ABSTRACT
Due to its unique electronic structure, graphene has become a widely studied new material. It is desirable to enrich the physics and chemistry of graphene-based materials by electronic structure engineering. An important property-tuning means is introducing an sp2 to sp3 phase transformation. In this chapter, rst-principles studies of functionalization induced sp2 to sp3 phase transformations of graphene-like nanolm are reviewed. Diamondized graphene bilayer and graphene-BN hybrid bilayer have a tunable electronic structure, from magnetic semiconductor to nonmagnetic metal. More interestingly, hydrogenated wurtzite SiC nanolm is a two-dimensional bipolar magnetic semiconductor material, where its spin polarization can be conveniently controlled by a gate voltage. The tunable electronic and magnetic properties demonstrated here pave new avenues to construct graphenebased electronics and spintronics devices. Graphene, a one-atom thickness honeycomb sp2-hybridized carbon nanolm, has attracted considerable attention due to its many unique physical properties such as half-integer quantum Hall effect, massless Dirac fermion behavior, ambipolar electric eld effect, and high carrier mobility.1-5 Since graphene is a semimetal with a zero bandgap, exploring effective ways to open a bandgap is indispensable for its applications in electronic devices. Hence, physical or chemical-based graphene electronic structure engineering has attracted lots of research interests. For example, graphene’s electronic properties could be tuned by using appropriate substrate,6-10 substitutional atom doping,11-17 molecular doping,18-24 or by patterning graphene into nanoribbons.25-30 At the same time, some other two-dimensional (2D) structures similar to graphene have also been synthesized. Despite their structure similarity, properties of these 2D systems can be very different from
graphene. For example, sp2-hybridized SiC sheet is a semiconductor with a large direct energy gap.
