Advanced measurement techniques for the characterization of ReRAM devices

In some Resistive Random Access Memories (ReRAM), which could become the next generation of non-volatile memories [1], the voltage-controlled high and low resistance states (HRS and LRS, respectively) are associated to the creation (Set) and disruption (Reset) of a conductive filament (CF) that locally connects (LRS) or disconnects (HRS) the electrodes [2]. Usually, a current limit (CL) must be fixed during the Set process. Typically, these devices are characterized using source measurement units (SMU) to measure the current through the device. However, most of the SMU have a low sampling rate (around 1sample/1ms) and the current limitation mechanism used by the equipment is not well understood. To overcome these limitations, in this work, a low-cost setup with large sampling rate (larger than 1sample/10μs) is presented which, in addition, includes a well-controlled wide-range current limiting unit, CLCU (Fig. 1). The system is suitable to capture fast transients during the Set/Reset processes (Fig. 2) and to detect HRS Random Telegraph Noise (RTN) unresolvable by SMUs (Fig. 3) [3]. These device-level measurements can be combined with a Conductive Atomic Force Microscope, to get information on CF properties that cannot be directly measured at device level, as, for example, the spatial distribution of current in the CF at LRS and HRS (Fig. 4) [4]. Please click Additional Files below to see the full abstract

Spherical structures on torus knots and links

The present paper considers two infinite families of cone-manifolds endowed with spherical metric. The singular strata is either the torus knot ${\rm t}(2n+1, 2)$ or the torus link ${\rm t}(2n, 2)$. Domains of existence for a spherical metric are found in terms of cone angles and volume formul{\ae} are presented.Comment: 17 pages, 5 figures; typo

Gate current analysis of AlGaN/GaN on silicon heterojunction transistors at the nanoscale

The gate leakage current of AlGaN/GaN (on silicon)high electron mobility transistor(HEMT) is investigated at the micro and nanoscale. The gate current dependence (25-310 °C) on the temperature is used to identify the potential conduction mechanisms, as trap assisted tunneling or field emission. The conductive atomic force microscopy investigation of the HEMT surface has revealed some correlation between the topography and the leakage current, which is analyzed in detail. The effect of introducing a thin dielectric in the gate is also discussed in the micro and the nanoscale

A glimpse into Thurston's work

We present an overview of some significant results of Thurston and their impact on mathematics. The final version of this paper will appear as Chapter 1 of the book "In the tradition of Thurston: Geometry and topology", edited by K. Ohshika and A. Papadopoulos (Springer, 2020)

Geometry of the SL(3,ℂ)-character variety of torus knots.

Let G be the fundamental group of the complement of the torus knot of type (m, n). It has a presentation G = . We find a geometric description of the character variety X(G) of characters of representations of G into SL(3,ℂ), GL(3,ℂ) and PGL(3,ℂ)

Negatively oriented ideal triangulations and a proof of Thurston's hyperbolic Dehn filling theorem

We give a complete proof of Thurston's celebrated hyperbolic Dehn filling theorem, following the ideal triangulation approach of Thurston and Neumann-Zagier. We avoid to assume that a genuine ideal triangulation always exists, using only a partially flat one, obtained by subdividing an Epstein-Penner decomposition. This forces us to deal with negatively oriented tetrahedra. Our analysis of the set of hyperbolic Dehn filling coefficients is elementary and self-contained. In particular, it does not assume smoothness of the complete point in the variety of deformations.Comment: 23 pages, 4 figures, Late

A morse lemma for quasigeodesics in symmetric spaces and euclidean buildings

We prove a Morse lemma for regular quasigeodesics in nonpositively curved symmetric spaces and euclidean buildings. We apply it to give a new coarse geometric characterization of Anosov subgroups of the isometry groups of such spaces simply as undistorted subgroups which are uniformly regular

Anosov subgroups: dynamical and geometric characterizations

© 2017, Springer International Publishing AG. We study infinite covolume discrete subgroups of higher rank semisimple Lie groups, motivated by understanding basic properties of Anosov subgroups from various viewpoints (geometric, coarse geometric and dynamical). The class of Anosov subgroups constitutes a natural generalization of convex cocompact subgroups of rank one Lie groups to higher rank. Our main goal is to give several new equivalent characterizations for this important class of discrete subgroups. Our characterizations capture “rank one behavior” of Anosov subgroups and are direct generalizations of rank one equivalents to convex cocompactness. Along the way, we considerably simplify the original definition, avoiding the geodesic flow. We also show that the Anosov condition can be relaxed further by requiring only non-uniform unbounded expansion along the (quasi)geodesics in the group