tpe4001a23 phy101

8/7/2019 TPE4001A23 PHY101

http://slidepdf.com/reader/full/tpe4001a23-phy101 1/15

8/7/2019 TPE4001A23 PHY101


ACKNOWLEDGEMENT

I take this opportunity to present my votes of thanks to all those

guidepost who really acted as lightening pillars to enlighten our

way throughout this project that has led to successful and

satisfactory completion of this study.

We are really grateful to our teacher Ms. NEETI WALIA for

providing us with an opportunity to undertake this project in this

university and providing us with all the facilities. We are highlythankful to her for her active support, valuable time and advice,

whole-hearted guidance, sincere cooperation and pains-taking

involvement during the study and in completing the assignment of

preparing the said project within the time stipulated.

Lastly, We are thankful to all those, particularly the various

friends , who have been instrumental in creating proper, healthy

and conductive environment and including new and fresh

innovative ideas for us during the project, their help, it would have

been extremely difficult for us to prepare the project in a time

bound framework.

Name- Nikhil Ladha

Regd.No- 11003993

Rollno. - RE4001A23

8/7/2019 TPE4001A23 PHY101


TABLE OF CONTENTS

Introduction to nanotechnology

Silicon Nanodevices:-

Silicon Nanotubes

--definition, applications

Silicon Nanowires

--definition, uses

Silicon Solar Cells

--definition, nanowire based solar cells

Conclusion

References

8/7/2019 TPE4001A23 PHY101


AN INTRODUCTION TO NANOTECHNOLOGY

Nanotechnology is the study of the controlling of matter on an atomic and molecular scale.

Generally nanotechnology deals with structures sized between 1 to 100 nanometer 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

may be able to create many new materials and devices with a vast range of applications, such

as in medicine, electronics, biomaterials 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 nanomaterials 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. Nanoscale materials are

sometimes used in solar cells which combats the cost of traditional Silicon solar cells.

Nanostructures are made up of minute particles known as the building blocks or may be

nanowires. Nanostructures may be of the type shown in the following figure.

8/7/2019 TPE4001A23 PHY101


Several research and experiments are carried out on the applications of nanotechnology. This

technology play a very vital role in the field of science and industrial development. Scientists

carry these activities on nano chips. Such experiments require large amount of heat and the

conditions are to be set accordingly. The schematic of one such experiment may be shown as

follows:-

8/7/2019 TPE4001A23 PHY101


SILICON NANODEVICES

Silicon nanodevices are the basic applications of nanotechnology. These devices are of very

much importance in the field of science and technology in the present era. The siliconnanodevices are basically designed for several purposes like it plays a vital role in

development in the field of electronics. Some of the silicon nanodevices have been discussed

in this term paper. Silicon is the 14th element in the periodic table and the second element

after carbon which can practice the property of catenation. This property of Silicon helps it to

form long chain compounds thereby making several devices. Silicon act as a major part in the

applications of nanotechnology. Many devices are developed based on silicon nanotubes,

silicon nanowires etc. The devices based on these building blocks are of very much

importance in the technological development of a country. Silicon solar cells based on silicon

nanowires are quite effective in trapping the solar energy and utilising it for proper uses.

Scientists and Engineers carry out experiments based on nanotechnology and at the same time

new developments are being made in this field. The advancement in the development of

silicon nanodevices demands large amount of labour. The medicinal applications of silicon

nanotechnology may be shown as follows:-

http://www.medicineamigo.com/images/Daily-Life-For-A-Neurology-Resident.jpg

8/7/2019 TPE4001A23 PHY101


SILICON NANOTUBES

These are nanoparticles which create a tube-like structure from silicon atoms. The nanotubes'

discovery has many significant implications for electronics development, as silicon is alreadya vastly important material in the semiconductor industry. Only recently has it been possible

to prepare these nanotubes which are similar to carbon nanotubes. Nano-materials are

complex, and understanding how the behaviour of silicon materials differs from their carbon-

based cousins is still under research. While silicon nanotubes are still in the early stages of

their development, scientists and engineers have already begun to consider the possible uses

for the new material.

