FEM and FIM of Graphene: Possible Observation of Electronic States at Edges

Field emission microscopy images of a graphene edge show a striped pattern (or “lip pattern”) consisting of an array of streaked spots; the direction of striation is perpendicular to the graphene sheet, and each stripe is divided into two wings by a central dark band running parallel to the graphene sheet. The “lip pattern” reflects the spatial distribution of pi- rbitals at the graphene edge. Field ion microscopy of graphene edge also exhibits an array of paired spots with higher resolution than FEM patterns. Preliminary results on measure spin polarization of electrons field-emitted from graphene edges are also carried out, showing the spin polarization of 20 to 25 % at room temperature.