moleculer electronic

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ASeminar Report

on

Moletronics

SUBMITTED BY

SHIVANGI TIWARI

Roll No.: - 1143131906

B.Tech. IIIrd Year

VIth Semester

SEMINAR INCHARGE

HEAD OF DEPARTMENT

Mr. Awill Anurag Misra Mrs. Monica Mehrotra

Departmentof

Electronics & Communication Engineering

B. N. COLLEGE OF ENGINEERING & TECHNOLOGY,

LUCKNOW-227202

2012-2013

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ACKNOWLEDGEMENT

I would like to acknowledge our indebtedness to all those who willingly helped me in completion

this seminar work. Without their help the completion of seminar would have been move like groping in th

dark for a way-out. First of all I owe my thanks to Mrs. Monica Mehrotra (Head of Departmen

Electronics & Communication Engineering) for her guidance.

I would like to extend my thanks to Mr. Awill Anurag Misra (Lecturer, Electronics

Communication Engineering Department) for his proper guidance, valuable suggestions and constructiv

approach to clear all my doubts during the course of this Seminar. Without his valuable suggestion an

advice, completion of this seminar would have been a mammoth task.

Shivangi Tiwari

B.Tech -3rd Year (EC)

Roll No.- 1143131906

B.N.C.E.T,

Lucknow

Table Of Content

Content Page no.

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1. List of figure 4

2. Abstract 5

3. Introduction to Moletronics 6

4. History 9

5. Molecular circuit- QCA basis 10

5.1. Fundamental aspects of QCA

6. Interconnection Nanotube 13

7. Molecular Electronic System 167.1. Electronic structure

7.2. Different alligator clips in SAMs

7.3. Electrode Effect

8. Advantages of Moletronics 21

9. Disadvantages of Moletronics 22

10. Applications 23

11. Future of Molecular Electronic 30

12. Conclusion 31

13. Reference 32

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1. List of Figure

Figure no. Figure name

1. Molecular electronics ; An Interdiciplinary field

2. the birth of Molecular electronics

3. Schematic of the geometry of the basic four sitecell.

4. Coulombic repulsion

5. The cell-cell response

6. The Majority Gate

7. Carbon nanotubes

8. Break Junction

9. Schematic of shapes of Moletronics

10. Library of molecules under investigation

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2. Abstract

Molecular electronics (moletronics) represent the ultimate challenge in device miniaturization. The concept

of molecular electronics has aroused great excitement, both in science fiction and among scientists. This is

because of the prospect of size reduction in electronics which is offered by molecular-level control ofproperties. Molecular electronics provides means to extend Moores Law beyond the foreseen limits of

small-scale conventional silicon integrated circuits.

It implements one or a few molecules to function as connections, switches, and other logic devices in futurecomputational devices.

Moletronics has following advantages over semiconductor devices:

o Low Power Consumption.

o Small and compact size.

o High Speed

o Low Cost

o Low Temperature Manufacturing

o Stereochemistry can be applied

o Synthetic Flexibility is there

Moletronics has got a wide range of scope applications.

Till now we have created Switch and Memory units from a single molecule.With more research we will soo

be able to find smaller devices which are faster, cost effective, having large battery life .

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3. Introduction

Moletronics involves the study and application of molecular building blocks forthe fabrication of electronic components.1. Includes

conductive polymers

single-molecule electronic components2. 2 most promising conducting molecular species are:

Polyphenylene

Carbon nanotubes3. It is useful in the prospect ofsize reduction.4. Extends Moore's Law beyond the foreseen limits of small-scale conventional

silicon integrated circuits.

Molecular electronics, also called moletronics, is an interdisciplinary subject that spans chemistry, physics

and materials science. The unifying feature of molecular electronics is the use of molecular building blocksto fabricate electronic components, both active (e.g. transistors) and passive (e.g. resistive wires). The

concept of molecular electronics has aroused great excitement, both in science fiction and among scientists.

This is because of the prospect of size reduction in electronics which is offered by molecular-level control oproperties. Molecular electronics provides means to extend Moores Law beyond the foreseen limits of

small-scale conventional silicon integrated circuits.