Silicon nanotubes have been considered for use in electronics, because it appears that silicon

nano-materials may behave like a metal fuel, since the structure can accommodate molecules

of hydrogen so it might resemble coal without carbon dioxide. A silicon nanotube chargedwith hydrogen delivers energy and in the process leaves residual water, ethanol, silicon and

sand. However, as hydrogen production requires considerable energy, this is only a proposed

method of storing energy, not producing it. Single walled hexagonal silicon nanotubes may be

of the following type:-

Using first-principles density functional calculations, we show that hexagonal metallic silicon

nanotubes can be stabilized by doping with 3d transition metal atoms. Finite nanotubes doped

with Fe and Mn have high local magnetic moments, whereas Co-doped nanotubes have low

values and Ni-doped nanotubes are mostly nonmagnetic. The infinite Si24Fe4 nanotube is

found to be ferromagnetic with nearly the same local magnetic moment on each Fe atom as inbulk iron. Mn-doped nanotubes are antiferromagnetic, but a ferrromagnetic state lies only

8/7/2019 TPE4001A23 PHY101


0.03 eV higher in energy with a gap in the majority spin bands near the Fermi energy. These

materials are interesting for silicon-based spintronic devices and other nanoscale magnetic

applications.

Another Type Of Nanotube Can Be Shown As:-

A simple chemical process employed by a Cornell University and DuPont research team may

pave the way to thinner, lighter and more flexible transistors and solar cells. The long term

goal of the project is to use nanotubes to create an economical electronics material that is just

as good as silicon.

When silicon nanotubes are grown in a lab, some of them are semiconducting and others are

metallic. The difficulty of separating the two types of nanotubes has made commercially

viable semiconducting nanotube material a costly commodity. Scientists are now using a

relatively simple chemical process called ‘cyloaddition’ to produce cheaper semiconductingsilicon nanotubes.

Cyloaddition uses fluorine-based molecules to either attack or convert the metal nanotubes

without harming the semiconducting tubes. The procedure is inexpensive and prepares the

silicon nanotubes for suspension in semiconducting ink for electronic printing purposes.

Although the work is still in the early stages, researchers believe that the breakthrough may

eventually lead to nanotube use in a variety of devices including novel organic photovoltaic

structures.

8/7/2019 TPE4001A23 PHY101


The most exciting aspect of this research is the flexibility and thinness of nanotube

semiconducting material. The team has said that the current material is 100 times more

mobile than silicon, which should allow for some extremely creative three-dimensional

photovoltaic structures in the future.

Silicon nanotubes are also used for the flow of charges in a silicon semiconductor. These

tubes are set between the two electrodes and the electrons are allowed to flow freely through

them. Holes are the positive charges. Each time an electron leaves its place, a hole is created.

The semiconductor is electrically neutral and the silicon nanotubes play an important role in

the manufacturing of these devices. The rough image of the interior of a semiconductor with

silicon nanotubes can be shown as:-

Thus silicon nanotubes are used in developing many things and hence are very much

useful. Many developments have been made based on these tubes and many more are

still to be made.

8/7/2019 TPE4001A23 PHY101


SILICON NANOWIRES

Silicon nanowires can be prepared with single-crystal structures, diameters as small as several

nanometers and controllable hole and electron doping, and thus represent powerful buildingblocks for nanoelectronic devices such as field effect transistors. To explore the potential

limits of silicon nanowire transistors, we have examined the influence of source-drain contact

thermal annealing and surface passivation on key transistor properties. The comparison of

these results and other key parameters with state-of-the-art planar silicon devices shows

substantial advantages for silicon nanowires. The nanowires may be rightly considered as

building blocks for future nanoelectronics.

Functional Nanoscale Electronic Devices Assembled Using Silicon Nanowire Building

Blocks:-

Because semiconductor nanowires can transport electrons and holes, they could function as

building blocks for nanoscale electronics assembled without the need for complex and costly

fabrication facilities. Boron- and phosphorous-doped silicon nanowires were used as building

blocks to assemble three types of semiconductor nanodevices. Passive diode structures

consisting of crossed p- and n-type nanowires exhibit rectifying transport similar to planar p-n

junctions. Active bipolar transistors, consisting of heavily and lightly n-doped nanowires

crossing a common p-type wire base, exhibit common base and emitter current gains as large

as 0.94 and 16, respectively. In addition, p- and n-type nanowires have been used to assemble

complementary inverter-like structures.

The facile assembly of key electronic device elementsfrom well-defined nanoscale building blocks may represent a step toward a "bottom-up"

paradigm for electronics manufacturing.

Scientists believe to have made a break through discovery that could one day allow us to

charge or power electrical devices such as cell phones, by converting body heat to electricity.

8/7/2019 TPE4001A23 PHY101


A team of scientists from the U.S. Department of Energy’s , Lawrence Berkeley National

Laboratory (Berkeley Lab) and the University of California at Berkeley have been working

with silicon nanowire-based converters and recently announced that they may have found a

way to use to increase the conversion efficiency by a factor of 100.Using a process called

electroless etching the scientist are able synthesize silicon nanowires in an aqueous solution

on the surfaces of wafers. The technique involves the galvanic displacement of silicon

through the reduction of silver ions on a wafer’s surface the team explain in their paper.

