TiOx-based self-rectifying memory device for crossbar WORM memory array applications

Resistive switching with a self-rectifying feature is one of the most effective solutions to overcome the crosstalk issue in a crossbar array. In this paper, a memory device based on Pt/TiO_x/W structure with self-rectifying property is demonstrated for write-once-read-many-times(WORM) memory application. After programming, the devices exhibit excellent uniformity and keep in the low resistance state(LRS) permanently with a rectification ratio as high as 10⁴ at ±1 V. The self-rectifying resistive switching behavior can be attributed to the Ohmic contact at TiO_x/W interface and the Schottky contact at Pt/TiO_x interface. The results in this paper demonstrate the potential application of TiO_x-based WORM memory device in crossbar arrays.     

量子存储(Quantum memory)

量子存储技术在量子信息理论的各个领域都有着十分重要的意义.例如在BB84密钥分配方案中,引入量子存储器的"先公布基后测量"的策略就可以使它的效率提高一倍从而接近100%.     

Three-dimensional multilevel memory based on laser-polarization-dependence birefringence

The femtosecond laser-modified region in isotropic glass medium shows a big optical birefringence. Transmission of the birefringent regions between two crossed polarizers depends on phase retardation and the orientation angle of the birefringent optical axes. Based on this effect, three-dimensional (3D) multilevel memory was proposed and demonstrated for nonvolatile memory up to eight levels, in contrast to the standard two-level technology. Eight-level writing and reading are distinguishable in fused silica with a near-infrared femtosecond laser. The retention of this memory is characterized for nonvolatile applications.     

Shape memory effect in antiferromagnetic γ - manganese alloys

Conclusion Thus, the crystallography and the character of antiferromagnetic transformations in manganese alloys determine several specific features of the manifestation of the shape memory effect in these materials. Among these features are: clearer manifestation of reversible deformation, even in the case of small initial strains; a broad temperature range associated with deformation; the practically hysteresis-free character of the reversible deformation in polycrystalline materials; the existence of alternating reversible deformation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 104–117, May, 1985.     

Optical “memory” centers on an adsorption silicon surface

The charging of an illuminated silicon surface discovered by Abkevich [1] is of considerable interest for a number of practical applications (for example, semiconductor photography [2] and gas analysis). The present paper gives the results of investigations aimed at establishing the possibility of controlling the optical charge memory on the silicon surface by adsorption methods.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 92–96, January, 1981.We thank V. F. Kiselev for discussing the work and for helpful comments.     

Relaxation in Ni–Mn–Ga ferromagnetic shape memory alloys

Evidence of relaxation has been observed in ferromagnetic Ni–Mn–Ga single crystals. The relaxation may be explained by a change in symmetry-conforming short-range ordering according to Ren and Otsuka in this off-stoichimetric ordered alloy. Martensite stabilization has also been found after martensite ageing.     

In memory of Igor’ Il’ich Sobel’man

Miscellaneous

In memory of Igor’ Il’ich Sobel’man Member of the Editorial Board of JETP Letters from 1969 to 1988     

Improvement of water softening efficiency in capacitive deionization by ultra purification process of reduced graphene oxide

Capacitive deionization (CDI) is the next generation of water desalination and softening technology by using relatively low capacitive current of electrochemical double layer. Among various carbon-based materials used for making electrode, reduced graphene oxide (rGO) has been intensively studied due to its excellent electrical conductivity and high surface area. Although Hummer method for making graphene oxide (GO) and rGO is a simple process, it remains some impurities in inherent GO and rGO which affect negatively to the CDI performance. In this work, we successfully prepared ultra purified GO and rGO by modifying Hummer method in order to remove entirely excess elements degrading the CDI performance. The electrosorption capacity of ultra purified rGO is considerably better than that of previous rGO, and maximum removal achieves 3.54 mg g⁻¹ at applied voltage of 2.0 V. Thus, this result could be comparable to other researches in CDI process.     

Effect of copper oxide on the resistive switching responses of graphene oxide film

The role of CuO films in meliorating resistive switching behavior of graphene oxide (GO) in CuO/GO/CuO memory structure was investigated. An increase in the set voltage from 1.3 to 3.0 V and a step-like switching current was clearly observed when the GO film was sandwiched between two CuO layers. It is attributed to the fact that the set voltage of GO is lower than that of CuO and accumulated charge carriers located at the interface of GO and CuO can pass through CuO abruptly at set voltage of 3.0 V. Our results suggested that designed sandwich structure of materials with different set voltage enables to amend resistive switching response characteristics.     

Scanning transmission X‐ray microscopy probe for in situ mechanism study of graphene‐oxide‐based resistive random access memory

Here, an in situ probe for scanning transmission X‐ray microscopy (STXM) has been developed and applied to the study of the bipolar resistive switching (BRS) mechanism in an Al/graphene oxide (GO)/Al resistive random access memory (RRAM) device. To perform in situ STXM studies at the C K‐ and O K‐edges, both the RRAM junctions and the I₀ junction were fabricated on a single Si₃N₄ membrane to obtain local XANES spectra at these absorption edges with more delicate I₀ normalization. Using this probe combined with the synchrotron‐based STXM technique, it was possible to observe unique chemical changes involved in the BRS process of the Al/GO/Al RRAM device. Reversible oxidation and reduction of GO induced by the externally applied bias voltages were observed at the O K‐edge XANES feature located at 538.2 eV, which strongly supported the oxygen ion drift model that was recently proposed from ex situ transmission electron microscope studies.     

