GRAPHENE TRANSISTORS: SPEEDING UP THE ELECTRONIC ...

basketontarioElectronics - Devices

Nov 2, 2013 (3 years and 11 months ago)

87 views

GRAPHENE TRANSISTORS:

SPEEDING UP THE ELECTRONIC
CONVERSION

Z
ACH

G
ANNON

J
ACOB

G
UTTENPLAN

THE TRANSISTOR TODAY


T
RANSISTORS

ARE

AN

INTEGRAL

PART

OF

OUR

LIVES


C
ONTROLS

VOLTAGE

AND

AMPLIFICATION


MANIPULATES

THE

FLOW

OF

ELECTRONS

VIA

SEMICONDUCTING

MATERIAL
.


U
TILIZED

SILICON

FOR

THE

METAL
-
OXIDE

SEMICONDUCTOR

SINCE

1960’
S


V
ERY

COMMONLY

USED

AS

INVERTERS

TRANSISTOR BREAKDOWN


T
RANSISTORS

ARE

AN

ESSENTIAL

PART

OF

ALL

MODERN

ELECTRONICS
.


T
HE

SEMICONDUCTING

SUBSTRATE

CAN

BE



P
-
CHANNEL



GRID

OF

HOLES


N
-
CHANNEL



ELECTRONS

HOW DOES GRAPHENE COME INTO PLAY?


Q
UALITIES

IN

THE

MECHANICAL
,
PHYSICAL
,
ELECTRONIC
,
AND

THERMAL

ASPECTS

GREATLY

SURPASS

THOSE

OF

SILICON


I
MPROVED

SUSTAINABILITY


L
ATTICE

STRUCTURE

FORMS

THE

TUNNELS

AND

PATHWAYS

THROUGH

WHICH

ELECTRONS

FLOW



MECHANICAL QUALITIES


ONLY

AN

ATOM

THICK



NEARLY

INVISIBLE

TO

THE

NAKED

EYE


YET

GRAPHENE

IS

EXTREMELY

STRONG
.


ABOUT

300
TIMES

HARDER

THAN

STEEL


A
LMOST

1000
TIMES

STRONGER

THAN

S
ILICON


C
AN

BE

MANIPULATED

INTO

MUCH

SMALLER

SIZES

BEFORE

FRACTURING

OR

MALFUNCTIONING
.


C
AN

STRETCH

20%
NATURAL

LENGTH

PHYSICAL QUALITIES


S
INGLE

ATOM

THICKNESS

AND

STRUCTURE

DEMONSTRATES

ONE

OF

GRAPHENE
'
S

GREATEST

ADVANTAGES
:


EXCEPTIONALLY

HIGH

QUALITY

CRYSTAL

FORMATIONS



ORGANIZED

LAYER

OF

HEXAGONAL

LATTICES

Graphene crystal lattice structure

Silicon crystal structure

ELECTRICAL QUALITIES


HIGH

CARRIER

MOBILITY

-

EXTENT

TO

WHICH

ELECTRONS

CAN

FREELY

FLOW


D
UE

TO

HEXAGONAL

LATTICE

STRUCTURE



S
O

HIGH

THAT

ELECTRONS

ARE

ABLE

TO

FLOW

THROUGH

GRAPHENE

MORE

EASILY

THAN

THROUGH

EVEN

COPPER
!


MUCH

MORE

EFFICIENT

THAN

SILICON


ALLOWS

ELECTRONS

TO

FLOW

MUCH

MORE

EASILY


GENERATES

LESS

HEAT



RESULTING

IN

A

MUCH

LOWER

LOSS

OF

ENERGY

THERMAL QUALITIES


H
IGH

THERMAL

CONDUCTIVITY


ABLE

TO

RETAIN

HEAT

WELL


NOT

HEAT

UP

TO

EXCESSIVE

TEMPERATURES



T
HIS

ABILITY

ALLOWS

GRAPHENE

TRANSISTORS

TO



OPERATE

AT

MORE

COMFORTABLE

TEMPERATURES



HAVE

A

LONGER

LIFESPAN

THAN

SILICON

COUNTERPARTS

(
WHICH

TEND

TO

HEAT

UP

OFTEN

AND

EASILY
!)


