Chapter 1 Web viewNanotechnology is very ... storing fuels such as hydrogen or methanol for use in fuel cells and they make good ... be used to select a single cell for

NANO-RAM

ABSTRACT

NRAM, short for nano-RAM or nanotube-based/nonvolatile random access memory, is a new

memory storage technology owned by the company Nantero. The technology blends together

tiny carbon nanotubes with conventional semiconductors. Because the memory-containing

elements, nanotubes, are so small, NRAM technology will achieve very high memory densities:

at least 10-100 times our current best. NRAM will operate electromechanically rather than just

electrically, setting it apart from other memory technologies as a nonvolatile form of memory,

meaning data will be retained even when the power is turned off. The creators of the technology

claim it has the advantages of all the best memory technologies with none of the disadvantages,

setting it up to be the universal medium for memory in the future.

Carbon nanotubes are small tubes of carbon atoms, only a few nanometers wide --

1/100,000th the width of a human hair. The wall of a carbon nanotube is composed of a single

carbon atom. Nanotubes are as rigid as diamond and conduct electricity as well as copper. In

recent years, the cost of mass-producing nanotubes has plummeted.

By creating a thin "fabric" of nanotubes and arranging them in junctions on

a silicon wafer embedded with conventional circuitry, a hybrid electro-mechanical memory

system can be created. A nanotube configured in one position would indicate a 1, and in another

position could indicate a 0. Manufacturing begins when a thin layer of nanotubes are spread

across the surface of the wafer, then functionally unnecessary nanotubes are removed using

conventional lithography techniques.

Currently the method of removing the unwanted nanotubes makes the system impractical.

The accuracy and size of the epitaxial 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.

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INDEX

1. Introduction ……..…………………………………………..3

2. Nanotechnology ………………………………………….....8

3. Carbon Nano Tube …………….…………………………..12

4. Nano-Ram……………….…………………………………21

5. Advantages ……………………….………………………..29

6. Disadvantages……………………………………………...27

7. Application………………………………….……………..30

8. Comparison with other proposed systems ………………....31

9. Future Scope……………………………………………….32

10.Conclusion…………………………….…….……………..33

11.References & Bibliography………………………………..34

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Chapter 1

INTRODUCTIONToday the world is of digital. All the electronic devices are formalized to manipulate the digital

data. The back-bone of today’s research and development “The Computer” is also a digital

device. Digital by name deals with digits and all the gadgets available today (like PDA’s,

laptops, etc…) need to manipulate the digital data. To manipulate first we have to store it at a

place. Thus MEMORY in today’s world plays a key role and a constant research to improve the

memory in today’s electronic gadgets is ON.

RAM (random access memory) is the main storage device in all digital systems. The

speed of the system mainly depends on how speed and vast the RAM is. Today with increasing

power need of man even the POWER consumed is also a major part to look at. By generations

RAM also had under gone many changes. Some of the versions of RAM’s which are in use are

DRAM, SRAM and FLASH MEMORY. DRAM (dynamic RAM) although has a capability to

hold large amounts of data it is slower and volatile.

SRAM (static RAM) even superior to DRAM in speed but less dense. Even this is

volatile in nature. Overcoming the volatile nature of these two, FLASH MEMORY is the latest

of today random access memories. Even this fails in power saving. Overcoming all these failures

of above mentioned RAM’s , researchers developed a new RAM which unlike the semiconductor

technology alone used by the former, uses a combination of NANOTECHNOLOGY and

contemporary SEMICONDUCTOR TECHNOLOGY and is

given the name NRAM.

Fig 1.1 NANO RAM

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Greek prefix which means dwarf. In science this prefix denotes a fraction of 10-9 a given unit.

For instance 1nm = 10-9m

RAM (Random-Access Memory) is a form of computer data storage. It takes the form of integrated circuits that allow stored volatile

data to be accessed in random order.

NANO-RAM

1.1 RAM (Random Access Memory):

It is a form of computer data storage. It takes the form of integrated circuits that allow

stored volatile data to be accessed in random order. By contrast, storage devices such as

magnetic discs and optical discs rely on the physical movement of the recording medium

or a reading head. In these devices, the movement takes longer than data transfer, and the

retrieval time varies based on the physical location of the next item.

The word RAM is often associated with volatile types of memory (such as DRAM

memory modules), where the information is lost after the power is switched off. Many

other types of memory are RAM too, including most types of ROM and a type of flash

memory called NOR Flash.

1.2 Types of RAM:

There are mainly two types of RAM

1.2.1 DRAM:

Dynamic RAM is the most common type of memory in use today. Inside a dynamic RAM

chip, each memory cell holds one bit of information and is made up of two parts: a

transistor and a capacitor. These are, of course, extremely small transistors and capacitors

so that millions of them can fit on a single memory chip. The capacitor holds the bit of

information -- a 0 or a 1. The transistor acts as a switch that lets the control circuitry on the

memory chip read the capacitor or change its state.

A capacitor is like a small bucket that is able to store electrons. To store a 1 in the

memory cell, the bucket is filled with electrons. To store a 0, it is emptied. The problem

with the capacitor's bucket is that it has a leak. In a matter of a few milliseconds a full

bucket becomes empty. Therefore, for dynamic memory to work, either the CPU or the

memory controller has to come along and recharge all of the capacitors holding a 1 before

they discharge. To do this, the memory controller reads the memory and then writes it right

back. This refresh operation happens automatically thousands of times per second.

