Sample Copy. Not For Distribution. · 1 Top-down & Bottom-up techniques: Formation of nanostructures by mechanical milling (ball.milling) and mechanical attrition, Chemical vapor

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Nanomaterial Volume II -

Nanomaterial Vol II


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Nanomaterial Volume II Nanomaterial Vol II

Dr. Jyotsna Chauhan,

And

Varsha mehto

EDUCREATION PUBLISHING (Since 2011)

www.educreation.in


iv


v

Nanomaterial Vol II

By

Dr Jyotsna Chauhan,

HOD Nanotechnology Deparment,

RGPV, Bhopal

Dr Varsha rani mehto


vi

ACKNOWLEDGEMENT

This book covers Mtech Nanotechnology syllabus .I express my

heartfelt gratitude and regards to my Husband shailendra

Chauhan,. HIS observation and comments help me to establish

the overall direction of the work and to move forward with my

work in depth. I thank him for providing me facilities and making

available literature and computer facility.I am highly grateful to

SHRI SUNIL GUPTAJI VICE CHANCELLOR , RGPV

Bhopal for providing me his consistent valuable and erudite

guidance, excellent cooperation and motivation at every step of

this project work that helped me to accomplish it successfully. I am

very much grateful to him not only for providing me indomitable

moral support but also for inspiring me to work hard, to the best of

my ability, efficiently and to excel.I express my sincere thanks to

my father , mother and my children shaswat and shatakshi

for continuous support during my project work


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part 1

Synthesis of Nanomaterials

Sr.No Chapter Page

Chapter I:

1 Top-down & Bottom-up techniques:

Formation of nanostructures by mechanical

milling (ball.milling) and mechanical

attrition, Chemical vapor deposition (CVD),

Physical vapour deposition.(PVD) thermal

and e beam evaporation, Pulsed laser

ablation (PLD).

1

Chapter II:

2 Chemical Routes for synthesis of.

Nanomaterials: Chemical.precipitation and

coprecipitation,

chemical bath deposition (CBD), Sol-gel

synthesis, Microemulsions or reverse

micelles,

Solvothermal synthesis, Thermolysis routes

and spray pyrolysis,

39

Chapter III:

3 Optical lithography: Light sources – photo

mask and alignment, Resolution in

projection systems

– positive and negative photo resists,

Electron beam lithography (Maskless

lithography),

70


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Semiconductor.processing.

Nanolithography, Nanoimprint lithography,

Dip-pen

nanolithography.

Chapter IV:

4 Preparation of amorphous materials, metallic

glass, thermal evaporation techniques such

as

sputtering, CVD Techniques, quenching.

Glasses, theory of glass transition, glass

transition

temperature. Structure of disordered

materials. Experimental techniques,

electronic density of

states. Localization phenomenon, transport,

optical and dielectric properties.

111


ix

part 2

Characterization Techniques of

Nanomaterials

Sr.No Chapter Page

Chapter I

1 X-ray Diffraction (XRD), powder and single

crystal Diffraction, X-ray fluorescence

(XRF), X ray photoelectron spectroscopy

(XPS), Energy Dispersive X-ray analysis

(EDAX), Extended X ray absorption fine

structures (EXAFS), Dispersive high

pressure XRD– Characterization of

Nanomaterials and Diamond anvil cells

(DAC)

174

Chapter II

2 Scanning tunneling microscopy (STM),

Contact and non contact atomic force

microscopy (AFM), Conductive AFM,

Magnetic force microscopy (MFM),

scanning tunneling spectroscopy (STS),

Nano indentation.

275

Chapter III

3 X-ray Diffraction (XRD), powder and single

crystal Diffraction, X-ray fluorescence

(XRF), X ray photoelectron spectroscopy

(XPS), Energy Dispersive X-ray analysis

(EDAX), Extended X ray absorption fine

321


x

structures (EXAFS), Dispersive high

pressure XRD– Characterization of

Nanomaterials and Diamond anvil cells

(DAC)

Chapter IV

4 Spectrophotometers,UV-Vis

spectrophotometers, IR spectrophotometers,

Fourier Transform Infrared radiation (FTIR),

photoluminescence, electroluminesce and

thermoluminescence spectroscopy, Nearfield

scanning optical microscopy (NSOM).

