Nanoscience An area dealing with study of material of very small dimension typically of order of 10e-9. Concerns with chemistry, physics & biology all science streams. Promotes better understanding our world.

What can we see there Various effects that occur at various physical processes are: i. Electrostatic ii. Vander Waal affects that can be seen iii. Brownian iv. quantum v. Gravity vi. Friction vii. Combustion

TYPES OF FABRICATION TECHNIQUES BOTTOM UPTECHNIQUES TOP DOWN TECHNIQUES OTHER PRODUCTION PROCESS

I)BOTTOM UP TECHNIQUES SOL GEL METHOD SELF ASSEMBLY AEROSOL BASED PROCESS CHEMICAL VAPOUR DEPOSITION INERT GAS CONDENSATION

1.SOL GEL METHOD Wet-chemical technique used in the field of material science and ceramic engineering. Used to generate nano-particles by gelation, precipitation and hydro thermal treatment. Formation of nanomaterials involves connecting the metal centers (M-O-M) &(M-OH-M) bridges. in this sol is transformed into diphasic system.

Advantages of sol-gel process Produces material at ultra low temp. low cost. Produces extremely homogeneous alloy. Ultra high purity material(99.99%).

2.SELF ASSEMBLY Assembling of components by bouncing around in a solution till a stable structure is reached. This starts with atoms or molecules and builds up nanostructures. It is important to understand and control the intra molecular behavior of synthesized molecules. It is done using a surface to localize and stabilize them.

3.AEROSOL – BASED PROCESSES Aerosols – based processes are a common method for industrial production of nano particles e.g. CdS nanoparticles - micro–droplets containing Cd salt in atmosphere of H 2 S.

4.CHEMICAL VAPOUR DEPOSITION(CVD) The two most important CVD technologies are: 1. LPCVD(LOW PRESSURE CVD) 2. PECVD(PLASMA ENHANCED CVD) A schematic diagram of typical LPCVD reactor is shown in Fig.

5.INERT GAS CONDENSATION Solid material evaporated by resistive heating. Rapidly condensed in the inert gas in the form of crystals on a cold finger maintained at liquid nitrogen temp. Nano particles scrapped & collected. Useful to produce composite material. Particle size can be controlled by evaporation rate & condensation gas pressure.

Inert gas condensation Fig. Resembles finger

II) TOP DOWN APPROACH  NANO LITHOGRAPHY  ELECTRON BEAM LITHOGRAPHY  DIP PEN LITHOGRAPHY  UV LITHOGRAPHY  HIGH ENERGY BALL MILLING

1.NANO LITHOGRAPHY LITHOGRAPHY Is transfer of a pattern to a photosensitive material by selective exposure to a radiation source such as light.

a) Pattern transfer from patterned photo resist to underlying layer by etching. b) Pattern transfer from patterned photo resist to overlying layer by lift-off.

Dip –pen Lithography The key features of this method are:  Resolution nm  Liquid environment  Multiple layer writing  Multiple pen writing

2.HIGH ENERGY BALL MILLING GRAIN SIZE REDUCED TO NANOMETER RANGE. MECHANICAL DEFORMATION BY BALL MILLING. MAGNETIC & CATALYTIC NANOPARTICLES ARE PRODUCED.

III)OTHER PROCESSES ELECTRO DEPOSITION EPITAXY THERMAL OXIDATION PHYSICAL VAPOUR DEPOSITION COMBUSTION THERMAL PLASMA MILLING THERMAL SPRAY CASTING

1.ELECTRODEPOSIT ION This process is also known as “electroplating”and is typically restricted to electrically conductive materials.

2.Epitaxy THIS technology is similar to what happens in CVD processes.It is possible with this process to continue building on the substrate with the same crystallographic orientation.

3.THERMAL OXIDATION This is one of the most basic deposition technologies. It is simply oxidation of the substrate surface in an oxygen rich atmosphere.

4. PHYSICAL VAPOUR DEPOSITION PVD Covers a number of deposition technologies in which material is released from a source and transferred to the substrate.The two most important techniques are : A. Evaporation B. Sputtering

A.evaporati on. There are two popular evaporation technologies,which are: I. E-beam evaporation II. Resistive evaporation each Referring to the heating methods.

B. SPUTTERING Sputtering is a technology in which the material is released from the source at much lower temperature than evaporation.

5.COMBUSTION THESE ARE USED TO CREATE NANO – SCALE MATERIALS IN BULK.

6.THERMAL PLASMA The main features of process are: 1. Operated in high pressure or atmospheric pressure. 2. Used for creating chemical reactions in a high –purity atmosphere. 3. Used for creating rapid large area nano-scale building. 4. Used for building nano-scale particles and materials in large quantities.

7. MILLING In milling process,sub micrometer particles are accelerated to bombard the surface of a substrate. They remove any material not protected by a resist material. The main features are: Primarily an etching process but used to create new materials resolution around 50 nanometer used for surface chemistry.

8.THERMAL SPRAY It takes the source of energy such as inflammable and ionized gas, explosive gas and electric energy.It then heats the powder of the thermal spray coating material(metal, nonmetal,ceramics).After that, it melts it or strongly blows the particles. Types of thermal spray are: 1. Plasma 2. HVOF(High velocity oxygen fuel) 3. Wire flame 4. Electric arc spray Some features: Creating chemical reactions in an arbitrary atmospohere Creating rapid large area nano –scale coatings Creating nano-scale particles Creating nano –materials in large quantities

9.CASTING In this process the material to be deposited is dissolved in liquid form in a solvent. The material can be applied to the substrate by spraying or spinning.

NANO FLOWER BEAUTIFUL CREATION DONE USING NANOTECHNOLOGY.

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