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This refresh operation is where dynamic RAM gets its name. Dynamic RAM has to

be dynamically refreshed all of the time or it forgets what it is holding. The downside of all

of this refreshing is that it takes time and slows down the memory.

1.2.2 SRAM:

Static RAM uses a completely different technology. In static RAM, a form of flip-flop

holds each bit of memory. A flip-flop for a memory cell takes 4 or 6 transistors along with

some wiring, but never has to be refreshed. This makes static RAM significantly faster

than dynamic RAM. However, because it has more parts, a static memory cell takes a lot

more space on a chip than a dynamic memory cell. Therefore you get less memory per

chip, and that makes static RAM a lot more expensive. So static RAM is fast and

expensive, and dynamic RAM is less expensive and slower. Therefore static RAM is used

to create the CPU's speed-sensitive cache, while dynamic RAM forms the larger system

RAM space.

1.3 There are some other types of RAM:

There are many different types of RAM which have appeared over the years and it is often

difficult knowing the difference between them both performance wise and visually

identifying them. This article tells a little about each RAM type, what it looks like and how

it performs.

1.3.1 FPM RAMFPM RAM, which stands for Fast Page Mode RAM is a type of Dynamic RAM (DRAM).

The term “Fast Page Mode comes from the capability of memory being able to access data

that is on the same page and can be done with less latency. Most 486 and Pentium based

systems from 1995 and earlier use FPM Memory.

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fig 1.2 FPM RAM

1.3.2 EDORAM EDO RAM, which stands for “Extended Data Out RAM came out in 1995 as a new type

of memory available for Pentium based systems. EDO is a modified form of FPM RAM

which is commonly referred to as “Hyper Page Mode. Extended Data Out refers to fact that

the data output drivers on the memory module are not switched off when the memory

controller removes the column address to begin the next cycle, unlike FPM RAM. Most

early Penitum based systems use EDO.

fig 1.3 EDO RAM

1.3.3 SDRAM SDRAM, which is short for Synchronous DRAM is a type of DRAM that runs in

synchronization with the memory bus. Beginning in 1996 most Intel based chipsets began

to support SDRAM which made it a popular choice for new systems in 2001.

SDRAM is capable of running at 133MHz which is about three times faster than FPM

RAM and twice as fast as EDO RAM. Most Pentium or Celeron systems purchased in

1999 have SDRAM.

fig 1.4 SD RAM

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1.3.4 DDRRAMDDR RAM, which stands for “Double Data Rate which is a type of SDRAM and appeared

first on the market around 2001 but didn’t catch on until about 2001 when the mainstream

motherboards started supporting it. The difference between SDRAM and DDR RAM is

that instead of doubling the clock rate it transfers data twice per clock cycle which

effectively doubles the data rate. DDRRAM has become mainstream in the graphics card

market and has become the memory standard.

fig 1.5 DDR RAM

1.4 Difference between DDR1, DDR2 & DDR3 types of RAM?

In computing, a computer bus operating with double data rate, transfers data on both the rising

and falling edges of the clock signal. This is also known as double pumped and double transition.

DDR2 stores memory in memory cells that are activated with the use of a clock signal to

synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer

data both on the rising and falling edge of the clock (a technique called "dual pumping"). The

key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of

the memory cells, so four words of data can be transferred per memory cell cycle.

DDR3 memory comes with a promise of a power consumption reduction of 30%

compared to current commercial DDR2 modules due to DDR3's 1.5 V supply voltage, compared

to DDR2's 1.8 V or DDR's 2.5 V. This supply voltage works well with the 90 nm fabrication

technology used for most DDR3 chips. Some manufacturers further propose to use "dual-gate"

transistors to reduce leakage of current.

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Chapter 2

NANOTECHNOLOGY

Nanotechnology, shortened to "nanotech", is the study of the controlling of matter on an

atomic and molecular scale. Generally nanotechnology deals with structures of the size 100

nanometers or smaller in at least one dimension, and involves developing materials or

devices within that size. Nanotechnology is very diverse, ranging from extensions of

conventional device physics to completely new approaches based upon molecular self-

assembly, from developing new materials with dimensions on the nanoscale to

investigating whether we can directly control matter on the atomic scale.

There has been much debate on the future implications of nanotechnology.

Nanotechnology has the potential to create many new materials and devices with a vast

range of applications, such as in medicine, electronics and energy production. On the other

hand, nanotechnology raises many of the same issues as with any introduction of new

technology, including concerns about the toxicity and environmental impact of

nonmaterial, and their potential effects on global economics, as well as speculation about

various doomsday scenarios. These concerns have led to a debate among advocacy groups

and governments on whether special regulation of nanotechnology is warranted.