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Molecular electronics is a poorly defined term. Some authors refer to itas any molecular-based system, such as a film or a liquid crystalline array. Otherauthors, including Tour J. M., prefer to reserve the term molecular electronics for single-molecule tasks,such as single molecule-based devices or even single molecular wires. Due to the broad use of this term,

molecular electronics are split into two related but separate subdisciplines by Petty M. C.: molecularmaterials for electronics utilizes the properties of the molecules to affect the bulk properties of a material,

while molecular scale electronics focuses on single-molecule applications.

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Fig. 1- Molecular electronics ; An Interdiciplinary field


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Molecular electronics represent the ultimate challenge in device miniaturization. Molecular devices can hav

any no of termini with current-voltage responses that would be expected to be nonlinear due to intermediate

barriers or hetero functionalities in the molecular framework while molecular wires refer to especially

tailored molecular nanostructures energetic properties. Molecular-scale devices actually operating todayinclude: FETs, junction transistors, diodes, and, molecular and mechanical switches. Logic gates with voltag

gain have been built, and many techniques have been demonstrated to assemble nanometer wide wires intolarge arrays. Programmable and non-volatile devices which hold their state in a few molecules or in square

nanometers of material have been demonstrated.

MOORES LAW

1. The number of transistors that can be fabricated on a silicon integrated circuit and therefore the

computing speed of such a circuit is doubling every 18 to 24 months.2. After four decades, solid-state microelectronics has advanced to the point at which 100 million

transistors, with feature size measuring 180 nm can be put onto a few square centimeters of silicon

4.History

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Figure-2s


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a. 1950s - INVENTION OF TRANSISTOR

b. 1956 - ARTHUR VON GAVE IDEA ABOUT

MOLECULAR ENGINEERINGc. 1960s & 1970s- EXPERIMENTS ALL AROUND THE

WORLD

d. 1981 -STM INVENTED (FIRST TOOL TO

PROVIDE ABILITY TO SEE AT ATOMICLEVEL)

5. Moletronic circuit--QCA basics

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Figure-2s


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We discuss an approach to computing with quantum dots, Quantum-dot Cellular Automata (QCA), which

based on encoding binary information in the charge configuration of

quantum-dot cells. The interaction between cells is Coulombic, and provides the necessary computing powe

No current flows between cells and no power or information is delivered to individual internal cells. Loc

interconnections between cells are provided by the physics of cell-cell interaction. The links below describ

the QCA cell and the process of building up useful computational elements from it. The discussion is mostl

qualitative and based on the intuitively clear behavior of electrons in the cell.

5.1-Fundamental Aspects of QCA

A QCA cell consists of 4 quantum dots positioned at the vertices of a square and contains 2 extra electron

The configuration of these electrons is used to encode binary information. The 2 electrons sitting on diagon

sites of the square from left to right and right to left are used to represent the binary "1" and "0" state

respectively. For an isolated cell these 2 states will have the same energy. However for an array of cells, thstate of each cell is determined by its interaction with neighboring cells through the Coulomb interaction.

schematic diagram of a four-dot QCA cell is shown in Fig. 1.

.

Figure:3- Schematic of the geometry of the basic four site

cell.The tunneling energy between two neighboring sites is

designated by t, while a is the near-neighbor distance

If the barriers between cells are sufficiently high, the electrons will be well localized on individual dots. Th

Coulomb repulsion between the electrons will tend to make them occupy antipodal sites in the square

shown in Fig. 2. For an isolated cell there are two energetically equivalent arrangements of the ext

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electrons which we denote as a cell polarization P = +1 and P = -1. The term "cell polarization" refers only t

this arrangement of charge and does not imply a dipole moment for the cell. The cell polarization is used

encode binary information - P = +1 represents a binary 1 and P = -1 represents a binary 0.

Figure:4-Coulombic repulsion causes the electrons to occupy antipodal sites within the cell. These two bistable states result

cell polarizations of P = +1 and P = -1.

