Making graphene is a critical part of any graphene based project, like mine. But how do we make it? Actually its much easier than one might expect – during lab outreach events we’ve had children with no training whatsoever make perfectly presentable pieces, a fact that really calls into question the value of my two master’s degrees.
The first step in creating graphene involves using scientific-grade adhesive tape to peel a thin layer from a larger piece of graphite, a material composed entirely of carbon atoms arranged in a layered structure. Graphite is similar to the “lead” found in pencils, but in this process, we are interested in isolating its single-layer form, known as graphene. The tape serves as a tool to cleave the graphite, capturing the topmost layers.
Next, the adhesive side of the tape, now holding thin graphite flakes, is pressed firmly onto a meticulously cleaned silicon wafer. Silicon is chosen because its properties enhance graphene visibility under certain lighting conditions, as well as being a convenient surface to do further work on the graphene. The wafer is then heated to improve adhesion, ensuring that some graphite flakes stick properly to its surface. After allowing sufficient time for this process, the tape is slowly and carefully peeled away. This peeling leaves behind an uneven distribution of graphene flakes on the silicon wafer, with pieces varying in size and thickness.
To locate a suitable piece of graphene, we turn to an optical microscope. This instrument allows us to inspect the wafer’s surface with precision. Graphene interacts uniquely with visible light, absorbing it efficiently, which causes it to appear darker than the surrounding silicon. This optical contrast makes it possible to differentiate between flakes of varying thickness. By observing how dark each flake looks, we can estimate the number of graphene layers present, ultimately selecting the desired single-layer graphene for further experimentation.
