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48-405: NRAM may refer to: Nano-RAM , a proprietary computer memory technology Landmark Mortgages , formerly NRAM plc, a British asset holding and management company Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title NRAM . If an internal link led you here, you may wish to change

96-466: A Poisson’s ratio of 0.43±0.12 and an average Young’s modulus of 52 KPa. Defining the elastic properties of skin may become the first step in turning elasticity into a clinical tool. For homogeneous isotropic materials simple relations exist between elastic constants that allow calculating them all as long as two are known: Young's modulus represents the factor of proportionality in Hooke's law , which relates

144-658: A battery can provide. Flash systems include a " charge pump " that slowly builds up power and releases it at higher voltage. This process is not only slow, but degrades the insulators. For this reason flash has a limited number of writes before the device will no longer operate effectively. NRAM reads and writes are both "low energy" in comparison to flash (or DRAM for that matter due to "refresh"), meaning NRAM could have longer battery life. It may also be much faster to write than either, meaning it may be used to replace both. Modern phones include flash memory for storing phone numbers, DRAM for higher performance working memory because flash

192-469: A material can be used to calculate the force it exerts under specific strain. where F {\displaystyle F} is the force exerted by the material when contracted or stretched by Δ L {\displaystyle \Delta L} . Hooke's law for a stretched wire can be derived from this formula: where it comes in saturation Note that the elasticity of coiled springs comes from shear modulus , not Young's modulus. When

240-459: A material sample extends under tension or shortens under compression. The Young's modulus directly applies to cases of uniaxial stress; that is, tensile or compressive stress in one direction and no stress in the other directions. Young's modulus is also used in order to predict the deflection that will occur in a statically determinate beam when a load is applied at a point in between the beam's supports. Other elastic calculations usually require

288-513: A material: E = σ ε {\displaystyle E={\frac {\sigma }{\varepsilon }}} Young's modulus is commonly measured in the International System of Units (SI) in multiples of the pascal (Pa) and common values are in the range of gigapascals (GPa). Examples: A solid material undergoes elastic deformation when a small load is applied to it in compression or extension. Elastic deformation

336-453: A non-linear material, the response will be linear, but if very high stress or strain is applied to a linear material, the linear theory will not be enough. For example, as the linear theory implies reversibility , it would be absurd to use the linear theory to describe the failure of a steel bridge under a high load; although steel is a linear material for most applications, it is not in such a case of catastrophic failure. In solid mechanics ,

384-462: A non-woven fabric matrix of carbon nanotubes (CNTs), crossed nanotubes can either be touching or slightly separated depending on their position. When touching, the carbon nanotubes are held together by Van der Waals forces . Each NRAM "cell" consists of an interlinked network of CNTs located between two electrodes as illustrated in Figure 1. The CNT fabric is located between two metal electrodes, which

432-554: A small amount of a ferro-electric material to a DRAM cell. The state of the field in the material encodes the bit in a non-destructive format. FeRAM has advantages of NRAM, although the smallest possible cell size is much larger than for NRAM. FeRAM is used in applications where the limited number of writes of flash is an issue. FeRAM read operations are destructive, requiring a restoring write operation afterwards. Other more speculative memory systems include magnetoresistive random-access memory (MRAM) and phase-change memory (PRAM). MRAM

480-460: A spring is stretched, its wire's length doesn't change, but its shape does. This is why only the shear modulus of elasticity is involved in the stretching of a spring. The elastic potential energy stored in a linear elastic material is given by the integral of the Hooke's law: now by explicating the intensive variables: This means that the elastic potential energy density (that is, per unit volume)

528-421: A three-terminal semiconductor device where a third terminal is used to switch the memory cell between memory states. The second generation NRAM technology is based on a two-terminal memory cell. The two-terminal cell has advantages such as a smaller cell size, better scalability to sub-20 nm nodes (see semiconductor device fabrication ), and the ability to passivate the memory cell during fabrication. In

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576-482: Is a calculable material property which is dependent on the crystal structure (for example, BCC, FCC). φ 0 {\displaystyle \varphi _{0}} is the electron work function at T=0 and β {\displaystyle \beta } is constant throughout the change. Young's modulus is calculated by dividing the tensile stress , σ ( ε ) {\displaystyle \sigma (\varepsilon )} , by

