As one of the allotropes of carbon, graphene, a two-dimensional single atomic layer of graphite, is considered as a promising material for future nano-electronic devices due to its excellence in electrical properties. Since its emergence in 2004, graphene has attracted much interest for its great potential in replacing silicon in modern electronic industry.

This thesis focuses on graphene with disorders. By covering graphene with metal electrode, disorders, which are metal atoms, are introduced in graphene. Therefore, modification has been made in conventional sample fabrication of graphene device for capacitance measurement in order to ensure metal-covered graphene. Furthermore, the application of hexagonal boron nitride and pick-up dry transfer technique lay the foundation fo...[ Read more ]

As one of the allotropes of carbon, graphene, a two-dimensional single atomic layer of graphite, is considered as a promising material for future nano-electronic devices due to its excellence in electrical properties. Since its emergence in 2004, graphene has attracted much interest for its great potential in replacing silicon in modern electronic industry.

This thesis focuses on graphene with disorders. By covering graphene with metal electrode, disorders, which are metal atoms, are introduced in graphene. Therefore, modification has been made in conventional sample fabrication of graphene device for capacitance measurement in order to ensure metal-covered graphene. Furthermore, the application of hexagonal boron nitride and pick-up dry transfer technique lay the foundation for graphene in high quality and cleanness and the negative influence of PMMA and SiO₂ has been eliminated.

A capacitance bridge system has been proposed, in which the out-of-balance signal reflects the capacitance of the device under test. Results show enhanced performance for capacitance bridge over commercial LCR meter.

Properties of metal-covered graphene have been investigated through capacitance measurement. Yttrium-covered samples show broken ambipolar property resulting from perturbed electronic structure of graphene. We attribute this unusual phenomenon to the strong bonding between graphene carbon atoms and yttrium atoms. In the meanwhile, niobium-covered samples display intact ambipolar properties and the amount of doping is in good agreement with theoretical mismatch in work function. Although the binding energy between graphene carbon atom and niobium atom is less than that between graphene carbon atom and yttrium atom, the weak bonding between graphene and niobium atom induces resonant states in graphene. The evolution and competition with Landau level is in good consistence with previous work concerning resonant impurities in graphene. What’s more, this resonant states induced by niobium atom is weaker than those in previous works since resonant states in our samples are easily destroyed by temperature.

Possible future work is proposed. Sputter would realize more controllable amount of metal atom impurities and the interaction between graphene and other metals should be interesting.