The two polarization states of the cell will not be energetically equivalent if other cells are nearby. Consid

two cells close to one another as shown in the inset of Fig. 3. The figure inset illustrates the case when cell

has a polarization of +1. It is clear that in that case the ground-state configuration of cell 1 is also a +

polarization. Similarly if cell 2 is in the P = -1 state, the ground state of cell 1 will match it. The figure show

the nonlinear response of the cell-cell interaction.

Figure:5-The cell-cell response

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A Majority Gate

Fig. 4 shows the fundamental QCA logical device, a three-input majority gate, from which more comple

circuits can be built. The central cell, labeled the device cell, has three fixed inputs, labeled A, B, and C. Th

device cell has its lowest energy state if it assumes the polarization of the majority of the three input cell

The output can be connected to other wires from the output cell. The difference between input and outpu

cells in this device, and in QCA arrays in general, is simply that inputs are fixed and outputs are free

change. The inputs to a particular device can come from previous calculations or be directly fed in from arra

edges. The schematic symbol used to represent such a gate is also shown in Fig. 4.

Figure:6- The Majority Gate

6. Interconnection: nanotube

Today, one way to pack transistors more densely on a chip is to make the already microscopic wires small

and thinner. But the wires are approaching the thickness of a few hundred atoms. Once wires get down t

only several atoms thick, says IBM researcher Phaedon Avouris, they blow up when you try to send electric

signals through them. Nanotubes don't. IBM and others are racing to use nanotubes to make the first carbo

chips, perhaps the successor to silicon chips, though the program is only in the earliest stages. A carbo

nanotube is a tubular form of carbon with a diameter as smaller as 1 nm. The length can be from a fe

nanometers to several microns. (1 micron is equal to 1,000 nanometers.) It is made of only carbo atoms. T

understand the CNT's structure, it helps to imagine folding a two-dimensional graphene sheet. Depending o

the dimensions of he sheet and how it is folded, several variations of nanotubes can arise. Also, just like th

singel or the multilayer nature of graphene sheets, the resulting tubes may be a single- or a multiwall type.

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The tube's orientation is denoted by a roll-up vector(See Fig.8) . Along this vector, th

graphene sheet is rolled into a tubular from. The and are vectors defining a unit cell in the plan

graphene sheet. n and m are integers, and is the angle. A variety of tubes-based on the orientations of th

benzyne rings on the graphene tube-are possible.

If the orientation is parallel to the tube axis, then the resulting "zigzag" tubes are semiconductorWhen the orientation is perpendicular to the tube axis, the corresponding "arm chair" tubes are metallic.

between the two extremes, when (n-m)/3 is an integer, the nanotubes are semimetallic. The two ke

parameters, the diameterdand the chiral angle , are related to (n,m) by ,.

For example, a(10,10) nanotube is 1.35 nm in diameter whereas a (10,10) tube is 0.78nm

diameter. Carbon nanotubes exhibit extraordinary mechanical properties as will. For example, the Young

modulus is typically over 1 Tera Pascal. Also, the nanotube along the axis is as stiff as a diamond.

The estimated tensile strength is about 200 Gpa, which is an order of magnitude higher than that o

any other material. Here we are mainly interested in carbon nanotube's electronic behavior and application

The metallic and semiconducting nature described previously has given rise to the possibilities of meta

semiconductor or semiconductor junctions. These junctions may form nanoelectronic devices based entire

on single atomic species such as carbon.

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Figure:7- Carbon nanotubes: their structure, properties and

uses in nano-electronic devices

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.

7.Molecular Electronic Systems

In order to perform as an electronic material, molecules need a set of overlapping electronic states. Thesstates should connect two or more distant functional points or groups in the molecule. A conjugated orbit

system is required for a typical candidate of molecular electronics. This conjugated system needs to exten

on an -framework with terminal functional groups. Molecules for electronic applications generally have 1

2-, or 3-dimensional shapes as depicted in Figure . Alligator clip, which provides stable connection of thmaterial to the metallic electrodes or inorganic substrates, is the caudal functional group of the organ

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Figure. 8


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electronic material. It is important to note that each part of an organic molecule used as the active componenin nano scale electronic device has their own contribution. In general, by measuring the conductivity of

series of systematically modified molecules, the contribution of each component can be determined. F

example, by varying the molecular alligator clip and examining the molecules conductivity, the contributio

of the alligator clip to the conductivity can be determined .

