kus, P.; Plecenik, A.

2016-11-01

We have studied a bipolar resistive switching phenomenon in c-axis oriented normal-state YBa2Cu3O7-c (YBCO) thin films at room temperature by scanning spreading resistance microscopy (SSRM) and scanning tunneling microscopy (STM) techniques. The most striking experimental finding has been the opposite (in contrast to the previous room and low-temperature data for planar metal counter-electrode-YBCO bilayers) voltage-bias polarity of the switching effect in all SSRM and a number of STM measurements. We have assumed that the hysteretic phenomena in current-voltage characteristics of YBCO-based contacts can be explained by migration of oxygen-vacancy defects and, as a result, by the formation or dissolution of more or less conductive regions near the metal-YBCO interface. To support our interpretation of the macroscopic resistive switching phenomenon, a minimalist model that describes radical modifications of the oxygen-vacancy effective charge in terms of a charge-wind effect was proposed. It was shown theoretically that due to the momentum exchange between current carriers (holes in the YBCO compound) and activated oxygen ions, the direction in which oxygen vacancies are moving is defined by the balance between the direct electrostatic force on them and that caused by the current-carrier flow.

Junction size dependence of ferroelectric properties in e-beam patterned BaTiO{sub 3} ferroelectric tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, A. V.; Gupta, A.; Althammer, M.

We investigate the switching characteristics in BaTiO{sub 3}-based ferroelectric tunnel junctions patterned in a capacitive geometry with circular Ru top electrode with diameters ranging from ∼430 to 2300 nm. Two different patterning schemes, viz., lift-off and ion-milling, have been employed to examine the variations in the ferroelectric polarization, switching, and tunnel electro-resistance resulting from differences in the pattering processes. The values of polarization switching field are measured and compared for junctions of different diameter in the samples fabricated using both patterning schemes. We do not find any specific dependence of polarization switching bias on the size of junctions in both samplemore » stacks. The junctions in the ion-milled sample show up to three orders of resistance change by polarization switching and the polarization retention is found to improve with increasing junction diameter. However, similar switching is absent in the lift-off sample, highlighting the effect of patterning scheme on the polarization retention.« less

Flexible resistive switching device based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/poly(4-vinylphenol) (PVP) composite and methyl red heterojunction

NASA Astrophysics Data System (ADS)

Hassan, Gul; Ali, Shawkat; Bae, Jinho; Lee, Chong Hyun

2017-04-01

To obtain a desired performance of non-volatile memory applications, heterojunction-based resistive switching devices have tremendous attractions. In this paper, we demonstrate resistive switching characteristics for heterojunction of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/poly(4-vinylphenol) (PVP) composite and methyl red sandwiched in between bottom and top silver (Ag) electrodes. The proposed heterojunction layers are fabricated through spin coater at 3000 rpm for 60 s each, and the Ag electrodes are deposited through a commercialized inkjet printer DMP-3000 on polyethyleneterephthalate (PET) substrate. To verify the proposed device, the resistive switching on dual polarity voltage of ±10.2 V is measured over more than 500 endurance cycles. The paper also presents an R off/ R on ratio which can adjust through an active layer's area and a blending ratio of the PEDOT:PSS and PVP. By applying the area of 100 μm2 and the blending ratio of 3:1, we achieve the higher R off/ R on ratio of 121, and its high resistance state (HRS) and low resistance state (LRS) are observed as 3000 kΩ and 24.7 kΩ, respectively. To maintain a long retention time, the device is encapsulated with PDMS, which changes a little variations of 52 Ω for HRS 498 Ω for LRS over 60 days. For the flexible realization to be utilized in wearable applications, it can be easily applied on a plastic substrate using printed technologies.

Brownmillerite thin films as fast ion conductors for ultimate-performance resistance switching memory.

PubMed

Acharya, Susant Kumar; Jo, Janghyun; Raveendra, Nallagatlla Venkata; Dash, Umasankar; Kim, Miyoung; Baik, Hionsuck; Lee, Sangik; Park, Bae Ho; Lee, Jae Sung; Chae, Seung Chul; Hwang, Cheol Seong; Jung, Chang Uk

2017-07-27

An oxide-based resistance memory is a leading candidate to replace Si-based flash memory as it meets the emerging specifications for future memory devices. The non-uniformity in the key switching parameters and low endurance in conventional resistance memory devices are preventing its practical application. Here, a novel strategy to overcome the aforementioned challenges has been unveiled by tuning the growth direction of epitaxial brownmillerite SrFeO 2.5 thin films along the SrTiO 3 [111] direction so that the oxygen vacancy channels can connect both the top and bottom electrodes rather directly. The controlled oxygen vacancy channels help reduce the randomness of the conducting filament (CF). The resulting device displayed high endurance over 10 6 cycles, and a short switching time of ∼10 ns. In addition, the device showed very high uniformity in the key switching parameters for device-to-device and within a device. This work demonstrates a feasible example for improving the nanoscale device performance by controlling the atomic structure of a functional oxide layer.

Efficiency of broadband terahertz rectennas based on self-switching nanodiodes

NASA Astrophysics Data System (ADS)

Briones, Edgar; Cortes-Mestizo, Irving E.; Briones, Joel; Droopad, Ravindranath; Espinosa-Vega, Leticia I.; Vilchis, Heber; Mendez-Garcia, Victor H.

2017-04-01

The authors investigate the efficiency of a series of broadband rectennas designed to harvest the free-propagating electromagnetic energy at terahertz frequencies. We analyze by simulations the case of self-complementary square- and Archimedean-spiral antennas coupled to L-shaped self-switching diodes (L-SSDs). First, the geometry (i.e., the width and length of the channel) of the L-SSD was optimized to obtain a remarkable diode-like I-V response. Subsequently, the optimized L-SSD geometry was coupled to both types of spiral antennas and their characteristic impedance was studied. Finally, the energy conversion efficiency was evaluated for both rectenna architectures.

Parallel logic gates in synthetic gene networks induced by non-Gaussian noise.

PubMed

Xu, Yong; Jin, Xiaoqin; Zhang, Huiqing

2013-11-01

The recent idea of logical stochastic resonance is verified in synthetic gene networks induced by non-Gaussian noise. We realize the switching between two kinds of logic gates under optimal moderate noise intensity by varying two different tunable parameters in a single gene network. Furthermore, in order to obtain more logic operations, thus providing additional information processing capacity, we obtain in a two-dimensional toggle switch model two complementary logic gates and realize the transformation between two logic gates via the methods of changing different parameters. These simulated results contribute to improve the computational power and functionality of the networks.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Switching Characteristics of Phase Change Memory Cell Integrated with Metal-Oxide Semiconductor Field Effect Transistor

NASA Astrophysics Data System (ADS)

Xu, Cheng; Liu, Bo; Chen, Yi-Feng; Liang, Shuang; Song, Zhi-Tang; Feng, Song-Lin; Wan, Xu-Dong; Yang, Zuo-Ya; Xie, Joseph; Chen, Bomy

2008-05-01

A Ge2Sb2Te5 based phase change memory device cell integrated with metal-oxide semiconductor field effect transistor (MOSFET) is fabricated using standard 0. 18 μm complementary metal-oxide semiconductor process technology. It shows steady switching characteristics in the dc current-voltage measurement. The phase changing phenomenon from crystalline state to amorphous state with a voltage pulse altitude of 2.0 V and pulse width of 50 ns is also obtained. These results show the feasibility of integrating phase change memory cell with MOSFET.

Learning from nature: binary cooperative complementary nanomaterials.

PubMed

Su, Bin; Guo, Wei; Jiang, Lei

2015-03-01

In this Review, nature-inspired binary cooperative complementary nanomaterials (BCCNMs), consisting of two components with entirely opposite physiochemical properties at the nanoscale, are presented as a novel concept for the building of promising materials. Once the distance between the two nanoscopic components is comparable to the characteristic length of some physical interactions, the cooperation between these complementary building blocks becomes dominant and endows the macroscopic materials with novel and superior properties. The first implementation of the BCCNMs is the design of bio-inspired smart materials with superwettability and their reversible switching between different wetting states in response to various kinds of external stimuli. Coincidentally, recent studies on other types of functional nanomaterials contribute more examples to support the idea of BCCNMs, which suggests a potential yet comprehensive range of future applications in both materials science and engineering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dehydroxyl effect of Sn-doped silicon oxide resistance random access memory with supercritical CO2 fluid treatment

NASA Astrophysics Data System (ADS)

Tsai, Tsung-Ming; Chang, Kuan-Chang; Chang, Ting-Chang; Syu, Yong-En; Liao, Kuo-Hsiao; Tseng, Bae-Heng; Sze, Simon M.

2012-09-01

The tin-doped can supply conduction path to induce resistance switching behavior. However, the defect of tin-doped silicon oxide (Sn:SiOx) increased the extra leakage path lead to power consumption and joule heating degradation. In the study, supercritical CO2 fluids treatment was used to improve resistive switching property. The current conduction of high resistant state in post-treated Sn:SiOx film was transferred to Schottky emission from Frenkel-Poole due to the passivation effect. The molecular reaction model is proposed that the defect was passivated through dehydroxyl effect of supercritical fluid technology, verified by material analyses of x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

Nano-cone resistive memory for ultralow power operation.

PubMed

Kim, Sungjun; Jung, Sunghun; Kim, Min-Hwi; Kim, Tae-Hyeon; Bang, Suhyun; Cho, Seongjae; Park, Byung-Gook

2017-03-24

SiN x -based nano-structure resistive memory is fabricated by fully silicon CMOS compatible process integration including particularly designed anisotropic etching for the construction of a nano-cone silicon bottom electrode (BE). Bipolar resistive switching characteristics have significantly reduced switching current and voltage and are demonstrated in a nano-cone BE structure, as compared with those in a flat BE one. We have verified by systematic device simulations that the main cause of reduction in the performance parameters is the high electric field being more effectively concentrated at the tip of the cone-shaped BE. The greatly improved nonlinearity of the nano-cone resistive memory cell will be beneficial in the ultra-high-density crossbar array.

Impact of interfacial resistance switching on thermoelectric effect of Nb-doped SrTiO3 single crystalline

NASA Astrophysics Data System (ADS)

Zhang, Peijian; Meng, Yang; Liu, Ziyu; Li, Dong; Su, Tao; Meng, Qingyu; Mao, Qi; Pan, Xinyu; Chen, Dongmin; Zhao, Hongwu

2012-03-01

The thermoelectric properties of the bistable resistance states in Nb doped SrTiO3 single crystal have been investigated. The Seebeck coefficients for both low and high resistance states change linearly with temperature. The three-terminals contrast measurement demonstrates that a large fraction of the voltage drop is applied at the tiny volume near the bottom interface between the electrode and the oxide bulk. Therefore, the metallic oxide bulk plays a dominant role in the temperature dependence of Seebeck coefficients. The thermoelectric properties of new resistance switching (RS) devices with minimized non-RS volume could be exploited for the RS mechanism and novel applications.

Switching-type regulator circuit has increased efficiency

NASA Technical Reports Server (NTRS)

Clapp, W. M.

1967-01-01

Switching series regulator circuit uses an inductive network to feed most of the current applied to the control circuit to the load. This circuit eliminates resistive losses and the need for heat sinks.

Miniature Intermittent Contact Switch

NASA Technical Reports Server (NTRS)

Sword, Antony

1972-01-01

This tech brief concerns work to provide a shock-resistant switch capable of being actuated by forces of varying magnitude and direction, primarily for use as a sensor on remote control (tele-operator) and prosthetic devices.

Effect of halide-mixing on the switching behaviors of organic-inorganic hybrid perovskite memory

NASA Astrophysics Data System (ADS)

Hwang, Bohee; Gu, Chungwan; Lee, Donghwa; Lee, Jang-Sik

2017-03-01

Mixed halide perovskite materials are actively researched for solar cells with high efficiency. Their hysteresis which originates from the movement of defects make perovskite a candidate for resistive switching memory devices. We demonstrate the resistive switching device based on mixed-halide organic-inorganic hybrid perovskite CH3NH3PbI3-xBrx (x = 0, 1, 2, 3). Solvent engineering is used to deposit the homogeneous CH3NH3PbI3-xBrx layer on the indium-tin oxide-coated glass substrates. The memory device based on CH3NH3PbI3-xBrx exhibits write endurance and long retention, which indicate reproducible and reliable memory properties. According to the increase in Br contents in CH3NH3PbI3-xBrx the set electric field required to make the device from low resistance state to high resistance state decreases. This result is in accord with the theoretical calculation of migration barriers, that is the barrier to ionic migration in perovskites is found to be lower for Br- (0.23 eV) than for I- (0.29-0.30 eV). The resistive switching may be the result of halide vacancy defects and formation of conductive filaments under electric field in the mixed perovskite layer. It is observed that enhancement in operating voltage can be achieved by controlling the halide contents in the film.

Resistance switching in polyvinylidene fluoride (PVDF) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramod, K.; Sahu, Binaya Kumar; Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in

2015-06-24

Polyvinylidene fluoride (PDVF), one of the best electrically active polymer material & an interesting candidate to address the electrical control of its functional properties like ferroelectricity, piezoelectricity, pyroelectricity etc. In the current work, with the help of spin coater and DC magnetron sputtering techniques, semi-crystallized PVDF thin films prominent in alpha phase is prepared in capacitor like structure and their electrical characterization is emphasized. In current-voltage (I-V) and resistance-voltage (R-V) measurements, clear nonlinearity and resistance switching has been observed for films prepared using 7 wt% 2-butanone and 7 wt% Dimethyl Sulfoxide (DMSO) solvents.

Reversible voltage dependent transition of abnormal and normal bipolar resistive switching.

PubMed

Wang, Guangyu; Li, Chen; Chen, Yan; Xia, Yidong; Wu, Di; Xu, Qingyu

2016-11-14

Clear understanding the mechanism of resistive switching is the important prerequisite for the realization of high performance nonvolatile resistive random access memory. In this paper, binary metal oxide MoO x layer sandwiched by ITO and Pt electrodes was taken as a model system, reversible transition of abnormal and normal bipolar resistive switching (BRS) in dependence on the maximum voltage was observed. At room temperature, below a critical maximum voltage of 2.6 V, butterfly shaped I-V curves of abnormal BRS has been observed with low resistance state (LRS) to high resistance state (HRS) transition in both polarities and always LRS at zero field. Above 2.6 V, normal BRS was observed, and HRS to LRS transition happened with increasing negative voltage applied. Temperature dependent I-V measurements showed that the critical maximum voltage increased with decreasing temperature, suggesting the thermal activated motion of oxygen vacancies. Abnormal BRS has been explained by the partial compensation of electric field from the induced dipoles opposite to the applied voltage, which has been demonstrated by the clear amplitude-voltage and phase-voltage hysteresis loops observed by piezoelectric force microscopy. The normal BRS was due to the barrier modification at Pt/MoO x interface by the accumulation and depletion of oxygen vacancies.

Cell-type-specific genome editing with a microRNA-responsive CRISPR-Cas9 switch.

PubMed

Hirosawa, Moe; Fujita, Yoshihiko; Parr, Callum J C; Hayashi, Karin; Kashida, Shunnichi; Hotta, Akitsu; Woltjen, Knut; Saito, Hirohide

2017-07-27

The CRISPR-Cas9 system is a powerful genome-editing tool useful in a variety of biotechnology and biomedical applications. Here we developed a synthetic RNA-based, microRNA (miRNA)-responsive CRISPR-Cas9 system (miR-Cas9 switch) in which the genome editing activity of Cas9 can be modulated through endogenous miRNA signatures in mammalian cells. We created miR-Cas9 switches by using a miRNA-complementary sequence in the 5΄-UTR of mRNA encoding Streptococcus pyogenes Cas9. The miR-21-Cas9 or miR-302-Cas9 switches selectively and efficiently responded to miR-21-5p in HeLa cells or miR-302a-5p in human induced pluripotent stem cells, and post-transcriptionally attenuated the Cas9 activity only in the target cells. Moreover, the miR-Cas9 switches could differentially control the genome editing by sensing endogenous miRNA activities within a heterogeneous cell population. Our miR-Cas9 switch system provides a promising framework for cell-type selective genome editing and cell engineering based on intracellular miRNA information. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Magnetoresistance Behavior of Conducting Filaments in Resistive-Switching NiO with Different Resistance States.

PubMed

Zhao, Diyang; Qiao, Shuang; Luo, Yuxiang; Chen, Aitian; Zhang, Pengfei; Zheng, Ping; Sun, Zhong; Guo, Minghua; Chiang, Fu-Kuo; Wu, Jian; Luo, Jianlin; Li, Jianqi; Kokado, Satoshi; Wang, Yayu; Zhao, Yonggang

2017-03-29

The resistive switching (RS) effect in various materials has attracted much attention due to its interesting physics and potential for applications. NiO is an important system and its RS effect has been generally explained by the formation/rupture of Ni-related conducting filaments. These filaments are unique since they are formed by an electroforming process, so it is interesting to explore their magnetoresistance (MR) behavior, which can also shed light on unsolved issues such as the nature of the filaments and their evolution in the RS process, and this behavior is also important for multifunctional devices. Here, we focus on MR behavior in NiO RS films with different resistance states. Rich and interesting MR behaviors have been observed, including the normal and anomalous anisotropic magnetoresistance and tunneling magnetoresistance, which provide new insights into the nature of the filaments and their evolution in the RS process. First-principles calculation reveals the essential role of oxygen migration into the filaments during the RESET process and can account for the experimental results. Our work provides a new avenue for exploration of the conducting filaments in resistive switching materials and is significant for understanding the mechanism of RS effect and multifunctional devices.

Functional nanometer-scale structures

NASA Astrophysics Data System (ADS)

Chan, Tsz On Mario

Nanometer-scale structures have properties that are fundamentally different from their bulk counterparts. Much research effort has been devoted in the past decades to explore new fabrication techniques, model the physical properties of these structures, and construct functional devices. The ability to manipulate and control the structure of matter at the nanoscale has made many new classes of materials available for the study of fundamental physical processes and potential applications. The interplay between fabrication techniques and physical understanding of the nanostructures and processes has revolutionized the physical and material sciences, providing far superior properties in materials for novel applications that benefit society. This thesis consists of two major aspects of my graduate research in nano-scale materials. In the first part (Chapters 3--6), a comprehensive study on the nanostructures based on electrospinning and thermal treatment is presented. Electrospinning is a well-established method for producing high-aspect-ratio fibrous structures, with fiber diameter ranging from 1 nm--1 microm. A polymeric solution is typically used as a precursor in electrospinning. In our study, the functionality of the nanostructure relies on both the nanostructure and material constituents. Metallic ions containing precursors were added to the polymeric precursor following a sol-gel process to prepare the solution suitable for electrospinning. A typical electrospinning process produces as-spun fibers containing both polymer and metallic salt precursors. Subsequent thermal treatments of the as-spun fibers were carried out in various conditions to produce desired structures. In most cases, polymer in the solution and the as-spun fibers acted as a backbone for the structure formation during the subsequent heat treatment, and were thermally removed in the final stage. Polymers were also designed to react with the metallic ion precursors during heat treatment in some cases, which led to desired chemical phase formation. The residue of polymer thermal decomposition was also controlled and utilized for certain functionality in some nanostructures. Throughout this study, we successfully fabricated several novel functional structures and revealed a new formation mechanism of metal/metal oxide nanotubes. The magnetic and electrical properties of these nanostructures were studied and optimized for applications in soft magnetic materials and spintronics devices. In the second part, (Chapter 7) a study on memristive switching devices with magnetron-sputtered metal-semiconductor-metal thin film structures based on ZnO is presented. Resistive random access memory (RRAM) is a new, non-volatile memory based on the memristor effect theoretically predicted by Leon Chua in 1971 and first experimentally demonstrated by Hewlett Packard in 2008. The unit cell of a RRAM (a memristor) is a two-terminal device in which the switching medium is sandwiched between the top and bottom electrodes and the resistance of the switching medium can be modulated by applying an electrical signal (current or voltage) to the electrodes. On the other hand, the significance of a memristor, as the fourth element of circuit elements besides resistor, capacitor and inductor, is not limited to just being a candidate for next-generation memory. Owing to the unique i-v characteristics of non-linear memristors that cannot be duplicated with any combinations of the other three basic elements in a passive circuitry, many new electrical functions are being developed based on the memristors. In our study, various contact electrode combinations and semiconductor doping profiles were utilized to achieve different functional resistive switching behaviors and to help fundamentally understand the underlying switching mechanisms in ZnO-based thin film structures. Two distinctive switching mechanisms (ferroelectric charge-induced resistive switching and dopant-induced filament-type resistive switching) have been identified in specified structures. Among them, the ferroelectric charge induced resistive switching is new to the existing mechanisms; and the crucial role of the electrode oxide layer in the filament type resistive switching was reported for the first time. Based on these studies, a unique structure that is believed to combine the two competing switching mechanisms was demonstrated. The new memory structure acts like a complimentary resistive switching memory (CRS) that is designed to eliminate the cross-talk issue in RRAM.

Low-temperature DC-contact piezoelectric switch operable in high magnetic fields

NASA Astrophysics Data System (ADS)

Kaltenbacher, Thomas; Caspers, Fritz; Doser, Michael; Kellerbauer, Alban; Pribyl, Wolfgang

2013-11-01

A piezoelectric single-pole single-throw (SPST) switch has been developed, since there is no satisfying commercial low-resistance, high current DC-contact RF switch available which is operable at 4.2 K and in a high magnetic field of at least 0.5 T. This piezoelectric switch shows very low insertion loss of less than -0.1 dB within a bandwidth of 100 MHz when operated at 4.2 K. The switch could also be used to mechanically disconnect and connect electrodes or electrical circuits from one another.

Novel Material Integration for Reliable and Energy-Efficient NEM Relay Technology

NASA Astrophysics Data System (ADS)

Chen, I.-Ru

Energy-efficient switching devices have become ever more important with the emergence of ubiquitous computing. NEM relays are promising to complement CMOS transistors as circuit building blocks for future ultra-low-power information processing, and as such have recently attracted significant attention from the semiconductor industry and researchers. Relay technology potentially can overcome the energy efficiency limit for conventional CMOS technology due to several key characteristics, including zero OFF-state leakage, abrupt switching behavior, and potentially very low active energy consumption. However, two key issues must be addressed for relay technology to reach its full potential: surface oxide formation at the contacting surfaces leading to increased ON-state resistance after switching, and high switching voltages due to strain gradient present within the relay structure. This dissertation advances NEM relay technology by investigating solutions to both of these pressing issues. Ruthenium, whose native oxide is conductive, is proposed as the contacting material to improve relay ON-state resistance stability. Ruthenium-contact relays are fabricated after overcoming several process integration challenges, and show superior ON-state resistance stability in electrical measurements and extended device lifetime. The relay structural film is optimized via stress matching among all layers within the structure, to provide lower strain gradient (below 10E-3/microm -1) and hence lower switching voltage. These advancements in relay technology, along with the integration of a metallic interconnect layer, enable complex relay-based circuit demonstration. In addition to the experimental efforts, this dissertation theoretically analyzes the energy efficiency limit of a NEM switch, which is generally believed to be limited by the surface adhesion energy. New compact (<1 microm2 footprint), low-voltage (<0.1 V) switch designs are proposed to overcome this limit. The results pave a pathway to scaled energy-efficient electronic device technology.