M
EASURED

ENERGY

LOSS

IS

NEGLIGIBLE


A
GAINST

S
ILICON

S

5
TO

10%
LOSS

THE PROBLEM WITH GRAPHENE

A
ND

HOW

IT

CAN

BE

RESOLVED

GRAPHENE THE SUPERCONDUCTOR


T
RANSISTORS

REQUIRE

SEMICONDUCTORS
, NOT
SUPERCONDUCTORS
!


H
IGH

CARRIER

MOBILITY

(
FROM

STRUCTURE
!) =
LOW

RESISTIVITY


R
ESISTIVITY

IS

SO

SMALL

THAT

IT

IS

ESSENTIALLY

ZERO



C
ONSTANTLY


ON
”,
NEVER

ABLE

TO

TURN


OFF



T
HIS

INABILITY

TO

SWITCH

OFF

IS

KNOWN

AS

A

L
ACK

OF

B
ANDGAP

BANDGAP


BANDGAP

-

THE

DIFFERENCE

IN

ENERGY

REQUIRED

TO

TRIGGER

THE

TRANSISTOR

(
SWITCHING
)


S
ILICON

= 1.1
ELECTRON

VOLTS


V
ERY

LOW
,
WHICH

IS

WHY

IT

IS

SO

WIDELY

USED
.


G
RAPHENE

S

PERFECT

HEXAGONAL

NATURE

REQUIRES

NO

ADDITIONAL

ENERGY



B
ECAUSE

ITS

ALWAYS

ON
!

CREATING A BANDGAP

W
ITH

SUCCESSFUL

ATTEMPTS
!

SILICON CARBIDE WAFERS


S
IMPLE

COMPLEX

OF

SILICON

AND

C
ARBON


T
OPMOST

SINGLE

ATOM

LAYER

OF

SILICON

IS

DRIVEN

OFF


L
EAVES

A

LAYER

OF

CARBON

(
GRAPHENE
)


L
ITHOGRAPHIC

ETCHING

CARVES

OUT

THE

TRANSISTOR

BASE


KEY STEP!


INTRODUCE

HYDROGEN

GAS

IN

MIDDLE

SECTION


C
REATES

THE

GATE

IBM’S GFET


U
TILIZES

SILICON

CARBIDE

WAFERS


H
OWEVER
,
USES

GOLD

CONTACTS


C
HEMICALLY

BONDS

MORE

EASILY

WITH

SILICON

CARBIDE


P
ERFORMED

AT

EXTREME

FREQUENCIES


U
PWARDS

OF

100 GH
Z


10
TIMES

FASTER

THAN

MOST

SILICON

TRANSISTORS


P
LUS

ITS

LIQUID

RESISTANT
!

TUNGSTEN DISULPHIDE


N
ATURALLY

FORMS

LAYERS


C
AN

FORM

WAFERS

OF

TUNGSTEN

DISULPHIDE

BETWEEN

TWO

LAYERS

OF

GRAPHENE


L
AYERING

NEEDS

NO

EXTERNAL

CONTACTS


P
REVENTS

HOTSPOTS


V
ERY

HIGH

MELTING

POINT



1523 K (1250
DEGREES

C)


C
HEMICALLY

INACTIVE


O
VERALL
,
ALMOST

NO

ENERGY

LOSS
!

UNI. OF MANCHESTER’S GFET


T
UNGSTEN

D
ISULPHIDE

WAFER

PROVIDES

BANDGAP


W
HEN

ON
,
ELECTRONS

CAN

BURROW

ABOVE

OR

UNDER

T
UNGSTEN

D
ISULPHIDE


W
HEN

OFF
,
NO

FLOW


W
ORKS

IN

THE

TRADITIONAL

SENSE


R
ECEIVES

CONTROL

VOLTAGE

FROM

GATE


M
ANIPULATES

WAFER

SEMICONDUCTING

SUBSTRATE

CONCLUSION



G
RAPHENE

IS

AN

OBVIOUSLY

VIABLE

SUBSTITUTE


B
UT

IS

IT

READY

YET
?


W
E

SAY
: T
HERE

S

ALWAYS

ROOM

TO

IMPROVE
.


Graphene

Silicon

Tensile
Strength

>1 Trillion
Pa

1.2 Billion
Pa

Size

1 Atom
Thick

Several atoms
thick

Electron
Mobility

1.0
×

10
6
cm
2
Vs

1

1.4
×

10
3

cm
2
Vs

1

Energy
Loss

negligible

5
-
10%