Producing graphene

Strongly crumpled graphene sheet on a Si wafer

There are many different ways to create or isolate graphene. Graphene can exist as tiny flakes, large sheets or in a solution. Each form lends itself to unique applications.

Graphene flakes of different thickness
Graphene flakes of different thickness

Creating graphene using the CVD process

One of the most popular methods to create graphene at this moment in time is by using a process called chemical vapour deposition (CVD). The benefits of using CVD to deposit materials onto a substrate are that the quality of the resulting materials is usually very high.

CVD is a way of depositing gaseous reactants onto a heated substrate such as nickel or copper. Gas molecules are combined in a reaction chamber, the resulting reaction creates a graphene film upon contact with the substrate.

Mechanical exfoliation of graphene

Mechanical exfoliation is the original method used by Prof Sir Andre Geim and Prof Sir Kostya Novoselov to isolate a single graphene flake. Scotch tape was used to remove layers from bulk graphite, these layers are then transferred to a substrate such as silicon. On removing the tape single layer graphene with large crystal sizes is left on the substrate.

Liquid exfoliation of graphene

Liquid exfoliation of graphite involves blasting the raw bulk material into small fragments of graphene using ultrasonic energy. Powdered graphite is typically sonicated in a solvent over a number of hours to extract individual layers.

Electrochemical exfoliation of graphene

Electrochemical exfoliation is one phase of liquid exfoliation. An electrode of graphite is introduced to a solvent with a current applied. If the graphite is positive electrode graphene oxide is produced, conversely when the graphite is present at the negative electrode non-oxidised graphene flakes are produced. The graphene or graphene oxide will deposit at the bottom of the reaction chamber.

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