32 × 32 silicon electro-optic switch with built-in monitors and balanced-status units.

PubMed

Qiao, Lei; Tang, Weijie; Chu, Tao

2017-02-09

To construct large-scale silicon electro-optical switches for optical interconnections, we developed a method using a limited number of power monitors inserted at certain positions to detect and determine the optimum operating points of all switch units to eliminate non-uniform effects arising from fabrication errors. We also introduced an optical phase bias to one phase-shifter arm of a Mach-Zehnder interferometer (MZI)-type switch unit to balance the two operation statuses of a silicon electro-optical switch during push-pull operation. With these methods, a 32 × 32 MZI-based silicon electro-optical switch was successfully fabricated with 180-nm complementary metal-oxide-semiconductor (CMOS) process technology, which is the largest scale silicon electro-optical switch to the best of our knowledge. At a wavelength of 1520 nm, the on-chip insertion losses were 12.9 to 16.5 dB, and the crosstalk ranged from -17.9 to -24.8 dB when all units were set to the 'Cross' status. The losses were 14.4 to 18.5 dB, and the crosstalk ranged from -15.1 to -19.0 dB when all units were in the 'Bar' status. The total power consumptions of the 32 × 32 switch were 247.4 and 542.3 mW when all units were set to the 'Cross' and 'Bar' statuses, respectively.

32 × 32 silicon electro-optic switch with built-in monitors and balanced-status units

PubMed Central

Qiao, Lei; Tang, Weijie; Chu, Tao

2017-01-01

To construct large-scale silicon electro-optical switches for optical interconnections, we developed a method using a limited number of power monitors inserted at certain positions to detect and determine the optimum operating points of all switch units to eliminate non-uniform effects arising from fabrication errors. We also introduced an optical phase bias to one phase-shifter arm of a Mach–Zehnder interferometer (MZI)-type switch unit to balance the two operation statuses of a silicon electro-optical switch during push–pull operation. With these methods, a 32 × 32 MZI-based silicon electro-optical switch was successfully fabricated with 180-nm complementary metal–oxide–semiconductor (CMOS) process technology, which is the largest scale silicon electro-optical switch to the best of our knowledge. At a wavelength of 1520 nm, the on-chip insertion losses were 12.9 to 16.5 dB, and the crosstalk ranged from −17.9 to −24.8 dB when all units were set to the ‘Cross’ status. The losses were 14.4 to 18.5 dB, and the crosstalk ranged from −15.1 to −19.0 dB when all units were in the ‘Bar’ status. The total power consumptions of the 32 × 32 switch were 247.4 and 542.3 mW when all units were set to the ‘Cross’ and ‘Bar’ statuses, respectively. PMID:28181557

Contact resistance change memory using N-doped Cr2Ge2Te6 phase-change material showing non-bulk resistance change

NASA Astrophysics Data System (ADS)

Shuang, Y.; Sutou, Y.; Hatayama, S.; Shindo, S.; Song, Y. H.; Ando, D.; Koike, J.

2018-04-01

Phase-change random access memory (PCRAM) is enabled by a large resistance contrast between amorphous and crystalline phases upon reversible switching between the two states. Thus, great efforts have been devoted to identifying potential phase-change materials (PCMs) with large electrical contrast to realize a more accurate reading operation. In contrast, although the truly dominant resistance in a scaled PCRAM cell is contact resistance, less attention has been paid toward the investigation of the contact property between PCMs and electrode metals. This study aims to propose a non-bulk-resistance-dominant PCRAM whose resistance is modulated only by contact. The contact-resistance-dominated PCM exploited here is N-doped Cr2Ge2Te6 (NCrGT), which exhibits almost no electrical resistivity difference between the two phases but exhibits a typical switching behavior involving a three-order-of-magnitude SET/RESET resistance ratio owing to its large contact resistance contrast. The conduction mechanism was discussed on the basis of current-voltage characteristics of the interface between the NCrGT and the W electrode.

Condition factor calibration for load and resistance factor rating of steel girder bridges : final report.

DOT National Transportation Integrated Search

2016-06-01

Load and Resistance Factor Rating (LRFR) is a reliability-based rating procedure complementary to Load and Resistance Factor Design (LRFD). The intent of LRFR is to provide consistent reliability for all bridges regardless of in-situ condition. The p...

Analysis of switch and examine combining with post-examining selection in cognitive radio

NASA Astrophysics Data System (ADS)

Agarwal, Rupali; Srivastava, Neelam; Katiyar, Himanshu

2018-06-01

To perform spectrum sensing in fading environment is one of the most challenging tasks for a CR system. Diversity combining schemes are used to combat the effect of fading and hence detection probability of CR gets improved. Among many diversity combining techniques, switched diversity offers one of the lowest complexity solutions. The receiver embedded with switched diversity looks for an acceptable diversity path (having signal to noise ratio (SNR) above the required threshold) to receive the data. In conventional switch and examine combining (SEC) scheme, when no acceptable path is found after all the paths are examined, the receiver randomly chooses an unacceptable path. Switch and examine combining with post-examining selection (SECp) is a modified version of conventional SEC. In SECp, the conventional SEC scheme is altered in a way that it selects the best path when no acceptable path is found after all paths have been examined. In this paper, formula for probability of detection ( ?) is derived using SECp and SEC diversity combining technique over Rayleigh fading channel. Also the performance of SECp is compared with SEC and no diversity case. Performance comparison is done with the help of SNR vs. ? and complementary receiver operating characteristic curves.

Stochastic switching of TiO2-based memristive devices with identical initial memory states

PubMed Central

2014-01-01

In this work, we show that identical TiO2-based memristive devices that possess the same initial resistive states are only phenomenologically similar as their internal structures may vary significantly, which could render quite dissimilar switching dynamics. We experimentally demonstrated that the resistive switching of practical devices with similar initial states could occur at different programming stimuli cycles. We argue that similar memory states can be transcribed via numerous distinct active core states through the dissimilar reduced TiO2-x filamentary distributions. Our hypothesis was finally verified via simulated results of the memory state evolution, by taking into account dissimilar initial filamentary distribution. PMID:24994953

Valence change detection in memristive oxide based heterostructure cells by hard X-ray photoelectron emission spectroscopy

NASA Astrophysics Data System (ADS)

Kindsmüller, A.; Schmitz, C.; Wiemann, C.; Skaja, K.; Wouters, D. J.; Waser, R.; Schneider, C. M.; Dittmann, R.

2018-04-01

The switching mechanism of valence change resistive memory devices is widely accepted to be an ionic movement of oxygen vacancies resulting in a valence change of the metal cations. However, direct experimental proofs of valence changes in memristive devices are scarce. In this work, we have employed hard X-ray photoelectron emission microscopy (PEEM) to probe local valence changes in Pt/ZrOx/Ta memristive devices. The use of hard X-ray radiation increases the information depth, thus providing chemical information from buried layers. By extracting X-ray photoelectron spectra from different locations in the PEEM images, we show that zirconia in the active device area is reduced compared to a neighbouring region, confirming the valence change in the ZrOx film during electroforming. Furthermore, we succeeded in measuring the Ta 4f spectrum for two different resistance states on the same device. In both states, as well as outside the device region, the Ta electrode is composed of different suboxides without any metallic contribution, hinting to the formation of TaOx during the deposition of the Ta thin film. We observed a reduction of the Ta oxidation state in the low resistance state with respect to the high resistive state. This observation is contradictory to the established model, as the internal redistribution of oxygen between ZrOx and the Ta electrode during switching would lead to an oxidation of the Ta layer in the low resistance state. Instead, we have to conclude that the Ta electrode takes an active part in the switching process in our devices and that oxygen is released and reincorporated in the ZrOx/TaOx bilayer during switching. This is confirmed by the degradation of the high resistance state during endurance measurements under vacuum.

Excellent resistive memory characteristics and switching mechanism using a Ti nanolayer at the Cu/TaOx interface

PubMed Central

2012-01-01

Excellent resistive switching memory characteristics were demonstrated for an Al/Cu/Ti/TaOx/W structure with a Ti nanolayer at the Cu/TaOx interface under low voltage operation of ± 1.5 V and a range of current compliances (CCs) from 0.1 to 500 μA. Oxygen accumulation at the Ti nanolayer and formation of a defective high-κ TaOx film were confirmed by high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photo-electron spectroscopy. The resistive switching memory characteristics of the Al/Cu/Ti/TaOx/W structure, such as HRS/LRS (approximately 104), stable switching cycle stability (>106) and multi-level operation, were improved compared with those of Al/Cu/TaOx/W devices. These results were attributed to the control of Cu migration/dissolution by the insertion of a Ti nanolayer at the Cu/TaOx interface. In contrast, CuOx formation at the Cu/TaOx interface was observed in an Al/Cu/TaOx/W structure, which hindered dissolution of the Cu filament and resulted in a small resistance ratio of approximately 10 at a CC of 500 μA. A high charge-trapping density of 6.9 × 1016 /cm2 was observed in the Al/Cu/Ti/TaOx/W structure from capacitance-voltage hysteresis characteristics, indicating the migration of Cu ions through defect sites. The switching mechanism was successfully explained for structures with and without the Ti nanolayer. By using a new approach, the nanoscale diameter of Cu filament decreased from 10.4 to 0.17 nm as the CC decreased from 500 to 0.1 μA, resulting in a large memory size of 7.6 T to 28 Pbit/sq in. Extrapolated 10-year data retention of the Ti nanolayer device was also obtained. The findings of this study will not only improve resistive switching memory performance but also aid future design of nanoscale nonvolatile memory. PMID:22734564

A new coupling mechanism between two graphene electron waveguides for ultrafast switching

NASA Astrophysics Data System (ADS)

Huang, Wei; Liang, Shi-Jun; Kyoseva, Elica; Ang, Lay Kee

2018-03-01

In this paper, we report a novel coupling between two graphene electron waveguides, in analogy the optical waveguides. The design is based on the coherent quantum mechanical tunneling of Rabi oscillation between the two graphene electron waveguides. Based on this coupling mechanism, we propose that it can be used as an ultrafast electronic switching device. Based on a modified coupled mode theory, we construct a theoretical model to analyze the device characteristics, and predict that the switching speed is faster than 1 ps and the on-off ratio exceeds 106. Due to the long mean free path of electrons in graphene at room temperature, the proposed design avoids the limitation of low temperature operation required in the traditional design by using semiconductor quantum-well structure. The layout of our design is similar to that of a standard complementary metal-oxide-semiconductor transistor that should be readily fabricated with current state-of-art nanotechnology.

Mechanical Computing Redux: Limitations at the Nanoscale

NASA Astrophysics Data System (ADS)

Liu, Tsu-Jae King

2014-03-01

Technology solutions for overcoming the energy efficiency limits of nanoscale complementary metal oxide semiconductor (CMOS) technology ultimately will be needed in order to address the growing issue of integrated-circuit chip power density. Off-state leakage current sets a fundamental lower limit in energy per operation for any voltage-level-based digital logic implemented with transistors (CMOS and beyond), which leads to practical limits for device density (i.e. cost) and operating frequency (i.e. system performance). Mechanical switches have zero off-state leakag and hence can overcome this fundamental limit. Contact adhesive force sets a lower limit for the switching energy of a mechanical switch, however, and also directly impacts its performance. This paper will review recent progress toward the development of nano-electro-mechanical relay technology and discuss remaining challenges for realizing the promise of mechanical computing for ultra-low-power computing. Supported by the Center for Energy Efficient Electronics Science (NSF Award 0939514).

High speed magneto-resistive random access memory

NASA Technical Reports Server (NTRS)

Wu, Jiin-Chuan (Inventor); Stadler, Henry L. (Inventor); Katti, Romney R. (Inventor)

1992-01-01

A high speed read MRAM memory element is configured from a sandwich of magnetizable, ferromagnetic film surrounding a magneto-resistive film which may be ferromagnetic or not. One outer ferromagnetic film has a higher coercive force than the other and therefore remains magnetized in one sense while the other may be switched in sense by a switching magnetic field. The magneto-resistive film is therefore sensitive to the amplitude of the resultant field between the outer ferromagnetic films and may be constructed of a high resistivity, high magneto-resistive material capable of higher sensing currents. This permits higher read voltages and therefore faster read operations. Alternate embodiments with perpendicular anisotropy, and in-plane anisotropy are shown, including an embodiment which uses high permeability guides to direct the closing flux path through the magneto-resistive material. High density, high speed, radiation hard, memory matrices may be constructed from these memory elements.

A thorough investigation of the progressive reset dynamics in HfO{sub 2}-based resistive switching structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenzi, P., E-mail: lorenzi@die.uniroma1.it; Rao, R.; Irrera, F.

2015-09-14

According to previous reports, filamentary electron transport in resistive switching HfO{sub 2}-based metal-insulator-metal structures can be modeled using a diode-like conduction mechanism with a series resistance. Taking the appropriate limits, the model allows simulating the high (HRS) and low (LRS) resistance states of the devices in terms of exponential and linear current-voltage relationships, respectively. In this letter, we show that this simple equivalent circuit approach can be extended to represent the progressive reset transition between the LRS and HRS if a generalized logistic growth model for the pre-exponential diode current factor is considered. In this regard, it is demonstrated heremore » that a Verhulst logistic model does not provide accurate results. The reset dynamics is interpreted as the sequential deactivation of multiple conduction channels spanning the dielectric film. Fitting results for the current-voltage characteristics indicate that the voltage sweep rate only affects the deactivation rate of the filaments without altering the main features of the switching dynamics.« less

Nonvolatile resistive switching in metal/La-doped BiFeO3/Pt sandwiches.

PubMed

Li, Mi; Zhuge, Fei; Zhu, Xiaojian; Yin, Kuibo; Wang, Jinzhi; Liu, Yiwei; He, Congli; Chen, Bin; Li, Run-Wei

2010-10-22

The resistive switching (RS) characteristics of a Bi(0.95)La(0.05)FeO(3) (La-BFO) film sandwiched between a Pt bottom electrode and top electrodes (TEs) made of Al, Ag, Cu, and Au have been studied. Devices with TEs made of Ag and Cu showed stable bipolar RS behaviors, whereas those with TEs made of Al and Au exhibited unstable bipolar RS. The Ag/La-BFO/Pt structure showed an on/off ratio of 10(2), a retention time > 10(5) s, and programming voltages < 1 V. The RS effect can be attributed to the formation/rupture of nanoscale metal filaments due to the diffusion of the TEs under a bias voltage. The maximum current before the reset process (on-to-off switching) was found to increase linearly with the current compliance applied during the set process (off-to-on switching).

Radio frequency-assisted fast superconducting switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solovyov, Vyacheslav; Li, Qiang

A radio frequency-assisted fast superconducting switch is described. A superconductor is closely coupled to a radio frequency (RF) coil. To turn the switch "off," i.e., to induce a transition to the normal, resistive state in the superconductor, a voltage burst is applied to the RF coil. This voltage burst is sufficient to induce a current in the coupled superconductor. The combination of the induced current with any other direct current flowing through the superconductor is sufficient to exceed the critical current of the superconductor at the operating temperature, inducing a transition to the normal, resistive state. A by-pass MOSFET maymore » be configured in parallel with the superconductor to act as a current shunt, allowing the voltage across the superconductor to drop below a certain value, at which time the superconductor undergoes a transition to the superconducting state and the switch is reset.« less

Intermittent metabolic switching, neuroplasticity and brain health

PubMed Central

Mattson, Mark P.; Moehl, Keelin; Ghena, Nathaniel; Schmaedick, Maggie; Cheng, Aiwu

2018-01-01

During evolution, individuals whose brains and bodies functioned well in a fasted state were successful in acquiring food, enabling their survival and reproduction. With fasting and extended exercise, liver glycogen stores are depleted and ketones are produced from adipose-cell-derived fatty acids. This metabolic switch in cellular fuel source is accompanied by cellular and molecular adaptations of neural networks in the brain that enhance their functionality and bolster their resistance to stress, injury and disease. Here, we consider how intermittent metabolic switching, repeating cycles of a metabolic challenge that induces ketosis (fasting and/or exercise) followed by a recovery period (eating, resting and sleeping), may optimize brain function and resilience throughout the lifespan, with a focus on the neuronal circuits involved in cognition and mood. Such metabolic switching impacts multiple signalling pathways that promote neuroplasticity and resistance of the brain to injury and disease. PMID:29321682

Investigation into Contact Resistance And Damage of Metal Contacts Used in RF-MEMS Switches

DTIC Science & Technology

2009-09-01

mechanically cycled by a piezo- electric transducer ( PZT ). The resistance through the simulated switch was measured using a four-wire measurement technique...research, including a brief overview of contact theory. Then chapter 3 gives an overview of engi- 13 V I PZT Sample Mount Cantilever Lower Contact...as described in [3, 118]. The measurement of surface texture and 4These figures were published in Materials Selection in Mechanical Design, Michael F

Influence of argon and oxygen pressure ratio on bipolar-resistive switching characteristics of CeO2- x thin films deposited at room temperature

NASA Astrophysics Data System (ADS)

Ismail, Muhammad; Ullah, Rehmat; Hussain, Riaz; Talib, Ijaz; Rana, Anwar Manzoor; Hussain, Muhammad; Mahmood, Khalid; Hussain, Fayyaz; Ahmed, Ejaz; Bao, Dinghua

2018-02-01

Cerium oxide (CeO2-x) film was deposited on Pt/Ti/SiO2/Si substrate by rf magnetron sputtering at room temperature. Resistive switching characteristics of these ceria films have been improved by increasing oxygen content during deposition process. Endurance and statistical analyses indicate that the operating stability of CeO2-x-based memory is highly dependent on the oxygen content. Results indicate that CeO2-x film-based RRAM devices exhibit optimum performance when fabricated at an argon/oxygen ratio of 6:24. An increase in the oxygen content introduced during CeO2-x film deposition not only stabilizes the conventional bipolar RS but also improves excellent switching uniformity such as large ON/OFF ratio (102), excellent switching device-to-device uniformity and good sweep endurance over 500 repeated RS cycles. Conduction in the low-resistance state (LRS) as well as in the low bias field region in the high-resistance state (HRS) is found to be Ohmic and thus supports the conductive filament (CF) theory. In the high voltage region of HRS, space charge limited conduction (SCLC) and Schottky emission are found to be the dominant conduction mechanisms. A feasible filamentary RS mechanism based on the movement of oxygen ions/vacancies under the bias voltage has been discussed.

Development and fabrication of low ON resistance high current vertical VMOS power FETs

NASA Technical Reports Server (NTRS)

Kay, S.

1979-01-01

The design of a VMOS Power FET exhibiting low ON resistance, high current as well as high breakdown voltage and fast switching speeds is described. The design which is based on a 1st-order device model, features a novel polysilicon-gate structure and fieldplated groove termination to achieve high packing density and high breakdown voltage, respectively. One test chip, named VNTKI, can block 180 V at an ON resistence of 2.5 ohm. A 150 mil x 200 mil (.19 sq cm) experimental chip has demonstrated a breakdown voltage of 200v, an ON resistance of 0.12 ohm, a switching time of less than 100 ns, and a pulse drain - current of 50 A with 10 V gate drive.

Multi-step resistive switching behavior of Li-doped ZnO resistance random access memory device controlled by compliance current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Chun-Cheng; Department of Mathematic and Physical Sciences, R.O.C. Air Force Academy, Kaohsiung 820, Taiwan; Tang, Jian-Fu

2016-06-28

The multi-step resistive switching (RS) behavior of a unipolar Pt/Li{sub 0.06}Zn{sub 0.94}O/Pt resistive random access memory (RRAM) device is investigated. It is found that the RRAM device exhibits normal, 2-, 3-, and 4-step RESET behaviors under different compliance currents. The transport mechanism within the device is investigated by means of current-voltage curves, in-situ transmission electron microscopy, and electrochemical impedance spectroscopy. It is shown that the ion transport mechanism is dominated by Ohmic behavior under low electric fields and the Poole-Frenkel emission effect (normal RS behavior) or Li{sup +} ion diffusion (2-, 3-, and 4-step RESET behaviors) under high electric fields.

Highly sensitive self-complementary DNA nanoswitches triggered by polyelectrolytes

NASA Astrophysics Data System (ADS)

Wu, Jincai; Yu, Feng; Zhang, Zheng; Chen, Yong; Du, Jie; Maruyama, Atsushi

2015-12-01

Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(l-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation.Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(l-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation. Electronic supplementary information (ESI) available: I. Sequences of DIS25, DIS25-2a and DIS25-3a. II. Structural formula of poly(l-lysine)-graft-dextran (PLL-g-Dex). 1H-NMR spectra of PLL-g-Dex in D2O. III. Gel electrophoretic analysis of dimerization of DIS25 with various N/P ratios. IV. The effect of polyelectrolyte on the fluorescence polarity of TAMRA-labeled duplex. V. UV absorption/Tm profiles of DIS25. VI. Arrhenius plots for spontaneous dissociation of the DIS25 dimer and PLL-g-Dex-assisted dimerization of DIS25.VII. Switching between double stem-loop DIS42 and extended multiplex drived by PLL-g-Dex and PVS. See DOI: 10.1039/c5nr05193b

TaOx-based resistive switching memories: prospective and challenges

PubMed Central

2013-01-01

Resistive switching memories (RRAMs) are attractive for replacement of conventional flash in the future. Although different switching materials have been reported; however, low-current operated devices (<100 μA) are necessary for productive RRAM applications. Therefore, TaOx is one of the prospective switching materials because of two stable phases of TaO2 and Ta2O5, which can also control the stable low- and high-resistance states. Long program/erase endurance and data retention at high temperature under low-current operation are also reported in published literature. So far, bilayered TaOx with inert electrodes (Pt and/or Ir) or single layer TaOx with semi-reactive electrodes (W and Ti/W or Ta/Pt) is proposed for real RRAM applications. It is found that the memory characteristics at current compliance (CC) of 80 μA is acceptable for real application; however, data are becoming worst at CC of 10 μA. Therefore, it is very challenging to reduce the operation current (few microampere) of the RRAM devices. This study investigates the switching mode, mechanism, and performance of low-current operated TaOx-based devices as compared to other RRAM devices. This topical review will not only help for application of TaOx-based nanoscale RRAM devices but also encourage researcher to overcome the challenges in the future production. PMID:24107610

Uniform Self-rectifying Resistive Switching Behavior via Preformed Conducting Paths in a Vertical-type Ta2O5/HfO2-x Structure with a Sub-μm(2) Cell Area.

PubMed

Yoon, Jung Ho; Yoo, Sijung; Song, Seul Ji; Yoon, Kyung Jean; Kwon, Dae Eun; Kwon, Young Jae; Park, Tae Hyung; Kim, Hye Jin; Shao, Xing Long; Kim, Yumin; Hwang, Cheol Seong

2016-07-20

To replace or succeed the present NAND flash memory, resistive switching random access memory (ReRAM) should be implemented in the vertical-type crossbar array configuration. The ReRAM cell must have a highly reproducible resistive switching (RS) performance and an electroforming-free, self-rectifying, low-power-consumption, multilevel-switching, and easy fabrication process with a deep sub-μm(2) cell area. In this work, a Pt/Ta2O5/HfO2-x/TiN RS memory cell fabricated in the form of a vertical-type structure was presented as a feasible contender to meet the above requirements. While the fundamental RS characteristics of this material based on the electron trapping/detrapping mechanisms have been reported elsewhere, the influence of the cell scaling size to 0.34 μm(2) on the RS performance by adopting the vertical integration scheme was carefully examined in this work. The smaller cell area provided much better switching uniformity while all the other benefits of this specific material system were preserved. Using the overstressing technique, the nature of RS through the localized conducting path was further examined, which elucidated the fundamental difference between the present material system and the general ionic-motion-related bipolar RS mechanism.