2.1 History of Nanotechnology

The first use of the concepts found in 'nano-technology' (but pre-dating use of that name)

was in "There's Plenty of Room at the Bottom," a talk given by physicist Richard Feynman

at an American Physical Society meeting at Caltech on December 29, 1959. Feynman

described a process by which the ability to manipulate individual atoms and molecules

might be developed, using one set of precise tools to build and operate another

proportionally smaller set, and so on down to the needed scale. In the course of this, he

noted, scaling issues would arise from the changing magnitude of various physical

phenomena: gravity would become less important, surface tension and Vander Waals

attraction would become increasingly more significant, etc. This basic idea appeared

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plausible, and exponential assembly enhances it with parallelism to produce a useful

quantity of end products. The term "nanotechnology" was defined by Tokyo Science

University Professor Norio Taniguchi in a 1974 paper as follows:

"'Nano-technology' mainly consists of the processing of, separation, consolidation, and

deformation of materials by one atom or by one molecule." In the 1980s the basic idea of

this definition was explored in much more depth by Dr. K. Eric Drexler, who promoted the

technological significance of nano-scale phenomena and devices through speeches and the

books Engines of Creation: The Coming Era of Nanotechnology (1986) and Nanosystems:

Molecular Machinery, Manufacturing, and Computation, and so the term acquired its

current sense. Engines of Creation: The Coming Era of Nanotechnology is considered the

first book on the topic of nanotechnology. Nanotechnology and nanoscience got started in

the early 1980s with two major developments; the birth of cluster science and the invention

of the scanning tunneling microscope (STM). This development led to the discovery of

fullerenes in 1985 and carbon nanotubes a few years later. In another development, the

synthesis and properties of semiconductor nanocrystals was studied; this led to a fast

increasing number of metal and metal oxide nanoparticles and quantum dots. The atomic

force microscope (AFM or SFM) was invented six years after the STM was invented. In

2000, the United States National Nanotechnology Initiative was founded to coordinate

Federal nanotechnology research and development and is evaluated by the President's

Council of Advisors on Science and Technology.

Electronics is fuelled by miniaturization. According to Drexler product can be made by

combining atom by atom or molecule by molecule with the help of programmed microscopic

robotic arms. It is possible because each atom is identical to any other atom of its flavor and has

a remarkable attribute of sticking to each other. Nanotechnology’s goal is a device called

“Universal Assembler” that takes raw atoms in one side and delivers consumer goods out the

other. It should have following properties:

1. Fractional atomic diameter accuracy.

2. Capability to execute finely controlled motions to transfer one or a few atom in a

guided chemical reaction.

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By building objects on such a fine scale, we could make extraordinary things from

ordinary matter

2.2 The Motivation

Why do companies want to get small? Because getting small means getting smarter, more

powerful and more economical. Consider the first computer’s developed in the 1940’s. They

were the size of a large room, were very expensive to build, required virtually constant

maintenance, needed a considerable amount of electricity to power, and were useable only by a

handful of highly trained specialists. Compare that to today’s common laptop computers. They

are millions of times faster and more powerful than the first computers, thousands of times

smaller, a mere fraction of the cost, requires virtually no maintenance, run on very little

electricity and are useable by almost anyone.

Miniaturization has led to an exponential growth in computer’s effect on our everyday

lives because:

(1) Processing power has enabled them to do an almost unthinkable amount of work almost

instantaneously; and

(2) Large percentages of our population and businesses are able to computers as diverse tools

because they are easy to use and relatively inexpensive to build and operate. Virtually all of the

major advances in the electronic industries, from the vacuum tube to modern computer chip, are

a direct result of miniaturization and utilizing new materials. Nanotechnology is the next step in

the evolution of miniaturization. It increases the value of existing products and opens the door

to new technologies and products.

2.3 Theory

At the simplest level, nanotechnology is the manipulation single atoms and molecules to create

objects that can be smaller than 100 nanometers. A nanometer is a billionth of a meter, which is

about a hundred-thousandth of the diameter of a human hair, or 10 times the diameter of a

hydrogen atom.

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Manufactured products are made from atoms. The properties of those products depend on

how those atoms are arranged. If we rearrange the atoms in coal we can make diamond. If we

rearrange the atoms in sand (and add a few other trace elements) we can make computer chips.

If we rearrange the atoms in dirt, water and air, we can make potatoes.

There are two more concepts commonly associated with Nanotechnology:

1. Positional assembly

2. Self replication

Positional assembly refers to the arrangement of molecules so as to get the right

molecular parts in the right places. The need for positional assembly implies an interest in

molecular robotics e.g., robotic devices that are molecular both in their size and precision.

These molecular scale positional devices are likely to resemble very small versions of their

everyday macroscopic counterparts.

The self replicating systems are able both to make copies of themselves and to

manufacture useful products. If we can design and build one such system the manufacturing

costs for more such systems and the products they make (assuming they can make copies of

themselves in some reasonably inexpensive environment) will be very low.

You won’t think about installing Microsoft Office anymore. You’ll think about growing

software. The line is blurring in several ways. Scientists are learning to imitate biological

patterns; biological entities are being used in technology products; and in the distant future,

nanomachines may be circulating through our bloodstreams, attacking tumours and dispersing

medicine.

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Chapter 3

CARBON NANOTUBES

The term nanotubes is normally used to refer to the carbon nanotubes, which has received

enormous attention from researchers over the last few years and promises, along with close

relatives such as the nanohorn, a host of interesting applications. There are many others types of

nanotubes, from various inorganic kinds such as, those made from boron nitride, to organic ones,

such as those made from self-assembling cyclic peptides (proteins components) or from naturally

occurring heat shock proteins(extracted from bacteria that thrive in extreme environments).

However, carbon nanotubes excites the most interest, promise the greatest variety of application

and currently appear to have by far the highest commercial potential.