Schematic of 1D, 2D and 3D shapes for molecular electronics.

7.1. Electronic Structures

The simplest molecules studied in molecular electronics are the alkylthiols, which only have -bonds. Thothers are organic molecules represented by alternating double and single bonds or alternating triple an

single bonds.

These are indicative of an -bonded C-C backbone with -electron delocalization. The conjugatio

length is defined as the extent over which the - electrons are delocalized. The double or triple bond

between carbon atoms in the molecules have an electron excess to that normally required for just -bond

These extra electrons are in the pz orbitals which are mainly perpendicular to the bonding orbitals betweeadjacent carbon atoms.

These electrons overlap with adjacent pz orbitals to form a delocalized -electron cloud. This clouspreads over several units along the backbone. When this happens, delocalized valence (bonding) and

conduction (anti-bonding) bands with defined bandgap are formed which meets the requirements fo

(semi)conducting behavior. Normally the electrons reside in the lower energy valence band. If givesufficient energy, they can be excited into the normally empty upper conduction band, giving rise to a

transition.

Intermediate states are forbidden by quantum mechanics. The delocalized -electron system confe

the (semi)conducting properties on the molecule and gives it the ability to support charge transport.

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Fig. 9


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Modifications can be done based on the backbone to improve electron transfer properties. Scheme showseveral popular backbones for a 1D molecular electronic material. Backbones for 2D and 3D molecul

electronics are similar to 1Ds.

Library of molecules under investigation

7.2. Different Alligator Clips in SAMs

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Representativestructures for 1Dmolecular electronicmaterials;(a) Alkyldithiol;(b) Oligo(p-

phenylene)-dithiol(c) (p-phenyleneethynylene)-dithiol.

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Scheme 2Representative alligator clips for forming SAMs. 1,2-dioctyldisulfane (a); bis(4,4-biphenyl)ditelluride (b); benzenethiol (c); benzene-1,4-dithiol (d); S-phenylethanethioate (e); S,S-1,4-

phenylene diethanethioate (f); 4,4-biphenyl selenoacetate (g); phenyl isocyanide (h);1,4-phenylene

diisocyanide (i); 2-nitro-1,4-bis(phenylethynyl)benzene diazonium tetrafluoroboride (j)

Scheme 2 shows some common alligator clips used in molecular electronics for forming SAMs. The acetyprotected thiols and dithiols can be deprotected in situ under acid or base conditions to form SAMs on go

substrate. The diazonium salt generates an aryl radical by loss of N 2 and ultimately produces an irreversibgold-aryl bond. Isocyanide and diisocyanide also perform gold-carbon bond. Among all the alligator clip

sulfur compounds have a strong affinity to transition metal surfaces. This is probably because of th

possibility to form multiple bonds with surface metal clusters. The number of reported surface activ

organosulfur compounds and their derivatives that form monolayers on gold include, di- n-alkyl sulfide, di-alkyl disulfides, thiophenols, thiophenes, mercaptopyridines, mercaptoanilines, xanthate

cysteines,thiocarbamates, thiocarbaminates, thioureas, mercaptoimidazoles, ditellurides and alkaneselenol

SAMs of alkanethiolates on Au surfaces are the most studied and well understood.

7.3. Electrode Effects

There has been great interest in molecular electronics since the observation of electrical conductivity of th

molecules from early experiments with the junction formed by sandwiching the molecule between two met

electrodes. However, it has been shown that in some systems, it was not the molecules themselves but th

metal contacts that mainly contribute to the junction conductivity. The misleading observations from ear

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experiments are due to the so called metal nanofilaments effect. The metal nanofilaments effect is causeby the movements of metal atoms from the contacts to the tiny gap (several nanometers) between the tw

contacts with a bundle of molecules in between when an electric field is applied. The metal atoms in the ga

act as a low resistance bridge between the two contacts. Instead of flowing through the molecule, electriccurrent tends to pass through the low-resistance bridge. More recently, He et al. proposed a metal-free syste

in which the two sides of a molecular monolayer attached to single-crystal silicon and a mat of single-walle

carbon nanotubes, respectively Figure .Such a design eliminated the metal nanofilaments effect an

switching property was observed under an applied field.

