Abstract:
Graphene is one of the most promising nanomaterial due to its unique combination of
exceptional properties with wide range of applications. Single atomic thickness with
extremely high electron mobility and a zero-band gap provides many advantages to the
graphene as an electronic material. Sri Lanka is one of the countries having a vein graphite
with high purity of carbon. However, Sri Lanka is still exporting the graphite as a raw material.
This research was carried out to exfoliate mono layer graphene from Sri Lankan vein graphite
and to fabricate field effect transistors and to study electronic properties. We used a simple
scotch tape technique to transfer single layer of graphene onto a 300 nm SiO2 coated Si
substrate. The graphene sheets which are produced using this method have been given a high
quality, incomparable with other methods with lateral sizes up to 100µm. The thickness and
the uniformity of the graphene layer were tested using Atomic Force Microscopy (AFM). The
thickness was confirmed to be 0.4 nm as shown in the Figure. The AFM images also confirmed
the presence of double layer graphene with thickness of 0.9 nm. The Field Effect Transistor
was fabricated by making electrical contact using thermal evaporation of gold and we found
that the graphene layer showed an ambipolar current response with a positive Dirac voltage.
Also, we calculated the electron and hole mobility in the graphene channel. Electron mobility
of the FETs was smaller than the hole mobility which indicates the increase effective mass of
electrons in Sri Lankan graphene Our studies suggested that the Sri Lankan graphite is one of
best raw material for graphene exfoliation and the graphene exfoliated can be used for device
applications.