Controllable Organic Resistive Switching Achieved by One-Step Integration of Cone-Shaped Contact.

PubMed

Ling, Haifeng; Yi, Mingdong; Nagai, Masaru; Xie, Linghai; Wang, Laiyuan; Hu, Bo; Huang, Wei

2017-09-01

Conductive filaments (CFs)-based resistive random access memory possesses the ability of scaling down to sub-nanoscale with high-density integration architecture, making it the most promising nanoelectronic technology for reclaiming Moore's law. Compared with the extensive study in inorganic switching medium, the scientific challenge now is to understand the growth kinetics of nanoscale CFs in organic polymers, aiming to achieve controllable switching characteristics toward flexible and reliable nonvolatile organic memory. Here, this paper systematically investigates the resistive switching (RS) behaviors based on a widely adopted vertical architecture of Al/organic/indium-tin-oxide (ITO), with poly(9-vinylcarbazole) as the case study. A nanoscale Al filament with a dynamic-gap zone (DGZ) is directly observed using in situ scanning transmission electron microscopy (STEM) , which demonstrates that the RS behaviors are related to the random formation of spliced filaments consisting of Al and oxygen vacancy dual conductive channels growing through carbazole groups. The randomicity of the filament formation can be depressed by introducing a cone-shaped contact via a one-step integration method. The conical electrode can effectively shorten the DGZ and enhance the localized electric field, thus reducing the switching voltage and improving the RS uniformity. This study provides a deeper insight of the multiple filamentary mechanisms for organic RS effect. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A low-loss, single-pole, four-throw RF MEMS switch driven by a double stop comb drive

NASA Astrophysics Data System (ADS)

Kang, S.; Kim, H. C.; Chun, K.

2009-03-01

Our goal was to develop a single-pole four-throw (SP4T) radio frequency microelectromechanical system (RF MEMS) switch for band selection in a multi-band, multi-mode, front-end module of a wireless transceiver system. The SP4T RF MEMS switch was based on an arrangement of four single-pole single-throw (SPST) RF MEMS switches. The SP4T RF MEMS switch was driven by a double stop (DS) comb drive, with a lateral resistive contact, and composed of single crystalline silicon (SCS) on glass. A large contact force at a low-drive voltage was achieved by electrostatic actuation of the DS comb drive. Good RF characteristics were achieved by the large contact force and the lateral resistive Au-to-Au contact. Mechanical reliability was achieved by using SCS which has no residual stress as a structure material. The developed SP4T RF MEMS switch has a drive voltage of 15 V, an insertion loss below 0.31 dB at 6 GHz after more than one million cycles under a 10 mW signal, a return loss above 20 dB and an isolation value above 36 dB.

Control of Nanofilament Structure and Observations of Quantum Point Contact Behavior in Ni/NiO Nanowire Junctions

NASA Astrophysics Data System (ADS)

Oliver, Sean; Fairfield, Jessamyn; Lee, Sunghun; Bellew, Allen; Stone, Iris; Ruppalt, Laura; Boland, John; Vora, Patrick

Resistive switching is ideal for use in non-volatile memory where information is stored in a metallic or insulating state. Nanowire junctions formed at the intersection of two Ni/NiO core/shell nanowires have emerged as a leading candidate structure where resistive switching occurs due to the formation and destruction of conducting filaments. However, significant knowledge gaps remain regarding the conduction mechanisms as measurements are typically only performed at room temperature. Here, we combine temperature-dependent current-voltage (IV) measurements from 15 - 300 K with magnetoresistance studies and achieve new insight into the nature of the conducting filaments. We identify a novel semiconducting state that behaves as a quantum point contact and find evidence for a possible electric-field driven phase transition. The insulating state exhibits unexpectedly complex IV characteristics that highlight the disordered nature of the ruptured filament while we find clear signs of anisotropic magnetoresistance in the metallic state. Our results expose previously unobserved behaviors in nanowire resistive switching devices and pave the way for future applications where both electrical and magnetic switching can be achieved in a single device. This work was supported by ONR Grant N-00014-15-1-2357.

Electrically tunable transport and high-frequency dynamics in antiferromagnetic S r3I r2O7

NASA Astrophysics Data System (ADS)

Seinige, Heidi; Williamson, Morgan; Shen, Shida; Wang, Cheng; Cao, Gang; Zhou, Jianshi; Goodenough, John B.; Tsoi, Maxim

2016-12-01

We report dc and high-frequency transport properties of antiferromagnetic S r3I r2O7 . Temperature-dependent resistivity measurements show that the activation energy of this material can be tuned by an applied dc electrical bias. The latter allows for continuous variations in the sample resistivity of as much as 50% followed by a reversible resistive switching at higher biases. Such a switching is of high interest for antiferromagnetic applications in high-speed memory devices. Interestingly, we found the switching behavior to be strongly affected by a high-frequency (microwave) current applied to the sample. The microwaves at 3-7 GHz suppress the dc switching and produce resonancelike features that we tentatively associated with the dissipationless magnonics recently predicted to occur in antiferromagnetic insulators subject to ac electric fields. We have characterized the effects of microwave irradiation on electronic transport in S r3I r2O7 as a function of microwave frequency and power, strength and direction of external magnetic field, strength and polarity of applied dc bias, and temperature. Our observations support the potential of antiferromagnetic materials for high-speed/high-frequency spintronic applications.

Hafnia-based resistive switching devices for non-volatile memory applications and effects of gamma irradiation on device performance

NASA Astrophysics Data System (ADS)

Arun, N.; Kumar, K. Vinod; Pathak, A. P.; Avasthi, D. K.; Nageswara Rao, S. V. S.

2018-04-01

Non-volatile memory (NVM) devices were fabricated as a Metal- Insulator-Metal (MIM) structures by sandwiching Hafnium dioxide (HfO2) thin film in between two metal electrodes. The top and bottom metal electrodes were deposited by using the thermal evaporation, and the oxide layer was deposited by using the RF magnetron sputtering technique. The Resistive Random Access Memory (RRAM) device structures such as Ag/HfO2/Au/Si were fabricated and I-V characteristics for the pristine and gamma-irradiated devices with a dose 24 kGy were measured. Further we have studied the thermal annealing effects, in the range of 100°-400°C in a tubular furnace for the HfO2/Au/Si samples. The X-ray diffraction (XRD), Rutherford Backscattering Spectrometry (RBS), field emission-scanning electron microscopy (FESEM) analysis measurements were performed to determine the thickness, crystallinity and stoichiometry of these films. The electrical characteristics such as resistive switching, endurance, retention time and switching speed were measured by a semiconductor device analyser. The effects of gamma irradiation on the switching properties of these RRAM devices have been studied.

Influence of carbon content on the copper-telluride phase formation and on the resistive switching behavior of carbon alloyed Cu-Te conductive bridge random access memory cells

NASA Astrophysics Data System (ADS)

Devulder, Wouter; Opsomer, Karl; Franquet, Alexis; Meersschaut, Johan; Belmonte, Attilio; Muller, Robert; De Schutter, Bob; Van Elshocht, Sven; Jurczak, Malgorzata; Goux, Ludovic; Detavernier, Christophe

2014-02-01

In this paper, we investigate the influence of the carbon content on the Cu-Te phase formation and on the resistive switching behavior in carbon alloyed Cu0.6Te0.4 based conductive bridge random access memory (CBRAM) cells. Carbon alloying of copper-tellurium inhibits the crystallization, while attractive switching behavior is preserved when using the material as Cu-supply layer in CBRAM cells. The phase formation is first investigated in a combinatorial way. With increasing carbon content, an enlargement of the temperature window in which the material stays amorphous was observed. Moreover, if crystalline phases are formed, subsequent phase transformations are inhibited. The electrical switching behavior of memory cells with different carbon contents is then investigated by implementing them in 580 μm diameter dot TiN/Cu0.6Te0.4-C/Al2O3/Si memory cells. Reliable switching behavior is observed for carbon contents up to 40 at. %, with a resistive window of more than 2 orders of magnitude, whereas for 50 at. % carbon, a higher current in the off state and only a small resistive window are present after repeated cycling. This degradation can be ascribed to the higher thermal and lower drift contribution to the reset operation due to a lower Cu affinity towards the supply layer, leading cycle-after-cycle to an increasing amount of Cu in the switching layer, which contributes to the current. The thermal diffusion of Cu into Al2O3 under annealing also gives an indication of the Cu affinity of the source layer. Time of flight secondary ion mass spectroscopy was used to investigate this migration depth in Al2O3 before and after annealing, showing a higher Cu, Te, and C migration for high carbon contents.

Electrical resistivity well-logging system with solid-state electronic circuitry

USGS Publications Warehouse

Scott, James Henry; Farstad, Arnold J.

1977-01-01

An improved 4-channel electrical resistivity well-logging system for use with a passive probe with electrodes arranged in the 'normal' configuration has been designed and fabricated by Westinghouse Electric Corporation to meet technical specifications developed by the U.S. Geological Survey. Salient features of the system include solid-state switching and current regulation in the transmitter circuit to produce a constant-current source square wave, and synchronous solid-state switching and sampling of the potential waveform in the receiver circuit to provide an analog dc voltage proportions to the measured resistivity. Technical specifications and design details are included in this report.

Simplification to single-tablet regimen of elvitegravir, cobicistat, emtricitabine, tenofovir DF from multi-tablet ritonavir-boosted protease inhibitor plus coformulated emtricitabine and tenofovir DF regimens: week 96 results of STRATEGY-PI.

PubMed

Arribas, Jose R; DeJesus, Edwin; van Lunzen, Jan; Zurawski, Christine; Doroana, Manuela; Towner, William; Lazzarin, Adriano; Nelson, Mark; McColl, Damian; Andreatta, Kristen; Swamy, Raji; Szwarcberg, Javier; Nguyen, Thai

2017-05-01

Antiretroviral therapy (ART) simplification to a single-tablet regimen can benefit HIV-1-infected, virologically suppressed, individuals on ART composed of multiple pills. We assessed long-term efficacy and safety of switching to co-formulated elvitegravir, cobicistat, emtricitabine, and tenofovir disoproxil fumarate (E/C/F/TDF) from multi-tablet ritonavir-boosted protease inhibitor (PI + RTV) plus F/TDF (TVD) regimens. STRATEGY-PI was a 96-week, phase 3b, randomized (2:1), open-label, non-inferiority study examining the efficacy, safety, and tolerability of switching to E/C/F/TDF from PI + RTV + TVD regimens in virologically suppressed individuals (HIV-1 RNA <50 copies/mL). Participants were randomized to switch to E/C/F/TDF (switch group) or to continue their PI + RTV + TVD regimens (no-switch group). Eligibility criteria included no resistance to F/TDF or history of virologic failure, and estimated creatinine clearance ≥70 mL/min. At week 96, 87% (252/290) of switch and 70% (97/139) of no-switch participants maintained HIV-1 RNA <50 copies/mL (difference: 17%, 95% CI 8.7-26.0%, p < 0.001). Superiority of the switch to E/C/F/TDF vs. no-switch was due to a smaller proportion of both virologic failures (switch, 1% [3/290]; no-switch, 6% [8/139]) and discontinuations for non-virologic reasons (switch, 11% [31/290]; no-switch, 24% [33/139]). No treatment-emergent resistance was observed in switch subjects with virologic failure. Discontinuation rates from adverse events were 3% in both groups (9/293, switch; 4/140, no-switch). Switching from PI + RTV + TVD to E/C/F/TDF was associated with significant improvements in patient-reported outcomes related to gastrointestinal symptoms (nausea and bloating). E/C/F/TDF is a safe, effective long-term alternative to multi-tablet PI + RTV + TVD-based regimens in virologically suppressed, HIV-1-infected adults, and improves patient-reported gastrointestinal symptoms.

Pulse width and height modulation for multi-level resistance in bi-layer TaOx based RRAM

NASA Astrophysics Data System (ADS)

Alamgir, Zahiruddin; Beckmann, Karsten; Holt, Joshua; Cady, Nathaniel C.

2017-08-01

Mutli-level switching in resistive memory devices enables a wide range of computational paradigms, including neuromorphic and cognitive computing. To this end, we have developed a bi-layer tantalum oxide based resistive random access memory device using Hf as the oxygen exchange layer. Multiple, discrete resistance levels were achieved by modulating the RESET pulse width and height, ranging from 2 kΩ to several MΩ. For a fixed pulse height, OFF state resistance was found to increase gradually with the increase in the pulse width, whereas for a fixed pulse width, the increase in the pulse height resulted in drastic changes in resistance. Resistive switching in these devices transitioned from Schottky emission in the OFF state to tunneling based conduction in the ON state, based on I-V curve fitting and temperature dependent current measurements. These devices also demonstrated endurance of more than 108 cycles with a satisfactory Roff/Ron ratio and retention greater than 104 s.

Detection of target-probe oligonucleotide hybridization using synthetic nanopore resistive pulse sensing.

PubMed

Booth, Marsilea Adela; Vogel, Robert; Curran, James M; Harbison, SallyAnn; Travas-Sejdic, Jadranka

2013-07-15

Despite the plethora of DNA sensor platforms available, a portable, sensitive, selective and economic sensor able to rival current fluorescence-based techniques would find use in many applications. In this research, probe oligonucleotide-grafted particles are used to detect target DNA in solution through a resistive pulse nanopore detection technique. Using carbodiimide chemistry, functionalized probe DNA strands are attached to carboxylated dextran-based magnetic particles. Subsequent incubation with complementary target DNA yields a change in surface properties as the two DNA strands hybridize. Particle-by-particle analysis with resistive pulse sensing is performed to detect these changes. A variable pressure method allows identification of changes in the surface charge of particles. As proof-of-principle, we demonstrate that target hybridization is selectively detected at micromolar concentrations (nanomoles of target) using resistive pulse sensing, confirmed by fluorescence and phase analysis light scattering as complementary techniques. The advantages, feasibility and limitations of using resistive pulse sensing for sample analysis are discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

An analysis of the temperature dependence of the gate current in complementary heterojunction field-effect transistors

NASA Technical Reports Server (NTRS)

Cunningham, Thomas J.; Fossum, Eric R.; Baier, Steven M.

1992-01-01

The temperature dependence of the gate current versus the gate voltage in complementary heterojunction field-effect transistors (CHFET's) is examined. An analysis indicates that the gate conduction is due to a combination of thermionic emission, thermionic-field emission, and conduction through a temperature-activated resistance. The thermionic-field emission is consistent with tunneling through the AlGaAs insulator. The activation energy of the resistance is consistent with the ionization energy associated with the DX center in the AlGaAs. Methods reducing the gate current are discussed.

A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5-x/TaO2-x bilayer structures

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Lee, Chang Bum; Lee, Dongsoo; Lee, Seung Ryul; Chang, Man; Hur, Ji Hyun; Kim, Young-Bae; Kim, Chang-Jung; Seo, David H.; Seo, Sunae; Chung, U.-In; Yoo, In-Kyeong; Kim, Kinam

2011-08-01

Numerous candidates attempting to replace Si-based flash memory have failed for a variety of reasons over the years. Oxide-based resistance memory and the related memristor have succeeded in surpassing the specifications for a number of device requirements. However, a material or device structure that satisfies high-density, switching-speed, endurance, retention and most importantly power-consumption criteria has yet to be announced. In this work we demonstrate a TaOx-based asymmetric passive switching device with which we were able to localize resistance switching and satisfy all aforementioned requirements. In particular, the reduction of switching current drastically reduces power consumption and results in extreme cycling endurances of over 1012. Along with the 10 ns switching times, this allows for possible applications to the working-memory space as well. Furthermore, by combining two such devices each with an intrinsic Schottky barrier we eliminate any need for a discrete transistor or diode in solving issues of stray leakage current paths in high-density crossbar arrays.

Peroxide induced volatile and non-volatile switching behavior in ZnO-based electrochemical metallization memory cell

NASA Astrophysics Data System (ADS)

Mangasa Simanjuntak, Firman; Chandrasekaran, Sridhar; Pattanayak, Bhaskar; Lin, Chun-Chieh; Tseng, Tseung-Yuen

2017-09-01

We explore the use of cubic-zinc peroxide (ZnO2) as a switching material for electrochemical metallization memory (ECM) cell. The ZnO2 was synthesized with a simple peroxide surface treatment. Devices made without surface treatment exhibits a high leakage current due to the self-doped nature of the hexagonal-ZnO material. Thus, its switching behavior can only be observed when a very high current compliance is employed. The synthetic ZnO2 layer provides a sufficient resistivity to the Cu/ZnO2/ZnO/ITO devices. The high resistivity of ZnO2 encourages the formation of a conducting bridge to activate the switching behavior at a lower operation current. Volatile and non-volatile switching behaviors with sufficient endurance and an adequate memory window are observed in the surface-treated devices. The room temperature retention of more than 104 s confirms the non-volatility behavior of the devices. In addition, our proposed device structure is able to work at a lower operation current among other reported ZnO-based ECM cells.

Studies of current-perpendicular-to-plane magnetoresistance (CPP-MR) and current-induced magnetization switching (CIMS)

NASA Astrophysics Data System (ADS)

Kurt, Huseyin

2005-08-01

We present two CPP-MR studies of spin-valves based upon ferromagnetic/nonmagnetic/ferromagnetic (F/N/F) trilayers. We measure the spin-diffusion lengths of N = Pd, Pt, and Au at 4.2K, and both the specific resistances (sample area A times resistance R) and spin-memory-loss of N/Cu interfaces. Pd, Pt and Au are of special device interest because they give perpendicular anisotropy when sandwiching very thin Co layers. Comparing our spin-memory-loss data at Pd/Cu and Pt/Cu interfaces with older data for Nb/Cu and W/Cu gives insight into the importance of spin-orbit coupling in producing such loss. We reproduce and extend prior studies by Eid of 'magnetic activity' at the interface of Co and N-metals (or combinations of N-metals), when the other side of the N-metal contacts a superconductor (S). Our data suggest that magnetic activity may require strong spin-flipping at the N/S interface. We present five studies of a new phenomenon, CIMS, in F1/N/F2 trilayers, with F1 a thick 'polarizing' layer and F2 a thin 'switching' layer. In all prior studies of CIMS, positive current caused the magnetization of F2 to switch from parallel (P) to anti-parallel (AP) to that of F1- 'normal' switching. By judicious addition of impurities to F-metals, we are able to controllably produce both 'normal' and 'inverse' switching- where positive current switches the magnetization of F2 from AP to P to that of F1. In the samples studied, whether the switching is normal or inverse is set by the 'net polarization' produced by F1 and is independent of the properties of F2. As scattering in the bulk of F1 and F2 is essential to producing our results, these results cannot be described by ballistic models, which allow scattering only at interfaces. Most CIMS experiments use Cu as the N-layer due to its low resistivity and long spin-diffusion length. We show that Ag and Au have low enough resistivities and long enough spin-diffusion lengths to be useful alternatives to Cu for some devices. While most technical applications of CIMS require low switching currents, some, like read-heads, require high switching currents. We show that use of a synthetic antiferromagnet can increase the switching current. Manschot et al. recently predicted that the positive critical current for switching from P to AP could be reduced by up to a factor of five by using asymmetric current leads. In magnetically uncoupled samples, we find that highly asymmetric current leads do not significantly reduce the switching current. A CIMS equation given by Katine et al. predicts that lowering the demagnetization field should reduce the switching current. To test this prediction, we compare switching currents for Co/Au/Co(t)/Au nanopillars with t = 1 to 4 nm (where the easy axis should be normal to the layer planes at least for t = 1 and 2 nm) with those for Co/Cu/Co(t)/Au nanopillars (where the easy axis should be in the layer planes). We do not find significant differences in switching currents for the two systems.

High performance nonvolatile memory devices based on Cu2-xSe nanowires

NASA Astrophysics Data System (ADS)

Wu, Chun-Yan; Wu, Yi-Liang; Wang, Wen-Jian; Mao, Dun; Yu, Yong-Qiang; Wang, Li; Xu, Jun; Hu, Ji-Gang; Luo, Lin-Bao

2013-11-01

We report on the rational synthesis of one-dimensional Cu2-xSe nanowires (NWs) via a solution method. Electrical analysis of Cu2-xSe NWs based memory device exhibits a stable and reproducible bipolar resistive switching behavior with a low set voltage (0.3-0.6 V), which can enable the device to write and erase data efficiently. Remarkably, the memory device has a record conductance switching ratio of 108, much higher than other devices ever reported. At last, a conducting filaments model is introduced to account for the resistive switching behavior. The totality of this study suggests that the Cu2-xSe NWs are promising building blocks for fabricating high-performance and low-consumption nonvolatile memory devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Suhas; Wang, Ziwen; Huang, Xiaopeng

While the recent establishment of the role of thermophoresis/diffusion-driven oxygen migration during resistance switching in metal oxide memristors provided critical insights required for memristor modeling, extended investigations of the role of oxygen migration during ageing and failure remain to be detailed. Such detailing will enable failure-tolerant design, which can lead to enhanced performance of memristor-based next-generation storage-class memory. Furthermore, we directly observed lateral oxygen migration using in-situ synchrotron x-ray absorption spectromicroscopy of HfO x memristors during initial resistance switching, wear over millions of switching cycles, and eventual failure, through which we determined potential physical causes of failure. Using this information,more » we reengineered devices to mitigate three failure mechanisms and demonstrated an improvement in endurance of about three orders of magnitude.« less

Evolution of Linked Avirulence Effectors in Leptosphaeria maculans Is Affected by Genomic Environment and Exposure to Resistance Genes in Host Plants

PubMed Central

Van de Wouw, Angela P.; Cozijnsen, Anton J.; Hane, James K.; Brunner, Patrick C.; McDonald, Bruce A.; Oliver, Richard P.; Howlett, Barbara J.