(a) (b)(a) Metal-molecule-metal junction with metal nanofilaments effect.(b) Carbon nanotube-molecule-silicon junction.

Molecule-electrode interface is therefore a critically important component in molecular electronics. It ma

limit the current flow or completely modify the measured electrical response of the junction. Moexperimental platforms for constructing the molecular-electronic devices are based on the fact that th

sulfurgold bond is an excellent chemical handle for forming self-assembled, robust organic monolayers o

metal surfaces. Other methods, such as contacting a scanning probe tip with the surface of the molecule, arfrequently employed. Ideally, the choice of electrode materials should not be based on the ease of fabricatio

or measurement. They must follow the first-principles considerations of the molecule-electrode interaction

However, the current level of understanding of the molecule-electrode interface is rather poor. Very litttheory exists that can adequately predict how the energy levels of the molecular orbitals will align with th

Fermi energy of the electrode. Small changes in energy levels can dramatically affect the junctio

conductance.

Therefore it is critical to understand the correlation of the interface energy levels which demands bo

theoretical and experimental study. A relevant consideration involves how the chemical nature of th

molecule-electrode interface affects the rest of the molecule. The zero-bias coherent conductance of molecular junction may be described as a product of functions that describe the molecules electron

structure and the molecule-electrode interfaces. However, it is likely that the chemical interaction betwee

the molecule and the electrode will modify the molecules electron density in the vicinity of the contactinatoms and, in turn, modify the molecular energy levels or the barriers within the junction. There is little doub

that the molecular and interface functions must be considered in tandem in theoretical studies.

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8. Advantages of Molecular Electronics

Molecular structures are very important in determining the properties of bulk materials, especially f

application as electronic devices. The intrinsic properties of existing inorganic electronic materials may n

be capable of forming a new generation of electronic devices envisioned, in terms of feature sizes, operatiospeeds and architectures. However, electronics based on organic molecules could offer the followin

advantages:

Size Molecules are in the nanometer scale between 1 and 100 nm. This scale permits small devices wi

more efficient heat dissipation and less overall production cost to be made.

Power: One of the reasons that transistors are not stacked into 3D volumes today is that the silicon wou

melt. The inefficiency of the modern transistor is staggering. It is much less efficient at its task than th

internal combustion engine. The brain provides an existence proof of what is possible; it is 100 million timmore efficient in power/calculation than our best processors. Sure it is slow (under a kHz) but it is massive

interconnected (with 100 trillion synapses between 60 billion neurons), and it is folded into a 3D volum

Power per calculation will dominate clock speed as the metric of merit for the future of computation.

Assembly One can exploit different intermolecular interactions to form a variety of structures by the arra

of self-assembly techniques which are reported in the literature. The scope of application of the self-assemb

technique is only limited by the researchers ability to explore.

Manufacturing Cost - Many of the molecular electronics designs use simple spin coating or molecular sel

assembly of organic compounds. The process complexity is embodied in the synthesized moleculstructures, and so they can literally be splashed on to a prepared silicon wafer. The complexity is not in th

deposition or the manufacturing process or the systems engineering. Much of the conceptual difference o

nanotech products derives from a biological metaphor: complexity builds from the bottom up and pivo

about conformational changes, weak bonds, and surfaces. It is not engineered from the top with precismanipulation and static placement.

Low Temperature Manufacturing: Biology does not tend to assemble complexity at 1000 degrees in a hig

vacuum. It tends to be room temperature or body temperature. In a manufacturing domain, this opens thpossibility of cheap plastic substrates instead of expensive silicon ingots.

Stereochemistry A large number of molecules can be made with indistinguishable chemical structures an

properties. On the other hand, many molecules can exist as distinct stable geometric structures or isomer

Such geometric isomers exhibit unique electronic properties. Moreover, electronic properties of conforme

can be affected by pressure and temperature. We can therefore make use of stereochemistry to tunproperties.

