Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Anyone who ever took an electronics laboratory class will be familiar with the fundamental passive circuit elements: the resistor, the capacitor and the inductor. However, in 1971 Leon Chua reasoned from symmetry arguments that there should be a fourth fundamental element, which he called a memristor (short for memory resistor). Although he showed that such an element has many interesting and valuable circuit properties, until now no one has presented either a useful physical model or an example of a memristor. Here we show, using a simple analytical example, that memristance arises naturally in nanoscale systems in which solid-state electronic and ionic transport are coupled under an external bias voltage. These results serve as the foundation for understanding a wide range of hysteretic current-voltage behaviour observed in many nanoscale electronic devices that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches.

/pdf/the-missing-memristor-found-55upit5xe7.pdf

The missing memristor found

Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

Memristive devices are electrical resistance switches that can retain a state of internal resistance based on the history of applied voltage and current. These devices can store and process information, and offer several key performance characteristics that exceed conventional integrated circuit technology. An important class of memristive devices are two-terminal resistance switches based on ionic motion, which are built from a simple conductor/insulator/conductor thin-film stack. These devices were originally conceived in the late 1960s and recent progress has led to fast, low-energy, high-endurance devices that can be scaled down to less than 10 nm and stacked in three dimensions. However, the underlying device mechanisms remain unclear, which is a significant barrier to their widespread application. Here, we review recent progress in the development and understanding of memristive devices. We also examine the performance requirements for computing with memristive devices and detail how the outstanding challenges could be met.

Memristive devices for computing

We report on the fabrication and characterization of nanoscale memory elements based on solid electrolytes. When combined with silver, chalcogenide glasses such as Se-rich Ge-Se are good solid electrolytes, exhibiting high Ag ion mobility and availability. By placing an anode that has oxidizable Ag and an inert cathode (e.g., Ni) in contact with a thin layer of such a material, a device is formed that has an intrinsically high resistance, but which can be switched to a low-resistance state at small voltage via reduction of the silver ions. An opposite bias will return the device to a high-resistance state, and this reversible switching effect is the basis of programmable metallization cell technology. In this paper, electron beam lithography was used to make sub-100-nm openings in polymethylmethacrylate layers used as the dielectric between the device electrodes. The solid electrolyte film was formed in these via-holes so that their small diameter defined the active switching area between the electrodes. The Ag-Ge-Se electrolyte was created by the photodiffusion, with or without thermal assistance, of an Ag layer into the Ge-Se base glass. Combined thermal and photodiffusion leads to a nanophase separated material with a dispersed Ag ion-rich material with an average crystallite size of 7.5 nm in a glassy insulating Ge-rich continuous phase. The nanoscale devices write at an applied bias as low as 0.2 V, erase by -0.5 V, and fall from over 10/sup 7/ /spl Omega/ to a low-resistance state (e.g., 10/sup 4/ /spl Omega/ for a 10-/spl mu/A programming current) in less than 100 ns. Cycling appears excellent with projected endurance well beyond 10/sup 11/ cycles.

Nanoscale memory elements based on solid-state electrolytes

A microelectronic programmable structure suitable for storing information, and array including the structure and methods of forming and programming the structure are disclosed. The programmable structure generally includes an ion conductor and a plurality of electrodes. Electrical properties of the structure may be altered by applying energy to the structure, and thus information may be stored using the structure.

Scalable programmable structure, an array including the structure, and methods of forming the same

A microelectronic programmable structure and methods of forming and programming the structure are disclosed. The programmable structure generally include an ion conductor and a plurality of electrodes. Electrical properties of the structure may be altered by applying a bias across the electrodes, and thus information may be stored using the structure.

Microelectronic programmable device and methods of forming and programming the same

We describe the materials aspects and electrical characteristics of W-(Cu/WO3)-Cu switching elements. These materials are compatible with back-end-of-line processing in CMOS integrated circuits where both tungsten and copper already play a significant role. Devices based on Cu/WO3 solid electrolytes formed by photodiffusion of copper into tungsten oxide switch via the electrochemical formation of a conducting filament within the high resistance electrolyte film. They are able to switch reversibly between widely spaced nonvolatile resistance states at low voltage ( 125 degC). This difference in behavior was attributed to the observation that the copper tends to oxidize in the plasma-grown oxide whereas the copper in the deposited oxide exists in an unbound state and is, therefore, more able to participate in the switching process

A Low-Power Nonvolatile Switching Element Based on Copper-Tungsten Oxide Solid Electrolyte

Ag as an additive in chalcogenide glasses (CGs), and particularly thin films of such glasses, has attracted widespread interest in glass science [1‐3]. The interest stems inpartfromlight-inducedeffectsrelevanttoopticalrecording and information processing [3]. It also stems from the drastically increased electrical conductivity [4] of Ag-CGs, some of which are solid electrolytes [4]. The structure of glasses containing group IB (Cu, Ag) additives in CGs, as for the celebrated cases of group IV (Si, Ge) and group V (P, As) additives in CGs, has been generally modeled [5], and diffraction results analyzed [6‐8], in the spirit of homogeneous random networks. In Ag-CGs, Ag-centered local structures apparently phase separate from the host network, and one observes bimodal glass transition temperatures ! Tg" . These new structure results provide an attractive starting point to model electrical transport and light-induced effects in Ag-CGs. Glass forming compositions [9], and particularly the composition variation [10] of Tg in network glasses, contain vital clues on the connectivity of the backbone. Ideas on constraint counting [11] have provided the tools to decode these clues and to gain insights into the structure of glasses. Binary GexSe12x glasses are rather well studied [12], and it thus appeared attractive to closely examine the chemical role of Ag as an additive in such glasses. Ternary ! GexSe12x" 12yAgy glasses form in two distinct compositional regions [7,13,14], a Se-rich region ! 0 , x , 1 " , la

/pdf/dual-chemical-role-of-ag-as-an-additive-in-chalcogenide-4qri4o8lj9.pdf

Maria Mitkova

Papers

Nanoscale memory elements based on solid-state electrolytes

Scalable programmable structure, an array including the structure, and methods of forming the same

Microelectronic programmable device and methods of forming and programming the same

A Low-Power Nonvolatile Switching Element Based on Copper-Tungsten Oxide Solid Electrolyte

Dual Chemical Role of Ag as an Additive in Chalcogenide Glasses