2010-01-01

Brassica napus (canola) cultivars and isolates of the blackleg fungus, Leptosphaeria maculans interact in a ‘gene for gene’ manner whereby plant resistance (R) genes are complementary to pathogen avirulence (Avr) genes. Avirulence genes encode proteins that belong to a class of pathogen molecules known as effectors, which includes small secreted proteins that play a role in disease. In Australia in 2003 canola cultivars with the Rlm1 resistance gene suffered a breakdown of disease resistance, resulting in severe yield losses. This was associated with a large increase in the frequency of virulence alleles of the complementary avirulence gene, AvrLm1, in fungal populations. Surprisingly, the frequency of virulence alleles of AvrLm6 (complementary to Rlm6) also increased dramatically, even though the cultivars did not contain Rlm6. In the L. maculans genome, AvrLm1 and AvrLm6 are linked along with five other genes in a region interspersed with transposable elements that have been degenerated by Repeat-Induced Point (RIP) mutations. Analyses of 295 Australian isolates showed deletions, RIP mutations and/or non-RIP derived amino acid substitutions in the predicted proteins encoded by these seven genes. The degree of RIP mutations within single copy sequences in this region was proportional to their proximity to the degenerated transposable elements. The RIP alleles were monophyletic and were present only in isolates collected after resistance conferred by Rlm1 broke down, whereas deletion alleles belonged to several polyphyletic lineages and were present before and after the resistance breakdown. Thus, genomic environment and exposure to resistance genes in B. napus has affected the evolution of these linked avirulence genes in L. maculans. PMID:21079787

Resistive Switching in All-Printed, Flexible and Hybrid MoS2-PVA Nanocomposite based Memristive Device Fabricated by Reverse Offset

PubMed Central

Rehman, Muhammad Muqeet; Siddiqui, Ghayas Uddin; Gul, Jahan Zeb; Kim, Soo-Wan; Lim, Jong Hwan; Choi, Kyung Hyun

2016-01-01

Owing to the increasing interest in the nonvolatile memory devices, resistive switching based on hybrid nanocomposite of a 2D material, molybdenum disulphide (MoS2) and polyvinyl alcohol (PVA) is explored in this work. As a proof of concept, we have demonstrated the fabrication of a memory device with the configuration of PET/Ag/MoS2-PVA/Ag via an all printed, hybrid, and state of the art fabrication approach. Bottom Ag electrodes, active layer of hybrid MoS2-PVA nanocomposite and top Ag electrode are deposited by reverse offset, electrohydrodynamic (EHD) atomization and electrohydrodynamic (EHD) patterning respectively. The fabricated device displayed characteristic bistable, nonvolatile and rewritable resistive switching behavior at a low operating voltage. A decent off/on ratio, high retention time, and large endurance of 1.28 × 102, 105 sec and 1000 voltage sweeps were recorded respectively. Double logarithmic curve satisfy the trap controlled space charge limited current (TCSCLC) model in high resistance state (HRS) and ohmic model in low resistance state (LRS). Bendability test at various bending diameters (50-2 mm) for 1500 cycles was carried out to show the mechanical robustness of fabricated device. PMID:27811977

Effects of sol aging on resistive switching behaviors of HfOx resistive memories

NASA Astrophysics Data System (ADS)

Hsu, Chih-Chieh; Sun, Jhen-Kai; Tsao, Che-Chang; Chen, Yu-Ting

2017-03-01

This work investigates effects of long-term sol-aging time on sol-gel HfOx resistive random access memories (RRAMs). A nontoxic solvent of ethanol is used to replace toxic 2-methoxyethanol, which is usually used in sol-gel processes. The top electrodes are fabricated by pressing indium balls onto the HfOx surface rather than by using conventional sputtering or evaporation processes. The maximum process temperature is limited to be 100 ℃. Therefore, influences of plasma and high temperature on HfOx film can be avoided. Under this circumstance, effects of sol aging time on the HfOx films can be more clearly studied. The current conduction mechanisms in low and high electric regions of the HfOx RRAM are found to be dominated by Ohmic conduction and trap-filled space charge limited conduction (TF-SCLC), respectively. When the sol aging time increases, the resistive switching characteristic of the HfOx layer becomes unstable and the transition voltage from Ohmic conduction to TF-SCLC is also increased. This suggests that an exceedingly long aging time will give a HfOx film with more defect states. The XPS results are consistent with FTIR analysis and they can further explain the unstable HfOx resistive switching characteristic induced by sol aging.

If Trees Would Talk: The Communication of Resistance in Ex-Slave Narratives. Working Paper.

ERIC Educational Resources Information Center

Clift, Arlene L.

Examples drawn from books and interviews of blacks reveal techniques of oral and literate communication both during and after slavery. These techniques fall into two complementary categories: communication as surreptitious resistance and communication about overt resisters. Surreptitious communication occurred through the use of code words which…

Conduction Mechanism and Improved Endurance in HfO2-Based RRAM with Nitridation Treatment

NASA Astrophysics Data System (ADS)

Yuan, Fang-Yuan; Deng, Ning; Shih, Chih-Cheng; Tseng, Yi-Ting; Chang, Ting-Chang; Chang, Kuan-Chang; Wang, Ming-Hui; Chen, Wen-Chung; Zheng, Hao-Xuan; Wu, Huaqiang; Qian, He; Sze, Simon M.

2017-10-01

A nitridation treatment technology with a urea/ammonia complex nitrogen source improved resistive switching property in HfO2-based resistive random access memory (RRAM). The nitridation treatment produced a high performance and reliable device which results in superior endurance (more than 109 cycles) and a self-compliance effect. Thus, the current conduction mechanism changed due to defect passivation by nitrogen atoms in the HfO2 thin film. At a high resistance state (HRS), it transferred to Schottky emission from Poole-Frenkel in HfO2-based RRAM. At low resistance state (LRS), the current conduction mechanism was space charge limited current (SCLC) after the nitridation treatment, which suggests that the nitrogen atoms form Hf-N-Ox vacancy clusters (Vo +) which limit electron movement through the switching layer.

Spectromicroscopic insights for rational design of redox-based memristive devices

PubMed Central

Baeumer, Christoph; Schmitz, Christoph; Ramadan, Amr H. H.; Du, Hongchu; Skaja, Katharina; Feyer, Vitaliy; Müller, Philipp; Arndt, Benedikt; Jia, Chun-Lin; Mayer, Joachim; De Souza, Roger A.; Michael Schneider, Claus; Waser, Rainer; Dittmann, Regina

2015-01-01

The demand for highly scalable, low-power devices for data storage and logic operations is strongly stimulating research into resistive switching as a novel concept for future non-volatile memory devices. To meet technological requirements, it is imperative to have a set of material design rules based on fundamental material physics, but deriving such rules is proving challenging. Here, we elucidate both switching mechanism and failure mechanism in the valence-change model material SrTiO3, and on this basis we derive a design rule for failure-resistant devices. Spectromicroscopy reveals that the resistance change during device operation and failure is indeed caused by nanoscale oxygen migration resulting in localized valence changes between Ti4+ and Ti3+. While fast reoxidation typically results in retention failure in SrTiO3, local phase separation within the switching filament stabilizes the retention. Mimicking this phase separation by intentionally introducing retention-stabilization layers with slow oxygen transport improves retention times considerably. PMID:26477940

Write once read many memory device from Tris-8 (-hydroxyquinoline) aluminum and Indium tin oxide nano particles

NASA Astrophysics Data System (ADS)

Aneesh, J.; Predeep, P.

2011-10-01

Consequent to the fast increase in data storage requirements new materials and device structures are explored in a war footing. Organic memory devices are attracting lot of interest among the researchers and are becoming a hot topic of investigations. This study is an attempt to develop a tri-layer organic memory device using indium tin oxide (ITO) nanoparticles as charge trapping middle layer between tris-8(-hydroxyquinoline)aluminum (Alq3) layers employing spin coating technique. Device switching is studied by applying a current-voltage (I-V) sweep. On increasing the applied bias the device switched from the initial high resistance (OFF) state to a low resistance (ON) state at a switch on voltage of around 4 V. ON/OFF ratio is of the order of 100 at a read voltage of 2 V. The device is found to remain in the low resistance state on further scans, showing the applicability of this device as a write once read many times (WORM) memory.

Improved performance of Ta2O5-x resistive switching memory by Gd-doping: Ultralow power operation, good data retention, and multilevel storage

NASA Astrophysics Data System (ADS)

Shi, K. X.; Xu, H. Y.; Wang, Z. Q.; Zhao, X. N.; Liu, W. Z.; Ma, J. G.; Liu, Y. C.

2017-11-01

Resistive-switching memory with ultralow-power consumption is very promising technology for next-generation data storage and high-energy-efficiency neurosynaptic chips. Herein, Ta2O5-x-based multilevel memories with ultralow-power consumption and good data retention were achieved by simple Gd-doping. The introduction of a Gd ion, as an oxygen trapper, not only suppresses the generation of oxygen vacancy defects and greatly increases the Ta2O5-x resistance but also increases the oxygen-ion migration barrier. As a result, the memory cells can operate at an ultralow current of 1 μA with the extrapolated retention time of >10 years at 85 °C and the high switching speeds of 10 ns/40 ns for SET/RESET processes. The energy consumption of the device is as low as 60 fJ/bit, which is comparable to emerging ultralow-energy consumption (<100 fJ/bit) memory devices.

Transient Resistive Switching Devices Made from Egg Albumen Dielectrics and Dissolvable Electrodes.

PubMed

He, Xingli; Zhang, Jian; Wang, Wenbo; Xuan, Weipeng; Wang, Xiaozhi; Zhang, Qilong; Smith, Charles G; Luo, Jikui

2016-05-04

Egg albumen as the dielectric, and dissolvable Mg and W as the top and bottom electrodes are used to fabricate water-soluble memristors. 4 × 4 cross-bar configuration memristor devices show a bipolar resistive switching behavior with a high to low resistance ratio in the range of 1 × 10(2) to 1 × 10(4), higher than most other biomaterial-based memristors, and a retention time over 10(4) s without any sign of deterioration, demonstrating its high stability and reliability. Metal filaments accompanied by hopping conduction are believed to be responsible for the switching behavior of the memory devices. The Mg and W electrodes, and albumen film all can be dissolved in water within 72 h, showing their transient characteristics. This work demonstrates a new way to fabricate biocompatible and dissolvable electronic devices by using cheap, abundant, and 100% natural materials for the forthcoming bioelectronics era as well as for environmental sensors when the Internet of things takes off.

Ferroelectricity-induced resistive switching in Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3/Nb-doped SrTiO3 epitaxial heterostructure

NASA Astrophysics Data System (ADS)

Md. Sadaf, Sharif; Mostafa Bourim, El; Liu, Xinjun; Hasan Choudhury, Sakeb; Kim, Dong-Wook; Hwang, Hyunsang

2012-03-01

We investigated the effect of a ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin film on the generation of resistive switching in a stacked Pr0.7Ca0.3MnO3 (PCMO)/Nb-doped SrTiO3 (Nb:STO) heterostructure forming a p-n junction. To promote the ferroelectric effect, the thin PZT active layer was deposited on an epitaxially grown p-type PCMO film on a lattice-matched n-type Nb:STO single crystal. It was concluded that the observed resistive switching behavior in the all-perovskite Pt/PZT/PCMO/Nb:STO heterostructure was related to the modulation of PCMO/Nb:STO p-n junction's depletion width, which was caused either by the PZT ferroelectric polarization field effect, the electrochemical drift of oxygen ions under an electric field, or both simultaneously.

Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) Interlayer Insertion Enables Organic Quaternary Memory.

PubMed

Cheng, Xue-Feng; Hou, Xiang; Qian, Wen-Hu; He, Jing-Hui; Xu, Qing-Feng; Li, Hua; Li, Na-Jun; Chen, Dong-Yun; Lu, Jian-Mei

2017-08-23

Herein, for the first time, quaternary resistive memory based on an organic molecule is achieved via surface engineering. A layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was inserted between the indium tin oxide (ITO) electrode and the organic layer (squaraine, SA-Bu) to form an ITO/PEDOT-PSS/SA-Bu/Al architecture. The modified resistive random-access memory (RRAM) devices achieve quaternary memory switching with the highest yield (∼41%) to date. Surface morphology, crystallinity, and mosaicity of the deposited organic grains are greatly improved after insertion of a PEDOT-PSS interlayer, which provides better contacts at the grain boundaries as well as the electrode/active layer interface. The PEDOT-PSS interlayer also reduces the hole injection barrier from the electrode to the active layer. Thus, the threshold voltage of each switching is greatly reduced, allowing for more quaternary switching in a certain voltage window. Our results provide a simple yet powerful strategy as an alternative to molecular design to achieve organic quaternary resistive memory.

Gold-based thin multilayers for ohmic contacts in RF-MEMS switches

NASA Astrophysics Data System (ADS)

Mulloni, V.; Iannacci, J.; Bartali, R.; Micheli, V.; Colpo, S.; Laidani, N.; Margesin, B.

2011-06-01

In RF-MEMS switches many reliability issues are related to the metal contacts in the switching area. The characteristics of this contact influence not only contact resistance and insertion loss, but also the most relevant switch failure mechanisms that are wear of ohmic contact, adhesion and stiction. Gold is widely used for this purpose because of its good conductivity and chemical inertness, but is a soft metal, and the development of hard contact materials with low resistivity is of great interest for RF-MEMS switch reliability. It is possible to increase the contact hardness preserving the convenient gold properties alternating gold layers with thin layers of different metals. The material becomes harder not only by simple alloying but also by the presence of interfaces which act as barriers for mechanical dislocation migration. A detailed study of mechanical, electrical and morphological properties of gold-chromium, gold-platinum and gold-palladium multilayers is presented and discussed. It is found that the annealing treatments are important for tuning hardness values, and a careful choice of the alloying metal is essential when the material is inserted in a real switch fabrication cycle, because hardness improvements can vanish during oxygen plasma treatments usually involved in RF-switches fabrication. Platinum is the only metal tested that is unaffected by oxidation, and also modifies the chromium adhesion layer diffusion on the contact surface.

Fabrication of resistive switching memory structure using double-sided-anodized porous alumina

NASA Astrophysics Data System (ADS)

Morishita, Yoshitaka; Hosono, Takaya; Ogawa, Hiroto

2017-05-01

Double-sides of aluminum sheet were anodized; at first, one side (front-side) of aluminum sheet was anodized, and the pores were filled with nickel using electroplating technique. Next, the other side (back side) of aluminum sheet was anodized. After formation of electrodes on both sides of anodic porous alumina, the current-voltage characteristics were examined, and reversible change in the resistance between metallic and insulating states was measured during mono-polar operation. This switching behavior could be measured for the sample with the depth of backside pores of about 100 μm. The bias voltage, at which the resistance state changed into the lower-resistance state from the higher-resistance state, decreased with decreasing the depth of backside pores, and the bias voltage was about 1 V in the case of the backside pores of about 10 μm.

Novel control system of the high-voltage IGBT-switch

NASA Astrophysics Data System (ADS)

Ponomarev, A. V.; Mamontov, Y. I.; Gusev, A. I.; Pedos, M. S.

2017-05-01

HV solid-state switch control circuit was developed and tested. The switch was made with series connection IGBT-transistors. The distinctive feature of the circuit is an ability to fine-tune the switching time of every transistor. Simultaneous switching provides balancing of the dynamic voltage at all switch elements. A separate control board switches on and off every transistor. On and off signals from the main conductor are sent to the board by current pulses of different polarity. A positive pulse provides the transistor switch-on, while a negative pulse provides their switch-off. The time interval between pulses defines the time when the switch is turned on. The minimum time when the switch is turned on equals to a few microseconds, while the maximum time is not limited. This paper shows the test results of 4 kV switch prototype. The switch was used to produce rectangular pulses of a microsecond range under resistive load. The possibility to generate the damped harmonic oscillations was also tested. On the basis of this approach, positive testing results open up a possibility to design switches under an operating voltage of tens kilovolts.

A solid-state dielectric elastomer switch for soft logic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chau, Nixon; Slipher, Geoffrey A., E-mail: geoffrey.a.slipher.civ@mail.mil; Mrozek, Randy A.

In this paper, we describe a stretchable solid-state electronic switching material that operates at high voltage potentials, as well as a switch material benchmarking technique that utilizes a modular dielectric elastomer (artificial muscle) ring oscillator. The solid-state switching material was integrated into our oscillator, which self-started after 16 s and performed 5 oscillations at a frequency of 1.05 Hz with 3.25 kV DC input. Our materials-by-design approach for the nickel filled polydimethylsiloxane based switch has resulted in significant improvements over previous carbon grease-based switches in four key areas, namely, sharpness of switching behavior upon applied stretch, magnitude of electrical resistance change, ease ofmore » manufacture, and production rate. Switch lifetime was demonstrated to be in the range of tens to hundreds of cycles with the current process. An interesting and potentially useful strain-based switching hysteresis behavior is also presented.« less

Coaxial fast metal-to-metal switch for high current.

PubMed

Boissady, C; Rioux-Damidau, F

1978-11-01

A fast mechanical switch of coaxial configuration, driven by a magnetic field, is described. It presents a low inductance (6 nH), a low resistance (3 muOmega) and delay-times of 25 micros with a jitter of 0.08 micros.

High-speed logic integrated circuits with solution-processed self-assembled carbon nanotubes

NASA Astrophysics Data System (ADS)

Han, Shu-Jen; Tang, Jianshi; Kumar, Bharat; Falk, Abram; Farmer, Damon; Tulevski, George; Jenkins, Keith; Afzali, Ali; Oida, Satoshi; Ott, John; Hannon, James; Haensch, Wilfried

2017-09-01

As conventional monolithic silicon technology struggles to meet the requirements for the 7-nm technology node, there has been tremendous progress in demonstrating the scalability of carbon nanotube field-effect transistors down to the size that satisfies the 3-nm node and beyond. However, to date, circuits built with carbon nanotubes have overlooked key aspects of a practical logic technology and have stalled at simple functionality demonstrations. Here, we report high-performance complementary carbon nanotube ring oscillators using fully manufacturable processes, with a stage switching frequency of 2.82 GHz. The circuit was built on solution-processed, self-assembled carbon nanotube arrays with over 99.9% semiconducting purity, and the complementary feature was achieved by employing two different work function electrodes.

High-speed logic integrated circuits with solution-processed self-assembled carbon nanotubes.

PubMed

Han, Shu-Jen; Tang, Jianshi; Kumar, Bharat; Falk, Abram; Farmer, Damon; Tulevski, George; Jenkins, Keith; Afzali, Ali; Oida, Satoshi; Ott, John; Hannon, James; Haensch, Wilfried

2017-09-01

As conventional monolithic silicon technology struggles to meet the requirements for the 7-nm technology node, there has been tremendous progress in demonstrating the scalability of carbon nanotube field-effect transistors down to the size that satisfies the 3-nm node and beyond. However, to date, circuits built with carbon nanotubes have overlooked key aspects of a practical logic technology and have stalled at simple functionality demonstrations. Here, we report high-performance complementary carbon nanotube ring oscillators using fully manufacturable processes, with a stage switching frequency of 2.82 GHz. The circuit was built on solution-processed, self-assembled carbon nanotube arrays with over 99.9% semiconducting purity, and the complementary feature was achieved by employing two different work function electrodes.

Improved fatigue resistance in Gsα-deficient and aging mouse skeletal muscles due to adaptive increases in slow fibers

PubMed Central

Feng, Han-Zhong; Chen, Min; Weinstein, Lee S.

2011-01-01

Genetically modified mice with deficiency of the G protein α-subunit (Gsα) in skeletal muscle showed metabolic abnormality with reduced glucose tolerance, low muscle mass, and low contractile force, along with a fast-to-slow-fiber-type switch (Chen M, Feng HZ, Gupta D, Kelleher J, Dickerson KE, Wang J, Hunt D, Jou W, Gavrilova O, Jin JP, Weinstein LS. Am J Physiol Cell Physiol 296: C930–C940, 2009). Here we investigated a hypothesis that the switching to more slow fibers is an adaptive response with specific benefit. The results showed that, corresponding to the switch of myosin isoforms, the thin-filament regulatory proteins troponin T and troponin I both switched to their slow isoforms in the atrophic soleus muscle of 3-mo-old Gsα-deficient mice. This fiber-type switch involving coordinated changes of both thick- and thin-myofilament proteins progressed in the Gsα-deficient soleus muscles of 18- to 24-mo-old mice, as reflected by the expression of solely slow isoforms of myosin and troponin. Compared with age-matched controls, Gsα-deficient soleus muscles with higher proportion of slow fibers exhibited slower contractile and relaxation kinetics and lower developed force, but significantly increased resistance to fatigue, followed by a better recovery. Gsα-deficient soleus muscles of neonatal and 3-wk-old mice did not show the increase in slow fibers. Therefore, the fast-to-slow-fiber-type switch in Gsα deficiency at older ages was likely an adaptive response. The benefit of higher fatigue resistance in adaption to metabolic deficiency and aging provides a mechanism to sustain skeletal muscle function in diabetic patients and elderly individuals. PMID:21680879

Simplified ZrTiO x -based RRAM cell structure with rectifying characteristics by integrating Ni/n + -Si diode.

PubMed

Lin, Chia-Chun; Wu, Yung-Hsien; Chang, You-Tai; Sun, Cherng-En

2014-01-01

A simplified one-diode one-resistor (1D1R) resistive switching memory cell that uses only four layers of TaN/ZrTiO x /Ni/n(+)-Si was proposed to suppress sneak current where TaN/ZrTiO x /Ni can be regarded as a resistive-switching random access memory (RRAM) device while Ni/n(+)-Si acts as an Schottky diode. This is the first RRAM cell structure that employs metal/semiconductor Schottky diode for current rectifying. The 1D1R cell exhibits bipolar switching behavior with SET/RESET voltage close to 1 V without requiring a forming process. More importantly, the cell shows tight resistance distribution for different states, significantly rectifying characteristics with forward/reverse current ratio higher than 10(3) and a resistance ratio larger than 10(3) between two states. Furthermore, the cell also displays desirable reliability performance in terms of long data retention time of up to 10(4) s and robust endurance of 10(5) cycles. Based on the promising characteristics, the four-layer 1D1R structure holds the great potential for next-generation nonvolatile memory technology.

Ultraviolet-assisted direct patterning and low-temperature formation of flexible ZrO2 resistive switching arrays on PET/ITO substrates

NASA Astrophysics Data System (ADS)

Li, Lingwei; Chen, Yuanqing; Yin, Xiaoru; Song, Yang; Li, Na; Niu, Jinfen; Wu, Huimin; Qu, Wenwen

2017-12-01

We demonstrate a low-cost and facile photochemical solution method to prepare the ZrO2 resistive switching arrays as memristive units on flexible PET/ITO substrates. ZrO2 solution sensitive to UV light of 337 nm was synthesized using zirconium n-butyl alcohol as the precursor, and benzoylacetone as the complexing agent. After the dip-coated ZrO2 gel films were irradiated through a mask under the UV lamp (with wavelength of 325-365 nm) at room temperature and rinsed in ethanol, the ZrO2 gel arrays were obtained on PET/ITO substrates. Subsequently, the ZrO2 gel arrays were irradiated by deep UV light of 254 and 185 nm at 150 °C, resulting in the amorphous ZrO2 memristive micro-arrays. The ZrO2 units on flexible PET/ITO substrates exhibited excellent memristive properties. A high ratio of 104 of on-state and off-state resistance was obtained. The resistive switching behavior of the flexible device remained stable after being bent for 103 times. The device showed stable flexibility up to a minimum bending diameter of 1.25 cm.

Current-limiting and ultrafast system for the characterization of resistive random access memories.

PubMed

Diaz-Fortuny, J; Maestro, M; Martin-Martinez, J; Crespo-Yepes, A; Rodriguez, R; Nafria, M; Aymerich, X

2016-06-01

A new system for the ultrafast characterization of resistive switching phenomenon is developed to acquire the current during the Set and Reset process in a microsecond time scale. A new electronic circuit has been developed as a part of the main setup system, which is capable of (i) applying a hardware current limit ranging from nanoampers up to miliampers and (ii) converting the Set and Reset exponential gate current range into an equivalent linear voltage. The complete system setup allows measuring with a microsecond resolution. Some examples demonstrate that, with the developed setup, an in-depth analysis of resistive switching phenomenon and random telegraph noise can be made.