Carbon nanotubes were discovered in 1991 by Sumio Iijima of NEC and are effectively

long, thin cylinders of graphite, which you will be familiar with as the material in a pencil or as

the basis of some lubricants. Graphite is made up of layers of carbon atoms arranged in a

hexagonal lattice, like chicken wire. Though the chicken wire structure itself is very strong, the

layers themselves sure not chemically bonded to each other but held together by weak forces

called Vander Waals. It is the sliding across each other of these layers that gives graphite its

lubricating qualities and makes the mark on a piece of paper as you draw your pencil over it.

Now imagine taking one of these sheets of chicken wire and rolling it up into a cylinder

and joining the loose wore ends. The result is a tube that was once described by Richard Smalley

(who shared the Nobel Prize for the discovery of a related form of carbon called

buckminsterfullerene) as nanotube.

“In one direction….the strongest damn thing you’ll ever make in this universe”. In

addition to their remarkable strength, this is usually quoted, that nanotube is 100 times stronger

than steel & one-sixth of its weight, if steel is drawn with same size as that of nanotube (this is

tensile strength-the ability to withstand a stretching force without breaking), carbon nanotubes

have shown a surprising array of other properties. They can conduct heat as efficiently as

diamond, conduct electricity as efficiently as copper, yet also be semiconducting (like the

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materials that make up the chips in our computers). They can produce streams of electrons very

efficiently (field emission), which can be used to create light in displays for televisions or

computers, or even in domestic lighting, and they can enhance the fluorescence of materials they

are close to. Their electrical properties can be made to change in the presence can act like

miniature springs and they can even be stuffed with other material. Nanotubes and their variants

hold promise for storing fuels such as hydrogen or methanol for use in fuel cells and they make

good support for catalysts.

3.1 Structure of CARBON NANOTUBES

Carbon nanotubes (CNTs; also known as buck tubes) are allotropes of carbon with a cylindrical

nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to

132,000,000:1] which is significantly larger than any other material. These

cylindrical carbon molecules have novel properties that make them potentially useful in many

applications in nanotechnology, electronics, optics and other fields of materials science, as well

as potential uses in architectural fields. They exhibit extraordinary strength and

unique electrical properties, and are efficient thermal conductors.

The nature of the bonding of a nanotube is described by applied quantum chemistry,

specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely

of sp2 bonds, similar to those of graphite. This bonding structure, which is stronger than

the sp3 bonds found in diamonds, provides the molecules with their unique strength. Nanotubes

naturally align themselves into "ropes" held together by Van der Waals forces.

Since carbon nanotubes were discovered on accident by Sumio Iijima in 1991 during

another experiment, hundreds of studies have been started and dedicated to achieving a better

understanding of the structure of carbon nanotubes. Although the structure of carbon nanotubes

has been extensively studied by researchers and scientists in a wide variety of fields including

materials science, architecture, agriculture and engineering, the full implications of this tiny

microscopic wonder are still locked away in its unique natural creation, varied structural

components and its ability to be both immensely flexible as well as incredibly strong.

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Carbon comes in many forms. Two well-known forms of carbon are graphite and

diamond. Graphite and diamond have drastically different mechanical properties such as

hardness. Diamond is one of the hardest materials known to man. It can cut through glass.

Fig.3.1 structure of CNT

Graphite, on the other hand, is a very soft material, used in pencil lead. The difference in

properties is due to the structure of the atoms and their bonds in the material, also known as the

materials crystal structure. Graphite is made up of stacked sheets of

hexagons with a carbon atom at each corner of the hexagon, and looks much like chicken wire.

These sheets are stacked one on top of the other, but easily slip and slide. Diamond has a

tetragonal crystal structure with very few slip planes.

Carbon nanotubes are a fairly new form of carbon. A carbon nanotube structure looks

like sheets of graphite that have been rolled up to form small tubes. This small difference in

structure leads to a much stronger, stiffer material. Carbon nanotubes have a diameter of 1 to 10

nanometers, yet they are 50 times stronger than steel.

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such as electrical and thermal conductivity, strength, stiffness, and toughness. No other

element in the periodic table bonds to itself in an extended network with the strength of the

carbon-carbon bond. The delocalised pi-electron donated by each atom is free to move about

the entire structure, rather than stay home with its donor atom, giving rise to the first molecule

with metallic-type electrical conductivity. The high-frequency carbon-carbon bond vibrations

provide an intrinsic thermal conductivity higher than even diamond.

In most materials, however, the actual observed material properties - strength, electrical

conductivity, etc. - are degraded very substantially by the occurrence of defects in their

structure. For example, high strength steel typically fails at about 1% of its theoretical breaking

strength. Buckytubes, however, achieve values very close to their theoretical limits because of

their perfection of structure - their molecular perfection. This aspect is part of the unique story

of buckytubes.

Buckytubes are an example of true nanotechnology: only a nanometre in diameter, but

molecules that can be manipulated chemically and physically. They open incredible

applications in materials, electronics, chemical processing and energy management.

