Silicon-Based Nanotechnology: There’s Still Plenty of Room at the Bottom

  • Hydrogen resist lithography can be used to build patterns of clean silicon at the nano scale. Spraying other molecules onto such patterned silicon causes selective adherence. Feedback controlled lithography allowed for single atom arrays and this level of precision has given rise to quantum cellular automata and single atom transistor experiments. To improve the robustness of the patterning, deuterium was used in place of hydrogen with measurable success. Samsung and Global Foundaries are now using deuterium in their chip production.
  • Joe experimented with graphene as well, stamping graphene ribbons onto silicon surfaces. Theoretically it should be possible to build a nanoribbon inverter via nanoscale metallization. STM is used to deposit metals onto the surface in an atomically precise fashion.
  • These principles have been demonstrated to work at the atomic scale, but there is still more to be done before getting to the point of building a functional application. Perhaps DNA origami could be used in tandem with graphene nanoribbon tech to build nanoscale computation arrays.


  • Making systems even more heterogeneous – integrating metals, semiconductors, and insulators.
  • Scaling up atomically precise fabrication – useful for commercial production purposes. One could potentially utilize top-down EUV lithography for massively parallel fabrication down to the 1nm scale to constrain bottom-up atomically precise self-assembly. This could lead to massively parallel fabrication of atomically precise structures on an atomically precise grid.

Every Atom Counts: Manipulating Single Molecules on Surfaces

  • Leonard is investigating many different mechanisms for manipulating atoms at the nano scale. Tetra-tert-butyl-azobenzene conformations can be altered using voltage. Attaching side groups alters the nature of the switches, changing the arrangement pattern and their switch properties. Porphycene, a molecule which allows internal hydrogen rearrangements, is another interesting molecular switch. Imaging the molecule at different voltages induces switching, and the presence of even a single copper atom nearby modulates the switching behavior.
  • Covalent on-surface polymerization between dibromoterfluorene creates long conjugated polymers of >100 nm in length. These polymers act like wires, and current has been measured passing through them. These polymers appear to move very quickly over a field of silver atoms, which led to the idea of using two imaging tips to send a short polymer section over a very long distance using electrical charges. The speed of this transmission was measured by detecting voltage fluctuations.
  • Leonard also participated in the first nanocar race with an average speed of 95.2 nm/h, leading his lab to first place.


  • Moving a motor molecule from one place to another remotely – directing nanoscale motion at a distance
  • Cooperative behavior using motors – integrating motors into machines that are more than the sum of its parts