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8/30/18
Semiconductor Physics and devices
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https://drive.google.com/open?id=1bCn33FMObalIvO6bnUQbhxG_wkAKLUn6
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Introduction to Electrodynamics by David J Griffith
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https://drive.google.com/open?id=1r9Hw08KiY2Dyc2g7oQBKR40aHMLkisWQ
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8/29/18
GRAPHENE: A VERSATILE MATERIAL
Introduction
.Graphene can be described as a one-
atom thick layer (Single layer) of graphite.
.It is the basic structural element of other
allotropes, including graphite, charcoal,
carbon nanotubes and fullerenes.
.Graphene is the strongest, thinnest
material known to exist.
Graphene is an atomic-scale honeycomb lattice
made of carbon atoms.
History
.First conceived in 1946. But they didn’t believe it
could be created at room temperature.
.One of the very first patents pertaining to the
production of graphene was filed in October,
2002 entitled, "Nano-scaled Graphene Plates“.
.Two years later, in 2004 Andre Geim and Kostya
Novoselov at University of Manchester extracted
single-atom-thick crystallites from bulk graphite
History
.Geim and Novoselov received
several awards for their
pioneering research on
graphene, notably the 2010
Nobel Prize in Physics.
.Graphene as we know it was
theoretically mentioned as
recent as 1984 to describe the
layers of graphite.
Graphene Properties
.2-dimensional, one of the crystalline allotrope of carbon
.Allotrope: property of chemical elements to exist in two or more forms
.It posses High electron mobility (which enhances the speed of device) and
lowered power usage.
.Graphene can be described as a one-atom thick layer of graphite.
.It facilitates high Sensitivity and device Miniaturization
Structure
.Graphene is a 2-dimensional network of carbon atoms.
.These carbon atoms are bound within the plane by strong bonds into a honeycomb
array comprised of six-membered rings.
.By stacking of these layers on top of each other, the well known 3-dimensional
graphite crystal is formed.
.It is a basic building block for graphitic materials of all other dimensionalities.
.It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes or stacked into 3D
graphite.
.Thus, graphene is nothing else than a single graphite layer.
Chemical Properties
.Graphene is chemically the most reactive form of carbon.
.Only form of carbon (and generally all solid materials) in which
each single atom is in exposure for chemical reaction from two
sides (due to the 2D structure).
.graphene is chemically stable, it can’t attack easily by strong
acids or bases
.At room temperature, it is stable with oxygen (GO), but at high
temperature nearly 700 it becomes carbon dioxide
.Graphene is commonly modified with oxygen- and nitrogen-
containing functional groups
Electronic Properties
.It is a zero-overlap semimetal (with both holes and electrons as charge carriers)
with very high electrical conductivity.
.Electrons are able to flow through graphene more easily than through even
copper.
.The electrons travel through the graphene sheet as if they carry no mass, as fast
as just one hundredth that of the speed of light.
.High charge carrier mobility, for which values of 10,000 cm2/Vs, in some cases
even 200,000 cm2/Vs were reported.
In an insulator or semiconductor, an electron bound to an atom can break free only if it
gets enough energy from heat or passing photon to jump the ‘band gap’.
But in graphene the gap is infinitesimal. This is the main reason why graphene’s
electron can move easily and very fast.
Mechanical Properties
.To calculate the strength of graphene, scientists
used a technique called Atomic Force Microscopy.
.It was found that graphene is harder than
diamond and about 300 times harder than steel.
.The tensile strength of graphene exceeds 1 TPa.
.It is stretchable up to 20% of its initial length.
Mechanical Properties
.Bond length is .142 nm long = very strong bond
.Very light at 0.77 milligrams per square metre, paper is 1000 times heavier
.Single sheet of graphene can cover a whole football field while weighing
under 1 gram
.Also, graphene is very flexible, yet brittle (preventing structural use)
It is expected that graphene’s
mechanical properties will find
applications into making a new
generation of super strong
composite materials and along
combined with its optical
properties, making flexible
displays.