3.2 Basic Structure

Buck tubes are single-wall carbon nanotubes, in

which a single layer of graphite - graphene - is rolled

up into a seamless tube. Graphene consists of a

hexagonal structure like chicken wire. If you imagine

rolling up graphene or chicken wire into a seamless

tube, this can be accomplished in various ways. For

example, carbon-carbon bonds (the wires in chicken

wire) can be parallel or perpendicular to the tube axis,

resulting in a tube where the hexagons circle the tube

like a belt, but are oriented differently. Alternatively, the carbon-carbon fig

3.2 basic structure

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bonds need not be either parallel or perpendicular, in which case the hexagons will spiral

around the tube with a pitch depending on how the tube is wrapped. Fig 7 illustrates these

point.

Carbon nanotubes appear to be sheets of graphite cells that have been mended together to look

almost like a latticework fence and then rolled up in a tube shape. Although this is a simple

explanation for the look of the structure of carbon nanotubes, this is not how carbon nanotubes

are created, nor does it explain their immense strength or other incredible structural abilities.

3.3

Classification of CARBON NANOTUBES

fig 3.3 classification of CNT

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One of the major classifications of carbon nanotubes is into singled-walled varieties (SWNT’s)

which have a single cylinder wall and multi-walled varieties (MWNT’s) which have cylinders

within cylinders.

The length of both type vary greatly, depending upon on the way they are made and

are generally nanoscopic rather than microscopic i.e. greater than 100 micrometers. The aspect

ratio (length divided by diameter) is typically greater than100 and can be up to 10,000, but

recently even this was made to look small. IN May 2002, SWNT strand were made in which the

SWNT’s were claimed to be as long as 20 cm. Even more recently, the same group has made

strand of SWNT’s 160cm long, but the precise make up of these strand has not yet been made

clear. A group in china has found, purely by accident that packs of relatively short carbon

nanotubes can be drawn out into a bundle of fibers, making a thread only 0.2 mm in diameter but

up to 30 cm long. The joins between the nanotubes in this thread represent a weakness but

heating the thread has been found to increase the strength significantly, presumably through

some sort of fusing of the individual tubes.

3.3.1 SINGLE-WALLED CARBON NANOTUBES (SWNT’S)

Single-wall nanotubes (SWNT) are tubes of graphite that are normally capped at the ends. They

have a single cylindrical wall. The structure of a SWNT can be visualized as a layer of graphite,

a single atom thick, called graphene, which is rolled into a seamless cylinder. Most SWNT

typically have a diameter of close to 1 nm. The tube length, however, can be many thousands of

times longer.

3.3.2 MULTI-WALLED CARBON NANOTUBES (MWNT’s)

Multi-walled carbon nanotubes are basically concentric cylindrical graphite tubes. In these more

complex structures, the different SWNT’s that form the MWNT may have quite different

structures by length and chirality). MWNT’s are typically 100 times longer than they are wide

and have outer diameter mostly in the tens of nanometer. Although it is easier to produce

significant quantities of MWNT’s than SWNTs, their structures are less well understood than

SWNT because of their greater complexity and variety. Multitudes of exotic shapes and

arrangement, often with imaginative names such as bamboo-trunks, sea urchins etc.

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3.4 Two major problems have so far thwarted attempts to shrink metal wires further:

1. There is as yet no good way to remove the heat produced by the devices, so packing them in more tightly will only lead to rapid overheating.

2. As metal wires get smaller, the gust of electrons moving through them becomes strong

enough to bump the metal atoms around and before long, the wires fail like blown fuses.

3.5 How CARBON NANOTUBES solve them?

In theory, nanotubes could solve both these problems.

1. Scientists have predicted that carbon nanotubes would conduct heat nearly as well as

diamond or sapphire and preliminary experiments seem to confirm their prediction. So

nanotubes could efficiently cool very dense arrays of devices.

2. As bonds among carbon atoms are so much stronger than those in any metal, nanotubes

can transport terrific amount of electric current (the latest measurements show that a

bundle of nanotubes one square centimeter in cross section could conduct about one billion

amps. Such high currents would vaporize copper or gold)

3.6 Where NANOTUBES shine?1. When stood on end and electrified, carbon nanotubes will act just as lightning rods do,

concentrating the electrical field at their tips.

2. Their strong carbon bonds allow nanotubes to operate for longer periods without damage.

3. High current field emitter from nanotubes is possible by just mixing them into a composite

paste with plastics, & smearing them onto an electrode then applying voltage.

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4. The scientists have found ways to grow clusters of upright nanotubes in neat little grids. At

optimum density, such clusters can emit more than one amp per square centimetre, which

is more than sufficient to light up the phosphers on a screen and is even powerful enough

to drive microwave relays and high-frequency switches in cellular phones.

5. Ise Electronics in Ise, Japan, has used nanotube composite to make prototype vaccum-tube

lamps in six colours that are twice as bright as conventional lightbulbs, longer-lived and

atleast 10 times more energy efficient. The first prototype has run for well over 10,000

hours and has yet to fail.

6. Engineers at Samsung in Seol stread nanotubes in a thin film over control electronics and

then put phosphor-coated glass on top to make a prototype flat-pannel display. When they

demonstrated the display last year, they were optimistic that the company would have the

device-which will be as bright as a cathode-ray tube but it will consume one tenth as much

power. And the product is on the market now.

7. In defect-free nanotubes, electrons travel ”ballistically”-that is, without any of the

scattering that gives metal wires their resistance.