Bipolar resistive switching in metal-insulator-semiconductor nanostructures based on silicon nitride and silicon oxide

NASA Astrophysics Data System (ADS)

Koryazhkina, M. N.; Tikhov, S. V.; Mikhaylov, A. N.; Belov, A. I.; Korolev, D. S.; Antonov, I. N.; Karzanov, V. V.; Gorshkov, O. N.; Tetelbaum, D. I.; Karakolis, P.; Dimitrakis, P.

2018-03-01

Bipolar resistive switching in metal-insulator-semiconductor (MIS) capacitor-like structures with an inert Au top electrode and a Si3N4 insulator nanolayer (6 nm thick) has been observed. The effect of a highly doped n +-Si substrate and a SiO2 interlayer (2 nm) is revealed in the changes in the semiconductor space charge region and small-signal parameters of parallel and serial equivalent circuit models measured in the high- and low-resistive capacitor states, as well as under laser illumination. The increase in conductivity of the semiconductor capacitor plate significantly reduces the charging and discharging times of capacitor-like structures.

Reduced Fluorescent Protein Switching Fatigue by Binding-Induced Emissive State Stabilization

PubMed Central

Dedecker, Peter

2017-01-01

Reversibly switchable fluorescent proteins (RSFPs) enable advanced fluorescence imaging, though the performance of this imaging crucially depends on the properties of the labels. We report on the use of an existing small binding peptide, named Enhancer, to modulate the spectroscopic properties of the recently developed rsGreen series of RSFPs. Fusion constructs of Enhancer with rsGreen1 and rsGreenF revealed an increased molecular brightness and pH stability, although expression in living E. coli or HeLa cells resulted in a decrease of the overall emission. Surprisingly, Enhancer binding also increased off-switching speed and resistance to switching fatigue. Further investigation suggested that the RSFPs can interconvert between fast- and slow-switching emissive states, with the overall protein population gradually converting to the slow-switching state through irradiation. The Enhancer modulates the spectroscopic properties of both states, but also preferentially stabilizes the fast-switching state, supporting the increased fatigue resistance. This work demonstrates how the photo-physical properties of RSFPs can be influenced by their binding to other small proteins, which opens up new horizons for applications that may require such modulation. Furthermore, we provide new insights into the photoswitching kinetics that should be of general consideration when developing new RSFPs with improved or different photochromic properties. PMID:28930199

Switching behaviour of individual Ag-TCNQ nanowires: an in situ transmission electron microscopy study

NASA Astrophysics Data System (ADS)

Ran, Ke; Rösner, Benedikt; Butz, Benjamin; Fink, Rainer H.; Spiecker, Erdmann

2016-10-01

The organic semiconductor silver-tetracyanoquinodimethane (Ag-TCNQ) exhibits electrical switching and memory characteristics. Employing a scanning tunnelling microscopy setup inside a transmission electron microscope, the switching behaviour of individual Ag-TCNQ nanowires (NWs) is investigated in detail. For a large number of NWs, the switching between a high (OFF) and a low (ON) resistance state was successfully stimulated by negative bias sweeps. Fitting the experimental I-V curves with a Schottky emission function makes the switching features prominent and thus enables a direct evaluation of the switching process. A memory cycle including writing, reading and erasing features is demonstrated at an individual NW. Moreover, electronic failure mechanisms due to Joule heating are discussed. These findings have a significant impact on our understanding of the switching behaviour of Ag-TCNQ.

Heat switch technology for cryogenic thermal management

NASA Astrophysics Data System (ADS)

Shu, Q. S.; Demko, J. A.; E Fesmire, J.

2017-12-01

Systematic review is given of development of novel heat switches at cryogenic temperatures that alternatively provide high thermal connection or ideal thermal isolation to the cold mass. These cryogenic heat switches are widely applied in a variety of unique superconducting systems and critical space applications. The following types of heat switch devices are discussed: 1) magnetic levitation suspension, 2) shape memory alloys, 3) differential thermal expansion, 4) helium or hydrogen gap-gap, 5) superconducting, 6) piezoelectric, 7) cryogenic diode, 8) magneto-resistive, and 9) mechanical demountable connections. Advantages and limitations of different cryogenic heat switches are examined along with the outlook for future thermal management solutions in materials and cryogenic designs.

Ion beam synthesis of indium-oxide nanocrystals for improvement of oxide resistive random-access memories

NASA Astrophysics Data System (ADS)

Bonafos, C.; Benassayag, G.; Cours, R.; Pécassou, B.; Guenery, P. V.; Baboux, N.; Militaru, L.; Souifi, A.; Cossec, E.; Hamga, K.; Ecoffey, S.; Drouin, D.

2018-01-01

We report on the direct ion beam synthesis of a delta-layer of indium oxide nanocrystals (In2O3-NCs) in silica matrices by using ultra-low energy ion implantation. The formation of the indium oxide phase can be explained by (i) the affinity of indium with oxygen, (ii) the generation of a high excess of oxygen recoils generated by the implantation process in the region where the nanocrystals are formed and (iii) the proximity of the indium-based nanoparticles with the free surface and oxidation from the air. Taking advantage of the selective diffusivity of implanted indium in SiO2 with respect to Si3N4, In2O3-NCs have been inserted in the SiO2 switching oxide of micrometric planar oxide-based resistive random access memory (OxRAM) devices fabricated using the nanodamascene process. Preliminary electrical measurements show switch voltage from high to low resistance state. The devices with In2O3-NCs have been cycled 5 times with identical operating voltages and RESET current meanwhile no switch has been observed for non implanted devices. This first measurement of switching is very promising for the concept of In2O3-NCs based OxRAM memories.

Comparisons of switching characteristics between Ti/Al2O3/Pt and TiN/Al2O3/Pt RRAM devices with various compliance currents

NASA Astrophysics Data System (ADS)

Qi, Yanfei; Zhao, Ce Zhou; Liu, Chenguang; Fang, Yuxiao; He, Jiahuan; Luo, Tian; Yang, Li; Zhao, Chun

2018-04-01

In this study, the influence of the Ti and TiN top electrodes on the switching behaviors of the Al2O3/Pt resistive random access memory devices with various compliance currents (CCs, 1-15 mA) has been compared. Based on the similar statistical results of the resistive switching (RS) parameters such as V set/V reset, R HRS/R LRS (measured at 0.10 V) and resistance ratio with various CCs for both devices, the Ti/Al2O3/Pt device differs from the TiN/Al2O3/Pt device mainly in the forming process rather than in the following switching cycles. Apart from the initial isolated state, the Ti/Al2O3/Pt device has the initial intermediate state as well. In addition, its forming voltage is relatively lower. The conduction mechanisms of the ON and OFF state for both devices are demonstrated as ohmic conduction and Frenkel-Poole emission, respectively. Therefore, with the combined modulations of the CCs and the stop voltages, the TiN/Al2O3/Pt device is more stable for nonvolatile memory applications to further improve the RS performance.

A Strategy to Design High-Density Nanoscale Devices utilizing Vapor Deposition of Metal Halide Perovskite Materials.

PubMed

Hwang, Bohee; Lee, Jang-Sik

2017-08-01

The demand for high memory density has increased due to increasing needs of information storage, such as big data processing and the Internet of Things. Organic-inorganic perovskite materials that show nonvolatile resistive switching memory properties have potential applications as the resistive switching layer for next-generation memory devices, but, for practical applications, these materials should be utilized in high-density data-storage devices. Here, nanoscale memory devices are fabricated by sequential vapor deposition of organolead halide perovskite (OHP) CH 3 NH 3 PbI 3 layers on wafers perforated with 250 nm via-holes. These devices have bipolar resistive switching properties, and show low-voltage operation, fast switching speed (200 ns), good endurance, and data-retention time >10 5 s. Moreover, the use of sequential vapor deposition is extended to deposit CH 3 NH 3 PbI 3 as the memory element in a cross-point array structure. This method to fabricate high-density memory devices could be used for memory cells that occupy large areas, and to overcome the scaling limit of existing methods; it also presents a way to use OHPs to increase memory storage capacity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bipolar resistive switching in room temperature grown disordered vanadium oxide thin-film devices

NASA Astrophysics Data System (ADS)

Wong, Franklin J.; Sriram, Tirunelveli S.; Smith, Brian R.; Ramanathan, Shriram

2013-09-01

We demonstrate bipolar switching with high OFF/ON resistance ratios (>104) in Pt/vanadium oxide/Cu structures deposited entirely at room temperature. The SET (RESET) process occurs when negative (positive) bias is applied to the top Cu electrode. The vanadium oxide (VOx) films are amorphous and close to the vanadium pentoxide stoichiometry. We also investigated Cu/VOx/W structures, reversing the position of the Cu electrode, and found the same polarity dependence with respect to the top and bottom electrodes, which suggests that the bipolar nature is linked to the VOx layer itself. Bipolar switching can be observed at 100 °C, indicating that it not due to a temperature-induced metal-insulator transition of a vanadium dioxide second phase. We discuss how ionic drift can lead to the bipolar electrical behavior of our junctions, similar to those observed in devices based on several other defective oxides. Such low-temperature processed oxide switches could be of relevance to back-end or package integration processing schemes.

Improved switching reliability achieved in HfOx based RRAM with mountain-like surface-graphited carbon layer

NASA Astrophysics Data System (ADS)

Tao, Ye; Ding, Wentao; Wang, Zhongqiang; Xu, Haiyang; Zhao, Xiaoning; Li, Xuhong; Liu, Weizhen; Ma, Jiangang; Liu, Yichun

2018-05-01

In this work, we demonstrated an effective method to improve the switching reliability of HfOx based RRAM device by inserting mountain-like surface-graphited carbon (MSGC) layer. The MSGC layer was fabricated through thermal annealing of amorphous carbon (a-C) film with high sp2 proportion (49.7%) under 500 °C on Pt substrate, whose characteristics were validated by XPS and Raman spectrums. The local electric-field (LEF) was enhanced around the nanoscale tips of MSGC layer due to large surface curvature, which leads to simplified CFs and localization of resistive switching region. It takes responsibility to the reduction of high/low resistance states (HRS/LRS) fluctuation from 173.8%/64.9% to 23.6%/6.5%, respectively. In addition, the resulting RRAM devices exhibited fast switching speed (<65 ns), good retention (>104 s at 85 °C) and low cycling degradation. This method could be promising to develop reliable and repeatable high-performance RRAM for practical applications.

High density submicron magnetoresistive random access memory (invited)

NASA Astrophysics Data System (ADS)

Tehrani, S.; Chen, E.; Durlam, M.; DeHerrera, M.; Slaughter, J. M.; Shi, J.; Kerszykowski, G.

1999-04-01

Various giant magnetoresistance material structures were patterned and studied for their potential as memory elements. The preferred memory element, based on pseudo-spin valve structures, was designed with two magnetic stacks (NiFeCo/CoFe) of different thickness with Cu as an interlayer. The difference in thickness results in dissimilar switching fields due to the shape anisotropy at deep submicron dimensions. It was found that a lower switching current can be achieved when the bits have a word line that wraps around the bit 1.5 times. Submicron memory elements integrated with complementary metal-oxide-semiconductor (CMOS) transistors maintained their characteristics and no degradation to the CMOS devices was observed. Selectivity between memory elements in high-density arrays was demonstrated.

Transparent ceramic photo-optical semiconductor high power switches

DOEpatents

Werne, Roger W.; Sullivan, James S.; Landingham, Richard L.

2016-01-19

A photoconductive semiconductor switch according to one embodiment includes a structure of sintered nanoparticles of a high band gap material exhibiting a lower electrical resistance when excited by light relative to an electrical resistance thereof when not exposed to the light. A method according to one embodiment includes creating a mixture comprising particles, at least one dopant, and at least one solvent; adding the mixture to a mold; forming a green structure in the mold; and sintering the green structure to form a transparent ceramic. Additional system, methods and products are also presented.

Magnetization reversal and inverted magnetoresistance of exchange-biased spin valves with a gadolinium layer

NASA Astrophysics Data System (ADS)

Milyaev, M.; Naumova, L.; Chernyshova, T.; Proglyado, V.; Kamensky, I.; Krinitsina, T.; Ryabukhina, M.; Ustinov, V.

2017-03-01

FeMn-based spin valves with a gadolinium layer have been fabricated by magnetron sputtering. The magnetoresistive properties of the spin valves have been investigated at temperatures of 80-293 K. Temperature-induced switching between low- and high-resistance magnetic states has been revealed. Realization of the low- or high-resistance states depends on which magnetic moment dominates in the exchange-coupled Gd/CoFe, of Gd or CoFe. It has been shown that the switching temperature depends on the thickness of the gadolinium layer.

Multiferroic YCrO3 thin films grown on glass substrate: Resistive switching characteristics

NASA Astrophysics Data System (ADS)

Seo, Jeongdae; Ahn, Yoonho; Son, Jong Yeog

2016-01-01

Polycrystalline YCrO3 thin films were deposited on (111) Pt/Ta/glass substrates by pulsed laser deposition. The YCrO3 thin films exhibited good ferroelectric properties with remnant polarization of about 5 µC/cm2. Large leakage current was observed by I- V curve and ferroelectric hysteresis loop. The YCrO3 resistive random access memory (RRAM) capacitor showed unipolar switching behaviors with SET and RESET voltages higher than those of general NiO RRAM capacitors. [Figure not available: see fulltext.

TiO2-based memristors and ReRAM: materials, mechanisms and models (a review)

NASA Astrophysics Data System (ADS)

Gale, Ella

2014-10-01

The memristor is the fundamental nonlinear circuit element, with uses in computing and computer memory. Resistive Random Access Memory (ReRAM) is a resistive switching memory proposed as a non-volatile memory. In this review we shall summarize the state of the art for these closely-related fields, concentrating on titanium dioxide, the well-utilized and archetypal material for both. We shall cover material properties, switching mechanisms and models to demonstrate what ReRAM and memristor scientists can learn from each other and examine the outlook for these technologies.

Silicon switching transistor with high power and low saturation voltage

NASA Technical Reports Server (NTRS)

Stonebraker, E.; Stoneburner, D.; Ferree, H.

1973-01-01

Assembly of two individually encapsulated silicon-chip transistors produces silicon power-transistor that has low electrical resistance and low thermal impedance. Electrical resistance and thermal impedance are low because of short lead lengths, and external contact surfaces are plated to reduce resistance at interfaces.

30 CFR 7.64 - Technical requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... produce the required firing current is attained. (d) Firing switch. The switch used to initiate the... current is available to the blasting circuit. (e) Firing line terminals. The terminals used to connect the blasting circuit to the blasting unit shall— (1) Provide a secure, low-resistance connection to the...

30 CFR 7.64 - Technical requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... produce the required firing current is attained. (d) Firing switch. The switch used to initiate the... current is available to the blasting circuit. (e) Firing line terminals. The terminals used to connect the blasting circuit to the blasting unit shall— (1) Provide a secure, low-resistance connection to the...

Active counter electrode in a-SiC electrochemical metallization memory

NASA Astrophysics Data System (ADS)

Morgan, K. A.; Fan, J.; Huang, R.; Zhong, L.; Gowers, R.; Ou, J. Y.; Jiang, L.; De Groot, C. H.

2017-08-01

Cu/amorphous-SiC (a-SiC) electrochemical metallization memory cells have been fabricated with two different counter electrode (CE) materials, W and Au, in order to investigate the role of CEs in a non-oxide semiconductor switching matrix. In a positive bipolar regime with Cu filaments forming and rupturing, the CE influences the OFF state resistance and minimum current compliance. Nevertheless, a similarity in SET kinetics is seen for both CEs, which differs from previously published SiO2 memories, confirming that CE effects are dependent on the switching layer material or type. Both a-SiC memories are able to switch in the negative bipolar regime, indicating Au and W filaments. This confirms that CEs can play an active role in a non-oxide semiconducting switching matrix, such as a-SiC. By comparing both Au and W CEs, this work shows that W is superior in terms of a higher R OFF/R ON ratio, along with the ability to switch at lower current compliances making it a favourable material for future low energy applications. With its CMOS compatibility, a-SiC/W is an excellent choice for future resistive memory applications.

Resistive switching characteristics of solution-processed Al-Zn-Sn-O films annealed by microwave irradiation

NASA Astrophysics Data System (ADS)

Kim, Tae-Wan; Baek, Il-Jin; Cho, Won-Ju

2018-02-01

In this study, we employed microwave irradiation (MWI) at low temperature in the fabrication of solution-processed AlZnSnO (AZTO) resistive random access memory (ReRAM) devices with a structure of Ti/AZTO/Pt and compared the memory characteristics with the conventional thermal annealing (CTA) process. Typical bipolar resistance switching (BRS) behavior was observed in AZTO ReRAM devices treated with as-deposited (as-dep), CTA and MWI. In the low resistance state, the Ohmic conduction mechanism describes the dominant conduction of these devices. On the other hand, the trap-controlled space charge limited conduction (SCLC) mechanism predominates in the high resistance state. The AZTO ReRAM devices processed with MWI showed larger memory windows, uniform distribution of resistance state and operating voltage, stable DC durability (>103 cycles) and stable retention characteristics (>104 s). In addition, the AZTO ReRAM devices treated with MWI exhibited multistage storage characteristics by modulating the amplitude of the reset bias, and eight distinct resistance levels were obtained with stable retention capability.

Vertically integrated, three-dimensional nanowire complementary metal-oxide-semiconductor circuits.

PubMed

Nam, SungWoo; Jiang, Xiaocheng; Xiong, Qihua; Ham, Donhee; Lieber, Charles M

2009-12-15

Three-dimensional (3D), multi-transistor-layer, integrated circuits represent an important technological pursuit promising advantages in integration density, operation speed, and power consumption compared with 2D circuits. We report fully functional, 3D integrated complementary metal-oxide-semiconductor (CMOS) circuits based on separate interconnected layers of high-mobility n-type indium arsenide (n-InAs) and p-type germanium/silicon core/shell (p-Ge/Si) nanowire (NW) field-effect transistors (FETs). The DC voltage output (V(out)) versus input (V(in)) response of vertically interconnected CMOS inverters showed sharp switching at close to the ideal value of one-half the supply voltage and, moreover, exhibited substantial DC gain of approximately 45. The gain and the rail-to-rail output switching are consistent with the large noise margin and minimal static power consumption of CMOS. Vertically interconnected, three-stage CMOS ring oscillators were also fabricated by using layer-1 InAs NW n-FETs and layer-2 Ge/Si NW p-FETs. Significantly, measurements of these circuits demonstrated stable, self-sustained oscillations with a maximum frequency of 108 MHz, which represents the highest-frequency integrated circuit based on chemically synthesized nanoscale materials. These results highlight the flexibility of bottom-up assembly of distinct nanoscale materials and suggest substantial promise for 3D integrated circuits.

Reconfigurable logic in nanosecond Cu/GeTe/TiN filamentary memristors for energy-efficient in-memory computing.

PubMed

Jin, Miaomiao; Cheng, Long; Li, Yi; Hu, Siyu; Lu, Ke; Chen, Jia; Duan, Nian; Wang, Zhuorui; Zhou, Yaxiong; Chang, Ting-Chang; Miao, Xiangshui

2018-06-27

Owing to the capability of integrating the information storage and computing in the same physical location, in-memory computing with memristors has become a research hotspot as a promising route for non von Neumann architecture. However, it is still a challenge to develop high performance devices as well as optimized logic methodologies to realize energy-efficient computing. Herein, filamentary Cu/GeTe/TiN memristor is reported to show satisfactory properties with nanosecond switching speed (< 60 ns), low voltage operation (< 2 V), high endurance (>104 cycles) and good retention (>104 s @85℃). It is revealed that the charge carrier conduction mechanisms in high resistance and low resistance states are Schottky emission and hopping transport between the adjacent Cu clusters, respectively, based on the analysis of current-voltage behaviors and resistance-temperature characteristics. An intuitive picture is given to describe the dynamic processes of resistive switching. Moreover, based on the basic material implication (IMP) logic circuit, we proposed a reconfigurable logic method and experimentally implemented IMP, NOT, OR, and COPY logic functions. Design of a one-bit full adder with reduction in computational sequences and its validation in simulation further demonstrate the potential practical application. The results provide important progress towards understanding of resistive switching mechanism and realization of energy-efficient in-memory computing architecture. © 2018 IOP Publishing Ltd.

Non-equilibrium character of resistive switching and negative differential resistance in Ga-doped Cr2O3 system

NASA Astrophysics Data System (ADS)

Bhowmik, R. N.; Siva, K. Venkata

2018-07-01

The samples of Ga-doped Cr2O3 system in rhombohedral crystal structure with space group R 3 bar C were prepared by chemical co-precipitation route and annealing at 800 °C. The current-voltage (I-V) curves exhibited many unique non-linear properties, e.g., hysteresis loop, resistive switching, and negative differential resistance (NDR). In this work, we report non-equilibrium properties of resistive switching and NDR phenomena. The non-equilibrium I-V characteristics were confirmed by repetiting measurement and time relaxation of current. The charge conduction process was understood by analysing the I-V curves using electrode-limited and bulk-limited charge conduction mechanisms, which were proposed for metal electrode/metal oxide/metal electrode structure. The I-V curves in the NDR regime and at higher bias voltage regime in our samples did not obey Fowler-Nordheim equation, which was proposed for charge tunneling mechanism in many thin film junctions. The non-equilibrium I-V phenomena were explained by considering the competitions between the injection of charge carriers from metal electrode to metal oxide, the charge flow through bulk material mediated by trapping/de-trapping and recombination of charge carriers at the defect sites of ions, the space charge effects at the junctions of electrodes and metal oxides, and finally, the out flow of electrons from metal oxide to metal electrode.

Parameters controlling microstructures and resistance switching of electrodeposited cuprous oxide thin films

NASA Astrophysics Data System (ADS)

Yazdanparast, Sanaz

2016-12-01

Cuprous oxide (Cu2O) thin films were electrodeposited cathodically from a highly alkaline bath using tartrate as complexing agent. Different microstructures for Cu2O thin films were achieved by varying the applied potential from -0.285 to -0.395 V versus a reference electrode of Ag/AgCl at 50 °C in potentiostatic mode, and separately by changing the bath temperature from 25 to 50 °C in galvanostatic mode. Characterization experiments showed that both grain size and orientation of Cu2O can be controlled by changing the applied potential. Applying a high negative potential of -0.395 V resulted in smaller grain size of Cu2O thin films with a preferred orientation in [111] direction. An increase in the bath temperature in galvanostatic electrodeposition increased the grain size of Cu2O thin films. All the films in Au/Cu2O/Au-Pd cell showed unipolar resistance switching behavior after an initial FORMING process. Increasing the grain size of Cu2O thin films and decreasing the top electrode area increased the FORMING voltage and decreased the current level of high resistance state (HRS). The current in low resistance state (LRS) was independent of the top electrode area and the grain size of deposited films, suggesting a filamentary conduction mechanism in unipolar resistance switching of Cu2O.