Thermal Properties
.Graphene is a perfect thermal conductor
.Its thermal conductivity is much higher than all the other carbon structures as
carbon nanotubes, graphite and diamond (> 5000 W/m/K) at room temperature
.Being high thermal conductivity material, Under high temperature operating
conditions energy dissipation & temperature rise can’t occur in graphene devices
.Graphite, the 3 D version of graphene, shows a thermal conductivity about 5
times smaller (1000 W/m/K)
.The ballistic thermal conductance of graphene is isotropic, i.e. same in all
directions
Other properties
.Only known substance that is completely impermeable to gas.
.Graphene oxide reportedly has the ability to attract radioactive
material.
.Graphene has the ability to transmit up to 98% of light.
.It is possible to make graphene luminescent by inducing a suitable
band gap (doping), so that low costhigh efficient optoelectronic
devices can be manufactured
.Graphene enhances the photocatalytic properties of TiO2 like
materials
How graphene synthesized: Chemical
exfoliation
.The block graphite is submerged into a
solvent.
.An ultrasound is used to cause a
splitting effect within the graphite
structure.
.Prolonged exposure causes little
platelets to be formed.
.Enriched by a centrifuge.
Applications
While as of 2014, graphene is
not used in commercial
applications, many have been
proposed and/or are under
active development, in areas
including electronics, biological
engineering, filtration,
lightweight/strong composite
materials, photovoltaics and
energy storage.
Graphene
reinforced concrete
.Laboratory tests show that only 0.05% of GO
is needed to improve flexural strength of an
OPC matrix from between 41% to 59% and
compressive strength from between 15% to
33%.
.The addition of GO also improves the ductility
and reduces the likelihood of sudden failure
of concrete,
.Laboratory tests also show that the addition
of 0.05% GO improves pore structure and
decreases total porosity from 32.6% to
28.2%, providing higher compressive strength
and a more durable product
.The addition of GO improves the degree of
hydration of the cement paste and increases
the density of the cement matrix, creating a
more durable product.
Water
Desalination
Graphene oxide membranes allow
water vapor to pass through, but
are impermeable to other liquids,
harmful particles and gases. It can
be used to desalinate sea water
and filter it at a lower cost than
the reverse osmosis techniques
currently in use
Corrosion Resistant Coating
.It can be used as very important metallurgical tool.
.Corrosion – resistive coatings can be made from Graphene
sheets which could protect building and machinery elements
from corrosion
.It can help in doing so by conducting the charges responsible
for corrosion of the material
Integrated
circuits
oGraphene has a high carrier mobility, as well as low
noise, allowing it to be used as the channel in a field-
effect transistor.
oThe ability to build high frequency transistors with
Graphene is possible because in graphene electron
moves in higher speed than in silicon
oGraphene-based integrated circuit handled frequencies
up to 10 GHz.
oTransistors printed on flexible plastic that operate at
25 gigahertz
oTerahertz-speed transistor
Ultracapacitors
.Ultra capacitors store electrons on
Graphene sheets, taking advantage
of the large surface of graphene to
provide increase the electrical
power that can be stored in the
capacitor. This would help batteries
to be recharged in minutes instead
of hours
Opto
Electronics
.Graphene's high electrical conductivity and high
optical transparency make it a candidate for
transparent conducting electrodes.
.Graphene's mechanical strength and flexibility are
advantageous compared to indium tin oxide, which is
brittle.
.So it would work very well in optoelectronic
applications: touchscreens, liquid crystal displays,
organic photovoltaic cells, and organic light-emitting
diodes with low power consumption.
.Low cost, thinner display screens for smart phones &
TV screens
Solar cells
•Graphene turned to be a promising material
for photoelectrochemical energy conversion
in dye sensitized solar cells.
•The transparent, conductive, and ultrathin
graphene films are fabricated from exfoliated
graphite oxide, followed by thermal
reduction.
•The obtained films exhibit a high
conductivity of 550 S/cm and a transparency
of more than 70% over 1000-3000 nm.
Energy Storage
Devices
.Due to the extremely high
surface area to mass ratio of
graphene, one potential
application is in the conductive
plates of Supercapacitors.
