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In graphene channel FETs (referred to as GFETs), Si

is used as substrate. Several layers of graphene held together

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by vander-waal’s forces constitute Graphite. A stack of

graphene layers of 1-5 nm thick called exfoilated graphene, is

used as channel material [9,11]. These layers are extracted

from graphite using an adhesive tape that sticks to the graphite

material, and is then peeled off. This process is done

repetitively until single or multiple layers of graphene remain

on the tape. This tape is now stuck on the chip and is removed

after some time. Raman Spectroscopy is used to detect the

graphene flakes left on the Sio2 surface [11].

GFET Fabrication:

The Source and Drain regions of a GFET are created using

PMMA and subsequent e-beam lithography. Al2O3 deposition

is done using a chemical vapor deposition method with

sequential self-terminating gas-solid reactions called Atomic

Layer Deposition (ALD) which can be achieved by the

following steps [11]:

1. Trimethylaluminum reacts with hydroxyl group on

the surface and when concentration of hydroxyl ions

saturates the reaction is terminated.

2. Then the remaining gas and by product are let out.

3. Water vapour is the second reactant. Reaction will

terminate when surface concentration saturates.

Remaining components are let out.

Graphene has no hydroxyl group compound formed

naturally. Hence Al is first deposited using e-beam

lithography on Graphene surface and left to undergo natural

oxidation. Then ALD process is conducted over it using

Trimethylaluminum and water vapour for in-situ Al2O3

growth. Then Gate electrode is created in the similar method

as above [1,11].Electrical Properties: As we know in the conventional

mechani…

…s weak Vander

Waals bond, due to which the physical and chemical

properties of graphene FETs remains unaltered after the oxide

deposition. Hence there are less chances of transport of

electron through oxide and high-k dielectric integration is

compatible with graphene.

Exfoliated graphene still offers the highest mobility

116,117,118 cm2/V s but there is a bottleneck in fabrication.

Back-gated graphene FETs with SiO2 dielectric were

typically shown to have field-effect mobilities up to around

10,000 cm2/V s [11].Challenges with Graphene FETs:

Graphene with interface dielectrics results in charged

carrier scattering which degrades the mobility of the carriers.

To reduce this effect, density of carriers and charged

impurities is to be reduced. Use of High K dielectric helps in

shielding the scattering effect but is still not effective [1,11].

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