Resistive Random Access Memory from Materials Development fnd Engineering to Novel Encryption and Neuromorphic Applications

NASA Astrophysics Data System (ADS)

Beckmann, Karsten

Resistive random access memory (ReRAM or RRAM) is a novel form of non-volatile memory that is expected to play a major role in future computing and memory solutions. It has been shown that the resistance state of ReRAM devices can be precisely tuned by modulating switching voltages, by limiting peak current, and by adjusting the switching pulse properties. This enables the realization of novel applications such as memristive neuromorphic computing and neural network computing. I have developed two processes based on 100 and 300mm wafer platforms to demonstrate functional HfO2 based ReRAM devices. The first process is designed for a rapid materials engineering and device characterization, while the second is an advanced hybrid ReRAM/CMOS combination based on the IBM 65nm 10LPe process technology. The 100mm wafer efforts were used to show impacts of etch processes on ReRAM switching performance and the need for a rigorous structural evaluation of ReRAM devices before starting materials development. After an etch development, a bottom electrode comparison between the inert materials Pt, Ru and W was performed where Ru showed superior results with respect to yield and resilience against environmental impacts such as humidity over a 2-month period. A comparison of amorphous and crystalline devices showed no statistical difference in the performance with respect to random telegraph noise. This demonstrates, that the forming process fundamentally alters the crystallographic structure within and around the filament. The 300mm wafer development efforts were aimed towards implementing ReRAM in the FEOL, combined with CMOS, to yield a seamless process flow of 1 transistor 1 ReRAM structures (1T1R). This technology was customized with custom-developed tungsten metal 1 (M1) and dual tungsten/copper via 1 (V1) structures, within which the ReRAM stack is embedded. The ReRAM itself consists of an inert W bottom electrode, HfO2 based active switching layer, a Ti oxygen scavenger layer, and an inert TiN top electrode. Linear sweep and controlled pulse (down to 5 ns) based electrical characterization of 1 transistor 1 ReRAM (1T1R) elements was performed to determine key properties including endurance, reliability, and threshold voltages. We demonstrated endurance values above 1010 cycles with an average on/off ratio of 10, and pulse voltages for set/reset operation of +/-1.5V. The on-chip 1T1R structures show an excellent controllability with respect to the low and high resistive states by manipulating the peak current from 75 up to 350 mu?A resulting in 10 distinct low resistance states (LRS). Our results demonstrate that the set operation (which shifts the ReRAM device from the high to the low resistance state) is only dependent on the voltage of the switching pulse and the peak current limit. The reset operation, however, occurs in an analog fashion and appears to be dependent on the total energy of the applied switching pulse. Pulse energy was modulated by varying the peak voltage resulting in a larger relative change of the ReRAM device resistance. The incremental resistance changes are ideally suited to emulate synaptic weights for future implementation into neuromorphic architectures. Switching results from these devices were also used to develop a model time-delay physical unclonable function (PUF) circuit, which showed excellent performance when compared to a pure CMOS implementation with significant improvements in uniqueness, size and accuracy.

High Isolation Single-Pole Four-Throw RF MEMS Switch Based on Series-Shunt Configuration

PubMed Central

Khaira, Navjot

2014-01-01

This paper presents a novel design of single-pole four-throw (SP4T) RF-MEMS switch employing both capacitive and ohmic switches. It is designed on high-resistivity silicon substrate and has a compact area of 1.06 mm2. The series or ohmic switches have been designed to provide low insertion loss with good ohmic contact. The pull-in voltage for ohmic switches is calculated to be 7.19 V. Shunt or capacitive switches have been used in each port to improve the isolation for higher frequencies. The proposed SP4T switch provides excellent RF performances with isolation better than 70.64 dB and insertion loss less than 0.72 dB for X-band between the input port and each output port. PMID:24711730

DELINEATION OF SUBSURFACE HYDROCARBON CONTAMINANT DISTRIBUTION USING A DIRECT PUSH RESISTIVITY METHOD

EPA Science Inventory

A direct push resistivity method was evaluated as a complementary screening tool to provide rapid in-situ contaminant detection to aid in better defining locations for drilling, sampling, and monitoring well installation at hazardous waste sites. Nine continuous direct push resi...

A flexible nonvolatile resistive switching memory device based on ZnO film fabricated on a foldable PET substrate.

PubMed

Sun, Bai; Zhang, Xuejiao; Zhou, Guangdong; Yu, Tian; Mao, Shuangsuo; Zhu, Shouhui; Zhao, Yong; Xia, Yudong

2018-06-15

In this work, a flexible resistive switching memory device based on ZnO film was fabricated using a foldable Polyethylene terephthalate (PET) film as substrate while Ag and Ti acts top and bottom electrode. Our as-prepared device represents an outstanding nonvolatile memory behavior with good "write-read-erase-read" stability at room temperature. Finally, a physical model of Ag conductive filament is constructed to understanding the observed memory characteristics. The work provides a new way for the preparation of flexible memory devices based on ZnO films, and especially provides an experimental basis for the exploration of high-performance and portable nonvolatile resistance random memory (RRAM). Copyright © 2018 Elsevier Inc. All rights reserved.

Interface structure in Cu/Ta2O5/Pt resistance switch: a first-principles study.

PubMed

Xiao, Bo; Watanabe, Satoshi

2015-01-14

The interface structures of a Cu/Ta2O5/Pt resistance switch under various oxidation conditions have been examined from first-principles. The O-rich Cu/Ta2O5 interface is found to be stable within a wide range of O chemical potentials. In this interface structure, a considerable number of interface Cu atoms tend to migrate to the amorphous Ta2O5 (a-Ta2O5) layer, which causes the formation of the Cu2O layer. The interface Cu atoms become more ionized with an increase in the interface O concentration and/or temperature. These ionized Cu(+) ions could function as one of the main sources for the formation of conduction filaments in the Cu/a-Ta2O5/Pt resistance switch. In contrast, the ionization of the interface Cu atoms is not observed in the Cu/crystal-Ta2O5 interface primarily due to the much lower Cu ionic conductivity in crystal-Ta2O5 than that in amorphous state. In addition, the Pt electrode could not be ionized, irrespective of the interface O concentration and temperature. The formation of interface O vacancies in Pt/Ta2O5 is always energetically more stable than that in Cu/Ta2O5, which may be partly responsible for the cone shape of conduction filament formed in the Cu/a-Ta2O5/Pt resistance switch, where the base of the cone lies on the Pt/Ta2O5 interface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jae Sung; Lee, Shinbuhm; Noh, Tae Won

Here we report that resistive switching (RS) phenomena are reversible changes in the metastable resistance state induced by external electric fields. After discovery ~50 years ago, RS phenomena have attracted great attention due to their potential application in next-generation electrical devices. Considerable research has been performed to understand the physical mechanisms of RS and explore the feasibility and limits of such devices. There have also been several reviews on RS that attempt to explain the microscopic origins of how regions that were originally insulators can change into conductors. However, little attention has been paid to the most important factor inmore » determining resistance: how conducting local regions are interconnected. Here, we provide an overview of the underlying physics behind connectivity changes in highly conductive regions under an electric field. We first classify RS phenomena according to their characteristic current–voltage curves: unipolar, bipolar, and threshold switchings. Second, we outline the microscopic origins of RS in oxides, focusing on the roles of oxygen vacancies: the effect of concentration, the mechanisms of channel formation and rupture, and the driving forces of oxygen vacancies. Third, we review RS studies from the perspective of statistical physics to understand connectivity change in RS phenomena. We discuss percolation model approaches and the theory for the scaling behaviors of numerous transport properties observed in RS. Fourth, we review various switching-type conversion phenomena in RS: bipolar-unipolar, memory-threshold, figure-of-eight, and counter-figure-of-eight conversions. Finally, we review several related technological issues, such as improvement in high resistance fluctuations, sneak-path problems, and multilevel switching problems.« less

Cancer Drug Addiction is Relayed by an ERK2-Dependent Phenotype Switch

PubMed Central

Kong, Xiangjun; Kuilman, Thomas; Shahrabi, Aida; Boshuizen, Julia; Kemper, Kristel; Song, Ji-Ying; Niessen, Hans W.M.; Rozeman, Elisa A.; Geukes Foppen, Marnix H.; Blank, Christian U.; Peeper, Daniel S.

2017-01-01

Drug addiction denotes the dependency of tumors on the same therapeutic drugs to which they have acquired resistance. Observations from cultured cells1–3, animal models4 and patients5–7 raise the possibility that cancer drug addiction can instigate a potential cancer vulnerability, which may be used therapeutically. However, for this trait to become of clinical interest, it is imperative to first define the underlying mechanism. Therefore, we performed an unbiased CRISPR-Cas9 knockout screen to functionally mine the genome of melanoma cells that are both resistant and addicted to BRAF inhibition for “addiction genes”. Here, we describe a signaling pathway comprising ERK2, JUNB and FRA1, disruption of which allows tumor cells to reverse addiction and survive upon treatment discontinuation. This occurred both in culture and mice, and was irrespective of the acquired drug resistance mechanism. In melanoma and lung cancer cells, death induced by drug withdrawal was preceded by a specific ERK2-dependent phenotype switch, alongside transcriptional reprogramming reminiscent of EMT. In melanoma, this caused shutdown of the lineage survival oncoprotein MITF, restoration of which reversed both phenotype switching and drug addiction-associated lethality. In melanoma patients who had progressed on BRAF inhibition, treatment cessation was followed by increased expression of the phenotype switch-associated receptor tyrosine kinase AXL. Drug discontinuation synergized with the melanoma chemotherapeutic dacarbazine by further suppressing MITF and its prosurvival target BCL2 while inducing DNA damage. Our results uncover a pathway driving cancer drug addiction, which may guide alternating therapeutic strategies for enhanced clinical responses of drug-resistant cancers. PMID:28976960

Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials.

PubMed

Zalden, Peter; Shu, Michael J; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W; Wong, H-S Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M

2016-08-05

Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

A low insertion loss GaAs pHEMT switch utilizing dual n +-doping AlAs etching stop layers design

NASA Astrophysics Data System (ADS)

Chien, Feng-Tso; Lin, Da-Wei; Yang, Chih-Wei; Fu, Jeffrey S.; Chiu, Hsien-Chin

2010-03-01

A low insertion loss single-pole-single-throw (SPST) pseudomorphic high electron mobility transistor (pHEMT) switch utilizing the n +-type doping in AlAs etching stop layer was fabricated and investigated. This novel design reduces device sheet resistance resulting in an improvement of dc and rf power performance. In addition, the gate recess selectivity for GaAs/AlAs interface was not sacrificed after highly n +-type doping in AlAs etching stop layer. The pHEMT with n +-AlAs etching stop layer, also named Modified pHEMT (M-pHEMT), demonstrated a lower sheet resistance ( Rsh) of 65.9 Ω/γ, a higher maximum drain-to-source current ( Idmax) of 317.8 mA/mm and a higher peak transconductance ( gm) of 259.3 mS/mm which are superior to standard pHEMT performance with values of 71.9 Ω/γ, 290.3 mA/mm and 252.1 mS/mm, respectively. Due to a significant sheet resistance improvement from this novel epitaxial design, an SPST pHEMT switch was realized to manifest its industrial application potential. The results achieved an on-state insertion loss of 1.42 dB, an off-state isolation of 13.02 dB at 0.9 GHz, which were superior to traditional pHEMT switch under same condition of operation with values of 1.68 dB and 11.42 dB, respectively. It is proved that dual n +-doping AlAs etching stop layers scheme is beneficial for low loss microwave switches applications.

Resistive switching mechanism of ZnO/ZrO2-stacked resistive random access memory device annealed at 300 °C by sol-gel method with forming-free operation

NASA Astrophysics Data System (ADS)

Jian, Wen-Yi; You, Hsin-Chiang; Wu, Cheng-Yen

2018-01-01

In this work, we used a sol-gel process to fabricate a ZnO-ZrO2-stacked resistive switching random access memory (ReRAM) device and investigated its switching mechanism. The Gibbs free energy in ZnO, which is higher than that in ZrO2, facilitates the oxidation and reduction reactions of filaments in the ZnO layer. The current-voltage (I-V) characteristics of the device revealed a forming-free operation because of nonlattice oxygen in the oxide layer. In addition, the device can operate under bipolar or unipolar conditions with a reset voltage of 0 to ±2 V, indicating that in this device, Joule heating dominates at reset and the electric field dominates in the set process. Furthermore, the characteristics reveal why the fabricated device exhibits a greater discrete distribution phenomenon for the set voltage than for the reset voltage. These results will enable the fabrication of future ReRAM devices with double-layer oxide structures with improved characteristics.

A Pt/TiO(2)/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays.

PubMed

Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

2010-05-14

This study examined the properties of Schottky-type diodes composed of Pt/TiO(2)/Ti, where the Pt/TiO(2) and TiO(2)/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of approximately 10(9) was achieved at 1 V when the TiO(2) film thickness was 19 nm. TiO(2) film was grown by atomic layer deposition at a substrate temperature of 250 degrees C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to < 10 A cm(-2) for a large electrode (an area of approximately 60 000 microm(2)). However, the local current measurement showed a local forward current density as high as approximately 10(5) A cm(-2). Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

A study of the switching mechanism and electrode material of fully CMOS compatible tungsten oxide ReRAM

NASA Astrophysics Data System (ADS)

Chien, W. C.; Chen, Y. C.; Lai, E. K.; Lee, F. M.; Lin, Y. Y.; Chuang, Alfred T. H.; Chang, K. P.; Yao, Y. D.; Chou, T. H.; Lin, H. M.; Lee, M. H.; Shih, Y. H.; Hsieh, K. Y.; Lu, Chih-Yuan

2011-03-01

Tungsten oxide (WO X ) resistive memory (ReRAM), a two-terminal CMOS compatible nonvolatile memory, has shown promise to surpass the existing flash memory in terms of scalability, switching speed, and potential for 3D stacking. The memory layer, WO X , can be easily fabricated by down-stream plasma oxidation (DSPO) or rapid thermal oxidation (RTO) of W plugs universally used in CMOS circuits. Results of conductive AFM (C-AFM) experiment suggest the switching mechanism is dominated by the REDOX (Reduction-oxidation) reaction—the creation of conducting filaments leads to a low resistance state and the rupturing of the filaments results in a high resistance state. Our experimental results show that the reactions happen at the TE/WO X interface. With this understanding in mind, we proposed two approaches to boost the memory performance: (i) using DSPO to treat the RTO WO X surface and (ii) using Pt TE, which forms a Schottky barrier with WO X . Both approaches, especially the latter, significantly reduce the forming current and enlarge the memory window.

A fast, low resistance switch for small slapper detonators

NASA Astrophysics Data System (ADS)

Richardson, D. D.; Jones, D. A.

1986-10-01

A novel design for a shock compression conduction switch for use with slapper detonators is described. The switch is based on the concept of an explosively driven flyer plate impacting a plastic insulator and producing sufficient pressure within the insulator to produce a conduction transition. An analysis of the functioning of the switch is made using a simple Gurney model for the explosive, and basic shock wave theory to calculate impact pressure and switch closure times. The effect of explosive tamping is considered, and calculations are carried out for two donor explosive thicknesses and a range of flyer plate thicknesses. The new switch has been successfully tested in a series of experimental slapper detonator firings. The results of these tests show trends in overall agreement with those predicted by the calculations.

Picosecond electric-field-induced threshold switching in phase-change materials [THz-induced threshold switching and crystallization of phase-change materials

DOE PAGES

Zalden, Peter; Shu, Michael J.; Chen, Frank; ...

2016-08-05

Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag 4In 3Sb 67Te 26. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales—faster than crystals can nucleate. As a result, this supports purely electronic models of thresholdmore » switching and reveals potential applications as an ultrafast electronic switch.« less

Lassa virus entry requires a trigger-induced receptor switch

PubMed Central

Jae, Lucas T.; Raaben, Matthijs; Herbert, Andrew S.; Kuehne, Ana I.; Wirchnianski, Ariel S.; Soh, Timothy; Stubbs, Sarah H.; Janssen, Hans; Damme, Markus; Saftig, Paul; Whelan, Sean P.; Dye, John M.; Brummelkamp, Thijn R.

2014-01-01

Lassa virus spreads from rodents to humans and can lead to lethal hemorrhagic fever. Despite its broad tropism, chicken cells were reported to resist infection thirty years ago. We show that Lassa virus readily engaged its cell surface receptor α-dystroglycan in avian cells, but virus entry in susceptible species involved a pH-dependent switch to an intracellular receptor, the lysosome-resident protein LAMP1. Iterative haploid screens revealed that the sialyltransferase ST3GAL4 was required for the interaction of the virus glycoprotein with LAMP1. A single glycosylated residue in LAMP1, present in susceptible species but absent in birds, was essential for interaction with the Lassa virus envelope protein and subsequent infection. The resistance of Lamp1-deficient mice to Lassa virus highlights the relevance of this receptor switch in vivo. PMID:24970085

Generation and the role of dislocations in single-crystalline phase-change In 2 Se 3 nanowires under electrical pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mafi, Elham; Tao, Xin; Zhu, Wenguang

2016-07-08

Using single crystalline In2Se3 nanowires as a platform, we have studied the RESET switching (from low to high electrical resistance) in this phase-change material under electric pulses. Particularly, we correlated the atomic-scale structural evolutions with local electrical resistance variations, by performing transmission electron microscopy and scanning Kelvin probe microscopy on the same nanowires. By coupling the experimental results with density functional theory calculations, we show that the immobile dislocations generated via vacancy condensations are responsible for the RESET switching and that the material maintains the single crystallinity during the process. This new mechanism is fundamentally different from the crystalline-amorphous transition,more » which is commonly understood as the underlying process for the RESET switching in similar phase-change materials.« less

High-performance flexible resistive memory devices based on Al2O3:GeOx composite

NASA Astrophysics Data System (ADS)

Behera, Bhagaban; Maity, Sarmistha; Katiyar, Ajit K.; Das, Samaresh

2018-05-01

In this study a resistive switching random access memory device using Al2O3:GeOx composite thin films on flexible substrate is presented. A bipolar switching characteristic was observed for the co-sputter deposited Al2O3:GeOx composite thin films. Al/Al2O3:GeOx/ITO/PET memory device shows excellent ON/OFF ratio (∼104) and endurance (>500 cycles). GeOx nanocrystals embedded in the Al2O3 matrix have been found to play a significant role in enhancing the switching characteristics by facilitating oxygen vacancy formation. Mechanical endurance was retained even after several bending. The conduction mechanism of the device was qualitatively discussed by considering Ohmic and SCLC conduction. This flexible device is a potential candidate for next-generation electronics device.

Engineering amorphous-crystalline interfaces in TiO2-x/TiO2-y-based bilayer structures for enhanced resistive switching and synaptic properties

NASA Astrophysics Data System (ADS)

Bousoulas, P.; Asenov, P.; Karageorgiou, I.; Sakellaropoulos, D.; Stathopoulos, S.; Tsoukalas, D.

2016-10-01

The operating principle of resistive random access memories (RRAMs) relies on the distribution of ionic species and their influence on the electron transport. Taking into account that formation and annihilation of conducting filaments (CFs) is the driving mechanism for the switching effect, it is very important to control the regions where these filaments will evolve. Thus, homolayers of titanium oxide with different oxygen contents were fabricated in order to tune the local electrical and thermal properties of the CFs and narrow down the potential percolation paths. We show that the oxygen content in the top layer of the TiO2-x/TiO2-y bilayer memristors can directly influence the morphology of the layers which affect the diffusion barrier and consequently the diffusivity and drift velocity of oxygen vacancies, yielding in important enhancement of switching characteristics, in terms of spatial uniformity (σ/μ < 0.2), enlarged switching ratio (˜104), and synaptic learning. In order to address the experimental data, a physical model was applied, divulging the crucial role of temperature, electric potential and oxygen vacancy density on the switching effect and offering physical insights to the SET/RESET transitions and the analog switching. The forming free nature of all the devices in conjunction with the self-rectifying behavior, should also be regarded as important assets towards RRAM device optimization.

Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

NASA Astrophysics Data System (ADS)

Xia, Peng; Li, Luman; Wang, Pengfei; Gan, Ying; Xu, Wei

2017-11-01

A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM) Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF) state to low resistance (ON) state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process.

PubMed

Blázquez, O; Martín, G; Camps, I; Mariscal, A; López-Vidrier, J; Ramírez, J M; Hernández, S; Estradé, S; Peiró, F; Serna, R; Garrido, B

2018-06-08

The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole-Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

Memristive behaviour of Si-Al oxynitride thin films: the role of oxygen and nitrogen vacancies in the electroforming process

NASA Astrophysics Data System (ADS)

Blázquez, O.; Martín, G.; Camps, I.; Mariscal, A.; López-Vidrier, J.; Ramírez, J. M.; Hernández, S.; Estradé, S.; Peiró, F.; Serna, R.; Garrido, B.

2018-06-01

The resistive switching properties of silicon-aluminium oxynitride (SiAlON) based devices have been studied. Electrical transport mechanisms in both resistance states were determined, exhibiting an ohmic behaviour at low resistance and a defect-related Poole‑Frenkel mechanism at high resistance. Nevertheless, some features of the Al top-electrode are generated during the initial electroforming, suggesting some material modifications. An in-depth microscopic study at the nanoscale has been performed after the electroforming process, by acquiring scanning electron microscopy and transmission electron microscopy images. The direct observation of the devices confirmed features on the top electrode with bubble-like appearance, as well as some precipitates within the SiAlON. Chemical analysis by electron energy loss spectroscopy has demonstrated that there is an out-diffusion of oxygen and nitrogen ions from the SiAlON layer towards the electrode, thus forming silicon-rich paths within the dielectric layer and indicating vacancy change to be the main mechanism in the resistive switching.

Thin film memory matrix using amorphous and high resistive layers

NASA Technical Reports Server (NTRS)

Thakoor, Anilkumar P. (Inventor); Lambe, John (Inventor); Moopen, Alexander (Inventor)

1989-01-01

Memory cells in a matrix are provided by a thin film of amorphous semiconductor material overlayed by a thin film of resistive material. An array of parallel conductors on one side perpendicular to an array of parallel conductors on the other side enable the amorphous semiconductor material to be switched in addressed areas to be switched from a high resistance state to a low resistance state with a predetermined level of electrical energy applied through selected conductors, and thereafter to be read out with a lower level of electrical energy. Each cell may be fabricated in the channel of an MIS field-effect transistor with a separate common gate over each section to enable the memory matrix to be selectively blanked in sections during storing or reading out of data. This allows for time sharing of addressing circuitry for storing and reading out data in a synaptic network, which may be under control of a microprocessor.

Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruverman, Alexei; Tsymbal, Evgeny Y.; Eom, Chang-Beom

2017-05-03

This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modelingmore » of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.« less

LOGIC CIRCUIT

DOEpatents

Strong, G.H.; Faught, M.L.

