Plenty of examples online, it's a matter of purity and number of defects: https://www.acsmaterial.com/materials/graphene-series.html https://www.acsmaterial.com

Plenty of examples online, it's a matter of purity and number of defects: https://www.acsmaterial.com/materials/graphene-series.html https://www.acsmaterial.com/materials/graphene-series.html