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9. DISADVANTAGES

1) Molecular electronics must still be integrated with Silicon.

2) The determination of the resistance of a single molecule (both theoritical and experimental) is complex.

4) It is difficult to perform direct characterization since imaging at the molecular scale is often impossible

many experimental devices.

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10. Applications of Molecular Electronics

Molecular electronics seeks to be the next technology in the electronics industry where molecules assembthemselves into devices using environmentally friendly and low cost fabrication techniques. It goes beyon

the limitations of rigid silicon-based solutions. It implements one or a few molecules to function

connections, switches, and other logic devices in future computational devices. Molecular electronics can bused in emerging technologies ranging from novel optical discs based on bistable biomolecules to conceptu

design of the computers based on molecular switches and wires.

Molecular electronics seeks to be the next technology in the electronics industry where molecules assembthemselves into devices using environmentallyfriendly and low costfabrication techniques. It goes beyonthe limitations of rigid silicon-based solutions. It implements one or a few molecules to function

connections, switches, and other logic devices in future computational devices. Molecular electronics can b

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used in emerging technologies ranging from novel optical discs based on bistable biomolecules to conceptudesign of the computers based on molecular switches and wires. The processing speed of existing compute

is limited by the time it takes for an electron to travel between devices. Molecular electronics-base

computation addresses the ultimate requirements in a dimensionally scaled system: ultra dense, ultra fast anmolecular-scale. By the use of molecular scale electronic interconnects, the transmittance times could b

minimized. This could result in novel computational systems operating at far greater speeds tha

conventional inorganic electronics. The design of a molecular CPU can bring great technical renovation

computer science. Table 1 shows the main differences between the present bulk electronic devices and thproposed molecular electronic devices.

Table 1:Main characteristics of bulk and molecular CPU circuits.

Novel molecular electronics would approach the density of ~1013 logic gates/cm2. It offers a 105 decrease the size dimensions compared to the present feature of a silicon-based microchip. In addition, the presen

fastest devices can only operate in nanosecond while the response times of molecular-sized systems ca

reach the range of femtoseconds. Thus, the speed may be attained to a 10 6 increase. On the basis of the

estimates, a 1011

fold increase in the performance can be expected with molecular electronics, which offers aexciting impetus for intense research and development though numerous obstacles remain.

Many of the technological applications of molecular electronics, including the computational application

should be considered and viewed as the drivers for the field. Tours group has demonstrated thsynthetic/computational approach to digital computing of molecular scale electronics. In his paper, th

alligator clip SH acted as the contact to input or output in digital computing of molecular electronics. Th

alkyl groups which broke the conjugation of the wire served as the transport barrier in the integrated circuitThe successful development of molecular-electronic integrated circuitry would also benefit Nano mechanic

devices, ultra dense single-molecule sensor arrays, the interfaces to bio systems and the pathways towar

molecular mechanical systems.

Switch using Moletronics

Benzene ring of six carbon atoms (with a few hydrogen atoms thrown in as well) is held together in part by

pi bonda sort of smeared bond in which some of the electrons are loosely shared by all the atoms in a kin

of cloud that circles above and below the carbon ring. Its not a broken bond. Instead, its a sort of bonwithin which electrons are somewhat more able to move.

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By changing the structure of the molecule, the researchers found that they were able to alter its behaviou

They hung molecular fragmentsan NH2 group and an NO2 groupfrom the middle benzene ring. Thdistorted the electron cloud, making the molecule more susceptible to twisting. By applying a voltage to th

molecule, for example, they could cause a change, a bend or a twist in the molecule. This disrupted th

flow of electrons

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And, this twist was reversible. When the voltage was removed, the molecule returned to its original shap

allowing current to pass through once again. In other words, this molecule can act as a switch. It turnelectricity on and offa basic characteristic that a computer needs to process information in bits of 1 and 0.

Memory Chip

Data storage is done by multiporphyrin nanostructures into electronic memory. The application of a voltag

causes the molecules to oxidize, or give up electrons.The molecules then retain their positive charge after th

electric field is removed, producing a memory effect.

