Illustration: Top left and bottom left, courtesy of A. Geim

Figure 1: According to Drut and Lähde’s calculation, graphene on top of $SiO2$ (top left, as seen in an optical microscope) is a semimetal with a conical electronic dispersion (top right). Suspended graphene on the other hand (bottom left, bright-field TEM image of a suspended graphene membrane in vacuum) is a semiconductor with a finite energy gap (bottom right).