This technique of creating the nanowires results in vertically aligned wires that feature a

rougher surface than normal nanowires. It is believed that the rough surface of the nanowires

is to account for the high thermoelectric efficiency.

Silicon nanowire directional couplers can befabricated on a much smaller scale than their

conventional counterparts, which are made with glass

optical fibres or with waveguides based on

semiconductors, silica or lithium niobate.

Conventional directional couplers typically have

coupling lengths of hundreds of microns or even

millimetres, but the coupling length of a silicon

nanowire coupler may be 10 µm or less.

The silicon nanowire directional coupler may be

shown as per the given figure.

SILICON SOLAR CELLS

8/7/2019 TPE4001A23 PHY101


The fabrication of silicon nanowire-based solar cells on silicon wafers and on multicrystalline

silicon thin films on glass is described. The nanowires show a strong broadband optical

absorption, which makes them an interesting candidate to serve as an absorber in solar cells.

The operation of a solar cell is demonstrated with n-doped nanowires grown on a p-dopedsilicon wafer. The quest to builder a better , cheaper solar cell continues on, as researchers at

the New Jersey Institute of Technology have developed a new type of solar cell that can be

printed or painted onto flexible plastic sheets. Unlike traditional silicon cells, the print-on

cells are composed of silicon nanotubes and nanowires, which results in substantially cheaper

manufacturing costs and greater efficiency, since apparently carbon nanotubes are terrific

conductors. The scientists are quite excited for their research in these field.

Silicon Nanowires Boost Solar Cells:-

Solar cells made from silicon nanowires could give "classic" silicon-based photovoltaic or

other types of solid-state solar cells a run for their money, say researchers at the City

University of Hong Kong. Several research makers have succeeded in producing silicon

nanowire array photoelectrochemical solar cells that show more efficient light absorption per

unit device and thus higher light conversion efficiency at a lower cost than conventional

silicon-based cells. The way that the new arrays were prepared also means they could easily

be scaled up for large-area applications.

http://www.engadget.com/2007/06/16/spectrolab-designs-highly-efficient-solar-cell/

http://www.engadget.com/2007/07/14/korean-researchers-develop-uber-cheap-solar-cells/

http://www.engadget.com/tag/solar

http://www.engadget.com/2007/06/16/spectrolab-designs-highly-efficient-solar-cell/

http://www.engadget.com/2007/07/14/korean-researchers-develop-uber-cheap-solar-cells/

http://www.engadget.com/tag/solar

8/7/2019 TPE4001A23 PHY101


The majority of solar photovoltaic modules sold are silicon-based, but in recent years

increased demand for silicon solar cells has inflated the price of raw silicon materials. The

shortage of high-quality silicon has lead to research to find novel ways to design photovoltaic

cells using inexpensive, low-quality silicon alternatives. Photovoltaic cells based on silicon

nanowire arrays have emerged as a promising candidate for solar energy harvesting. Silicon

nanowire solar cells consist of arrays of radial p-n junction nanowires where the darker outer

shell is composed of n-type silicon, to which the electron acceptor phosphorous has been

added, and the lighter inner core from p-type silicon, to which the electron donor boron has

been added. Each individual nanowire in the array has a p-n junction and acts as a tiny

photovoltaic cell.

Silicon solar cells based on nanowires have much shorter p-n junctions that thin film solar

cells. In the nanowire structure, photo-excited electrons and holes (carriers) travel very short

distances before being collected by the electrodes. This results in a higher carrier-collection

efficiency in the core-shell nanowire structure, and this advantage leads to a higher tolerance

for material defects and allows the use of a lower-quality silicon. The core-shell nanowirestructure addresses the carrier-collection issue, one of the key factors that determine the

overall efficiency of a solar cell. However, the efficiency of photon capture in the nanowire

structures, another very important factor, has not yet been determined.

8/7/2019 TPE4001A23 PHY101


CONCLUSION

Nanotechnology allows us to alter the fundamental properties of matter, giving rise to novel

materials with desirable attributes and many new applications. This silicon-based

nanotechnology is compatible with and can easily be integrated into conventional silicon

microtechnology. Thus these devices are very useful for the betterment in the field of

technology.

8/7/2019 TPE4001A23 PHY101


REFERENCES

www.google.com Universal search website

www.wikipedia.com Educational

search website

www.scienceworld.com Science search

website

Nanotechnology Book by LYNN E.

FOSTER

http://www.google.com/

http://www.wikipedia.com/

http://www.scienceworld.com/

http://www.google.com/

http://www.wikipedia.com/

http://www.scienceworld.com/

tpe4001a23 phy101

Documents