Roland Rosezin

Beyond von Neumann—logic operations in passive crossbar arrays alongside memory operations

The realization of logic operations within passive crossbar memory arrays is a promising approach to expand the fields of application of such architectures. Material implication was recently suggested as the basic function of memristive crossbar junctions, and single bipolar resistive switches (BRS) as well as complementary resistive switches (CRS) were shown to be capable of realizing this logical functionality. Based on a systematic analysis of the Boolean functions, we demonstrate here that 14 of 16 Boolean functions can be realized with a single BRS or CRS cell in at most three sequential cycles. Since the read-out step is independent of the logic operation steps, the result of the logic operation is directly stored to memory, making logic-in-memory applications feasible.

Integrated Complementary Resistive Switches for Passive High-Density Nanocrossbar Arrays

Recently, the sneak-path obstacle in passive crossbar arrays has been overcome by the invention of complementary resistive switches (CRSs) consisting of two bipolar antiserially connected memristive elements. Here, we demonstrate the vertical integration of CRS cells based on Cu/SiO2/Pt bipolar resistive switches. CRS cells were fabricated and electrically characterized, showing high resistance ratios (Roff/Ron >; 1500) and fast switching speed (<; 120 μs). The results are one step further toward the realization of high-density passive nanocrossbar-array-based gigabit memory devices.

Crossbar Logic Using Bipolar and Complementary Resistive Switches

Memristive switches are promising devices for future nonvolatile nanocrossbar memory devices. In particular, complementary resistive switches (CRSs) are the key enabler for passive crossbar array implementation solving the sneak path obstacle. To provide logic along with memory functionality, “material implication” (IMP) was suggested as the basic logic operation for bipolar resistive switches. Here, we show that every bipolar resistive switch as well as CRSs can be considered as an elementary IMP logic unit and can systematically be understood in terms of finite-state machines, i.e., either a Moore or a Mealy machine. We prove our assumptions by measurements, which make the IMP capability evident. Local fusion of logic and memory functions in crossbar arrays becomes feasible for CRS arrays, particularly for the suggested stacked topology, which offers even more common Boolean logic operations such as and and nor .

Capacity based nondestructive readout for complementary resistive switches.

Complementary resistive switches (CRS) were recently suggested to solve the sneak path problem of larger passive memory arrays. CRS cells consist of an antiserial setup of two bipolar resistive switching cells. The conventional destructive readout for CRS cells is based on a current measurement which makes a considerable call on the switching endurance. Here, we report a new approach for a nondestructive readout (NDRO) based on a capacity measurement. We suggest a concept of an alternative setup of a CRS cell in which both resistive switching cells have similar switching properties but are distinguishable by different capacities. The new approach has the potential of an energy saving and fast readout procedure without decreasing cycling performance and is not limited by the switching kinetics for integrated passive memory arrays.

Electroforming and Resistance Switching Characteristics of Silver-Doped MSQ With Inert Electrodes

This paper reports on the resistance switching effect in silver-doped methylsilsesquioxane (MSQ) thin films with Pt top and bottom electrodes. Silver is thermally diffused into MSQ films for different times and the results prove that silver ions (or other oxidizable metal ions) are required in the system, but not necessarily as one of the two electrodes. SEM investigations at horizontal cells (gap width 15-100 nm) show the formation of metallic agglomerations in the gap. The forming process is found to be electric-field driven and the filament resistance is determined to be 30 Ω/nm. Under the assumption of conical-shaped filament growth, the diameter of a filament is calculated to 13.5 nm, which is in agreement with the SEM observations. Memory device related tests on 100 × 100 nm2 cross junctions show unipolar switching up to 2000 times and retention at 85°C for at least 6 × 104 s.

Modeling Complementary Resistive Switches by nonlinear memristive systems

Complementary Resistive Switches (CRS) alleviate size limitations for passive crossbar array memory devices by the elimination of sneak paths. Since CRS cells consist of two anti-serially connected bipolar resistive elements, e.g. electro-chemical metallization (ECM) elements, it is straightforward to use their corresponding memristive models for circuit simulation. Here we show that simple linear memristive models, which are often used in literature, are inapplicable. Therefore, we apply a physics based nonlinear model for ECM elements which is capable of simulating correct CRS behavior for anti-serially combined elements. Interconnecting memristive element models in CRS configuration is an advantageous way to check for memristive model consistency.

A multilayer RRAM nanoarchitecture with resistively switching Ag-doped spin-on glass

Next generation memory materials and novel memory architectures are in the focus of investigations because CMOS based systems are supposed to reach their physical limits during the next decade. To enhance the potential for very high integration density we fabricated multilayer crossbar memory architectures with integrated spin-on glass (methyl-silsesquioxane - MSQ). UV nanoimprint lithography, a widely proposed future technology, was used to structure down to 100 nm feature sizes. Electrical measurements on silver doped MSQ devices show the potential for the use of the material composition in the field of future memory applications.

LARGE AREA PIEZOELECTRIC ACTUATORS USING METAL FOIL SUBSTRATES WITH Pb(Zrx,Ti1 - x)O3 THIN FILMS

ABSTRACT We report on the deposition of Pb(Zrx,Ti1 - x)O3 (PZT) thin films by chemical solution deposition (CSD) on stainless steel foils. The electrical characterization proves good ferroelectric properties with a remnant polarization of 38 μ C/cm2. Since PZT is also piezoelectric the 35 μ m and 50 μ m thick metal foils are used to make piezoelectric actuated cantilever beams of several millimeter lengths. Actuated with 10–30 V a displacement up to 32 μ m was measured in quasi-static mode. In resonance mode the displacement increases several times at the same driving voltage.