8. At the small size of a nanotube, the flow of electrons can be controlled with almost perfect

precision. Scientists have recently demonstrated in nanotubes a phenomenon called

Coulomb blockade, in which more than one electron at a time on to a nanotube.

This phenomenon may make it easier to build single-electron transistors, the ultimate in

sensitive electronics.

3.7 Basic Ideas

What makes these tubes so stable is the strength with which carbon atoms bond to one another,

which is also what makes diamond so hard.

In diamond the carbon atoms link in to four-sided tetrahedral, but in nanotubes the

atoms arrange themselves in hexagonal rings. In fact, a nanotube looks like a sheet (or several

stacked sheets) of graphite rolled into a seamless cylinder. Graphite itself is a very unusual

material. Whereas most conductors can be classified as either metals or semiconductors,

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graphite is one of the rare materials known as semi metal, delicately balanced in the transitional

zone between the two.

By combining graphite semi-metallic properties with the quantum rules of energy levels

and electron waves, carbon nanotubes emerge as truly exotic conductor.One of the quantum

worlds is that electrons behave like as well as particles, and electron waves can reinforce or

cancel one another. As a consequence, an electron spreading around nanotubes circumference

can completely cancel itself out; thus, only electrons with just the right wavelength remain.

Out of all the possible electron wavelengths, or quantum states, available in a flat

graphite sheet, only a tiny subset is allowed when we roll that sheet into a nanotube. That subset

depends on the circumference of the nanotube, as well as whether the nanotube twists.

In a graphite sheet, one particular electron state gives graphite almost all of its

conductivity; none of the electrons in the other states are free to move about. Only one third of

all carbon nanotubes combine the right diameter and degree of twist to include this Fermi point

in their subset of allowed states. These nanotubes are truly metallic nano wires. The remaining

two third of the nanotubes are semiconductors.

This means that, like silicon, they do not pass current easily without an additional boost

of energy. The burst of light or a voltage can knock electrons from valence states into

conducting states where they can move about freely. The amount of energy needed depends on

the separation between the two levels and is the so called band gap of a semiconductor.

Carbon nanotubes don’t all have the same band gap, because for every circumference

there is a unique set of allowed valences and the conduction states. The smallest diameter

nanotubes have very few states that are spaced far apart in energy. As nanotube diameter

increase, more and more states are allowed and the spacing between them shrinks. No other

known material can be so easily tuned.

A single walled nanotube is only one carbon atom thick. It can be considered as a sheet

of graphite curled into the form of tube. Its properties can be changed by changing the direction

of the curl. It can be made highly conducting or semi-conducting based on the direction of the

curl.

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A carbon nanotube is highly elastic. It can be made in the shape of a spring, brush or

spiral. They have very low specific weight. Another very useful property of the nanotubes is

that their high mechanical and tensile strength. A carbon nanotube can be made into a length of

up to 100 microns. They are chemically inert.

In near future it is possible that microprocessors may be converted into ‘nanoprocessors’.

Chapter 4

NANO RAM

The proprietary NRAM design, invented by Dr.Thomas Rueckes, Nantero’s Chief

Technology Officer, Uses carbon nanotubes as active memory element. 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. It can replace DRAM, SRAM, flash and ultimately hard

disk storage. In other word a universal memory chip suitable for countless existing and

new applications in the field of electronics.

4.1 Technology (Operation & Fabrication):

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

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NANO-RAM

(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 Vander 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 (Epitaxy refers to the method

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NANO-RAM

of depositing a monocrystalline film on a monocrystalline substrate. The deposited film is

denoted as epitaxial film or epitaxial layer. The term epitaxy comes from the Greek roots

epi, meaning "above", and taxis, meaning "in ordered manner". 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.

4.2 Design, Structure & Description:

The design is quite simple. Nanotubes can serve as individually addressable electromechanical

switches arrayed across the surface of a microchip, storing hundreds of gigabits of information

may be even a terabit. An electric field applied to nanotubes would cause it to flex downward

into depression etched onto the chip’s surface, where it would contact rather another nanotube or

touch a metallic electrode. Once bent, the nanotubes can remain that way, including when the

power is turned off, allowing for non-volatile operation. Vanderwaals forces, which are weak

molecular forces of attractions, would hold the switch in place until application of fields of

different polarity causes the nanotube to return to its straightened position.

fig. 4.1 simple construction of NRAM showing its various components.

As shown in figure sagging and straightening represent ’1’ and ‘0’ states, respectively,

for a random access memory. In its ‘0’state, the nanotube fabric remains suspended above the

electrode. When the transistor below the electrode is turned on, the electrode is turned on, the

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NANO-RAM

electrode produces an electric field that causes the nanotubes fabric to bend and touch the

electrode - a configuration that denotes ‘1’ state. This is the principle of a switching device.

A nanotube memory is faster much smaller while consuming little power. Due to their

extraordinary tensile strength, resilience and very high conductivity, nanotubes can be flexed up

and down million times without any damage and can make a very good switching contact.

fig. 4.2 suspended nanotube switched connection

fig. 4.3 When reading an OFF state no current flows from the carbon nanotube ribbon to the

electrode

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NANO-RAM

fig. 4.4 When reading an ON state a current passes from the carbon nanotube to the electrode

4.3 Fabrication of NRAM

This nanoelectromechanical memory, called NRAM, is a memory with actual moving

parts, with dimensions measured in nanometers. Its carbon nano-tube-based technology takes

advantage of Vander Waals forces to create the basic on-off junctions of a bit. Vander Waals

forces are interactions between atoms that enable non-covalent binding. They rely on electron

attractions that arise only at the nano-scale level as a force to be reckoned with. The company

is using this property in its design to integrate nano-scale material properties with established

CMOS fabrication techniques.