624-637: Is based on a grid of magnetic tunnel junctions . MRAM's reads the memory using the tunnel magnetoresistance effect, allowing it to read the memory both non-destructively and with very little power. Early MRAM used field induced writing, reached a limit in terms of size, which kept it much larger than flash devices. However, new MRAM techniques might overcome the size limitation to make MRAM competitive even with flash memory. The techniques are Thermal Assisted Switching (TAS), developed by Crocus Technology , and Spin-transfer torque on which Crocus, Hynix , IBM , and other companies were working in 2009. PRAM

672-494: Is based on a technology similar to that in a writable CD or DVD, using a phase-change material that changes its magnetic or electrical properties instead of its optical ones. The PRAM material itself is scalable but requires a larger current source. Nantero was founded in 2001, and headquartered in Woburn, Massachusetts . Due to the massive investment in flash semiconductor fabrication plants , no alternative memory has replaced flash in

720-541: Is defined and etched by photolithography , and forms the NRAM cell. The NRAM acts as a resistive non-volatile random-access memory (RAM) and can be placed in two or more resistive modes depending on the resistive state of the CNT fabric. When the CNTs are not in contact the resistance state of the fabric is high and represents an "off" or "0" state. When the CNTs are brought into contact,

768-531: Is faster than DRAM but much less dense, and thus much more expensive. Compared with other non-volatile random-access memory (NVRAM) technologies, NRAM has several advantages. In flash memory , the common form of NVRAM, each cell resembles a MOSFET transistor with a control gate (CG) modulated by a floating gate (FG) interposed between the CG and the FG. The FG is surrounded by an insulating dielectric, typically an oxide. Since

816-548: Is given by: or, in simple notation, for a linear elastic material: u e ( ε ) = ∫ E ε d ε = 1 2 E ε 2 {\textstyle u_{e}(\varepsilon )=\int {E\,\varepsilon }\,d\varepsilon ={\frac {1}{2}}E{\varepsilon }^{2}} , since the strain is defined ε ≡ Δ L L 0 {\textstyle \varepsilon \equiv {\frac {\Delta L}{L_{0}}}} . In

864-407: Is loaded parallel to the fibers (along the grain). Other such materials include wood and reinforced concrete . Engineers can use this directional phenomenon to their advantage in creating structures. The Young's modulus of metals varies with the temperature and can be realized through the change in the interatomic bonding of the atoms, and hence its change is found to be dependent on the change in

912-426: Is removed. Thus the power needed to write and retain the memory state of the device is much lower than DRAM, which has to build up charge on the cell plates. This means that NRAM might compete with DRAM in terms of cost, but also require less power, and as a result also be much faster because write performance is largely determined by the total charge needed. NRAM can theoretically reach performance similar to SRAM, which

960-406: Is reversible, meaning that the material returns to its original shape after the load is removed. At near-zero stress and strain, the stress–strain curve is linear , and the relationship between stress and strain is described by Hooke's law that states stress is proportional to strain. The coefficient of proportionality is Young's modulus. The higher the modulus, the more stress is needed to create

1008-579: Is too slow, and some SRAM for even higher performance. Some NRAM could be placed on the CPU to act as the CPU cache , and more in other chips replacing both the DRAM and flash. NRAM is one of a variety of new memory systems, many of which claim to be " universal " in the same fashion as NRAM – replacing everything from flash to DRAM to SRAM. An alternative memory ready for use is ferroelectric RAM (FRAM or FeRAM). FeRAM adds

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1056-465: The Latin root term modus , which means measure . Young's modulus, E {\displaystyle E} , quantifies the relationship between tensile or compressive stress σ {\displaystyle \sigma } (force per unit area) and axial strain ε {\displaystyle \varepsilon } (proportional deformation) in the linear elastic region of

1104-598: The engineering extensional strain , ε {\displaystyle \varepsilon } , in the elastic (initial, linear) portion of the physical stress–strain curve : E ≡ σ ( ε ) ε = F / A Δ L / L 0 = F L 0 A Δ L {\displaystyle E\equiv {\frac {\sigma (\varepsilon )}{\varepsilon }}={\frac {F/A}{\Delta L/L_{0}}}={\frac {FL_{0}}{A\,\Delta L}}} where Young's modulus of

1152-464: The linear elastic region of the material. Although Young's modulus is named after the 19th-century British scientist Thomas Young , the concept was developed in 1727 by Leonhard Euler . The first experiments that used the concept of Young's modulus in its modern form were performed by the Italian scientist Giordano Riccati in 1782, pre-dating Young's work by 25 years. The term modulus is derived from

