May 23, 2011 — The UK National Physical Laboratories (NPL) scientists, in collaboration with Linköping University, Sweden, discovered that electrostatic force microscopy (EFM) can be used to identify graphene thicknesses under ambient conditions. The technique more accurately measures epitaxially grown graphene thickness on SiC wafers than traditional optical microscopy.

Figure. 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.

Optical microscopy identifies exfoliated graphene sheets up to ~100μm in size. For epitaxial graphene grown on silicon carbide (SiC) wafers, the nanomaterial’s thickness is difficult to determine with standard tools. EFM scanning probe microscopy is able to clearly identify different graphene thicknesses. The technique can also be used in ambient environments applicable to industrial requirements.

Thicker graphene sheets share common aspects with the bulk material graphite. Thin graphene sheets, such as 1 or 2 layers, have nano-induced properties. For semiconductor and photovoltaics device applications, one- and two-layer graphene needs to be precisely identified apart from the substrate and regions of thicker graphene.

The NPL/Linköping University work was recently published in Nano Letters. Access the article here: http://pubs.acs.org/doi/abs/10.1021/nl200581g

Learn more at www.npl.co.uk

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