First-principle investigations of nanoscale carbon-based materials for their electronic properties and potential applications
Date of Issue2011
School of Chemical and Biomedical Engineering
Centre for Advanced Bionanosystems
New materials and devices at nanoscale are greatly required to overcome Moore’s limits in engineering and technology. Recently, nanoscale carbon-based materials, have received considerable attention, due to their unique electronic, optical, and mechanical properties. All of the works in my PhD thesis are devoted to the following topic: first-principle investigations of carbon materials for their electronic properties and potential applications. First, three oxidized graphene structures with hydroxyl groups have been investigated through the spin-polarized density functional theory. The results reveal that in a graphene hexagonal ring structure, only chemical bond formation by two non-neighbored hydroxyl-bonded carbon atoms but with one carbon atom between can cause unpaired spins to produce a magnetic moment of 1.2 μB, while other two structures are nonmagnetic. This work paves the way for the controllable synthesis or/and oxidized graphene with hydroxyl groups at specific carbon positions for magnetic properties. Second, a series of structures with an epoxy-pair chain at various positions on zigzag graphene nanoribbons are considered. The results show that this kind of graphene oxide is ferromagnetic at ground state, providing great promise in the field of spintronics. In comparison with zigzag graphene nanoribbons of the same width, this graphene oxide is metallic and its spin density distribution is modified by epoxy pairs at different locations, thus offering some fundamental insights into graphene-based materials. Third, the electronic transport property of an epoxy-pair chain on zigzag graphene nanoribbons (ZGO) is studied theoretically. The results indicate that this graphene oxide can have a negative differential resistance (NDR) phenomenon, supported by bias dependent transmission curves of different orientation spins. This discovery may provide great potential for applications in NDR-based nanoelectronics by using modified graphene materials.