1200-421: The CNT layer so that the top metal electrode is patterned and etched during the definition of the NRAM cell. Following the dielectric passivation and fill of the array, the top metal electrode is exposed by etching back the overlying dielectric using a smoothing process such as chemical-mechanical planarization . With the top electrode exposed, the next level of metal wiring interconnect is fabricated to complete

1248-424: The CNTs (or a portion of them) are in contact and remain contacted due to Van der Waals forces between the CNTs, resulting in a low resistance or high current measurement state between the top and bottom electrodes. Note that other sources of resistance such as contact resistance between electrode and CNT can be significant and also need to be considered. To switch the NRAM between states, a small voltage greater than

1296-531: The FG is electrically isolated by the surrounding dielectric, any electrons placed on the FG will be trapped on the FG which screens the CG from the channel of the transistor and modifies the threshold voltage (VT) of the transistor. By writing and controlling the amount of charge placed on the FG, the FG controls the conduction state of the MOSFET flash device depending on the VT of the cell selected. The current flowing through

1344-499: The MOSFET channel is sensed to determine the state of the cell forming a binary code where a 1 state (current flow) when an appropriate CG voltage is applied and a 0 state (no current flow) when the CG voltage is applied. After being written to, the insulator traps electrons on the FG, locking it into the 0 state. However, in order to change that bit, the insulator has to be "overcharged" to erase any charge already stored in it. This requires higher voltage, about 10 volts, much more than

1392-431: The NRAM array. Figure 3 illustrates one circuit method to select a single cell for writing and reading. Using a cross-grid interconnect arrangement, the NRAM and driver, (the cell), forms a memory array similar to other memory arrays. A single cell can be selected by applying the proper voltages to the word line (WL), bit line (BL), and select lines (SL) without disturbing the other cells in the array. Alternatively between

1440-405: The NRAM cell is in contact with the underlying via (electronics) connecting the cell to the driver. The bottom electrode may be fabricated as part of the underlying via or it may be fabricated simultaneously with the NRAM cell, when the cell is photolithographically defined and etched. Before the cell is photolithographically defined and etched, the top electrode is deposited as a metal film onto

1488-515: The NRAM cell is in the 1 state, applying a voltage greater than the read voltage will generate CNT phonon excitations with sufficient energy to separate the CNT junctions. This is the phonon driven RESET operation. The CNTs remain in the OFF or high resistance state due to the high mechanical stiffness ( Young's Modulus 1 TPa) with an activation energy (E a ) much greater than 5 eV. Figure 2 illustrates both states of an individual pair of CNTs involved in

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1536-466: The bottom electrode and top metal layer they may be two layers of CNTs: one with uniformly arranged CNTs, and another with randomly arranged CNTs. The uniformly arranged CNTs are used to protect the randomly arranged CNTs from the top metal layer. NRAM has a density, at least in theory, similar to that of DRAM. DRAM includes capacitors, which are essentially two small metal plates with a thin insulator between them. NRAM has terminals and electrodes roughly

1584-411: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=NRAM&oldid=941574589 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Nano-RAM The first generation Nantero NRAM technology was based on

1632-455: The market. Young%27s Modulus Young's modulus (or Young modulus ) is a mechanical property of solid materials that measures the tensile or compressive stiffness when the force is applied lengthwise. It is the modulus of elasticity for tension or axial compression . Young's modulus is defined as the ratio of the stress (force per unit area) applied to the object and the resulting axial strain (displacement or deformation) in

1680-414: The marketplace, despite predictions as early as 2003 of the impending speed and density of NRAM. In 2005, NRAM was promoted as universal memory , and Nantero predicted it would be in production by the end of 2006. In August 2008, Lockheed Martin acquired an exclusive license for government applications of Nantero's intellectual property. By early 2009, Nantero had 30 US patents and 47 employees, but

1728-411: The read voltage is applied between top and bottom electrodes. If the NRAM is in the 0 state, the voltage applied will cause an electrostatic attraction between the CNTs close to each other causing a SET operation. After the applied voltage is removed, the CNTs remain in a 1 or low resistance state due to physical adhesion (Van der Waals force) with an activation energy (E a ) of approximately 5eV. If

1776-407: The resistance state of the fabric is low and represents an "on" or "1" state. NRAM acts as a memory because the two resistive states are very stable. In the 0 state, the CNTs (or a portion of them) are not in contact and remain in a separated state due to the stiffness of the CNTs resulting in a high resistance or low current measurement state between the top and bottom electrodes. In the 1 state,

