Creating custom-designed patterns of nanoscale graphene quantum dots

Graphene quantum dots (GQDs) have attracted extensive attention over the years because of their importance both in fundamental science and potential applications. However, fabricating patterns of the GQDs is still of great challenge in experiment. Here, we demonstrate a technique to create patterned nanometer-sized GQDs with nanoscale precision in their sites. By applying a voltage pulse from a scanning tunneling microscopy (STM) tip, we successfully create stationary nanoscale circular p-n junctions, i.e. GQDs, in a continuous graphene sheet on hydrogen terminated germanium (110) surface. With accurately tuning the coordinates of the STM tip, the designed patterns of the GQDs are successfully generated. Spatial-resolved measurements indicate that the patterns of the GQDs strongly affect the local electronic properties and two-dimensional distributions of local density of states in graphene.