Breakdown transients in high-k multilayered MOS stacks: Role of the oxide-oxide thermal boundary resistance

In this work, breakdown transients of multilayered gate oxide stacks were analyzed to study the impact of the interfaces between oxides on the heat dissipation considering an electromigration-based progressive breakdown model. Using two distinct measurement setups on four different sets of samples, featuring two layers and three layers of Al 2 O 3 and HfO 2 interspersed, the breakdown transients were captured and characterized in terms of the degradation rate. Experimental results show that the number of oxide-oxide interfaces present in the multilayered stack has no visible impact on the breakdown growth rate among our samples. This strongly supports the interpretation of the bulk materials dominating the heat transfer to the surroundings of a fully formed conductive filament that shows no electrical differences between our various multilayered stack configurations.Fil: Boyeras Baldomá, Santiago. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pazos, Sebastián Matías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; ArgentinaFil: Aguirre, F. L.. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; ArgentinaFil: Palumbo, Felix Roberto Mario. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Study on the Connection Between the Set Transient in RRAMs and the Progressive Breakdown of Thin Oxides

In this paper, the transition rate (TR) from the high-resistance state to the low-resistance state of a HfO2-based resistive random access memory (RRAM) is investigated. The TR is statistically characterized by applying constant voltage stresses in the range from 0.45 to 0.65 V. It is found that TR follows a voltage dependence which closely resembles the one exhibited by metal-insulator-semiconductor / metal-insulator-metal structures when subjected to constant voltage stress, but with remarkably different fitting parameters. This result suggests a common underlying mechanism in both evolutionary behaviors. Furthermore, the investigation provides additional evidence supporting the micro-structural changes in the oxide after the forming step as well as the role played by the atomic species during the SET event.Fil: Aguirre, Fernando Leonel. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodriguez Fernandez, Alberto. Universitat Autònoma de Barcelona; EspañaFil: Pazos, Sebastián Matías. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Suñé, Jordi. Universitat Autònoma de Barcelona; EspañaFil: Miranda, Enrique. Universitat Autònoma de Barcelona; EspañaFil: Palumbo, Felix Roberto Mario. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The Atomic Layer Deposition Technique for the Fabrication of Memristive Devices: Impact of the Precursor on Pre-deposited Stack Materials

Atomic layer deposition (ALD) is a standard technique employed to grow thin-film oxides for a variety of applications. We describe the technique and demonstrate its use for obtaining memristive devices. The metal/insulator/metal stack is fabricated by means of ALD-grown HfO2, deposited on top of a highly doped Si substrate with an SiO2 film and a Ti electrode. Enhanced device capabilities (forming free, self-limiting current, non-crossing hysteretic current-voltage features) are presented and discussed. Careful analysis of the stack structure by means of X-ray reflectometry, atomic force microscopy, and secondary ion mass spectroscopy revealed a modification of the device stack from the intended sequence, HfO2/Ti/SiO2/Si. Analytical studies unravel an oxidation of the Ti layer which is addressed for the use of the ozone precursor in the HfO2 ALD process. A new deposition process and the model deduced from impedance measurements support our hypothesis: the role played by ozone on the previously deposited Ti layer is found to determine the overall features of the device. Besides, these ALD-tailored multifunctional devices exhibit rectification capability and long enough retention time to deserve their use as memory cells in a crossbar architecture and multibit approach, envisaging other potential applications

Analytic circuit model for thermal drying behavior of electronic inks

Understanding the sintering process of conductive inks is a fundamental step in the development of sensors. The intrinsic properties (such as thermal conductivity, resistivity, thermal coefficient, among others) of the printed devices do not correspond to those of the bulk materials. In the field of biosensors porosity plays a predominant role, since it defines the difference between the geometric area of the working electrode and its electrochemical surface area. The analysis reported so far in the literature on the sintering of inks are based on their DC characterization. In this work, the shape and distribution of the nanoparticles that make up the silver ink have been studied employing a transmission electron microscopy. Images of the printed traces have been obtained through a scanning electron microscope at different sintering times, allowing to observe how the material decreases its porosity over time. These structural changes were supported through electrical measurements of the change in the trace impedance as a function of drying time. The resistivity and thermal coefficient of the printed tracks were analyzed and compared with the values of bulk silver. Finally, this work proposes an analytical circuit model of the drying behavior of the ink based on AC characterization at different frequencies. The characterization considers an initial time when the spheric nanoparticles are still surrounded by the capping agent until the conductive trace is obtained. This model can estimate the characteristics that the printed devices would have, whether they are used as biosensors (porous material) or as interconnections (compact material) in printed electronics

Chemical Analysis of Nutritional Content of Prickly Pads (Opuntia ficus indica) at Varied Ages in an Organic Harvest

Opuntia ficus indica, also known as prickly pads, are an important part of the human diet and are also used as forage for livestock. This is an interesting vegetable due the environmental conditions in which it grows and its resistance to climatic extremes; however, little is known about its nutritional properties, especially in the later stages of maturity. The objective of this study was to determine the composition of organic prickly pads (Opuntia ficus indica) at differing stages of growth maturity. Chemical proximate analysis and mineral constituent analysis at different maturation stages were carried out in this investigation. As a result, older prickly pads were found to be an important source of nutritional components such as calcium

Chemokines cooperate with TNF to provide protective anti-viral immunity and to enhance inflammation

The role of cytokines and chemokines in anti-viral defense has been demonstrated, but their relative contribution to protective anti-viral responses in vivo is not fully understood. Cytokine response modifier D (CrmD) is a secreted receptor for TNF and lymphotoxin containing the smallpox virus-encoded chemokine receptor (SECRET) domain and is expressed by ectromelia virus, the causative agent of the smallpox-like disease mousepox. Here we show that CrmD is an essential virulence factor that controls natural killer cell activation and allows progression of fatal mousepox, and demonstrate that both SECRET and TNF binding domains are required for full CrmD activity. Vaccination with recombinant CrmD protects animals from lethal mousepox. These results indicate that a specific set of chemokines enhance the inflammatory and protective anti-viral responses mediated by TNF and lymphotoxin, and illustrate how viruses optimize anti-TNF strategies with the addition of a chemokine binding domain as soluble decoy receptors.We thank Javier Salguero for help with animal experimentation and immunohistochemistry, Rocío Martín and Carolina Sánchez for technical assistance and Daniel Rubio for discussions on the project. This work was funded by Grants from the Spanish Ministry of Economy and Competitiviness and European Union (European Regional Development’s Funds, FEDER) (grant SAF2015-67485-R), and the Wellcome Trust (grant 051087/Z97/Z). M.B.R.-A. and A. Alejo were recipients of a Ramón y Cajal Contract from the Spanish Ministry of Science and Innovation

A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows

We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT