NRAM Nano Ram Nano-RAM is a proprietary computer memory technology from the company Nantero. It is a type of nonvolatile random access memory based on the mechanical position of carbon nanotubes deposited on a chip-like substrate. In theory the small size of the nanotubes allows for very high density memories. Nantero also refers to it as NRAM in short. Nantero's technology is based on a well-known effect in carbon nanotubes where crossed nanotubes on a flat surface can either be touching or slightly separated in the vertical direction (normal to the substrate) due to Van der Waal's interactions. In Nantero's technology, each NRAM "cell" consists of a number of nanotubes suspended on insulating "lands" over a metal electrode. At rest the nanotubes lie above the electrode "in the air", about 13 nm above it in the current versions, stretched between the two lands. A small dot of gold is deposited on top of the nanotubes on one of the lands, providing an electrical connection, or terminal. A second electrode lies below the surface, about 100 nm away.
Normally, with the nanotubes suspended above the electrode, a small voltage applied between the terminal and upper electrode will result in no current flowing. This represents a "0" state. However if a larger voltage is applied between the two electrodes, the nanotubes will be pulled towards the upper electrode until they touch it. At this point a small voltage applied between the terminal and upper electrode will allow current to flow (nanotubes are conductors), representing a "1" state. The state can be changed by reversing the polarity of the charge applied to the two electrodes.
What causes this to act as a memory is that the two positions of the nanotubes are both stable. In the off position the mechanical strain on the tubes is low, so they will naturally remain in this position and continue to read "0". When the tubes are pulled into contact with the upper electrode a new force, the tiny Van der Waals force, comes into play and attracts the tubes enough to overcome the mechanical strain. Once in this position the tubes will again happily remain there and continue to read "1". These positions are fairly resistant to outside interference like radiation that can erase or flip memory in a conventional DRAM.
NRAMs are built by depositing masses of nanotubes on a pre-fabricated chip containing rows of bar-shaped electrodes with the slightly taller insulating layers between them. Tubes in the "wrong" location are then removed, and the gold terminals deposited on top. Any number of methods can be used to select a single cell for writing, for instance the second set of electrodes can be run in the opposite direction, forming a grid, or they can be selected by adding voltage to the terminals as well, meaning that only those selected cells have a total voltage high enough to cause the flip.
Currently the method of removing the unwanted nanotubes makes the system impractical. The accuracy and size of the epitaxy machinery is considerably "larger" that the cell size otherwise possible. Existing experimental cells have very low densities compared to existing systems, some new method of construction will have to be introduced in order to make the system practical.
Advantages
NRAM has a density, at least in theory, similar to that of DRAM. DRAM consists of a number of capacitors, which are essentially two small metal plates with a thin insulator between them. NRAM is similar, with the terminals and electrodes being roughly 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 to be able to effectively read it. NRAM appears to be limited only by the current state of the art in lithography. This means that NRAM may be able to become much denser than DRAM, meaning that it will also be less expensive, if it becomes possible to control the locations of carbon nanotubes at the scale the semiconductor industry can control the placement of devices on silicon.
Additionally, unlike DRAM, NRAM does not require power to "refresh" it, and will retain its memory even after the power is removed. Additionally the power needed to write to the device is much lower than a DRAM, which has to build up charge on the plates. This means that NRAM will not only compete with DRAM in terms of cost, but will require much less power to run, and as a result also be much faster (write performance is largely determined by the total charge needed). NRAM can theoretically reach performance similar to SRAM, which is faster than DRAM but much less dense, and thus much more expensive.
In comparison with other NVRAM technologies, NRAM has the potential to be even more advantageous. The most common form of NVRAM today is Flash RAM, which combines a bistable transistor circuit known as a flip-flop (also the basis of SRAM) with a high-performance insulator wrapped around one of the transistor's bases. After being written to, the insulator traps electrons in the base electrode, locking it into the "1" state. However, in order to change that bit the insulator has to be "overcharged" to erase any charge already stored in it. This requires high voltage, about 10 volts, much more than a battery can provide. Flash systems thus have to include a "charge pump" that slowly builds up power and then releases it at higher voltage. This process is not only very slow, but degrades the insulators as well. For this reason Flash has a limited lifetime, between 10,000 and 1,000,000 "writes" before the device will no longer operate effectively.
NRAM potentially avoids all of these issues. The read and write process are both "low energy" in comparison to Flash (or DRAM for that matter), meaning that NRAM can result in longer battery life in conventional devices. It may also be much faster to write than either, meaning it may be used to replace both. A modern cell phone will often include Flash memory for storing phone numbers and such, DRAM for higher performance working memory because flash is too slow, and additionally some SRAM in the CPU because DRAM is too slow for its own use. With NRAM all of these may be replaced, with some NRAM placed on the CPU to act as the CPU cache, and more in other chips replacing both the DRAM and Flash.
Nano-RAM, is a proprietary computer memory technology from the company Nantero and NANOMOTOR is invented by University of bologna and California nano systems.NRAM is a type of nonvolatile random access memory based on the mechanical position of carbon nanotubes deposited on a chip-like substrate. In theory the small size of the nanotubes allows for very high density memories. Nantero also refers to it as NRAM in short, but this acronym is also commonly used as a synonym for the more common NVRAM, which refers to all nonvolatile RAM memories.Nanomotor is a molecular motor which works continuously without the consumption of fuels. It is powered by sunlight. The research are federally funded by national science foundation and national academy of science.
Carbon Nanotubes
Carbon nanotubes (CNTs) are a recently discovered allotrope of carbon. They take the form of cylindrical carbon molecules and have novel properties that make them potentially useful in a wide variety of applications in nanotechnology, electronics, optics, and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.
A nanotube is a member of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several millimeters in length. There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).
Manufacturing a nanotube is dependent on applied quantum chemistry, specifically, orbital hybridization. Nanotubes are composed entirely of sp2 bonds, similar to those of graphite. This bonding structure, stronger than the sp3 bonds found in diamond, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp2 bonds for sp3 bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking.
Fabrication Of NRAM
This nano electromechanical memory, called NRAM, is a memory with actual moving parts, with dimensions measured in nanometers. Its carbon nanotube based technology makes advantage of vaanderwaals force to create basic on off junctions of a bit. Vaanderwaals forces interaction between atoms that enable noncovalant binding. They rely on electron attractions that arise only at nano scale levels as a force to be reckoned with. The company is using this property in its design to integrate nanoscale material property with established cmos fabrication technique.
Storage In NRAM
NRAM works by balancing the on ridges of silicon. Under differing electric charges, the tubes can be physically swung into one or two positions representing one and zeros. Because the tubes are very small-under a thousands of time-this movement is very fast and needs very little power, and because the tubes are a thousand times conductive as copper it is very to sense to read back the data. Once in position the tubes stay there until a signal resets them.
The bit itself is not stored in the nano tubes, but rather is stored as the position of the nanotube. Up is bit 0 and down is bit 1.Bits are switched between the states by the application of the electric field.
The technology work by changing the charge placed on a latticework of crossed nanotube. By altering the charges, engineers can cause the tubes to bind together or separate, creating ones and zeros that form the basis of computer memory. If we have two nano tubes perpendicular to each other one is positive and other negative, they will bend together and touch. If we have two similar charges they will repel. These two positions are used to store one and zero. The chip will stay in the same state until you make another change in the electric field. So when you turn the computer off, it doesn't erase the memory .We can keep all the data in the NRAM and gives your computer an instant boot.