.It is believed that graphene could
be used to produce
Supercapacitors with a greater
energy storage density than is
currently available.
Anti-
Bacterial
•In 2010, the Chinese Academy of
Sciences has found that sheets
of graphene oxide are highly
effective at killing bacteria such
as Escherichia coli.
•This means graphene could be
useful in applications such as
hygiene products or packaging
that will help keep food fresh for
longer periods of time.
Biomedical
Graphene can be used to impact
drug directly inside the living
cells. Graphene could soon be
used to analyze DNA at a record-
breaking pace.
That’s the claim of a physicist in
the US who has proposed a new
way of reading the sequence of
chemical bases in a DNA strand
by sending the molecule through
a tiny slit in a graphene sheet.
Other Applications
.Graphene nanoribbons
.IR detectors
.Single-molecule gas detection
.Piezoelectric materials
.Energy Harvesting
.Composite Materials
.Liquid Cells for Electron Microscopy
.Thermal management materials
.Optical Modulators
.Chemical sensors
Challenges Surrounding Graphene
.High Price at this moment (1cm2 = Rs.3700/-)
.A very hydrophobic material
.Very expensive and hard to manufacture for most companies.
.When deployed it seemed that the results weren’t duplicated.
.Graphene is hard to produce in large usable sheets. Small flakes are what we use
to test usually.
References
.http://www.sciencedaily.com/releases/2012/09/120910082304.htm
.De la Fuente, Jesus. www.graphene.com.13 April 2015
.Colapinto, John. “Graphene may be the most remarkable substance ever discovered. But what is it for?”.The
New Yorker, 22 December, 2014.Web.13 April, 2015
.Wang, Brian.”Graphene Hybrid Supercapacitors storing as much as lead acid batteries which is six times
commercial supercapacitors” www.nextbigfuture.com 17 April, 2015. Web 20 April, 2015.
.Johnson, Dexter. “Graphene circuit competes head to head with Si technology.”www.spectrum.ieee.org 3
February, 2014.Web.20 April, 2014.
.Malasarn, Davin. “UCLA Researchers develop new technique to scale up production of graphene micro super
capacitors”.
Its a Wonder material that could
revolutionize the world
Its a Wonder material that could
revolutionize the world
.Graphene can be described as a one-
atom thick layer (Single layer) of graphite.
.It is the basic structural element of other
allotropes, including graphite, charcoal,
carbon nanotubes and fullerenes.
.Graphene is the strongest, thinnest
material known to exist.
Graphene is an atomic-scale honeycomb lattice
made of carbon atoms.
History
.First conceived in 1946. But they didn’t believe it
could be created at room temperature.
.One of the very first patents pertaining to the
production of graphene was filed in October,
2002 entitled, "Nano-scaled Graphene Plates“.
.Two years later, in 2004 Andre Geim and Kostya
Novoselov at University of Manchester extracted
single-atom-thick crystallites from bulk graphite
History
.Geim and Novoselov received
several awards for their
pioneering research on
graphene, notably the 2010
Nobel Prize in Physics.
.Graphene as we know it was
theoretically mentioned as
recent as 1984 to describe the
layers of graphite.
Graphene Properties
.2-dimensional, one of the crystalline allotrope of carbon
.Allotrope: property of chemical elements to exist in two or more forms
.It posses High electron mobility (which enhances the speed of device) and
lowered power usage.
.Graphene can be described as a one-atom thick layer of graphite.
.It facilitates high Sensitivity and device Miniaturization
Structure
.Graphene is a 2-dimensional network of carbon atoms.
.These carbon atoms are bound within the plane by strong bonds into a honeycomb
array comprised of six-membered rings.
.By stacking of these layers on top of each other, the well known 3-dimensional
graphite crystal is formed.
.It is a basic building block for graphitic materials of all other dimensionalities.
.It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes or stacked into 3D
graphite.
.Thus, graphene is nothing else than a single graphite layer.
Chemical Properties
.Graphene is chemically the most reactive form of carbon.