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NANO-RAM

fig. 4.5 Array of nanotubes

Nanotubes purchased from bulk suppliers are a form of high -tech carbon soot that

contains a residue of about 5 percent iron a containment that must be removed before further

processing. It requires a complex filtration process to reduce the amount of iron to the parts per

billion levels. The purified carbon nanotubes are deposited as a film on the surface of a silicon

wafer without interfering with adjoining electrical circuitry from which chips are carved.

Deposition of nanotubes onto the wafer using a gas vapour requires temperatures so high

that the circuitry already in place would be ruined. It is therefore done by spraying a special

solvent containing nanotube on the top of the silicon disk spinning like a phonograph record. The

thin film of nanotubes left after the solvent is evaporated, is subjected to standard semiconductor

lithography and etching, which leave the surface groupings of nanotubes with interconnecting

wires. Thereafter, chips are cut from the wafer and encapsulated by the standard IC technology

A nanotube is a form of fullerene carbon in which the hexagonally connected “graphite”

sheet is curled up to form a tube of nanometer-scale diameters they grow, the tubes align

perpendicular to each other with a slight gap between each pair.

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NANO-RAM

Nantero has said that each junction contains multiple nanotubes, providing redundancy

and protection against catastrophic bit-failure. Nantero also said the array was produced using

only standard semiconductor processes, thereby making manufacture of the NRAM in existing

wafer fabs more likely. It also results in substantial redundancy for the memory, because each

memory bit depends not on one single nanotube, but upon a large number of nanotubes that

resemble a fabric.

The biggest challenge was figuring out how to place the nanotubes in the correct

positions. Each nanotube is approximately 50-to-100,000 times smaller than a piece of your

hair. This means they’re about 1-to-2 nanometers in diameter, and a nanometer is a billionth of

a meter.

To build the array of nanotubes, Nantero used a manufacturing method that involved

depositing a very thin layer of carbon nanotubes over the entire surface of a wafer, and then

using lithography and etching to remove the nanotubes that are not in the correct position to

serve as elements in the array. This manufacturing method solved the problem of growing

nanotubes reliably in large arrays. At the end of our process only the nanotubes in the correct

positions are remaining. The present size of the array is 10GBit, but the process could be used

to make even larger arrays. Nantero claims to have developed an array of ten billion suspended

nanotube junctions on single silicon. The main variable now controlling the size is the

resolution of the lithography equipment.

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NANO-RAM

Chapter 5

ADVANTAGES OF NANO-RAM

Permanently nonvolatile

High speed similar to DRAM/SRAM

High density similar to DRAM

Unlimited lifetime

Low power consumption

Data storage

CMOS-compatible manufacturing process & compatible with all existing hardware devices such as the PC, digital camera, mp3 players etc

Very small in size.

Highly resistant to environmental forces (heat, cold and magnetism).

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 simply not enough charge is being stored to be able to effectively read it. NRAM

appears to be limited only by the current state of 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 speed is largely determined by the total charge

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NANO-RAM

needed). NRAM can theoretically reach speeds 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 speed 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.

NRAM is faster and denser than all existing memory technologies. It uses only one

tenth of the power used by existing RAM or flash memory to store information. NRAM is a non

volatile memory. That means that when you turn the power off, you don't lose the data. And that

means that you never have to wait for your computer to boot up again; it turns on instantly. Each

memory bit in an NRAM depends not on a single nanotube but on a large number of nanotubes

woven together. Thus the NRAM offers substantial redundancy of memory. NRAM is highly

resistant to environmental forces (heat, cold and magnetism).

NRAM can be manufactured using the existing machineries in semiconductor factories.

So no high capital is needed for its production. NRAM is compatible with all existing hardware

devices such as the PC, digital camera, mp3 players etc.

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Chapter 6

DISADVANTAGES OF NANO-RAM

Relatively high cost. Requirement of high precision.

Major problems with nano-tubes:1. All molecular devices, nanotubes included, are highly susceptible to the noise caused

by electrical, thermal and chemical fluctuations.

2. Contaminants (oxygen for eg) attaching to a nanotube can affect its electrical

properties. That may be useful for creating exquisitely sensitive chemical detectors, but

it is an obstacle to making single-molecule circuits.

Challenges faced:1. Barriers to market:

Nantero is developing an alternate technology in a field that already offers

multiple memory options. The company will need to convince potential users of

the benefits of NRAM over existing methods.

2. Nantero seems to lag behind MRAM developers -- Motorola and IBM, to name two --

in bringing its technology out of the research phase and into actual product

development.

3. The downside is the fact that the DRAM market is oversupplied and those chipmakers

frequently have to sell at a loss, making it difficult for any new technology to break in.

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Chapter 7

APPLICATIONSNon-volatile highly scalable fast memories are used for stand-alone, embedded, or application specific designs like,

Computer and Laptops. (Enabling instant on performance, with instant boot up)

Mobile devices. (Faster storage of more data for PDA’s and handhelds)

Embedded memory. (More powerful & faster microprocessor, microcontroller, other logic device can be built)

High speed network server. Faster and denser memory storages.(eg. hard disk).

