resulting in relatively low data throughput. On the other hand, another type of the new memories based on a solid state We report a novel nonvolatile dual-layered electrolytic electrolyte [5], in which ions such as Ag+ or Cu+ move along resistance memory composed of a conductive Cu ion the applied field and form the conductive bridge in the activated layer and a thin insulator for the first time. An electrolyte, is a promising candidate from the viewpoints of ON/OFF mechanism of this new type memory is postulated high speed switching and low set/reset current. Previous as follows: Cu ions pierce through the insulator layer by studies on the memories, however, seem to show their applied electric field, the ions form a Cu conductive bridge in insufficient retention. the insulator layer, and this bridge dissolves back to the ion To realize both high speed switching and sufficient activated layer when the field is reversed. The 4 kbit memory retention, we have newly developed a dual-layered array with IT-IR cell structure was fabricated based on 180 electrolytic resistance memory utilizing Cu conductive bridge nm CMOS process. Set/reset pulses were 5 ns, 110 gtA and 1 combined with a thin insulator. ns, 125 gA, respectively. Those conditions provide large set/reset resistance ratio of over 2 orders of magnitude and Memory Design satisfactory retention. Essential characteristics for high capacity memories including superb scalability down to 20In a solid state electrolytic memory, metallic ions such as nmo, sufficient endurance up to 107 cycles and preliminary Ag+ or Cu+ play an essential role in fast forming a conductive data for 4-level memory are also presented. These bridge when the electric field is applied. But without the field, characteristics promise the memory being the next generation the bridge should steadfastly keep the shape for the data high capacity nonvolatile memory even before the scaling retention. It seems hard to solve these incompatible limitation of flash memories is encountered. characteristics within a single layer. Therefore we divided the role into respective two layers: the conductive ion activated Introduction layer and the resistance change layer of the insulator as shown in Fig. 1. The resistance change layer is thin enough An imminent scaling limit of flash memories accelerates for the activated ions to pierce through the layer rapidly in the search for the new memories and so far several types of the electric field. The conductive bridge is stable in the layer resistive memories are proposed, such as phase change when no electric field is applied. When the reverse field is memory [1, 2], oxide base resistance change memory [3, 4] applied, the bridge is dissolved back to the ion layer, where and so on. However, each memory seems to have inherent both the electric field and joule heat are thought to be main drawbacks such as large reset current and/or slow set speed, driving forces. Because the insulator layer is thin enough, o o a %^o Cu od 1 l z | CT e | og g uC Gd Cu-Te base conz u...
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Hybrid memory systems that incorporate Storage Class Memory (SCM) as non-volatile cache or DRAM data backup are expected to bolster system efficiency and cost because SCM promises higher density than DRAM cache and higher speed than the storage I/F. This paper demonstrates a Cu-based resistive random access memory (ReRAM) cell that meets the SCM performance specifications for a 16Gb ReRAM with 200MB/s write and 1GB/s read [1]. Cell CharacteristicsThe cell in Fig. 1 consists of a Cu-based ion reservoir (IR) over an electrolyte (EL). When a positive bias is applied to the top electrode, ionized Cu is driven from the IR into the EL [2]. Switching from an initial high resistance state (HRS) to a low resistance state (LRS) occurs when the local Cu concentration in the EL becomes sufficient to facilitate electron transport.The cell I-V curve in Fig. 2 illustrates the forming, reset, and set events. While initial forming occurs at 4.2V, the set voltage during subsequent cycles is 2V lower, suggesting the structure is altered upon forming, such that a preferential, lower barrier path is established. This is interpreted as stress-induced channel formation [3]. The forming voltage for the cell materials in Fig. 3 is below the breakdown bias of the EL. Hence, the conductive bridge is formed without breakdown, since metal cations are supplied from an external reservoir; in contrast to oxygen vacancy ReRAM, which relies on soft breakdown to liberate oxygen anions from within the switching region [4]. The estimated number of Cu atoms required to form the conductive bridge ranges from 10-200, based on DFT simulations of a model system in Fig. 4, and the resistance of the bridge in Fig. 5 depends on the quantity of metal transported into the EL, which is inversely related to the set current compliance (I-set). To reset the device, a positive bias is applied to the bottom electrode, to oxidize Cu in the bridge and transport it back to the IR. The onset of reset in Fig. 2 begins at -0.5V, which is ~5x greater than that for similar Ag-based ReRAM cells [5,6].The switching times τ in Fig. 6 follow the form log(τ) ∝ -V , and under nominal conditions, reset occurs slightly faster than set, while forming occurs much slower than set and reset.The virgin and HRS currents both exhibit exponential dependence on voltage, consistent with trap assisted tunneling or hopping-type transport. The activation energy Ea in Fig. 7 is 155meV and is reduced by the applied electric field. While the LRS I-V behavior is roughly linear with voltage, an 8meV Ea suggests the conductance is not purely metallic; and LRS read noise exhibits RTN behavior with a 1/f power spectral density in Fig. 8, characteristic of multiple RTN centers.
Magnetically induced superresolution (MSR) has been realized in magneto-optical disks using exchange-coupled magnetic multilayer film. Two new detection methods have been developed. In front aperture detection (FAD), the heated area in the light spot is optically masked. In rear aperture detection (RAD), a signal is read out only from the heated area. For higher readout power in RAD, the aperture area is sandwiched by double masks, since another mask is generated in the highest temperature region. The cut-off spatial frequency in both types of detection is more than two times higher than that in conventional detection. A high C/N of 42 dB is obtained in the MSR disks by both methods for a mark length of 0.3 µm.
An inexpensive and practical mastering technology was developed using a blue-laser optical system with a wavelength of 405 nm and numerical aperture (NA) of 0.95 comprising an inorganic photoresist. The resist system showed a higher resolution for a successful 130 nm pit patterning than that obtained by an ordinary organic photoresist system. Based on this technology, a read only memory (ROM) disc with a recording capacity of 25.2 GB on a 120-mm-diameter surface was mastered at a high recording speed of 4.92 m/s. The disc showed a reasonable jitter value of 8.0% using a conventional equalizer, 4.6% using a limit equalizer and a push-pull signal using a conventional readout optical system of ¼ 405 nm and NA ¼ 0:85.
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