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Why can a single layer of graphene be seen on silicon dioxide with an optical microscope?
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graphene
Atomic force microscopy image of water structures that were trapped beneath a sheet of graphene one atom thick.
A single layer of graphene is visible on a silicon dioxide substrate under a standard optical microscope due to two primary factors:1
- Light Absorption: Electrons in graphene interact strongly with photons in visible light, causing the material to absorb approximately 2.3 percent of the light's intensity per atomic layer.1
- Optical Interference: The contrast is significantly enhanced by interference phenomena occurring within the silicon dioxide layer. This is the same physical process that produces the rainbow colours observed in thin films, such as oil on water or soap bubbles.1
Together, these effects create sufficient optical contrast to allow the detection of atomically thin graphene flakes.1