Recent advances in chemical vapour deposition have led
to the fabrication of large graphene sheets on metal foils for use in research
and development.
However, further breakthroughs are required in the way
these graphenes are transferred from their growth substrates onto the final
substrate because they normally break or conjugate in this process. Although
various methods have been developed, as yet there is no general way to reliably
transfer graphene onto arbitrary surfaces, such as ‘soft’ ones, like polymers
or textiles. Here, they reported a method that allows the graphene to be
transferred with high fidelity at the desired location on almost all surfaces,
including fragile polymer thin films and hydrophobic surfaces.
The method consisted on a sacrificial ‘self-releasing’
polymer layer placed between a conventional polydimethylsiloxane elastomer
stamp and the graphene that is to be transferred. This self-releasing layer
provides a low work of adhesion on the stamp, which facilitates delamination of
the graphene and its placement on the new substrate regardless of its nature.
This method synthesized the graphene by CVD over a metal (Cu or Ni) as it has
been reported previously. This makes easier to change the normal process that
has been used to adapted to this one.
To demonstrate that
the method can be done with any surface, they fabricate high field-strength
polymer capacitors using graphene as the top contact over a polymer dielectric
thin film.
These capacitors showed superior dielectric breakdown
characteristics compared with those made with evaporated metal top contactsby
CVD.
So they take it
to a new level by fabricating low-operation-voltage organic field-effect
transistors using graphene as the gate electrode placed over a thin polymer
gate dielectric layer.
So they finally made artificial graphite by
alternating layers of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ).
This compound, which comprises graphene sheets p-doped by partial hole transfer
from the F4TCNQ, shows a high and remarkably stable hole conductivity, even
when heated in the presence of moisture.