1963-12-24

A device for safety rod counting in a nuclear reactor is described. A Wheatstone bridge circuit is adapted to prevent de-energizing the hopper coils of a ball backup system if safety rods, sufficient in total control effect, properly enter the reactor core to effect shut down. A plurality of resistances form one arm of the bridge, each resistance being associated with a particular safety rod and weighted in value according to the control effect of the particular safety rod. Switching means are used to switch each of the resistances in and out of the bridge circuit responsive to the presence of a particular safety rod in its effective position in the reactor core and responsive to the attainment of a predetermined velocity by a particular safety rod enroute to its effective position. The bridge is unbalanced in one direction during normal reactor operation prior to the generation of a scram signal and the switching means and resistances are adapted to unbalance the bridge in the opposite direction if the safety rods produce a predetermined amount of control effect in response to the scram signal. The bridge unbalance reversal is then utilized to prevent the actuation of the ball backup system, or, conversely, a failure of the safety rods to produce the predetermined effect produces no unbalance reversal and the ball backup system is actuated. (AEC)

Frequency-Independent Response of Self-Complementary Checkerboard Screens

NASA Astrophysics Data System (ADS)

Urade, Yoshiro; Nakata, Yosuke; Nakanishi, Toshihiro; Kitano, Masao

2015-06-01

This research resolves a long-standing problem on the electromagnetic response of self-complementary metallic screens with checkerboardlike geometry. Although Babinet's principle implies that they show a frequency-independent response, this unusual characteristic has not been observed yet due to the singularities of the metallic point contacts in the checkerboard geometry. We overcome this difficulty by replacing the point contacts with resistive sheets. The proposed structure is prepared and characterized by terahertz time-domain spectroscopy. It is experimentally confirmed that the resistive checkerboard structures exhibit a flat transmission spectrum over 0.1-1.1 THz. It is also demonstrated that self-complementarity can eliminate even the frequency-dependent transmission characteristics of resonant metamaterials.

Programmability of nanowire networks

NASA Astrophysics Data System (ADS)

Bellew, A. T.; Bell, A. P.; McCarthy, E. K.; Fairfield, J. A.; Boland, J. J.

2014-07-01

Electrical connectivity in networks of nanoscale junctions must be better understood if nanowire devices are to be scaled up from single wires to functional material systems. We show that the natural connectivity behaviour found in random nanowire networks presents a new paradigm for creating multi-functional, programmable materials. In devices made from networks of Ni/NiO core-shell nanowires at different length scales, we discover the emergence of distinct behavioural regimes when networks are electrically stressed. We show that a small network, with few nanowire-nanowire junctions, acts as a unipolar resistive switch, demonstrating very high ON/OFF current ratios (>105). However, large networks of nanowires distribute an applied bias across a large number of junctions, and thus respond not by switching but instead by evolving connectivity. We demonstrate that these emergent properties lead to fault-tolerant materials whose resistance may be tuned, and which are capable of adaptively reconfiguring under stress. By combining these two behavioural regimes, we demonstrate that the same nanowire network may be programmed to act both as a metallic interconnect, and a resistive switch device with high ON/OFF ratio. These results enable the fabrication of programmable, multi-functional materials from random nanowire networks.Electrical connectivity in networks of nanoscale junctions must be better understood if nanowire devices are to be scaled up from single wires to functional material systems. We show that the natural connectivity behaviour found in random nanowire networks presents a new paradigm for creating multi-functional, programmable materials. In devices made from networks of Ni/NiO core-shell nanowires at different length scales, we discover the emergence of distinct behavioural regimes when networks are electrically stressed. We show that a small network, with few nanowire-nanowire junctions, acts as a unipolar resistive switch, demonstrating very high ON/OFF current ratios (>105). However, large networks of nanowires distribute an applied bias across a large number of junctions, and thus respond not by switching but instead by evolving connectivity. We demonstrate that these emergent properties lead to fault-tolerant materials whose resistance may be tuned, and which are capable of adaptively reconfiguring under stress. By combining these two behavioural regimes, we demonstrate that the same nanowire network may be programmed to act both as a metallic interconnect, and a resistive switch device with high ON/OFF ratio. These results enable the fabrication of programmable, multi-functional materials from random nanowire networks. Electronic supplementary information (ESI) available: Nanowire statistics (length, diameter statistics, and oxide thickness) are provided. Forming curves for single junctions and networks. Passive voltage contrast image demonstrating selectivity of conductive pathways in 100 μm network. See DOI: 10.1039/c4nr02338b

Voltage-induced Metal-Insulator Transitions in Perovskite Oxide Thin Films Doped with Strongly Correlelated Electrons

NASA Astrophysics Data System (ADS)

Wang, Yudi; Gil Kim, Soo; Chen, I.-Wei

2007-03-01

We have observed a reversible metal-insulator transition in perovskite oxide thin films that can be controlled by charge trapping pumped by a bipolar voltage bias. In the as-fabricated state, the thin film is metallic with a very low resistance comparable to that of the metallic bottom electrode, showing decreasing resistance with decreasing temperature. This metallic state switches to a high-resistance state after applying a voltage bias: such state is non-ohmic showing a negative temperature dependence of resistance. Switching at essentially the same voltage bias was observed down to 2K. The metal-insulator transition is attributed to charge trapping that disorders the energy of correlated electron states in the conduction band. By increasing the amount of charge trapped, which increases the disorder relative to the band width, increasingly more insulating states with a stronger temperature dependence of resistivity are accessed. This metal-insulator transition provides a platform to engineer new nonvolatile memory that does not require heat (as in phase transition) or dielectric breakdown (as in most other oxide resistance devices).

Light-induced new memory states in electronic resistive switching of NiO/NSTO junction

NASA Astrophysics Data System (ADS)

Wei, Ling; Li, G. Q.; Zhang, W. F.

2016-02-01

n-type and p-type NiO films were prepared on SrTiO3:Nb (NSTO) by controlling oxygen pressures during the process of pulsed laser deposition. The results of current-voltage (I-V) characteristics and photocurrent investigation indicate that the junction shows a typical electronic bipolar resistive switching (RS) behavior and the optical injection can add new resistance states. Photocurrents can obviously be modulated by different resistance states of NiO/NSTO junction. The linear fitting results of I-V curves reveal that the low resistance state follows Ohmic behavior and the high resistance state follows Schottky-emission mechanism. The depletion widths under forward and reverse bias in the dark and with the illumination were estimated respectively. Combined with the energy band structure, the mechanism of RS and photoresponse in the NiO/NSTO junction can be attributed to the variance of interfacial barrier during electrical and optical injection. These results pave the way for the application of the NiO/NSTO junction in the multilevel storage of optical-electrical devices.

Cu, Ag, Au: Electrical Resistivity Along their Melting Boundaries

NASA Astrophysics Data System (ADS)

Secco, R.; Littleton, J. A. H.; Berrada, M.; Ezenwa, I.; Yong, W.

2017-12-01

Electrical resistivity of Cu, Ag and Au was measured at pressures up to 5 GPa and temperatures up to 300 K above melting in a 1000-ton cubic anvil press. Two W/Re thermocouples placed at opposite ends of the wire sample served as T probes as well as 4-wire resistance electrodes in a switched circuit. A polarity switch was also used to remove any bias associated with current flow and voltage measurement using thermocouple legs. Examination of the composition of recovered and sectioned samples was carried out using electron microprobe analyses. Melting temperatures at high pressures were determined from the large jump in resistivity on heating at constant pressure and these agree well with previous experimental and theoretical phase diagram studies. With increasing P and T, electrical resistivity behavior in these noble metals is consistent with 1atm data. The resistivity values at the melting temperature of Cu and Ag decrease with increasing high pressure and Au seems to behave similarly. The results are compared to prediction by Stacey and Anderson (PEPI, 2001).

Evaluation of semiconductor devices for Electric and Hybrid Vehicle (EHV) ac-drive applications, volume 2

NASA Technical Reports Server (NTRS)

Lee, F. C.; Chen, D. Y.; Jovanic, M.; Hopkins, D. C.

1985-01-01

Test data of switching times characterization of bipolar transistors, of field effect transistor's switching times on-resistance and characterization, comparative data of field effect transistors, and test data of field effect transistor's parallel operation characterization are given. Data is given in the form of graphs.

Electrical Characterization of Critical Phase Change Conditions in Nanoscale Ge2Sb2Te5 Pillars

NASA Astrophysics Data System (ADS)

Ozatay, Ozhan; Stipe, Barry; Katine, Jordan; Terris, Bruce

2008-03-01

Following the original work of Ovshinsky on disordered semiconductors that exhibit ovonic threshold switching (OTS) there has been substantial interest in the electronic reversible switching properties of chalcogenides^1. The current induced phase transitions between polycrystalline and amorphous states in these materials offer orders of magnitude changes in the conductance which makes them an ideal candidate for non-volatile data storage applications. In this work we investigate the scaling of critical programming conditions required to observe such transitions between highly resistive (disordered) and highly conductive (ordered) states by constructing a resistance map with various pulse widths and amplitudes under different cooling conditions (as a function of pulse trailing edge). We study the evolution of critical phase change conditions as a function of contact size (50nm-1μm) and shape (circle-square-rectangle). We compare the resulting switching behaviour with the predictions of a finite-element model of the electro-thermal physics to analyze the nature of the switching dynamics at the nanoscale. ^1 S-H. Lee, Y. Jung, R. Agarwal, Nature Nanotechnology; doi:10:1038/nnano.2007.291

Resistive and Ferroelectric-Domain Switching in Multiferroic BiFeO3 Films

NASA Astrophysics Data System (ADS)

Ramirez, J. G.; Arango, I. C.; Gomez, M. F.; Dominguez, C.; Sulekar, S.; Cardona, A.; Trastoy, J.; Nino, J. C.; Schuller, I. K.; Gomez, M. E.

Resistive switching (RS) in oxides has attracted much attention due to its potential application for nonvolatile memory and neuromorphic computing devices. Here we study the voltage-induced RS mechanisms in metal/multiferroic/semiconductor (Au/BiFeO3/Nb:SrTiO3) thin film vertical devices. We found switching with RON and ROFF ratios as big as 0.16 at voltages starting at +/- 2V. Further voltage increase produced an intensification of the RS effects, until dielectric breakdown was reached. Interestingly, the voltage at which the RS effect appears coincides with the coercive voltage of the ferroelectric polarization in similar BiFeO3 films, as measured by piezoelectric force microscopy. This suggests that the primary RS mechanism is the ferroelectric switching. Impedance spectroscopy measurements show filamentary contributions after ferroelectric saturation, possible due to voltage-induced movement of charge defects across the device and therefore suggesting an additional RS mechanism. Work supported by: Univalle CI 7999; FAPA at Uniandes; Colciencias 120471250659 and 120424054303. J.T. acknowledges the support from the Fundación Areces (Spain); AFOSR and DoD for a Vannevar Bush Fellowship.

Performance comparison of hybrid resistive switching devices based on solution-processable nanocomposites

NASA Astrophysics Data System (ADS)

Rajan, Krishna; Roppolo, Ignazio; Bejtka, Katarzyna; Chiappone, Annalisa; Bocchini, Sergio; Perrone, Denis; Pirri, Candido Fabrizio; Ricciardi, Carlo; Chiolerio, Alessandro

2018-06-01

The present work compares the influence of different polymer matrices on the performance of planar asymmetric Resistive Switching Devices (RSDs) based on silver nitrate and Ionic Liquid (IL). PolyVinyliDene Fluoride-HexaFluoroPropylene (PVDF-HFP), PolyEthylene Oxide (PEO), PolyMethyl MethAcrylate (PMMA) and a blend of PVDF-HFP and PEO were used as matrices and compared. RSDs represent perhaps the most promising electron device to back the More than Moore development, and our approach through functional polymers enables low temperature processing and gives compatibility towards flexible/stretchable/wearable equipment. The switching mechanism in all the four sample families is explained by means of a filamentary conduction. A huge difference in the cyclability and the On/Off ratio is experienced when changing the active polymers and explained based on the polymer crystallinity degree and general morphology of the prepared nanocomposite. It is worth noting that all the RSDs discussed here present good switching behaviour with reasonable endurance. The current study displays one of the most cost-effective and effortless ways to produce an RSD based on solution-processable materials.

An Investigation Into Low Fuel Pressure Warnings on a Macchi-Viper Aircraft

DTIC Science & Technology

1988-05-01

was sufficient To activate the low pressure warning light. The pressure switch is normally set to a differential of between 2.5 - 3 psi. Partial...only a 2.1 psig margin for light illumination, if the pressure switch is set at 3 psig, and gives little scope for extra pipe or filter losses when... pressure switch is set between 2.5 - 3 psig. Any untoward pressure resistance in the fuel delivery line and filtering system would soon erode this

Materials growth and characterization of thermoelectric and resistive switching devices

NASA Astrophysics Data System (ADS)

Norris, Kate J.

In the 74 years since diode rectifier based radar technology helped the allied forces win WWII, semiconductors have transformed the world we live in. From our smart phones to semiconductor-based energy conversion, semiconductors touch every aspect of our lives. With this thesis I hope to expand human knowledge of semiconductor thermoelectric devices and resistive switching devices through experimentation with materials growth and subsequent materials characterization. Metal organic chemical vapor deposition (MOCVD) was the primary method of materials growth utilized in these studies. Additionally, plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD),ion beam sputter deposition, reactive sputter deposition and electron-beam (e-beam) evaporation were also used in this research for device fabrication. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Electron energy loss spectroscopy (EELS) were the primary characterization methods utilized for this research. Additional device and materials characterization techniques employed include: current-voltage measurements, thermoelectric measurements, x-ray diffraction (XRD), reflection absorption infra-red spectroscopy (RAIRS), atomic force microscopy (AFM), photoluminescence (PL), and raman spectroscopy. As society has become more aware of its impact on the planet and its limited resources, there has been a push toward developing technologies to sustainably produce the energy we need. Thermoelectric devices convert heat directly into electricity. Thermoelectric devices have the potential to save huge amounts of energy that we currently waste as heat, if we can make them cost-effective. Semiconducting thin films and nanowires appear to be promising avenues of research to attain this goal. Specifically, in this work we will explore the use of ErSb thin films as well as Si and InP nanowire networks for thermoelectric applications. First we will discuss the growth of erbium monoantimonide (ErSb) thin films with thermal conductivities close to or slightly smaller than the alloy limit of the two ternary alloy hosts. Second we consider an ex-situ monitoring technique based on glancing-angle infrared-absorption used to determine small amounts of erbium antimonide (ErSb) deposited on an indium antimonide (InSb) layer, a concept for thermoelectric devices to scatter phonons. Thirdly we begin our discussion of nanowires with the selective area growth (SAG) of single crystalline indium phosphide (InP) nanopillars on an array of template segments composed of a stack of gold and amorphous silicon. Our approach enables flexible and scalable nanofabrication using industrially proven tools and a wide range of semiconductors on various non-semiconductor substrates. Then we examine the use of graphene to promote the growth of nanowire networks on flexible copper foil leading to the testing of nanowire network devices for thermoelectric applications and the concept of multi-stage devices. We present the ability to tailor current-voltage characteristics to fit a desired application of thermoelectric devices by using nanowire networks as building blocks that can be stacked vertically or laterally. Furthermore, in the study of our flexible nanowire network multi-stage devices, we discovered the presence of nonlinear current-voltage characteristics and discuss how this feature could be utilized to increase efficiency for thermoelectric devices. This work indicates that with sufficient volume and optimized doping, flexible nanowire networks could be a low cost semiconductor solution to our wasted heat challenge. Resistive switching devices are two terminal electrical resistance switches that retain a state of internal resistance based on the history of applied voltage and current. The occurrence of reversible resistance switching has been widely studied in a variety of material systems for applications including nonvolatile memory, logic circuits, and neuromorphic computing. To this end we next we studied devices in each resistance state of a TaOx switch, which has previously shown high endurance and desirable switching behavior, to better understand the system in nanoscale devices. Finally, we will discuss a self-aligned NbO2 nano-cap demonstrated atop a TaO2.2 switching layer. The goal of this device is to create a nanoscale RRAM and selector device in a single stack. These results indicate that ternary resistive switching devices may be a beneficial method of combining behaviors of different material systems and that with proper engineering a self-aligned selector is possible.

Radiometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strickland, J. I.

1985-07-02

A radiometer of the switched type has an R.F. switch connecting a detector selectively either to an antenna whose temperature (in terms of noise energy) is to be determined, or to a reference temperature, i.e. a resistive termination. The detector output is passed through an amplifier whose gain is switched between positive and negative values (for example +1 and -1) synchronously with the R.F. switch. The output of the switched gain amplifier is integrated to produce a rising voltage when the gain is positive and a falling one when it is negative. When it is positive the detector is connectedmore » to the antenna. By means of a zero crossing detector, a counter is started when this voltage crosses zero. After a fixed period, the R.F. switch and switched gain amplifier are reversed by the counter to cause the voltage to fall in accordance with the temperature of the resistive termination. The zero crossing detector and a counter measure the time interval until the voltage again crosses zero, such time interval being compared to the fixed period to provide a comparison of the unknown and reference temperatures independent of the gain of the detector, which is a valuable improvement over prior radiometers. Also, by measuring time rather than voltage, the arrangement facilitates providing a digital output more suitable for storage and transmission of the data than the analog output of prior radiometers. The instrument, which is relatively simple, rugged and compact, lends itself well to unattended use in monitoring the effect of rain storms on transmission in the 11.7 to 12.2 GHz band employed for satelite communication.« less

Protective Role of the Capsule and Impact of Serotype 4 Switching on Streptococcus mitis

PubMed Central

Rukke, Håkon V.; Kalluru, Raja Sab; Repnik, Urska; Gerlini, Alice; José, Ricardo J.; Periselneris, Jimstan; Marshall, Helina; Griffiths, Gareth; Oggioni, Marco Rinaldo; Brown, Jeremy S.

2014-01-01

The polysaccharide capsule surrounding Streptococcus pneumoniae is essential for virulence. Recently, Streptococcus mitis, a human commensal and a close relative of S. pneumoniae, was also shown to have a capsule. In this study, the S. mitis type strain switched capsule by acquisition of the serotype 4 capsule locus of S. pneumoniae TIGR4, following induction of competence for natural transformation. Comparison of the wild type with the capsule-switching mutant and with a capsule deletion mutant showed that the capsule protected S. mitis against phagocytosis by RAW 264.7 macrophages. This effect was enhanced in the S. mitis strain expressing the S. pneumoniae capsule, which showed, in addition, increased resistance against early clearance in a mouse model of lung infection. Expression of both capsules also favored survival in human blood, and the effect was again more pronounced for the capsule-switching mutant. S. mitis survival in horse blood or in a mouse model of bacteremia was not significantly different between the wild type and the mutant strains. In all models, S. pneumoniae TIGR4 showed higher rates of survival than the S. mitis type strain or the capsule-switching mutant, except in the lung model, in which significant differences between S. pneumoniae TIGR4 and the capsule-switching mutant were not observed. Thus, we identified conditions that showed a protective function for the capsule in S. mitis. Under such conditions, S. mitis resistance to clearance could be enhanced by capsule switching to serotype 4, but it was enhanced to levels lower than those for the virulent strain S. pneumoniae TIGR4. PMID:24958712

High-Sequence Diversity and Rapid Virus Turnover Contribute to Higher Rates of Coreceptor Switching in Treatment-Experienced Subjects with HIV-1 Viremia.

PubMed

Nedellec, Rebecca; Herbeck, Joshua T; Hunt, Peter W; Deeks, Steven G; Mullins, James I; Anton, Elizabeth D; Reeves, Jacqueline D; Mosier, Donald E

2017-03-01

Coreceptor switching from CCR5 to CXCR4 is common during chronic HIV-1 infection, but is even more common in individuals who have failed antiretroviral therapy (ART). Prior studies have suggested rapid mutation and/or recombination of HIV-1 envelope (env) genes during coreceptor switching. We compared the functional and genotypic changes in env of viruses from viremic subjects who had failed ART just before and after coreceptor switching and compared those to viruses from matched subjects without coreceptor switching. Analysis of multiple unique functional env clones from each subject revealed extensive diversity at both sample time points and rapid diversification of sequences during the 4-month interval in viruses from both 9 subjects with coreceptor switching and 15 control subjects. Only two subjects had envs with evidence of recombination. Three findings distinguished env clones from subjects with coreceptor switching from controls: (1) lower entry efficiency via CCR5; (2) longer V1/V2 regions; and (3), lower nadir CD4 T cell counts during prior years of infection. Most of these subjects harbored virus with lower replicative capacity associated with protease (PR) and/or reverse transcriptase inhibitor resistance mutations, and the extensive diversification tended to lead either to improved entry efficiency via CCR5 or the gain of entry function via CXCR4. These results suggest that R5X4 or X4 variants emerge from a diverse, low-fitness landscape shaped by chronic infection, multiple ART resistance mutations, the availability of target cells, and reduced entry efficiency via CCR5.

Non-switching to switching transferring mechanism investigation for Ag/SiO x /p-Si structure with SiO x deposited by HWCVD

NASA Astrophysics Data System (ADS)

Liu, Yanhong; Wang, Ruoying; Li, Zhongyue; Wang, Song; Huang, Yang; Peng, Wei

2018-04-01

We proposed and fabricated an Ag/SiO x /p-Si sandwich structure, in which amorphous SiO x films were deposited through hot wire chemical vapor deposition (HWCVD) using tetraethylorthosilicate (TEOS) as Si and O precursor. Experimental results indicate that the I–V properties of this structure transfer from non-switching to switching operation as the SiO x deposition temperature increased. The device with SiO x deposited at high deposition temperature exhibits typical bipolar switching properties, which can be potentially used in resistive switching random accessible memory (RRAM). The transferring mechanism from non-switching to switching can be ascribed to the change of structural and electronic properties of SiO x active layer deposited at different temperatures, as evidenced by analyzing FTIR spectrum and fitting its I–V characteristics curves. This work demonstrates a safe and practicable low-temperature device-grade SiO x film deposition technology by conducting HWCVD from TEOS.

Resistive switching in ZnO/ZnO:In nanocomposite

NASA Astrophysics Data System (ADS)

Khakhulin, D. A.; Vakulov, Z. E.; Smirnov, V. A.; Tominov, R. V.; Yoon, Jong-Gul; Ageev, O. A.

2017-11-01

A lot of effort nowadays is put into development of new approaches to processing and storage of information in integrated circuits due to limitations in miniaturisation. Our research is dedicated to one of actively developed concepts - oxide based resistive memory devices. A material that draws interest due to its promising technological properties is ZnO but pure ZnO lacks in performance in comparison with some other transition metal oxides. Thus our work is focused on improvement of resistive switching parameters in ZnO films by creation of complex nanocomposites. In this work we report characterisation of a nanocomposite based on PLD grown ZnO films with inclusions of In. Such solution allows us to achieve improvements of main parameters that are critical for ReRAM device: RHRS/RLRS ratio, endurance and retention.

Improving Unipolar Resistive Switching Uniformity with Cone-Shaped Conducting Filaments and Its Logic-In-Memory Application.