NRAM could enable instant-on computers which boot and reboot instantly, PDAs with

10 gigabytes of memory, MP3 players with thousands of songs and replace flash memories in

digital cameras and cell phones. Other possible uses include high speed network servers. And

because the technology is considerable faster and denser than DRAM, Nantero believes NRAM

could eventually replace hard disk storage.

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Chapter 8

COMPARISON WITH OTHER PROPOSED SYSTEMS

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.

The only alternative memory currently ready for commercial use is ferroelectric RAM

(FRAM or FeRAM). FeRAM adds a small amount of a Ferro-electric material in an otherwise

"normal" DRAM cell, the state of the field in the material encoding the bit in a non-destructive

format. FeRAM has all of the advantages of NRAM, although the smallest possible cell size is

much larger than for NRAM. FeRAM is currently in use in a number of applications where the

limited number of writes in Flash is an issue. The FeRAM read operation is inherently

destructive, requiring a restoring write operation afterwards.

Other more speculative memory systems include MRAM and PRAM. MRAM is based

on a grid of magnetic tunnel junctions. Key to MRAM's potential is the way it reads the memory

using the tunnel magneto resistive effect, allowing it to read the memory both non-destructively

and with very little power. Unfortunately, the 1st generation MRAM, which utilized field

induced writing, reached a limit in terms of size, which kept it much larger than existing Flash

devices. However, two new MRAM techniques are currently in development and hold the

promises of overcoming the size limitation and making MRAM more competitive even with

Flash memory. The techniques are Thermal Assisted Switching (TAS) ,which is being developed

by Crocus Technology, and Spin Torque Transfer (STT) on which Crocus, Hynix, IBM, and

several other companies are working.

PRAM 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.

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Chapter 9

FUTURE SCOPE

Nanotubes, atomic-scale carbon based structures, are set to begin the migration from the lab

into the wafer fab. In the first effort of its kind, the Institute of Electrical and Electronics

Engineers (IEEE) has begun to develop a standard that will define electrical test methods for

individual nanotubes. The standard will seek to establish a common metrics foundation for the

many research programs underway on the use of nanotubes in electronics.

The standard, IEEE P1650 (TM), “Standard Test Methods for Measurement of

Electrical Proper ties of Carbon Nanotubes”, will recommend the tools and procedures needed

to generate reproducible electrical data on the structures. The efforts applied in nanotechnology

have surfaced a strong need for common ways to evaluate the electrical characteristics of

nanotubes, so what is done by one group can be confirmed by others. The standard will seek to

meet this need. The tests defined in the standard will help form a bridge between the lab and the

production.

In May 2003, Nantero announced it had created an array of billion suspended nanotube

junctions on a single wafer. The process involves depositing a very thin layer of carbon

nanotubes over the entire surface of the wafer, then using lithography and etching to remove the

nanotubes that are not in the right position to serve as elements in the array. The announcement

was significant because it demonstrates we can create NRAM using standard equipment, which

means NRAM can be made in any existing factory.

At present, Nantero is trying to make Nano-RAM a commercial product. In future, these

carbon nanotube technology memory devices can replace all memory storage devices which are

currently booming in market today.

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Chapter 10

CONCLUSIONIt's hard to imagine a more exciting area than nanoelectronics .This paper gives an over-view of

application of nanotechnology in field of electronics. Moore’s law has held true for almost 40

years now, but the current lithographic technology has physical limits when it comes to making

things smaller and the semiconductor industry which often refers to the collection of these as the

“red brick wall” thinks that the wall will be hit in around fifteen years. At the point a new

technology will have to take over and nanotechnology offers a variety of potentially viable

options and carbon nanotube are one of the most commonly mentioned building blocks of

nanotechnology.

Every day at our lab our engineers are coming up with new ideas and new ways to build

products on a molecular level that have never been done before. And the whole field of

nanotechnology is one that will, over the next few decades, affect just about every area of human

life, from electronics to medical care and beyond, so it's great to be right there on the leading

edge. We could say that the prospects of nanotechnology are very bright. It will take sometime to

really make an impact on human race. But when it finally comes, nanotechnology will be an

undeniable force which will change very course of life. Thus, with the beginning of the usage of

NRAM which gives instant-on computers, we can obtain a very fast and ever existing Random

Access Memory for very vast applications & large memories can be built with nanotube

technology.

Though this technology today is limited to laboratories and not economically viable,

some new method of construction will have to be introduced in order to make the system

practical.

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Chapter 11

REFERENCES/BIBLIOGRAPHY

[1]. www.nanterno.com

[2]. "EcoRAM held up as less power-hungry option than DRAM for server farms" by

Heather Clancy 2008

[3]. www.nano-tek.org

[4]. "Basic Concepts of Nanotechnology" History of Nano-Technology, News, Materials,

Potential Risks and Important People.

[5]. "Nanomaterials and Nanoparticles: Sources and Toxicity" by Cristina Buzea, Ivan

Pacheco, and Kevin Robbie (2007).

[6]. www.tech-report.com

[7]. www.siliconstrategies.com

[8]. 10 Emerging technologies – MIT technology review

[9]. Nano Engineered Memory solutions-IEEE journal

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