Graphene continues to tantalize and frustrate experimentalists. A year ago, we saw that graphene was susceptible to contamination by exposure to a cold-cathode vacuum gauge. This week, a group led by IHP in Germany reports that graphene grown on copper is irreversibly contaminated by copper and iron. The contaminant concentration is high enough to adversely affect not only the electronic properties of the graphene, but also those of the silicon to which the graphene is transferred.
Ref: Lupina, et al., “Residual metallic contamination of transferred chemical vapor deposited graphene”, arXiv:1505.0889.