navdeep kaur presentation

8/2/2019 Navdeep Kaur Presentation

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Nanomaterials is a field that takes a materialscience based approach to nanotechnology

It studies materials with morphologicalfeatures on the nanoscale, and especiallythose that have special properties stemmingfrom their nanoscale dimensions.

Nanoscale is usually defined as smaller than a

one tenth of a micrometer in at least onedimension.



1.Fullerenes

2.Nanoparticles

The fullerenes are a class of allotropes of

carbon which conceptually are graphenesheets rolled into tubes or spheres. Theseinclude the carbon nanotubes (or siliconnanotubes) which are of interest both

because of their mechanical strength and alsobecause of their electrical properties.



Nanoparticles or nanocrystals made of metals, semiconductors, or oxides are of particular interest for their mechanical,electrical, magnetic, optical, chemical and

other properties. Nanoparticles have beenused as quantum dots and as chemicalcatalysts.



Top-down approach

Bottom-up approach



Uses thetraditionalmethods to

pattern abulk waferas in EE 418lab.

Is limited bytheresolution of lIthography.

http



Adding a layer of material over theentire wafer andpatterning thatlayer throughphotolithography.

Patterning bulk

silicon by etchingaway certainareas.



Use of 193excimer laser with

phase shift masksto for size 65 nm.

Phase shift masksand complex of

optics are used toachieve thisresolution.

193 nm ArF excimer laser

photolithography stepper



Cost of new machinesand clean roomenvironments growsexponentially with

newer technologies. Physical limits of

photolithography arebecoming a problem.

With smallergeometries andconventional materials,heat dissipation is aproblem.



The opposite of thetop-downapproach.

Instead of takingmaterial away tomake structures,the bottom-upapproach selectivelyadds atoms tocreate structures.



Nature uses thebottom upapproach.◦ Cells◦ Crystals◦ Humans

Chemistry and

biology can helpto assemble andcontrol growth.



Etched wafer with

desired pattern

Apply layer of

photoresist

Expose wafer with UV

light through mask and

etch wafer

Start with bulk wafer

Top Down Process Bottom Up Process

Start with bulk wafer

Alter area of wafer wherestructure is to be created by

adding polymer or seed

crystals or other

techniques.

Grow or assemble the

structure on the area

determined by the seed

crystals or polymer.

(self assembly)

Similar results can be obtained through bottom-up and top-down processes



Allows smaller geometries thanphotolithography.

Certain structures such as CarbonNanotubes and Si nanowires are grown

through a bottom-up process. New technologies such as organicsemiconductors employ bottom-upprocesses to pattern them.

Can make formation of films and structures

much easier. Is more economical than top-down in that it

does not waste material to etching.



The principle behind bottom-up processing. Self assembly is the coordinated action of

independent entities to produce larger,ordered structures or achieve a desiredshape.

Found in nature.

Start on the atomic scale.



Self-organizingdeposition of siliconnanodots.

Formation of Nanowires.

Nanotube transistor.

Self-assembled

monolayers. Carbon nanotube

interconnects.



Most commonapplications are inoptical devices andmemory.

Silicon nanodots aredeposited ontosilicon dioxide withno need forlithographicpatterning.



Process for makingnanodots

1. Apply layer of self-assembledpolymer film.

2. Grow layer of

desired materialto createnanodot.

Polymer template for nanodot

65 billion nanodots per square cm



Each nanodot can

hold one bit of

information.

10 Trillion dotsper square inch.

13 nm high

80 nm wide

Self Assembled Nanodots

http://physics.nist.gov/Divisions/Div841/Gp3/Projects/Atom/images/nanodots.gif



Stronger than steel Multiple tubes slide

inside of each otherwith minimal effects of

friction. Electrical current

density 1000 timesgreater than silver orcopper.

Can range from havingmetallic properties tosemiconductorproperties based on it’sconfiguration.

http://en.wikipedia.org/wiki/Image:Kohlenstoffnanoroehre_Animation.gif



metallic

Semimetallic and

semiconducting



Deposit few particles of Iron (most common) toact as catalyst.

Apply a hot environment

of carbon containing gas(typically CH4) The particle catalyzes the

decomposition of the gasand carbon dissolves inthe particle.

When the particle issupersaturated withcarbon, it extrudes theexcess carbon in the formof a tube.



Basic diagram for ananotube transistor

Benefits of transistor

over conventionaldesigns:◦ Smaller◦ Faster

◦ Less material used

◦

Many of the problemsassociated withconventional devicesare solved

http://www.nanotech-now.com/images/Infineon-nanotube.jpg

http://www.nanotech-now.com/images/Infineon-nanotube.jpg



Diagram of Nanotube

transistor

Carbon Nanotube

SiO2

Ti/Au Contact

AFM Image

Amine silane



DNA strands connectto gold electrodes ontop of silicon.

DNA strands connectto ends of carbonnanotube.

Silicon and nanotubesare mixed and the

DNA makes theconnections to formnanotube transistors.

http://www.trnmag.com/Photos/2004/12150

4/DNA%20makes%20nanotube%20transist

ors%20Image.html



Interface between metalelectrodes and carbonnanotube is verysensitive.

Changing just oneatom can significantlyaffect transistorperformance.

Self-assemblingnanotubes is not

efficient. Growing nanotubes in

place has had littlesuccess.



Molecules aredepositedmolecule-by-

molecule to form aself-assembledmonolayer.

Creates a highquality layer of

material. Layers aredeposited one layerat a time.



Organic moleculescan’t be depositedusing extremeconditions because it

would damage theorganic molecules. SAMS technique does

not damage organicmolecules.

SAMS films are nearly

defect free. Used to deposit organic

semiconductors.



Metal contact actsas a catalyst topromote one-dimensionalcrystal growth.

Can one day be

implemented asinterconnects.

Silicon Nanowire Diameter <1nm



Can have a muchgreater conductivitythan copper.

Is more heat resistant

than copper. Carries a much larger

current than copper. Orientation of carbon

nanotubes remains aproblem.

Technology is notreliable enough to beused in devicemanufacturing.

Carbon nanotubes

grown on a metal

contact through

PECVD.

Carbon nanotubes after

layer of silicon dioxide

added.



Making sure that the structures grow andassemble in the correct way.

Forming complex patterns and structuresusing self assembly.

Contamination has a significant impact ondevices with such small geometries.

Fabricating robust structures.



Combination of top-down andbottom-up

processes tosimplifyconstruction.

Use catalysts andstresses to achievemore one-directional growth.



Carbon nanotubetransistor (StanfordU.)

Organic monolayersfor organic transistor(Yale U.)

Nanotube basedcircuit constructed

(IBM) Nanomotors and

gears created (NASA)



Vias and interconnectsbeing implemented withcarbon nanotubes.

Nanotube transistors

replacing conventionaldesigns.

SAMS being used tocreate organicsemiconductor baseddevices.

Carbon nanotubesbecoming more and moreprevalent as their growthis controlled.

Nanotube array possibly used in

future televisions.



Top-down processing has been and will bethe dominant process in semiconductormanufacturing.

Newer technologies such as nanotubes and

organic semiconductors will require abottom-up approach for processing.

Self-assembly eliminates the need forphotolithography.

Bottom-up processing will become moreand more prevalent in semiconductormanufacturing.



Submitted by Navdeep kaur Ch-8232 B.E Chemical 4th yr

navdeep kaur presentation

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