Electro‐optic switching with liquid crystal graphene

Graphene oxide (GO) particles in aqueous dispersions can form liquid crystal (LC) phases at extremely low concentrations due to the extremely high aspect ratio of the flakes and noticeably, they possess an extremely large Kerr coefficient attractive for low power consumption electro‐optic devices. Reduced graphene does not easily form LC phases in water due to its hydrophobic nature but here we show that stable dispersions of reduced graphene oxide can be realized with surfactants and that they exhibit birefringence upon shearing as well as under application of electric fields. The performance of the system is largely superior to GO LC possessing longer time stability and drastically improved electro‐optic properties with an induced birefringence twice as large at the same field strength thanks to the almost recovery of graphene properties upon reduction. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Oxygenated Functional Group Density on Graphene Oxide: Its Effect on Cell Toxicity

The association of cellular toxicity with the physiochemical properties of graphene‐based materials is largely unexplored. A fundamental understanding of this relationship is essential to engineer graphene‐based nanomaterials for biomedical applications. Here, an in vitro toxicological assessment of graphene oxide (GO) and reduced graphene oxide (RGO) and in correlation with their physiochemical properties is reported. GO is found to be more toxic than RGO of same size. GO and RGO induce significant increases in both intercellular reactive oxygen species (ROS) levels and messenger RNA (mRNA) levels of heme oxygenase 1 (HO1) and thioredoxin reductase (TrxR). Moreover, a significant amount of DNA damage is observed in GO treated cells, but not in RGO treated cells. Such observations support the hypothesis that oxidative stress mediates the cellular toxicity of GO. Interestingly, oxidative stress induced cytotoxicity reduces with a decreasing extent of oxygen functional group density on the RGO surface. It is concluded that although size of the GO sheet plays a role, the functional group density on the GO sheet is one of the key components in mediating cellular cytotoxicity. By controlling the GO reduction and maintaining the solubility, it is possible to minimize the toxicity of GO and unravel its wide range of biomedical applications.     

Physical properties and device applications of graphene oxide

Graphene oxide (GO), the functionalized graphene with oxygenated groups (mainly epoxy and hydroxyl), has attracted resurgent interests in the past decade owing to its large surface area, superior physical and chemical properties, and easy composition with other materials via surface functional groups. Usually, GO is used as an important raw material for mass production of graphene via reduction. However, under different conditions, the coverage, types, and arrangements of oxygen-containing groups in GO can be varied, which give rise to excellent and controllable physical properties, such as tunable electronic and mechanical properties depending closely on oxidation degree, suppressed thermal conductivity, optical transparency and fluorescence, and nonlinear optical properties. Based on these outstanding properties, many electronic, optical, optoelectronic, and thermoelectric devices with high performance can be achieved on the basis of GO. Here we present a comprehensive review on recent progress of GO, focusing on the atomic structures, fundamental physical properties, and related device applications, including transparent and flexible conductors, field-effect transistors, electrical and optical sensors, fluorescence quenchers, optical limiters and absorbers, surface enhanced Raman scattering detectors, solar cells, light-emitting diodes, and thermal rectifiers.     

Quantification of the Particle Size and Stability of Graphene Oxide in a Variety of Solvents

The exceptional solution processing potential of graphene oxide (GO) is always one of its main advantages over graphene in terms of its industrial relevance in coatings, electronics, and energy storage. However, the presence of a variety of functional groups on the basal plane and edges of GO makes understanding suspension behavior in aqueous and organic solvents, a major challenge. Acoustic spectroscopy can also measure zeta potential to provide unique insight into flocculating, meta‐stable, and stable suspensions of GO in deionized water and a variety of organic solvents (including ethanol, ethylene glycol, and mineral oil). As expected, a match between solvent polarity and the polar functional groups on the GO surface favors stable colloidal suspensions accompanied by a smaller aggregate size tending toward disperse individual flakes of GO. This work is significant since it describes the characteristics of GO in solution and its ability to act as a precursor for graphene‐based materials.     

Reduced graphene oxide foils for ion stripping applications

ABSTRACT

Reduced graphene oxide (rGO) films can be employed as ion strippers in an accelerator. They show some advantages with respect to the graphite foils, due to their high thermal and electrical conductivity, low density, high mechanical resistance and high stability. Thin graphene oxide (GO) films with a sub-micron thickness have been synthesized and transformed into reduced GO (rGO) by ion beam irradiations. Physical characterizations of the pristine and ion irradiated GO films have been performed. Measurements of stripping efficiency have been carried out by using helium, lithium, carbon and oxygen ion beams. The rGO stripper films demonstrate a significantly high charge production, comparable to that of the graphite films but with the advantage of a longer lifetime.     

基于银纳米线电极-rGO敏感材料的柔性NO2气体传感器

使用银纳米线作为材料制备柔性叉指电极,用还原氧化石墨烯(reduced graphene oxide, rGO)作为气体敏感材料制备出柔性气体传感器,并研究其对二氧化氮气体的响应特性以及柔韧性能.实验结果表明,制备的以银纳米线作为电极的r GO气体传感器可以实现室温下对浓度为5-50 ppm (1 ppm=10^–6)的NO2气体的检测,对50 ppm的NO2的响应能够达到1.19,传感器的重复性较好,恢复率能够保持在76%以上,传感器的灵敏度是0.00281 ppm^-1,对浓度为5 ppm的NO2气体的响应时间是990 s,恢复时间是1566 s.此外,传感器在0°-45°的弯曲角度下仍表现出优异的电学特性与气体传感性能,所制备的器件具有相对稳定的导电性和较好的弯曲耐受性.     

电化学超级电容器电极材料的研究进展

超级电容器是一种利用电化学双电层储能或在电极材料表面及近表面发生快速可逆氧化还原反应而储能的装置,具有高的比功率、比能量和长的循环寿命.文章综述了超级电容器电极材料的储能机理、特点及应用,并重点介绍了石墨烯、二氧化锰及其复合电极材料在超级电容器中应用的最新研究进展.