**2.2. Carbon nanotube unzipping**

As shown in Figure 6, graphene can be created by cutting open carbon nanotubes. [7] In one such method, multi-walled carbon nanotubes are cut open in a solution by action of potassium permanganate and sulfuric acid. [30] In another method, graphene nanoribbons were pro‐ duced by plasma etching of nanotubes partly embedded in a polymer film. [30] This method is useful for producing nanoribbons of graphene that induces a band gap in graphene through geometry breaking, which will be discussed in Section 3. However, the placement of the nanotubes on an integratable chip has been problematic, and thus this method once again is only good for the production of test structures to probe graphene characteristics.

**Figure 6.** Image showing the unzipping of a carbon nanotube to produce graphene sheets [21].
