nano materials

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NANO MATERIALS PRESENTED BY: ANJANA JAYASHRI BRANCH:CHE ‘A’

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Page 1: Nano materials

NANO MATERIALSPRESENTED BY: ANJANA JAYASHRIBRANCH:CHE ‘A’

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CONTENTS

PULSE LASER DEPOSITION

CHEMICAL DEPOSITION

PROPERTIES

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Pulsed Laser Depositiona) principleb) Experimental Setup

c)workingd) Advantages and

DisadvantagesTarget: Just about anything! (metals, semiconductors…)Laser: Typically excimer (UV, 10 nanosecond pulses)Vacuum: Atmospheres to ultrahigh vacuum

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CCD /PMT

spectrometer

Target

Substrates or Faraday

cup

laser beam

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PRINCIPLE: The laser pulse of high intensity and energy is used to evaporate carbon from graphiteThese carbon atoms are condensed to form nanotubes.DESCRIPTION:A quart tube contains a graphite target is kept inside a high temperature muffle furnace filled with argon gas and heated at 1473 K. A water cooled copper collector is fitted at other end.The target material contains small amount of Ni-Co to catalyse the formation of nano tubes.

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PROCESSES IN PVD:

LASER PULSE

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LATTICE

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· Flexible, easy to implement · Growth in any environment· Exact transfer of complicated materials

(YBCO)· Variable growth rate · Epitaxy at low temperature· Resonant interactions possible (i.e.,

plasmons in metals, absorption peaks in dielectrics and semiconductors)

· Atoms arrive in bunches, allowing for much more controlled deposition

· Greater control of growth (e.g., by varying laser parameters)

Advantages of PLD

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CHEMICAL VAPOUR DEPOSITION

INTRODUCTION Chemical Vapour Deposition (CVD) is a

chemical process used to produce high purity, high performance solid materials.

In a typical CVD process, the substrate is exposed to one or more volatile precursors which react and decompose on the substrate surface to produce the desired deposit.

During this process, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.

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Transport of reactants by forced

convection to the

deposition region

Transport of reactants

by diffusion from the main gas stream to

the substrate surface.

Adsorption of reactants in the wafer (substrate)

surface.

Chemical

decomposition and other

surface reactions

take place.Desorption

of by-products from the surface

Transport of by-products by diffusionTransport of

by-products by forced

convection away from

the deposition

region.

STEPS INVOLVED IN CHEMICAL VAPOUR DEPOSITION

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SCHEMATIC DIAGRAM - THE STEPS INVOLVED IN CVD

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CVD’s are classified into two types on the basis of Operating Pressure. 1. Atmospheric Pressure CVD 2. Low Pressure CVD Plasma Enhanced CVDPhotochemical Vapour DepositionThermal CVD

TYPES OF CVD

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Variable shaped surfaces, given reasonable access to the coating powders or gases, such as screw threads, blind holes or channels or recesses, can be coated evenly without build-up on edges.Versatile –any element or compound can be deposited. High Purity can be obtained. High Density – nearly 100% of theoretical value. Material Formation well below the melting point Economical in production, since many parts can be coated at the same time.

ADVANTAGES OF CHEMICAL VAPOUR DEPOSITION

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APPLICATIONS OF CHEMICAL VAPOUR DEPOSITION

CVD has applications across a wide range of industries such as: Coatings – Coatings for a variety of applications such as wear resistance, corrosion resistance, high temperature protection, erosion protection and combinations thereof.Semiconductors and related devices – Integrated circuits, sensors and optoelectronic devicesDense structural parts – CVD can be used to produce components that are difficult or uneconomical to produce using conventional fabrication techniques. Dense parts produced via CVD are generally thin walled and maybe deposited onto a mandrel or former.

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Properties of Nano Materials

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The melting point decreases dramatically as the particle size gets below 5 nm

Melting Point

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Band gap

The band gap is increases with reducing the size of the particles

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Surface Area

The total surface area (or) the number of surface atom increases with reducing size of the particles

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• For semiconductors such as ZnO, CdS, and Si, the bandgap changes with size

- Bandgap is the energy needed to promote an electron from the valence band to the conduction band

- When the bandgaps lie in the visible spectrum, changing bandgap with size means a change in color

• For magnetic materials such as Fe, Co, Ni, Fe3O4, etc., magnetic properties are size dependent

- The ‘coercive force’ (or magnetic memory) needed to reverse an internal magnetic field within the particle is size dependent

- The strength of a particle’s internal magnetic field can be size dependent

Size-DependentProperties of semiconductor and magnetic materials

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THANK YOU