Laser used to measure contaminants on graphene sheets

Researchers from Rice and Osaka Universities discovered a simple method to measure contaminants on graphene sheets using terahertz spectroscopy.

The researchers placed the graphene on a layer of Indium Phosphide, and then used a laser pulse on the graphene. This causes the materials to emit terahertz waves, which can then be used to map contaminants (which change graphene's electrical properties) on the graphene sheet.