The left hand image is the topography; the middle the topography error image; and right the electrostatic force microscopy image where the tip bias has been switched half way through the image. Image: NPL |
Scientists
from the National Physical Laboratory, in collaboration with Linköping
University, Sweden, have shown that regions of graphene of different
thickness can be easily identified in ambient conditions using
electrostatic force microscopy (EFM).
The
exciting properties of graphene are usually only applicable to the
material that consists of one or two layers of the graphene sheets.
Whilst synthesis of any number of layers is possible, the thicker layers
have properties closer to the more common bulk graphite.
For
device applications one- and two-layer graphene needs to be precisely
identified apart from the substrate and regions of thicker graphene.
Exfoliated graphene sheets up to ~100 ?m in size can be routinely
identified by optical microscopy. However, the situation is much more
complicated in the case of the epitaxial graphene grown on silicon
carbide wafers with a diameter up to 5 inches where the straightforward
identification of the graphene thickness is difficult using standard
techniques.
This
research shows that EFM, which is one of the most widely accessible and
simplest implementations of scanning probe microscopy, can clearly
identify different graphene thicknesses. The technique can also be used
in ambient environments applicable to industrial requirements.
This work was recently published in Nano Letters.