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Memory Hold Time

Silicon memory devices retain charged bits for only a millisecond before the charge leaks away. That meanthat each piece of information must be restored ten to a hundred times a second, which requires substantia

amounts of power.

Moletronic device retains its electrons for about nearly fifteen minutes. It has the ability to get th

information in and out of the systems and using significantly less

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power. Compared to, say, current equipment, which only runs for a few hours before the batteries wear ou

Reed says, machines using molecular memory could run for a week.

Theres an energy structure that explains how long a deviceeither silicon, or molecularwill hoelectrons. They leak out at a certain rate and when you go to a molecularstructure,the energies [holding thelectrons in place] become much bigger. So the leak-out rate is slower.

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.

11. Future of Molecular Electronics

The drive toward yet further miniaturization of silicon-based electronics has led to a revival of efforts t

build devices with molecular-scale organic components. However, the fundamental challenges of realizingtrue molecular electronics technology are daunting. Controlled fabrication within specified tolerances and i

experimental verification are major issues. Self-assembly schemes based on molecular recognition will b

crucial for that task. Ability to measure electrical properties of organic molecules more accurately anreliably is paramount in future developments. Fully reproducible measurements of junction conductance ar

just beginning to be realized in labs at Purdue, Harvard, Yale, Cornell, Delft, and Karlsruhe Universities an

at the Naval Research Laboratory and other centers.

Working molecular electronic devices exist today. Research progress is steady and strong, giving us cause t

believe that molecular electronic systems may be practical in five to ten years. If lithography reach

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fundamental physical or economic limits, molecular electronics may allow us to continue observing MooreLaw. Regardless, molecular bottom-up fabrication could give us a

much better alternative, whose price would depend mainly on design and test cost, instead of billion-dolla

factories.

Challenges to making this reality are plentiful at every level, some naturally in physics and chemistry, bu

many in ICCAD. These include fabricating and integrating devices, managing their power and timin

finding fault-tolerant and defect-tolerant circuits and architectures and the test algorithms needed to use themdeveloping latency-tolerant circuits and systems, doing defect-aware placement and routing, and designin

verifying and compiling billion-gate designs and the tools to handle them. Any one of these could bloc

practical molecular electronics if unsolved.

Many of these are challenges that will be faced regardless of the underlying technology. Molecul

electronics provides a pure and extreme example, and strengthens the case for solving them sooner raththan later.

Robust modeling methods are also necessary in order to bridge the gap between the synthesis anunderstanding of molecules in solution and the performance of solid-state molecular devices. In addition, th

searching of fabrication approaches which can couple the densities achievable through lithography with thoachievable through molecular assembly is also a great challenge. Controlling the properties of molecule

electrode interfaces and constructing molecular-electronic devices that can exhibit signal gain are also crucito the development in the field.

12.Conclusion

Molecular electronics is an exciting emergent field of study. The reward of research in this area is enormousas the birth of molecular computer implies unprecedented processing power that may enable breakthroughs

in artificial intelligence.

This paper has given a glimpse at how such an endeavor might be accomplished by introducing the basic

ideas in molecular device implementation and electrical characterization methods.

The path towards a full working system is still a long one, yet the prospects are bright and great strides havebeen taken.

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13. References

1. Wikipedia

2. Transcending Moore's Law with Molecular Electronics and Nanotechnology

http://www.dfj.com/files/TranscendingMoore.pdf

3. STANFORD and HARVARD University thesis links.

4. Hewlett-Packard Company Catalogue.

5. Zettacore Company Catalogue.

6. Elsevier Ltd link by Paula Gould.

7. 2011 Molecular electronics archive http://www.nature.com/nmat/archive/subject_nmatcode-

13_012011.html

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8. YALE Engineering http://www.eng.yale.edu/posters150/pdf/reed4.pdf

9. Other useful IEEE papers and links
http://www.eng.yale.edu/posters150/pdf/reed4.pdfhttp://www.eng.yale.edu/posters150/pdf/reed4.pdf

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