Researchers from Chalmers University of Technology in Sweden developed a method for fast and inexpensive quality control of graphene grown on silicon carbide (SiC). This method is based on optical microscopy and is used to understand the effect of the SiC substrate on the quality of the graphene layer. The researchers say this method paves the way for optical microscopy as an industrial quality control tool of epitaxial graphene on SiC.

The researchers explain that epitaxial graphene on silicon carbide often requires quality control because the surface of the silicon carbide reconstructs during graphene growth. Steps and defects in the substrate may lead to the appearance of stepped terraces and the formation of areas with many layers instead of a single layer. This limits the performance of the electronic devices and large-scale integration.

Graphene on silicon carbide has very little contrast so it wasn't considered possible to observe it directly by optical microscopy. By cross-checking optical data with electrical measurements the researchers discovered that a single layer of graphene on silicon carbide reflects about 1.3% of light which is enough to be detected in an optical microscope.

This method was developed as part of the EU project ConceptGraphene. Other partners in this project include Sweden’s Linkoping University and the UK’s National Physical Laboratory. The method is already used as a tool for epitaxial graphene growth at Linkoping University spin-off Graphensic.