Strong Field-Effect in Graphene on SiC(0001)

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2 Νοε 2013 (πριν από 3 χρόνια και 1 μήνα)

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Strong Field
-
Effect in Graphene on SiC(0001)


Randall Feenstra, Carnegie Mellon University, DMR
-
0503748

Graphene,

consisting

of

monolayer

thick

carbon,

can

be

produced

as

an

isolated

layer

(exfoliated

graphite)

or

as

an

epitaxial

layer

on

a

SiC(
0001
)

surface
.

We

have

used

the

latter

method

to

produce

graphene

on

4
H
-
SiC

by

heating

at

1300
°
C

in

ultra
-
high

vacuum

with

in
-
situ

monitoring

by

electron

diffraction
.

The

graphene

formation

is

performed

at

CMU,

while

transistor

fabrication

(with

1
.
5
x
0
.
5

mm
2

channel

area)

is

performed

at

Sarnoff

Corp
.

A

strong

field
-
effect

is

found

in

the

transistors,

with

mobility

of

535

cm
2
/Vs,

exceeding

that

of

prior

room

temperature

studies
.

Further

improvement

is

likely,

by

modification

of

the

graphene

formation

procedure

to

eliminate

surface

pits

[seen

in

panel

(c)]

that

are

believed

to

form

because

of

residual

surface

contamination

present

during

the

heating
.

Gu, Nie, Feenstra, Devaty, Choyke, Chan,
Kane,
Appl. Phys. Lett.
90
, 23507 (2007)

(a) Schematic cross
-
section of the semimetal
graphene based transistor, (b) AFM image of
the 4H SiC surface after H
-
etching prior to
graphitization, and (c) AFM image after
graphitization.

2.5 ML graphene

56 nm Au

Semi
-
insulating 4H SiC
substrate

530
nm

polystyrene

66 nm Au

(a)

Undergraduate Research Project for Improved
Graphene Formation


Kenji Oman and Randall Feenstra, Carnegie Mellon University

A

two
-
step

procedure

is

used

for

forming

graphene

on

SiC
:

first

the

SiC

is

heated

to

1700
°
C

in

hydrogen

to

etch

the

surface

thereby

removing

polishing

damage,

and

second

it

is

heated

to

1300
°
C

in

vacuum

to

sublimate

Si

and

leave

C

(graphene)

on

the

surface
.

The

two

steps

are

currently

performed

in

separate

vacuum

systems

in

Feenstra’s

laboratory
.

A

new

vacuum

system

capable

to

performing

both

processing

steps

without

intervening

air

exposure

was

developed

by

Kenji

Oman,

an

undergraduate

in

Feenstra’s

laboratory
.

The

system

contains

two

thin

Ta

strips

that

are

heated

resistively
;

one

strip

is

used

for

the

H
-
etching

(and

it

disintegrates

after

that

step)

and

the

second

for

the

graphitization
.

The

photo

shows

a

picture

of

Kenji

with

the

system

that

he

built

up
.