Optical observation of single layer graphene on silicon nitride substrate

Optical observation of graphene on substrates is an important aspect of graphene research. However, while graphene visibility on SiO2/Si substrates has already been thoroughly investigated, that on Si3N4/Si substrates, which excludes background oxygen, requires further investigation. Here, we present theoretical and experimental results of graphene visibility on Si3N4/Si substrates. On these substrates, the graphene contrast that diverges and changes sign over narrow ranges, which makes it more difficult to observe graphene on them, was predicted and experimentally verified. Under appropriate conditions, it was possible to observe single layer graphene on these substrates, as demonstrated by our experimentally observed results. Our findings will be useful for enabling the use of Si3N4/Si substrates in characterizing functionalized graphenes.