PubMed

Gao, Shuang; Liu, Gang; Chen, Qilai; Xue, Wuhong; Yang, Huali; Shang, Jie; Chen, Bin; Zeng, Fei; Song, Cheng; Pan, Feng; Li, Run-Wei

2018-02-21

Resistive random access memory (RRAM) with inherent logic-in-memory capability exhibits great potential to construct beyond von-Neumann computers. Particularly, unipolar RRAM is more promising because its single polarity operation enables large-scale crossbar logic-in-memory circuits with the highest integration density and simpler peripheral control circuits. However, unipolar RRAM usually exhibits poor switching uniformity because of random activation of conducting filaments and consequently cannot meet the strict uniformity requirement for logic-in-memory application. In this contribution, a new methodology that constructs cone-shaped conducting filaments by using chemically a active metal cathode is proposed to improve unipolar switching uniformity. Such a peculiar metal cathode will react spontaneously with the oxide switching layer to form an interfacial layer, which together with the metal cathode itself can act as a load resistor to prevent the overgrowth of conducting filaments and thus make them more cone-like. In this way, the rupture of conducting filaments can be strictly limited to the tip region, making their residual parts favorable locations for subsequent filament growth and thus suppressing their random regeneration. As such, a novel "one switch + one unipolar RRAM cell" hybrid structure is capable to realize all 16 Boolean logic functions for large-scale logic-in-memory circuits.

Sub-100 fJ and sub-nanosecond thermally driven threshold switching in niobium oxide crosspoint nanodevices.

PubMed

Pickett, Matthew D; Williams, R Stanley

2012-06-01

We built and measured the dynamical current versus time behavior of nanoscale niobium oxide crosspoint devices which exhibited threshold switching (current-controlled negative differential resistance). The switching speeds of 110 × 110 nm(2) devices were found to be Δt(ON) = 700 ps and Δt(OFF) = 2:3 ns while the switching energies were of the order of 100 fJ. We derived a new dynamical model based on the Joule heating rate of a thermally driven insulator-to-metal phase transition that accurately reproduced the experimental results, and employed the model to estimate the switching time and energy scaling behavior of such devices down to the 10 nm scale. These results indicate that threshold switches could be of practical interest in hybrid CMOS nanoelectronic circuits.

Reinventing the wheel: comparison of two wheel cage styles for assessing mouse voluntary running activity.

PubMed

Seward, T; Harfmann, B D; Esser, K A; Schroder, E A

2018-04-01

Voluntary wheel cage assessment of mouse activity is commonly employed in exercise and behavioral research. Currently, no standardization for wheel cages exists resulting in an inability to compare results among data from different laboratories. The purpose of this study was to determine whether the distance run or average speed data differ depending on the use of two commonly used commercially available wheel cage systems. Two different wheel cages with structurally similar but functionally different wheels (electromechanical switch vs. magnetic switch) were compared side-by-side to measure wheel running data differences. Other variables, including enrichment and cage location, were also tested to assess potential impacts on the running wheel data. We found that cages with the electromechanical switch had greater inherent wheel resistance and consistently led to greater running distance per day and higher average running speed. Mice rapidly, within 1-2 days, adapted their running behavior to the type of experimental switch used, suggesting these running differences are more behavioral than due to intrinsic musculoskeletal, cardiovascular, or metabolic limits. The presence of enrichment or location of the cage had no detectable impact on voluntary wheel running. These results demonstrate that mice run differing amounts depending on the type of cage and switch mechanism used and thus investigators need to report wheel cage type/wheel resistance and use caution when interpreting distance/speed run across studies. NEW & NOTEWORTHY The results of this study highlight that mice will run different distances per day and average speed based on the inherent resistance present in the switch mechanism used to record data. Rapid changes in running behavior for the same mouse in the different cages demonstrate that a strong behavioral factor contributes to classic exercise outcomes in mice. Caution needs to be taken when interpreting mouse voluntary wheel running activity to include potential behavioral input and physiological parameters.

Bipolar resistance switching in Pt/CuO x /Pt via local electrochemical reduction

DOE PAGES

D'Aquila, Kenneth; Phatak, Charudatta; Holt, Martin V.; ...

2014-06-17

We investigated the local changes in copper oxidation state and the corresponding resistance changes in Pt/CuO x/Pt nanoscale heterostructures using x-ray nanoprobe spectro-microscopy and current-voltage characterization. After gentle electroforming, during which the current-voltage behavior remains non-linear, the low resistance state was reached, and we also observed regions of 160 nm width that show an increase in Cu K-alpha fluorescence intensity, indicative of partial reduction of the CuO x. Analysis of the current voltage curves showed that the dominant conduction mechanism is Schottky emission and that the resistance state is correlated with the Schottky barrier height. We also propose that themore » reversible resistivity change in these Pt/CuO x/Pt heterostructures occurs through local electrochemical reduction leading to change of the Schottky barrier height at the interface between Pt and the reduced CuO x layers and to change of the CuO x resistivity within laterally confined portions of the CuO x layer. Our experiments reveal important insights into the mechanism of resistance switching of Pt/CuO x/Pt performed in a current and voltage regime that does not create a metallic conduction path.« less

Layered memristive and memcapacitive switches for printable electronics

NASA Astrophysics Data System (ADS)

Bessonov, Alexander A.; Kirikova, Marina N.; Petukhov, Dmitrii I.; Allen, Mark; Ryhänen, Tapani; Bailey, Marc J. A.

2015-02-01

Novel computing technologies that imitate the principles of biological neural systems may offer low power consumption along with distinct cognitive and learning advantages. The development of reliable memristive devices capable of storing multiple states of information has opened up new applications such as neuromorphic circuits and adaptive systems. At the same time, the explosive growth of the printed electronics industry has expedited the search for advanced memory materials suitable for manufacturing flexible devices. Here, we demonstrate that solution-processed MoOx/MoS2 and WOx/WS2 heterostructures sandwiched between two printed silver electrodes exhibit an unprecedentedly large and tunable electrical resistance range from 102 to 108 Ω combined with low programming voltages of 0.1-0.2 V. The bipolar resistive switching, with a concurrent capacitive contribution, is governed by an ultrathin (<3 nm) oxide layer. With strong nonlinearity in switching dynamics, different mechanisms of synaptic plasticity are implemented by applying a sequence of electrical pulses.

Interfacial Metal-Oxide Interactions in Resistive Switching Memories.

PubMed

Cho, Deok-Yong; Luebben, Michael; Wiefels, Stefan; Lee, Kug-Seung; Valov, Ilia

2017-06-07

Metal oxides are commonly used as electrolytes for redox-based resistive switching memories. In most cases, non-noble metals are directly deposited as ohmic electrodes. We demonstrate that irrespective of bulk thermodynamics predictions an intermediate oxide film a few nanometers in thickness is always formed at the metal/insulator interface, and this layer significantly contributes to the development of reliable switching characteristics. We have tested metal electrodes and metal oxides mostly used for memristive devices, that is, Ta, Hf, and Ti and Ta 2 O 5 , HfO 2 , and SiO 2 . Intermediate oxide layers are always formed at the interfaces, whereas only the rate of the electrode oxidation depends on the oxygen affinity of the metal and the chemical stability of the oxide matrix. Device failure is associated with complete transition of short-range order to a more disordered main matrix structure.

Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters

NASA Technical Reports Server (NTRS)

Tabib-Azar, Massood; Bhasin, Kul B.; Romanofsky, Robert R.

1991-01-01

The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors.

Negative differential resistance and switch behavior of T-BxNy (x, y = 5, 6, 11) molecular junctions

NASA Astrophysics Data System (ADS)

Wang, Shi-Liang; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Xin, Jian-Guo

2017-05-01

The electronic transport properties of T-BxNy (x, y = 5, 6, 11) molecular junction are investigated based on first-principle density functional theory and non-equilibrium Green's function method. Strong negative differential resistance (NDR) behavior is observed for T-B5N6 molecule under negative and positive bias voltages, with an obvious switch effect for T-B6N5. However, only small NDR is shown for the complex of the two molecules. The projected device density of states, the spatial distribution of molecular orbitals, and the effect of transmission spectra under various bias voltages on the electronic transport properties are analyzed. The obvious effect of bias voltage on the changes in the electronic distribution of frontier molecular orbitals is responsible for the NDR or switch behavior. Therefore, different functional molecular devices can be obtained with different structures of T-BxNy.

Engineering of the chemical reactivity of the Ti/HfO₂ interface for RRAM: experiment and theory.

PubMed

Calka, Pauline; Sowinska, Malgorzata; Bertaud, Thomas; Walczyk, Damian; Dabrowski, Jarek; Zaumseil, Peter; Walczyk, Christian; Gloskovskii, Andrei; Cartoixà, Xavier; Suñé, Jordi; Schroeder, Thomas

2014-04-09

The Ti/HfO2 interface plays a major role for resistance switching performances. However, clear interface engineering strategies to achieve reliable and reproducible switching have been poorly investigated. For this purpose, we present a comprehensive study of the Ti/HfO2 interface by a combined experimental-theoretical approach. Based on the use of oxygen-isotope marked Hf*O2, the oxygen scavenging capability of the Ti layer is clearly proven. More importantly, in line with ab initio theory, the combined HAXPES-Tof-SIMS study of the thin films deposited by MBE clearly establishes a strong impact of the HfO2 thin film morphology on the Ti/HfO2 interface reactivity. Low-temperature deposition is thus seen as a RRAM processing compatible way to establish the critical amount of oxygen vacancies to achieve reproducible and reliable resistance switching performances.

Cancer drug addiction is relayed by an ERK2-dependent phenotype switch.

PubMed

Kong, Xiangjun; Kuilman, Thomas; Shahrabi, Aida; Boshuizen, Julia; Kemper, Kristel; Song, Ji-Ying; Niessen, Hans W M; Rozeman, Elisa A; Geukes Foppen, Marnix H; Blank, Christian U; Peeper, Daniel S

2017-10-12

Observations from cultured cells, animal models and patients raise the possibility that the dependency of tumours on the therapeutic drugs to which they have acquired resistance represents a vulnerability with potential applications in cancer treatment. However, for this drug addiction trait to become of clinical interest, we must first define the mechanism that underlies it. We performed an unbiased CRISPR-Cas9 knockout screen on melanoma cells that were both resistant and addicted to inhibition of the serine/threonine-protein kinase BRAF, in order to functionally mine their genome for 'addiction genes'. Here we describe a signalling pathway comprising ERK2 kinase and JUNB and FRA1 transcription factors, disruption of which allowed addicted tumour cells to survive on treatment discontinuation. This occurred in both cultured cells and mice and was irrespective of the acquired drug resistance mechanism. In melanoma and lung cancer cells, death induced by drug withdrawal was preceded by a specific ERK2-dependent phenotype switch, alongside transcriptional reprogramming reminiscent of the epithelial-mesenchymal transition. In melanoma cells, this reprogramming caused the shutdown of microphthalmia-associated transcription factor (MITF), a lineage survival oncoprotein; restoring this protein reversed phenotype switching and prevented the lethality associated with drug addiction. In patients with melanoma that had progressed during treatment with a BRAF inhibitor, treatment cessation was followed by increased expression of the receptor tyrosine kinase AXL, which is associated with the phenotype switch. Drug discontinuation synergized with the melanoma chemotherapeutic agent dacarbazine by further suppressing MITF and its prosurvival target, B-cell lymphoma 2 (BCL-2), and by inducing DNA damage in cancer cells. Our results uncover a pathway that underpins drug addiction in cancer cells, which may help to guide the use of alternating therapeutic strategies for enhanced clinical responses in drug-resistant cancers.

Switching power pulse system

DOEpatents

Aaland, K.

1983-08-09

A switching system for delivering pulses of power from a source to a load using a storage capacitor charged through a rectifier, and maintained charged to a reference voltage level by a transistor switch and voltage comparator. A thyristor is triggered to discharge the storage capacitor through a saturable reactor and fractional turn saturable transformer having a secondary to primary turn ratio N of n:l/n = n[sup 2]. The saturable reactor functions as a soaker'' while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor charges, and then switches to a low impedance state to dump the charge of the storage capacitor into the load through the coupling capacitor. The transformer is comprised of a multilayer core having two secondary windings tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe for a linear particle accelerator and capacitance of a pulse forming network. To hold off discharge of the capacitance until it is fully charged, a saturable core is provided around the resistive beampipe to isolate the beampipe from the capacitance until it is fully charged. 5 figs.

Impact of electrically formed interfacial layer and improved memory characteristics of IrOx/high-κx/W structures containing AlOx, GdOx, HfOx, and TaOx switching materials.

PubMed

Prakash, Amit; Maikap, Siddheswar; Banerjee, Writam; Jana, Debanjan; Lai, Chao-Sung

2013-09-06

Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled 'SET/RESET' current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications.

Highly tunable local gate controlled complementary graphene device performing as inverter and voltage controlled resistor.

PubMed

Kim, Wonjae; Riikonen, Juha; Li, Changfeng; Chen, Ya; Lipsanen, Harri

2013-10-04

Using single-layer CVD graphene, a complementary field effect transistor (FET) device is fabricated on the top of separated back-gates. The local back-gate control of the transistors, which operate with low bias at room temperature, enables highly tunable device characteristics due to separate control over electrostatic doping of the channels. Local back-gating allows control of the doping level independently of the supply voltage, which enables device operation with very low VDD. Controllable characteristics also allow the compensation of variation in the unintentional doping typically observed in CVD graphene. Moreover, both p-n and n-p configurations of FETs can be achieved by electrostatic doping using the local back-gate. Therefore, the device operation can also be switched from inverter to voltage controlled resistor, opening new possibilities in using graphene in logic circuitry.

Fe, Co, Ni: Electrical Resistivity Along their Melting Boundaries

NASA Astrophysics Data System (ADS)

Silber, R. E.; Ezenwa, I.; Secco, R.; Yong, W.

2017-12-01

Electrical resistivity of Fe, Co, and Ni was measured at pressures up to 11 GPa and temperatures into their liquid states in multi-anvil and cubic-anvil presses. Two thermocouples placed at opposite ends of the wire sample served as T probes as well as 4-wire resistance electrodes in a switched circuit. A polarity switch was also used to remove any bias associated with current flow and voltage measurement using thermocouple legs. Post experimental examination of recovered and sectioned samples was done using electron microprobe analyses to check for diffusion in our samples. The observed large jumps in resistivity at the high P melting T of each metal is consistent with its known P,T phase diagram and with post-run compositional analyses. The electrical resistivity behavior in these late transition metals as a function of increasing P and T shows expected trends consistent with 1atm data. Within the error of measurement, the resistivity values at the melting T at high P of Co and Ni appear to mimic their 1 atm value suggesting constant resistivity along the melting boundary. For liquid Fe, resistivity decreases along the melting boundary up to the triple point at 5.2 GPa, and then is nearly constant at higher pressures. The results are compared to prediction by Stacey and Loper (PEPI, 2007).

L-DOPA-Coated Manganese Oxide Nanoparticles as Dual MRI Contrast Agents and Drug-Delivery Vehicles.

PubMed

McDonagh, Birgitte Hjelmeland; Singh, Gurvinder; Hak, Sjoerd; Bandyopadhyay, Sulalit; Augestad, Ingrid Lovise; Peddis, Davide; Sandvig, Ioanna; Sandvig, Axel; Glomm, Wilhelm Robert

2016-01-20

Manganese oxide nanoparticles (MONPs) are capable of time-dependent magnetic resonance imaging contrast switching as well as releasing a surface-bound drug. MONPs give T2/T2* contrast, but dissolve and release T1-active Mn(2+) and L-3,4-dihydroxyphenylalanine. Complementary images are acquired with a single contrast agent, and applications toward Parkinson's disease are suggested. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intrinsic SiO{sub x}-based unipolar resistive switching memory. II. Thermal effects on charge transport and characterization of multilevel programing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Yao-Feng, E-mail: yfchang@utexas.edu; Chen, Ying-Chen; Chen, Yen-Ting

2014-07-28

Multilevel programing and charge transport characteristics of intrinsic SiO{sub x}-based resistive switching memory are investigated using TaN/SiO{sub x}/n{sup ++}Si (MIS) and TiW/SiO{sub x}/TiW (MIM) device structures. Current transport characteristics of high- and low-resistance states (HRS and LRS) are studied in both device structures during multilevel operation. Analysis of device thermal response demonstrates that the effective electron energy barrier is strongly dependent on the resistance of the programed state, with estimates of 0.1 eV in the LRS and 0.6 eV in the HRS. Linear data fitting and conductance analyses indicate Poole-Frenkel emission or hopping conductance in the low-voltage region, whereas Fowler-Nordheim (F-N) ormore » trap-assisted tunneling (TAT) is indicated at moderate voltage. Characterizations using hopping transport lead to hopping distance estimates of ∼1 nm in the LRS for both device structures. Relative permittivity values (ε{sub r}) were extracted using the Poole-Frenkel formulism and estimates of local filament temperature, where ε{sub r} values were ∼80 in the LRS and ∼4 in the HRS, suggesting a strongly polarized medium in the LRS. The onset of F-N tunneling or TAT corresponds to an observed “overshoot” in the I-V response with an estimated threshold of 1.6 ± 0.2 V, in good agreement with reported electro-luminescence results for LRS devices. Resistive switching is discussed in terms of electrochemical reactions between common SiO{sub 2} defects, and specific defect energy levels are assigned to the dominant transitions in the I-V response. The overshoot response in the LRS is consistent with TAT through either the Eγ' oxygen vacancy or the hydrogen bridge defect, both of which are reported to have an effective bandgap of 1.7 eV. The SET threshold at ∼2.5 V is modeled as hydrogen release from the (Si-H){sub 2} defect to generate the hydrogen bridge, and the RESET transition is modeled as an electrochemical reaction that re-forms (SiH){sub 2}. The results provide further insights into charge transport and help identify potential switching mechanisms in SiO{sub x}-based unipolar resistive switching memory.« less

Memristive behavior in BaTiO 3 thin films integrated with semiconductors

NASA Astrophysics Data System (ADS)

Singamaneni, Srinivasa Rao; Prater, John; Narayan, Jay

BaTiO3 has been studied for emerging non-volatile memory applications. However, most of the previous work has focused on this material when it was deposited on insulting oxide substrates such as SrTiO3. Unfortunately, this substrate is not suitable for CMOS-based microelectronics applications. This motivated us to carry out the present work. We have studied the resistive switching behavior in BaTiO3/La0.7Sr0.3MnO3 (BTO/LSMO) heterostructures integrated with Si (100) using pulsed laser deposition1,2. I-V measurements were conducted on BTO (500nm)/LSMO (25nm) devices at 200K, with the compliance current of 10mA. Here, Pt was used as a top electrode and LSMO served as bottom electrode. A few important observations are noted: (a) broad hysteresis in forward and reverse voltage sweeps -ideal for memory applications, (b) the ratio of high resistance to low resistance state is ~600 -important for switching devices, (c) the device is stable at least up to 50 cycles. However, we found that hysteretic behavior was collapsed after 36 cycles upon oxygen annealing of the device at 1 atmospheric pressure, 200o C for 1 hour, inferring the important role of oxygen vacancies in the resistive switching behavior of BTO/LSMO device. The comprehensive experimental data will be presented and discussed.1,2.

Reversible Negative Resistive Switching in an Individual Fe@Al2O3 Hybrid Nanotube for Nonvolatile Memory.

PubMed

Ye, Yalong; Zhao, Jie; Xiao, Li; Cheng, Baochang; Xiao, Yanhe; Lei, Shuijin

2018-06-06

Hybrid nanostructures can show enormous potential in different areas because of their unique structural configurations. Herein, Fe@Al 2 O 3 hybrid nanotubes are constructed via a homogeneous coprecipitation method followed by subsequent annealing in a reducing atmosphere. The introduction of zero band gap Fe nanocrystals in the wall of ultrawide band gap Al 2 O 3 insulator nanotubes results in the formation of charge trap centers, and correspondingly a single hybrid nanotube-based two-terminal device can show reversible negative resistive switching (RS) characteristics with symmetrical negative differential resistance (NDR) at relatively high operation bias voltages. At a large bias voltage, holes and electrons can be injected into traps at two ends from electrodes, respectively, and then captured. The bias voltage dependence of asymmetrical filling of charges can lead to a reversible variation of built-in electromotive force, and therefore the symmetrical negative RS with NDR arises from two reversible back-to-back series bipolar RS. At a low readout voltage, the single Fe@Al 2 O 3 hybrid nanotube can show an excellent nonvolatile memory feature with a relatively large switching ratio of ∼30. The bias-governed reversible negative RS with superior stability, reversibility, nondestructive readout, and remarkable cycle performance makes it a potential candidate in next-generation erasable nonvolatile resistive random access memories.

Stress-Induced Resistive Switching in Pt/HfO2/Ti Devices

NASA Astrophysics Data System (ADS)

Zeevi, Gilad; Katsman, Alexander; Yaish, Yuval E.

2018-02-01

In the present work, we study the initial SET mechanism of resistive switching (RS) in Pt/HfO2/Ti devices under a static electrical stress and the RS mechanism under a bias sweeping mode with rates of 100 mV/s-300 mV/s. We characterize the thin HfO2 dielectric layer by x-ray photoelectron spectroscopy and x-ray diffraction. These findings show that the layer structure is stoichiometric and nanocrystalline with a crystal diameter of ˜ 14 Å. We measure the temporal dependence of the conductive filament growth at different temperatures and for various biases. Furthermore, these devices present stable bipolar resistive switching with a high-to-low resistive state (HRS/LRS) ratio of more than three orders of magnitude. Activation energy E RS ≈ 0.56 eV and drift current parameter V 0 ≈ 0.07 V were determined from the temporal dependence of the initial `SET' process, first HRS to LRS transition [for static electrical stress of V DS = (4.7-5.0 V)]. We analyze the results according to our model suggesting generation of double-charge oxygen vacancies at the anode and their diffusion across the dielectric layer. The double-charge vacancies transform to a single charge and then to neutral vacancies by capturing hot electrons, and form a conductive filament as soon as a critical neutral-vacancy cluster is formed across the dielectric layer.

Overcoming imatinib resistance conferred by the BIM deletion polymorphism in chronic myeloid leukemia with splice-switching antisense oligonucleotides

PubMed Central

Liu, Jun; Bhadra, Malini; Sinnakannu, Joanna Rajeswary; Yue, Wan Lin; Tan, Cheryl Weiqi; Rigo, Frank; Ong, S.Tiong; Roca, Xavier

2017-01-01

Many tyrosine kinase-driven cancers, including chronic myeloid leukemia (CML), are characterized by high response rates to specific tyrosine kinase inhibitors (TKIs) like imatinib. In East Asians, primary imatinib resistance is caused by a deletion polymorphism in Intron 2 of the BIM gene, whose product is required for TKI-induced apoptosis. The deletion biases BIM splicing from exon 4 to exon 3, generating splice isoforms lacking the exon 4-encoded pro-apoptotic BH3 domain, which impairs the ability of TKIs to induce apoptosis. We sought to identify splice-switching antisense oligonucleotides (ASOs) that block exon 3 but enhance exon 4 splicing, and thereby resensitize BIM deletion-containing cancers to imatinib. First, we mapped multiple cis-acting splicing elements around BIM exon 3 by minigene mutations, and found an exonic splicing enhancer acting via SRSF1. Second, by a systematic ASO walk, we isolated ASOs that corrected the aberrant BIM splicing. Eight of 67 ASOs increased exon 4 levels in BIM deletion-containing cells, and restored imatinib-induced apoptosis and TKI sensitivity. This proof-of-principle study proves that resistant CML cells by BIM deletion polymorphism can be resensitized to imatinib via splice-switching BIM ASOs. Future optimizations might yield a therapeutic ASO as precision-medicine adjuvant treatment for BIM-polymorphism-associated TKI-resistant CML and other cancers. PMID:29100409