A Complementary Resistive Switch-based Crossbar Array Adder

Redox-based resistive switching devices (ReRAM) are an emerging class of non-volatile storage elements suited for nanoscale memory applications. In terms of logic operations, ReRAM devices were suggested to be used as programmable interconnects, large-scale look-up tables or for sequential logic operations. However, without additional selector devices these approaches are not suited for use in large scale nanocrossbar memory arrays, which is the preferred architecture for ReRAM devices due to the minimum area consumption. To overcome this issue for the sequential logic approach, we recently introduced a novel concept, which is suited for passive crossbar arrays using complementary resistive switches (CRSs). CRS cells offer two high resistive storage states, and thus, parasitic sneak currents are efficiently avoided. However, until now the CRS-based logic-in-memory approach was only shown to be able to perform basic Boolean logic operations using a single CRS cell. In this paper, we introduce two multi-bit adder schemes using the CRS-based logic-in-memory approach. We proof the concepts by means of SPICE simulations using a dynamical memristive device model of a ReRAM cell. Finally, we show the advantages of our novel adder concept in terms of step count and number of devices in comparison to a recently published adder approach, which applies the conventional ReRAM-based sequential logic concept introduced by Borghetti et al.Comment: 12 pages, accepted for IEEE Journal on Emerging and Selected Topics in Circuits and Systems (JETCAS), issue on Computing in Emerging Technologie

Radical Alkynylations with EthynylBenziodoXolones: from Photocatalysis to Direct Excitation

Ethynylbenziodoxolones (EBXs) have recently emerged as potent reagents for the alkynylation of radicals. Their combination with photocatalysis allows the synthesis of valuable alkynes at room temperature. Herein, we discuss two photomediated strategies for the synthesis of internal alkynes. The first transformation is a 1,2-oxyalkynylation of N- and O-alkenes using 4ClCzIPN as a photocatalyst. The second strategy makes use of EBXs as strong photooxidants allowing the oxidation of a variety of substrates with no need for a photocatalyst

0-pi Josephson tunnel junctions with ferromagnetic barrier

We fabricated high quality Nb/Al_2O_3/Ni_{0.6}Cu_{0.4}/Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a step-like thickness, we obtain a 0-pi junction, with equal lengths and critical currents of 0 and pi parts. The ground state of our 330 microns (1.3 lambda_J) long junction corresponds to a spontaneous vortex of supercurrent pinned at the 0-pi step and carrying ~6.7% of the magnetic flux quantum Phi_0. The dependence of the critical current on the applied magnetic field shows a clear minimum in the vicinity of zero field.Comment: submitted to PR

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO$_{2-x}$) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC$_x$) at the surface during vacuum annealing at temperatures as low as 600 {\deg}C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC$_x$ surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO$_2$ thin films prepared and measured under identical conditions, the formation of HfC$_x$ was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating

Applicability of Well-Established Memristive Models for Simulations of Resistive Switching Devices

Highly accurate and predictive models of resistive switching devices are needed to enable future memory and logic design. Widely used is the memristive modeling approach considering resistive switches as dynamical systems. Here we introduce three evaluation criteria for memristor models, checking for plausibility of the I-V characteristics, the presence of a sufficiently non-linearity of the switching kinetics, and the feasibility of predicting the behavior of two anti-serially connected devices correctly. We analyzed two classes of models: the first class comprises common linear memristor models and the second class widely used non-linear memristive models. The linear memristor models are based on Strukovs initial memristor model extended by different window functions, while the non-linear models include Picketts physics-based memristor model and models derived thereof. This study reveals lacking predictivity of the first class of models, independent of the applied window function. Only the physics-based model is able to fulfill most of the basic evaluation criteria.Comment: 9 pages; accepted for IEEE TCAS-

Inhomogeneity of donor doping in SrTiO3 substrates studied by fluorescence-lifetime imaging microscopy

Fluorescence-lifetime imaging microscopy (FLIM) was applied to investigate the donor distribution in SrTiO3 single crystals. On the surfaces of Nb- and La-doped SrTiO3, structures with different fluorescence intensities and lifetimes were found that could be related to different concentrations of Ti3+. Furthermore, the inhomogeneous distribution of donors caused a non-uniform conductivity of the surface, which complicates the production of potential electronic devices by the deposition of oxide thin films on top of doped single crystals. Hence, we propose FLIM as a convenient technique (length scale: 1 $\mu$m) for characterizing the quality of doped oxide surfaces, which could help to identify appropriate substrate materials

Easy and convenient millimole‐scale synthesis of new, potential biomarkers for gamma‐hydroxybutyric acid (GHB) intake: Feasible for analytical laboratories

New biomarkers indicating the abuse of drugs and alcohol are still of major interest for clinical and forensic sciences. The endogenous neurotransmitter and approved drug, gamma-hydroxybutyric acid (GHB), is often illegally used for drug-facilitated crimes by spiking GHB into alcoholic beverages. Analytical detection windows of only 6 h in blood and 12 h in urine are often too short to provide reliable proof of GHB ingestion. Therefore, new biomarkers are needed to prove exogenous GHB administration. Previously, amino acid GHB conjugates were discovered in an untargeted metabolomics screening and fatty acid esters with GHB were recently discussed as promising biomarkers to enlarge the analytical detection time windows. However, the development of analytical methods is still slowed down since reference compounds for targeted screenings are still missing. In this paper, we describe simple procedures for the rapid synthesis and purification of amino acid GHB conjugates as well as fatty acid esters, which can be adopted in analytical and clinical/forensic laboratories. Structural characterization data, together with IR, $^1$H-nuclear magnetic resonance (NMR), $^{13}$C-NMR, high-resolution mass spectra (MS), and MS/MS spectra in positive and negative ionization mode are reported for all obtained GHB conjugates and GHB conjugate precursors

DISTRIBUTION AND KINETICS OF 14C-VECURONIUM IN RATS AND MICE

The distribution and kinetics of 14C-vecuronium were studied in rats and mice. 14C-Vecuronium accumulated rapidly in the liver. Both unchanged and metabolized vecuronium were excreted with the bile into the intestines and stomach. Reabsorption in the gut was probably responsible for an enterohepatic increase in radioactivity in the liver after one hour. Excretion through the kidneys increased continuously from low values after the initial peak. Binding in compartments with acid mucopolysaccharides such as cartilage, connective tissue etc., was less important. Bloodbrain barrier and placenta were permeable only to a small degre

Refinement of the crystal structure of sinigrin

The crystal structure of sinigrin (potassium myronate), KC_(10)H_(16)NO_9S_2. H_2O, has been refined on the basis of three-dimensional intensity data collected on an automated diffractometer. The final agreement index is 0·056 for 1906 reflections, and the estimated standard deviations in the atomic coordinates of the C, N, and 0 atoms are about 0·004 Å. The absolute configuration of the anion was confirmed from anomalous dispersion effects. The crystals are orthorhombic with space group P212121. The unit-cell dimensions of a new crystal are ɑ = 8·265 (1), b = l1·440(3), and c = 17·757 (3)A. An appreciable increase in the length of the c axis occurred during irradiation of the crystal. In addition, the vinyl group of the myronate ion appears to undergo large thermal motions. The distances between vinyl groups of adjacent myronate ions are such that a photopolymerization reaction between them would be possible, which might explain these two observations