Search results for "Memory"
showing 10 items of 2004 documents
Structural and Magnetic Properties of Epitaxial Ni<sub>2</sub>MnGa Thin Films
2009
We report on the preparation and investigation of epitaxial thin films of the magnetic shape memory alloy Ni2MnGa. For samples close to the stoichiometric composition we find that the phase transformation temperature is affected by the crystallographic orientation. Changes in the crystal structure due to the transformation are observed using temperature-dependent X-ray diffraction. Films with higher manganese content are in the martensitic state at room temperature. Those samples on Al2O3(11-20) reveal the 7-layered orthorhombic structure that allows strains up to 10 %. To avoid blocking of magnetostrictive effects by the substrate, free-standing films are prepared using water-soluble NaCl(…
Ternary and quaternary Ge-S-Se-Sb-Te amorphous chalcogenide thin films for mid-infrared applications
2017
International audience; Chalcogenide materials exhibit a unique portfolio of properties which has led to their wide use for nonvolatile memory applications such as optical storage (CD-RW and DVD-RAM), Conductive Bridging Random Access Memory or Phase Change Random Access Memory (PCRAM). More recently, thanks to huge electronic nonlinearities under electrical field application, chalcogenide glasses are considered as most promising materials to be used as Ovonic Threshold Switching (OTS) selectors [1]. Besides, thanks to high transparency window in the infrared range and large optical nonlinearities [2], chalcogenide alloys offer the opportunity of development of innovative mid-infrared (MIR)…
Threshold Voltage Variability of NROM Memories After Exposure to Ionizing Radiation
2012
Threshold voltage (V-th) behavior of nitride readonly memories (NROMs) was studied after irradiation with photons (gamma-and X-rays), light and heavy ions. Both programmed and nonprogrammed single cells were investigated. The data suggest that two main physical phenomena are contributing to V-th variation and that the V-th loss and the variability can be modeled by a Weibull statistics with a shape parameter k similar to 2.2 regardless of the irradiation species and total dose. The same peculiarities were found in large memory arrays, confirming the results from single-cell studies but with significantly larger statistics. Hence, once the irradiation dose is known, the V-th loss distributio…
Nanocrystal MOS memories obtained by LPCVD deposition of Si nanograins
2001
We have realized silicon quantum dots embedded in SiO2 which act as nano-floating gates of MOS memories. The dots with nanometer sizes have been deposited by LPCVD on a 3nm tunnel oxide. Two processes at a fixed pressure have been explored by varying the temperature. SiH4 with a N2 carrier gas have been used in the former case, SiH4 and H2 have been used in the latter. In both cases a nanocrystalline silicon layer is obtained, with nanocrystals a density higher than 1011 cm-2. The process with H2 carrier gas is more controllable and leads to the formation of nanocrystals with a more regular shape. In both cases the density of grains is able to originate detectable threshold shifts in the me…
Microstructure of freestanding single-crystalline Ni2MnGa thin films
2011
Abstract The complex crystal structure and variant distribution of single-crystalline freestanding Ni–Mn–Ga films was studied in detail using X-ray diffraction in two- and four-circle geometry. Selective chemical etching of a chromium buffer layer facilitates the release of the rigid MgO substrate that would inhibit magnetically induced reorientation (MIR) of variants. The substrate-constrained as well as the freestanding films possess identical crystal structure featuring a seven-layered (pseudo-)orthorhombic modulation (7 M/14 M). Of the 12 different variants observed before and after releasing the film from the substrate, four are predominantly represented. These have the short c -axis a…
Memory effects in MOS capacitors with silicon quantum dots
2001
To form crystalline Si dots embedded in SiO2, we have deposited thin films of silicon-rich oxide (SRO) by plasma-enhanced chemical vapor deposition of SiH4 and O2. Then the materials have been annealed in N2 ambient at temperatures between 950°C and 1100°C. Under such processing, the supersaturation of Si in the amorphous SRO film produces the formation of crystalline Si dots embedded in SiO2. The narrow dot size distributions, analyzed by transmission electron microscopy, are characterized by average grain radii and standard deviations down to about 1 nm. The memory functions of such structures has been investigated in MOS capacitors with a SRO film sandwiched between two thin SiO2 layers …
Peculiar aspects of nanocrystal memory cells: Data and extrapolations
2003
Nanocrystal memory cell are a promising candidate for the scaling of nonvolatile memories in which the conventional floating gate is replaced by an array of nanocrystals. The aim of this paper is to present the results of a thorough investigation of the possibilities and the limitations of such new memory cell. In particular, we focus on devices characterized by a very thin tunnel oxide layer and by silicon nanocrystals formed by chemical vapor deposition. The direct tunneling of the electrons through the tunnel oxide, their storage into the silicon nanocrystals, and furthermore, retention, endurance, and drain turn-on effects, well-known issues for nonvolatile memories, are all investigate…
Nanocrystal MOS with silicon-rich oxide
2001
By electrical measurements we investigate the charge trapping and the charge transport in MOS capacitors in which the gate oxide has been replaced with a silicon rich oxide (SRO) film sandwiched between two thin SiO2 layers.
Electrochemically prepared oxides for resistive switching memories
2018
Redox-based resistive switching memories (ReRAMs) are the strongest candidates for next generation nonvolatile memories. These devices are commonly composed of metal/solid electrolyte/metal junctions, where the solid electrolyte is usually an oxide layer. A key aspect in the ReRAMs development is the solid electrolyte engineering, since it is crucial to tailor the material properties for obtaining excellent switching properties (e.g. retention, endurance, etc.). Here we present an anodizing process as a non vacuum and low temperature electrochemical technique for growing oxides with tailored structural and electronic properties. The effect of the anodizing conditions on the solid state prop…
Transparent amorphous memory cell: A bipolar resistive switching in ZnO/Pr0.7Ca0.3MnO3/ITO for invisible electronics application
2014
Abstract ZnO/Pr0.7Ca0.3MnO3 (ZnO/PCMO) amorphous thin films were grown on an indium-tin-oxide (ITO)/glass by pulsed laser deposition at room temperature. Interestingly, a stable bipolar resistive switching behavior of the ITO/ZnO/PCMO/ITO cell can be longer than 2.5 × 103 cycles. The on/off ratio of switching behaviors is as high as 104. The structure of ITO/ZnO/PCMO/ITO exhibits a high average transparency of 79.6% in the visible range with a maximum transparency of 84.6% at 590 nm wavelength. The conductive mechanism during switching cycling in our structure can be described by a trapped-control space charge limited current behavior. The ZnO/PCMO/ITO/glass structure shows a potential of t…