.Only form of carbon (and generally all solid materials) in which
each single atom is in exposure for chemical reaction from two
sides (due to the 2D structure).
.graphene is chemically stable, it can’t attack easily by strong
acids or bases
.At room temperature, it is stable with oxygen (GO), but at high
temperature nearly 700 it becomes carbon dioxide
.Graphene is commonly modified with oxygen- and nitrogen-
containing functional groups
Electronic Properties
.It is a zero-overlap semimetal (with both holes and electrons as charge carriers)
with very high electrical conductivity.
.Electrons are able to flow through graphene more easily than through even
copper.
.The electrons travel through the graphene sheet as if they carry no mass, as fast
as just one hundredth that of the speed of light.
.High charge carrier mobility, for which values of 10,000 cm2/Vs, in some cases
even 200,000 cm2/Vs were reported.
In an insulator or semiconductor, an electron bound to an atom can break free only if it
gets enough energy from heat or passing photon to jump the ‘band gap’.
But in graphene the gap is infinitesimal. This is the main reason why graphene’s
electron can move easily and very fast.
Mechanical Properties
.To calculate the strength of graphene, scientists
used a technique called Atomic Force Microscopy.
.It was found that graphene is harder than
diamond and about 300 times harder than steel.
.The tensile strength of graphene exceeds 1 TPa.
.It is stretchable up to 20% of its initial length.
Mechanical Properties
.Bond length is .142 nm long = very strong bond
.Very light at 0.77 milligrams per square metre, paper is 1000 times heavier
.Single sheet of graphene can cover a whole football field while weighing
under 1 gram
.Also, graphene is very flexible, yet brittle (preventing structural use)
It is expected that graphene’s
mechanical properties will find
applications into making a new
generation of super strong
composite materials and along
combined with its optical
properties, making flexible
displays.
Thermal Properties
.Graphene is a perfect thermal conductor
.Its thermal conductivity is much higher than all the other carbon structures as
carbon nanotubes, graphite and diamond (> 5000 W/m/K) at room temperature
.Being high thermal conductivity material, Under high temperature operating
conditions energy dissipation & temperature rise can’t occur in graphene devices
.Graphite, the 3 D version of graphene, shows a thermal conductivity about 5
times smaller (1000 W/m/K)
.The ballistic thermal conductance of graphene is isotropic, i.e. same in all
directions
Other properties
.Only known substance that is completely impermeable to gas.
.Graphene oxide reportedly has the ability to attract radioactive
material.
.Graphene has the ability to transmit up to 98% of light.
.It is possible to make graphene luminescent by inducing a suitable
band gap (doping), so that low costhigh efficient optoelectronic
devices can be manufactured
.Graphene enhances the photocatalytic properties of TiO2 like
materials
How graphene synthesized: Chemical
exfoliation
.The block graphite is submerged into a
solvent.
.An ultrasound is used to cause a
splitting effect within the graphite
structure.
.Prolonged exposure causes little
platelets to be formed.
.Enriched by a centrifuge.
Applications
While as of 2014, graphene is
not used in commercial
applications, many have been
proposed and/or are under
active development, in areas
including electronics, biological
engineering, filtration,
lightweight/strong composite
materials, photovoltaics and
energy storage.
Graphene
reinforced concrete
.Laboratory tests show that only 0.05% of GO
is needed to improve flexural strength of an
OPC matrix from between 41% to 59% and
compressive strength from between 15% to
33%.
.The addition of GO also improves the ductility
and reduces the likelihood of sudden failure
of concrete,
.Laboratory tests also show that the addition
of 0.05% GO improves pore structure and
decreases total porosity from 32.6% to
28.2%, providing higher compressive strength
and a more durable product
.The addition of GO improves the degree of
hydration of the cement paste and increases
the density of the cement matrix, creating a
more durable product.
Water
Desalination
Graphene oxide membranes allow
water vapor to pass through, but
are impermeable to other liquids,
harmful particles and gases. It can
be used to desalinate sea water
and filter it at a lower cost than
the reverse osmosis techniques
currently in use
Corrosion Resistant Coating
.It can be used as very important metallurgical tool.