1824-466: The same amount of strain; an idealized rigid body would have an infinite Young's modulus. Conversely, a very soft material (such as a fluid) would deform without force, and would have zero Young's modulus. Material stiffness is a distinct property from the following: Young's modulus enables the calculation of the change in the dimension of a bar made of an isotropic elastic material under tensile or compressive loads. For instance, it predicts how much

1872-446: The same in all orientations. However, metals and ceramics can be treated with certain impurities, and metals can be mechanically worked to make their grain structures directional. These materials then become anisotropic , and Young's modulus will change depending on the direction of the force vector. Anisotropy can be seen in many composites as well. For example, carbon fiber has a much higher Young's modulus (is much stiffer) when force

1920-519: The same size as the plates in a DRAM, the nanotubes between them being so much smaller they add nothing to the overall size. However it seems there is a minimum size at which a DRAM can be built, below which there is simply not enough charge being stored on the plates. NRAM appears to be limited only by lithography . This means that NRAM may be able to become much denser than DRAM, perhaps also less expensive. Unlike DRAM, NRAM does not require power to "refresh" it, and will retain its memory even after power

1968-420: The slope of the stress–strain curve at any point is called the tangent modulus . It can be experimentally determined from the slope of a stress–strain curve created during tensile tests conducted on a sample of the material. Young's modulus is not always the same in all orientations of a material. Most metals and ceramics, along with many other materials, are isotropic , and their mechanical properties are

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2016-412: The stress and the strain. However, Hooke's law is only valid under the assumption of an elastic and linear response. Any real material will eventually fail and break when stretched over a very large distance or with a very large force; however, all solid materials exhibit nearly Hookean behavior for small enough strains or stresses. If the range over which Hooke's law is valid is large enough compared to

2064-416: The switch operation. Due to the high activation energy (> 5eV) required for switching between states, the NRAM switch resists outside interference like radiation and operating temperature that can erase or flip conventional memories like DRAM . NRAMs are fabricated by depositing a uniform layer of CNTs onto a prefabricated array of drivers such as transistors as shown in Figure 1. The bottom electrode of

2112-662: The temperature increases, the Young's modulus decreases via E ( T ) = β ( φ ( T ) ) 6 {\displaystyle E(T)=\beta (\varphi (T))^{6}} where the electron work function varies with the temperature as φ ( T ) = φ 0 − γ ( k B T ) 2 φ 0 {\displaystyle \varphi (T)=\varphi _{0}-\gamma {\frac {(k_{B}T)^{2}}{\varphi _{0}}}} and γ {\displaystyle \gamma }

2160-471: The typical stress that one expects to apply to the material, the material is said to be linear. Otherwise (if the typical stress one would apply is outside the linear range), the material is said to be non-linear. Steel , carbon fiber and glass among others are usually considered linear materials, while other materials such as rubber and soils are non-linear. However, this is not an absolute classification: if very small stresses or strains are applied to

2208-463: The use of one additional elastic property, such as the shear modulus G {\displaystyle G} , bulk modulus K {\displaystyle K} , and Poisson's ratio ν {\displaystyle \nu } . Any two of these parameters are sufficient to fully describe elasticity in an isotropic material. For example, calculating physical properties of cancerous skin tissue, has been measured and found to be

2256-600: The work function of the metal. Although classically, this change is predicted through fitting and without a clear underlying mechanism (for example, the Watchman's formula), the Rahemi-Li model demonstrates how the change in the electron work function leads to change in the Young's modulus of metals and predicts this variation with calculable parameters, using the generalization of the Lennard-Jones potential to solids. In general, as

2304-1303: Was still in the engineering phase. In May 2009, a radiation-resistant version of NRAM was tested on the STS-125 mission of the US Space Shuttle Atlantis . The company was quiet until another round of funding and collaboration with the Belgian research center imec was announced in November 2012. Nantero raised a total of over $ 42 million through the November 2012 series D round. Investors included Charles River Ventures , Draper Fisher Jurvetson , Globespan Capital Partners , Stata Venture Partners and Harris & Harris Group . In May 2013, Nantero completed series D with an investment by Schlumberger . EE Times listed Nantero as one of "10 top startups to watch in 2013". 31 Aug 2016: Two Fujitsu semiconductor businesses are licensing Nantero NRAM technology with joint Nantero–Fujitsu development to produce chips, announced in 2018. They are announced to have several thousand times faster rewrites and many thousands of times more rewrite cycles than embedded flash memory. As of 2024, these products are still announced but have not reached

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