Haigang Zhang

Tunability of Supramolecular Kagome Lattices of Magnetic Phthalocyanines Using Graphene-Based Moire Patterns as Templates

Self-assembly of various phthalocyanine (Pc) molecules and a derivative on an epitaxial graphene monolayer (MG) has been investigated by means of in situ ultrahigh vacuum scanning tunneling microscopy. The formation of regular Kagome lattices that duplicate the lattice of the moire pattern of MG was observed, demonstrating that MG can act as a wonderful template for the fabrication of unique nanoarchitectures with remarkable properties. Varying the central metal ion of the Pc molecule affords Kagome lattices with tunable molecular spins, providing ideal two-dimensional model systems for studying frustration physics.

Silicon layer intercalation of centimeter-scale, epitaxially grown monolayer graphene on Ru(0001)

We develop a strategy for graphene growth on Ru(0001) followed by silicon-layer intercalation that not only weakens the interaction of graphene with the metal substrate but also retains its superlative properties. This G/Si/Ru architecture, produced by silicon-layer intercalation approach (SIA), was characterized by scanning tunneling microscopy/spectroscopy and angle resolved electron photoemission spectroscopy. These experiments show high structural and electronic qualities of this new composite. The SIA allows for an atomic control of the distance between the graphene and the metal substrate that can be used as a top gate. Our results show potential for the next generation of graphene-based materials with tailored properties.

High quality sub-monolayer, monolayer, and bilayer graphene on Ru(0001)

High quality sub-monolayer, monolayer, and bilayer graphene were grown on Ru(0001). For the sub-monolayer graphene, the size of graphene islands with zigzag edges can be controlled by the dose of ethylene exposure. By increasing the dose of ethylene to 100 Langmuir at a high substrate temperature (800 °C), high quality single-crystalline monolayer graphene was synthesized on Ru(0001). High quality bilayer graphene was formed by further increasing the dose of ethylene while reducing the cooling rate to 5 °C/min. Raman spectroscopy revealed the vibrational states of graphene, G and 2D peaks appeared only in the bilayer graphene, which demonstrates that it behaves as the intrinsic graphene. Our present work affords methods to produce high quality sub-monolayer, monolayer, and bilayer graphene, both for basic research and applications.

Molecular Rotors Observed by Scanning Tunneling Microscopy

The motion of single molecules plays an important role in nanoscale engineering and holds great potential for bottom-up construction of complex devices at single molecular scale. In this chapter we review the recent progress on molecular rotors. We mainly focus on the motions of molecules at solid surfaces based on the most recent results obtained by scanning tunneling microscopy (STM). Several approaches to illustrate how the surface-supported molecular motor systems work are discussed. These results demonstrate solid advances in the field of molecular-based nanotechnology.