.Corrosion – resistive coatings can be made from Graphene
sheets which could protect building and machinery elements
from corrosion
.It can help in doing so by conducting the charges responsible
for corrosion of the material
Integrated
circuits
oGraphene has a high carrier mobility, as well as low
noise, allowing it to be used as the channel in a field-
effect transistor.
oThe ability to build high frequency transistors with
Graphene is possible because in graphene electron
moves in higher speed than in silicon
oGraphene-based integrated circuit handled frequencies
up to 10 GHz.
oTransistors printed on flexible plastic that operate at
25 gigahertz
oTerahertz-speed transistor
Ultracapacitors
.Ultra capacitors store electrons on
Graphene sheets, taking advantage
of the large surface of graphene to
provide increase the electrical
power that can be stored in the
capacitor. This would help batteries
to be recharged in minutes instead
of hours
Opto
Electronics
.Graphene's high electrical conductivity and high
optical transparency make it a candidate for
transparent conducting electrodes.
.Graphene's mechanical strength and flexibility are
advantageous compared to indium tin oxide, which is
brittle.
.So it would work very well in optoelectronic
applications: touchscreens, liquid crystal displays,
organic photovoltaic cells, and organic light-emitting
diodes with low power consumption.
.Low cost, thinner display screens for smart phones &
TV screens
Solar cells
•Graphene turned to be a promising material
for photoelectrochemical energy conversion
in dye sensitized solar cells.
•The transparent, conductive, and ultrathin
graphene films are fabricated from exfoliated
graphite oxide, followed by thermal
reduction.
•The obtained films exhibit a high
conductivity of 550 S/cm and a transparency
of more than 70% over 1000-3000 nm.
Energy Storage
Devices
.Due to the extremely high
surface area to mass ratio of
graphene, one potential
application is in the conductive
plates of Supercapacitors.
.It is believed that graphene could
be used to produce
Supercapacitors with a greater
energy storage density than is
currently available.
Anti-
Bacterial
•In 2010, the Chinese Academy of
Sciences has found that sheets
of graphene oxide are highly
effective at killing bacteria such
as Escherichia coli.
•This means graphene could be
useful in applications such as
hygiene products or packaging
that will help keep food fresh for
longer periods of time.
Biomedical
Graphene can be used to impact
drug directly inside the living
cells. Graphene could soon be
used to analyze DNA at a record-
breaking pace.
That’s the claim of a physicist in
the US who has proposed a new
way of reading the sequence of
chemical bases in a DNA strand
by sending the molecule through
a tiny slit in a graphene sheet.
Other Applications
.Graphene nanoribbons
.IR detectors
.Single-molecule gas detection
.Piezoelectric materials
.Energy Harvesting
.Composite Materials
.Liquid Cells for Electron Microscopy
.Thermal management materials
.Optical Modulators
.Chemical sensors
Challenges Surrounding Graphene
.High Price at this moment (1cm2 = Rs.3700/-)
.A very hydrophobic material
.Very expensive and hard to manufacture for most companies.
.When deployed it seemed that the results weren’t duplicated.
.Graphene is hard to produce in large usable sheets. Small flakes are what we use
to test usually.
References
.http://www.sciencedaily.com/releases/2012/09/120910082304.htm
.De la Fuente, Jesus. www.graphene.com.13 April 2015
.Colapinto, John. “Graphene may be the most remarkable substance ever discovered. But what is it for?”.The
New Yorker, 22 December, 2014.Web.13 April, 2015
.Wang, Brian.”Graphene Hybrid Supercapacitors storing as much as lead acid batteries which is six times
commercial supercapacitors” www.nextbigfuture.com 17 April, 2015. Web 20 April, 2015.
.Johnson, Dexter. “Graphene circuit competes head to head with Si technology.”www.spectrum.ieee.org 3
February, 2014.Web.20 April, 2014.
.Malasarn, Davin. “UCLA Researchers develop new technique to scale up production of graphene micro super
capacitors”.
Its a Wonder material that could
revolutionize the world
Its a Wonder material that could
revolutionize the world
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