Memristive Systems Based on Two-Dimensional Materials

The unique electronic and optical properties of newly discovered 2D crystals such as graphene, graphene oxide, molybdenum disulfide, and so on demonstrate the tremendous potential in creating ultrahigh-density nano- and bioelectronics for innovative image recognition systems, storage and processing of big data. A new type of memristors with a floating photogate based on biocompatible graphene and other 2D crystals with extremely low power consumption and footprint is considered. The photocatalytic oxidation of graphene is proposed as an effective method of creating synapse-like 2D memristive devices with photoresistive switching for nonvolatile electronic memory of ultrahigh density. Particular attention is paid to the new concept of the formation of self-assembled nanoscale memristive elements interfacing artificial electronic neural networks. 2D photomemristors with a floating photogate exhibit multiple states controlled in a wide range of electromagnetic radiation and can be used for neuromorphic computations, pattern recognition and image processing needed to create artificial intelligence

Low-Dimensional Layered Light-Sensitive Memristive Structures for Energy-Efficient Machine Vision

Layered two-dimensional (2D) and quasi-zero-dimensional (0D) materials effectively absorb radiation in the wide ultraviolet, visible, infrared, and terahertz ranges. Photomemristive structures made of such low-dimensional materials are of great interest for creating optoelectronic platforms for energy-efficient storage and processing of data and optical signals in real time. Here, photosensor and memristor structures based on graphene, graphene oxide, bismuth oxyselenide, and transition metal dichalcogenides are reviewed from the point of view of application in broadband image recognition in artificial intelligence systems for autonomous unmanned vehicles, as well as the compatibility of the formation of layered neuromorphic structures with CMOS technology

Homoepitaxial Nanostructures of Zinc Oxide

The homoepitaxial ZnO nanostructures (HENS) were obtained on different substrates using various techniques. The first type of homoepitaxial ZnO nanorod arrays was grown on Si or ITO substrates by using two alternative sequences: (a) seeding → growth from solution → growth from vapor and contrariwise (b) seeding → growth from vapor → growth from solution. As follows from transport and cathode luminescence measurements homoepitaxial growth allows enhancing electrical or luminescence properties. The second type of HENS was prepared by growth of vertically or horizontally oriented ZnO nanorod arrays depending on monocrystalline ZnO wafers with [0001] and [10-10] orientation. In all cases the growth occurs along the c-axis of fast growth

Novel Green Luminescent and Phosphorescent Material: Semiconductive Nanoporous ZnMnO with Photon Confinement

A novel green luminescent and phosphorescent material of semiconductive nanoporous ZnMnO was synthesized by the thermal nucleation of nanopores in the 20-period Zn_0.93Mn_0.07O/Zn_0.65Mn_0.35O multilayer structure. Nanoporous ZnMnO showed an <i>n</i>-type semiconducting property and exhibited an extremely strong green light emission in its luminescence and phosphorescence characteristics. This arises from the formation of the localized energy level (i.e., green emission band) within the energy band gap and the confinement of photons. The results suggest nanoporous ZnMnO to have a great potential for the new type of semiconducting green phosphors and semiconductor light-emitting diodes with lower thresholds, producing an efficient light emission. In-depth analyses on the structural, electrical, and optical properties are thoroughly examined, and the formation mechanism of nanoporous ZnMnO and the origin of the strong green light emission are discussed

Synthesis and Properties of Ethylene/propylene and Ethylene/propylene/5-ethylidene-2-norbornene Copolymers Obtained on Rac-Et(2-MeInd)2ZrMe2/Isobutylaluminium Aryloxide Catalytic Systems

Ethylene/propylene (E/P) and ethylene/propylene/5-ethylidene-2-norbornene (E/P/ENB) copolymers were obtained on rac-Et(2-MeInd)2ZrMe2 activated by a number of isobutylaluminium aryloxides: (2,6-tBu2PhO-)AliBu2 (1-DTBP) (2,6-tBu2,4-Me-PhO-)AliBu2 (1-BHT), (2,4,6-tBu2PhO-)AliBu2 (1-TTBP), (2,6-tBu2,4-Me-PhO-)2AliBu (2-BHT), (2,6-tBu2PhO-)2AliBu (2-DTBP), [(2-Me,6-tBu-C6H3O)AliBu2]2 (1-MTBP), [(2,6-Ph2-PhO)AliBu2]2 (1-DPP). This study shows how the structure of an activator influences catalytic activity and polymer properties, such as the copolymer composition, molecular weight characteristics, and thermophysical and mechanical properties. It has been shown that both the introduction of a bulky substituent in the para-position of the aryloxy group and the additional aryloxy group in the structure of an activator lead to a significant decrease in activity of the catalytic system in all studied copolymerization processes. Moreover, activation by bulkier aryloxides leads to lower levels of comonomer insertion and gives rise to higher molecular weight polymers. Broad or multiple endothermic peaks with different values of melting points are observed on the DSC curves of the copolymers obtained with different catalytic systems. The DSC of the thermally fractionated samples makes it possible to reveal the heterogeneity of the copolymer microstructure, which manifests itself in the presence of a set of lamellar crystallites of different thickness. The results also present the mechanical properties of the copolymers, such as the tensile strength (&sigma;), elongation at break (&epsilon;), and engineering strain (EL). The synthesized E/P and E/P/ENB copolymers contain about 1&ndash;4 wt.% of the sterically hindered phenols obtained in situ as a residue of the hydrolyzed activators in the course of reaction quenching. This determines the increased thermooxidative stability of the copolymers