441

Chapter V

5 Scanning Electron Microscopy (SEM),

Transmission electron microscoy (TEM),

High resolution TEM Field emission SEM,

Electron energy loss spectroscopy (EELS),

Electron probe micro analyzer (EPMA).

477


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Synthesis of

Nanomaterials


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Nanomaterial Volume II

1

CHAPTER I

Bottom -Up and Top-Down Approaches

There are two approaches to the synthesis of nanomaterials and the

fabrication of nanostructures: top-down and bottom-up. Attrition or

milling is a typical top-down method in making nanoparticles,

whereas the colloidal dispersion is a good example of bottom-up

approach in the synthesis of nanoparticles. Lithography may be

considered as a hybrid approach, since the growth of thin films is

bottom-up whereas etching is top-down, while nanolithography

and nanomanipulation are commonly a bottom-up approach. Both

approaches play very important roles in modern industry and most

likely in nanotechnology as well. There are advantages and

disadvantages in both approaches.

Among others, the biggest problem with top-down approach is the

imperfection of the surface structure. It is well known that the

conventional top-down techniques such as lithography can cause

significant crystallographic damage to the processed and additional

defects may be introduced even during the etching steps.28 For

example, nanowires made by lithography is not smooth and may

contain a lot of impurities and structural defects on surface. Such

imperfections would have a significant impact on physical

properties and surface chemistry of nanostructures and

nanomaterials, since the surface over volume ratio in

nanostructures and nanomaterials is very large. The surface

imperfection would result in a reduced conductivity due to inelastic

surface scattering, which in turn would lead to the generation of

excessive heat and thus impose extra challenges to the device

design and fabrication.

Regardless of the surface imperfections and other defects that top-

down approaches may introduce, they will continue to play an



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important role in the synthesis and fabrication of nanostructures

and nanomaterials.

Bottom-up approach is often emphasized in nanotechnology

literature, though bottom-up is nothing new in materials synthesis.

Typical material synthesis is to build atom by atom on a very large

scale, and has been in industrial use for over a century. Examples

include the production of salt and nitrate in chemical industry, the

growth of single crystals and deposition of films in electronic

industry. For most materials, there is no difference in physical

properties of materials regardless of the synthesis routes,

provided that chemical composition, crystallinity, and

microstructure of the material in question are identical. Of course,

different synthesis and processing approaches often result in

appreciable differences in chemical composition, crystallinity, and

microstructure of the material due to kinetic reasons.

Consequently, the material exhibits different physical properties.

Bottom-up approach refers to the build-up of a material from the

bottom: atom-by-atom, molecule-by-molecule, or cluster-by-

cluster. In organic chemistry and/or polymer science, we know

polymers are synthesized by connecting individual monomers

together.

In crystal growth, growth species, such as atoms, ions and

molecules, after impinging onto the growth surface, assemble into

crystal structure one after another.

Although the bottom-up approach is nothing new, it plays an

important role in the fabrication and processing of nanostructures

and nanomaterials. There are several reasons for this. When

structures fall into a nanometer scale, there is little choice for a top-

down approach. All the tools we have possessed are too big to deal

with such tiny subjects.

Bottom-up approach also promises a better chance to obtain

nanostructures with less defects, more homogeneous chemical

composition, and better short and long range ordering.This is



3

because the bottom-up approach is driven mainly by the reduction

of Gibbs free energy, so that nanostructures and nanomaterials

such produced are in a state closer to a thermodynamic equilibrium

state. On the contrary, top-down approach most likely introduces

internal stress, in addition to surface defects and contaminations.

Figure 1.5 shows a miniature bull fabricated by a technique called

twophoton polyrnerizati~nw~h~e reas Fig. 1.6 shows a “molecular

person”, consisting of 14 carbon monoxide molecules arranged on

a metal surface fabricated and imaged by STM.30 These two

figures show what the current technology or nanotechnology is

capable of, and new capabilities are being developed and the

existing techniques are being further improved pushing the current

limit to a smaller size.


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Sample Copy. Not For Distribution. · 1 Top-down & Bottom-up techniques: Formation of nanostructures by mechanical milling (ball.milling) and mechanical attrition, Chemical vapor