Visibility of dielectrically passivated graphene films.

The visibility of monolayer graphene is dependent on its surrounding dielectric environment and the presence of any contamination associated with 2D layer transfer. Here, the optical contrast of residually contaminated monolayer graphene encased within a range of dielectric stacks characteristic of realistic devices is examined, highlighting the utility of optical microscopy for a graphene assessment, both during and after lithographic processing. Practically, chemical vapor deposited graphene is encapsulated in dielectric stacks of varying thicknesses of SiO2. Optical contrast is then measured and compared to predictions of a multilayer model. Experimentally measured contrast is in close agreement with simulation only when contamination is included.